fix mlfqs tests, complete BSD scheduling

- only run when BSD scheduler is enabled

.gitignore

@@ -4,13 +4,6 @@
 #ignore pdf files (just keep source files)
 *.pdf
 
-#ignore Mac OS generated files
-.DS_Store
-
-#ignore code editor generated directories
-.idea
-.vscode
-
 #ignore junk files from latex output
 *.out
 *.log

.gitlab-ci.yml

@@ -1,40 +0,0 @@
-stages:
-  - test
-
-.pintos_tests:
-  stage: test
-  image: gitlab.doc.ic.ac.uk:4567/lab2425_autumn/pintos_22/pintos-testing:latest
-  artifacts:
-    when: always
-    paths:
-      - src/$DIR/build/tests/$DIR/
-  before_script:
-    - cd src/utils
-    - make
-    - export PATH=$PWD:$PATH
-    - cd ../..
-  script:
-    - cd src/$DIR
-    - make check | tee build.log
-    - grep -vE "^FAIL $IGNORE\$" build.log | grep -q "FAIL tests/$DIR" && exit 1 || exit 0
-
-test_devices:
-  extends: .pintos_tests
-  variables:
-    DIR: devices
-
-test_threads:
-  extends: .pintos_tests
-  variables:
-    DIR: threads
-
-test_userprog:
-  extends: .pintos_tests
-  variables:
-    DIR: userprog
-
-test_vm:
-  extends: .pintos_tests
-  variables:
-    DIR: vm
-    IGNORE: (tests/vm/pt-grow-stack|tests/vm/pt-grow-pusha|tests/vm/pt-big-stk-obj|tests/vm/pt-overflowstk|tests/vm/pt-write-code2|tests/vm/pt-grow-stk-sc|tests/vm/page-linear|tests/vm/page-parallel|tests/vm/page-merge-seq|tests/vm/page-merge-par|tests/vm/page-merge-stk|tests/vm/page-merge-mm|tests/vm/mmap-read|tests/vm/mmap-close|tests/vm/mmap-overlap|tests/vm/mmap-twice|tests/vm/mmap-write|tests/vm/mmap-exit|tests/vm/mmap-shuffle|tests/vm/mmap-clean|tests/vm/mmap-inherit|tests/vm/mmap-misalign|tests/vm/mmap-null|tests/vm/mmap-over-code|tests/vm/mmap-over-data|tests/vm/mmap-over-stk|tests/vm/mmap-remove)

Dockerfile.devel

@@ -1,3 +0,0 @@
-FROM debian:12-slim
-
-RUN apt update && apt install gcc perl make qemu-system-i386 gdb -y

src/Makefile.build

@@ -62,7 +62,6 @@ userprog_SRC += userprog/gdt.c		# GDT initialization.
 userprog_SRC += userprog/tss.c		# TSS management.
 
 # Virtual memory code.
-vm_SRC += vm/frame.c                    # Frame table manager.
 vm_SRC += devices/swap.c		# Swap block manager.
 #vm_SRC = vm/file.c			# Some other file.
 

src/devices/timer.c

@@ -119,6 +119,9 @@ timer_sleep (int64_t ticks)
                        NULL);
   intr_set_level (old_level);
   sema_down (&st.semaphore);
+  old_level = intr_disable ();
+  list_remove (&st.elem);
+  intr_set_level (old_level);
 }
 
 /* Sleeps for approximately MS milliseconds.  Interrupts must be
@@ -201,10 +204,7 @@ timer_interrupt (struct intr_frame *args UNUSED)
     {
       struct asleep_thread *st = list_entry (e, struct asleep_thread, elem);
       if (ticks >= st->end_at)
-        {
-          list_remove (&st->elem);
-          sema_up (&st->semaphore);
-        }
+        sema_up (&st->semaphore);
       else
         break;
     }

src/examples/Makefile

@@ -4,7 +4,7 @@ SRCDIR = ..
 # To add a new test, put its name on the PROGS list
 # and then add a name_SRC line that lists its source files.
 PROGS = cat cmp cp echo halt hex-dump mcat mcp rm \
-	bubsort insult lineup matmult recursor args-ovf
+	bubsort insult lineup matmult recursor
 
 # Should work from task 2 onward.
 cat_SRC = cat.c
@@ -18,7 +18,6 @@ lineup_SRC = lineup.c
 ls_SRC = ls.c
 recursor_SRC = recursor.c
 rm_SRC = rm.c
-args-ovf_SRC = args-ovf.c
 
 # Should work in task 3; also in task 4 if VM is included.
 bubsort_SRC = bubsort.c

src/filesys/file.h

@@ -4,9 +4,6 @@
 #include "filesys/off_t.h"
 #include <stdbool.h>
 
-/* The maximum length of a file name in PintOS. */
-#define FNAME_MAX_LEN 14
-
 struct inode;
 
 /* Opening and closing files. */

src/lib/kernel/list.c

@@ -170,9 +170,6 @@ list_insert (struct list_elem *before, struct list_elem *elem)
 {
   ASSERT (is_interior (before) || is_tail (before));
   ASSERT (elem != NULL);
-  // Sanity checks to prevent (some) loop lists
-  ASSERT (before != elem);
-  ASSERT (before->prev != elem);
 
   elem->prev = before->prev;
   elem->next = before;

src/lib/user/syscall.c

@@ -166,7 +166,7 @@ mkdir (const char *dir)
 }
 
 bool
-readdir (int fd, char name[FNAME_MAX_LEN + 1]) 
+readdir (int fd, char name[READDIR_MAX_LEN + 1]) 
 {
   return syscall2 (SYS_READDIR, fd, name);
 }

src/lib/user/syscall.h

@@ -3,7 +3,6 @@
 
 #include <stdbool.h>
 #include <debug.h>
-#include "../../filesys/file.h"
 
 /* Process identifier. */
 typedef int pid_t;
@@ -13,6 +12,9 @@ typedef int pid_t;
 typedef int mapid_t;
 #define MAP_FAILED ((mapid_t) -1)
 
+/* Maximum characters in a filename written by readdir(). */
+#define READDIR_MAX_LEN 14
+
 /* Typical return values from main() and arguments to exit(). */
 #define EXIT_SUCCESS 0          /* Successful execution. */
 #define EXIT_FAILURE 1          /* Unsuccessful execution. */
@@ -39,7 +41,7 @@ void munmap (mapid_t);
 /* Task 4 only. */
 bool chdir (const char *dir);
 bool mkdir (const char *dir);
-bool readdir (int fd, char name[FNAME_MAX_LEN + 1]);
+bool readdir (int fd, char name[READDIR_MAX_LEN + 1]);
 bool isdir (int fd);
 int inumber (int fd);
 

src/tests/userprog/Make.tests

@@ -9,14 +9,14 @@ sc-bad-arg sc-bad-num sc-boundary sc-boundary-2 halt exit create-normal		\
 create-empty create-null create-bad-ptr create-long create-exists	\
 create-bound open-normal open-missing open-boundary open-empty		\
 open-null open-bad-ptr open-twice close-normal close-twice close-stdin	\
-close-stdout close-bad-fd read-normal read-bad-ptr read-bad-buf read-boundary	\
-read-zero read-stdout read-bad-fd write-normal write-bad-ptr write-bad-buf	\
+close-stdout close-bad-fd read-normal read-bad-ptr read-boundary	\
+read-zero read-stdout read-bad-fd write-normal write-bad-ptr		\
 write-boundary write-zero write-stdin write-bad-fd exec-once exec-arg	\
 exec-large-arg exec-multiple exec-missing exec-over-arg exec-over-args \
 exec-bad-ptr wait-simple wait-twice wait-killed wait-load-kill \
 wait-bad-pid wait-bad-child multi-recurse multi-child-fd rox-simple	\
 rox-child rox-multichild bad-read bad-write bad-read2 bad-write2        \
-bad-jump bad-jump2 bad-maths overflow-stack)
+bad-jump bad-jump2 bad-maths)
 
 tests/userprog_PROGS = $(tests/userprog_TESTS) $(addprefix \
 tests/userprog/,child-simple child-args child-bad child-close child-rox exec-exit)
@@ -36,7 +36,6 @@ tests/userprog/bad-read2_SRC = tests/userprog/bad-read2.c tests/main.c
 tests/userprog/bad-write2_SRC = tests/userprog/bad-write2.c tests/main.c
 tests/userprog/bad-jump2_SRC = tests/userprog/bad-jump2.c tests/main.c
 tests/userprog/bad-maths_SRC = tests/userprog/bad-maths.c tests/main.c
-tests/userprog/overflow-stack_SRC = tests/userprog/overflow-stack.c tests/main.c
 tests/userprog/sc-boundary_SRC = tests/userprog/sc-boundary.c	\
 tests/userprog/boundary.c tests/main.c
 tests/userprog/sc-boundary-2_SRC = tests/userprog/sc-boundary-2.c	\
@@ -67,7 +66,6 @@ tests/userprog/close-stdout_SRC = tests/userprog/close-stdout.c tests/main.c
 tests/userprog/close-bad-fd_SRC = tests/userprog/close-bad-fd.c tests/main.c
 tests/userprog/read-normal_SRC = tests/userprog/read-normal.c tests/main.c
 tests/userprog/read-bad-ptr_SRC = tests/userprog/read-bad-ptr.c tests/main.c
-tests/userprog/read-bad-buf_SRC = tests/userprog/read-bad-buf.c tests/main.c
 tests/userprog/read-boundary_SRC = tests/userprog/read-boundary.c	\
 tests/userprog/boundary.c tests/main.c
 tests/userprog/read-zero_SRC = tests/userprog/read-zero.c tests/main.c
@@ -75,7 +73,6 @@ tests/userprog/read-stdout_SRC = tests/userprog/read-stdout.c tests/main.c
 tests/userprog/read-bad-fd_SRC = tests/userprog/read-bad-fd.c tests/main.c
 tests/userprog/write-normal_SRC = tests/userprog/write-normal.c tests/main.c
 tests/userprog/write-bad-ptr_SRC = tests/userprog/write-bad-ptr.c tests/main.c
-tests/userprog/write-bad-buf_SRC = tests/userprog/write-bad-buf.c tests/main.c
 tests/userprog/write-boundary_SRC = tests/userprog/write-boundary.c	\
 tests/userprog/boundary.c tests/main.c
 tests/userprog/write-zero_SRC = tests/userprog/write-zero.c tests/main.c
@@ -125,12 +122,10 @@ tests/userprog/close-normal_PUTFILES += tests/userprog/sample.txt
 tests/userprog/close-twice_PUTFILES += tests/userprog/sample.txt
 tests/userprog/read-normal_PUTFILES += tests/userprog/sample.txt
 tests/userprog/read-bad-ptr_PUTFILES += tests/userprog/sample.txt
-tests/userprog/read-bad-buf_PUTFILES += tests/userprog/sample.txt
 tests/userprog/read-boundary_PUTFILES += tests/userprog/sample.txt
 tests/userprog/read-zero_PUTFILES += tests/userprog/sample.txt
 tests/userprog/write-normal_PUTFILES += tests/userprog/sample.txt
 tests/userprog/write-bad-ptr_PUTFILES += tests/userprog/sample.txt
-tests/userprog/write-bad-buf_PUTFILES += tests/userprog/sample.txt
 tests/userprog/write-boundary_PUTFILES += tests/userprog/sample.txt
 tests/userprog/write-zero_PUTFILES += tests/userprog/sample.txt
 tests/userprog/multi-child-fd_PUTFILES += tests/userprog/sample.txt

src/tests/userprog/Rubric.robustnessCR

@@ -1,9 +1,5 @@
-Full robustness of argument passing and syscall handling code:
-- Test user stack overflow robustness of "exec" system calls and user code.
+Full robustness of argument passing code:
+- Test user stack overflow robustness of "exec" system calls.
 5	exec-over-arg
 5	exec-over-args
-5	overflow-stack
 
-- Test syscall user provided buffer validity checks.
-5	read-bad-buf
-5	write-bad-buf

src/tests/userprog/exec-bad-ptr.ck

@@ -2,7 +2,11 @@
 use strict;
 use warnings;
 use tests::tests;
-check_expected ([<<'EOF']);
+check_expected ([<<'EOF', <<'EOF']);
+(exec-bad-ptr) begin
+(exec-bad-ptr) end
+exec-bad-ptr: exit(0)
+EOF
 (exec-bad-ptr) begin
 exec-bad-ptr: exit(-1)
 EOF

src/tests/userprog/open-bad-ptr.ck

@@ -2,7 +2,11 @@
 use strict;
 use warnings;
 use tests::tests;
-check_expected ([<<'EOF']);
+check_expected ([<<'EOF', <<'EOF']);
+(open-bad-ptr) begin
+(open-bad-ptr) end
+open-bad-ptr: exit(0)
+EOF
 (open-bad-ptr) begin
 open-bad-ptr: exit(-1)
 EOF

src/tests/userprog/overflow-stack.c

@@ -1,17 +0,0 @@
-/* Attempt to overflow the user stack by allocating a 4kB buffer and writing into it.
-   The process must be terminated with -1 exit code until stack growth has been implemented in Task 3
-*/
-
-#include <string.h>
-#include <syscall.h>
-#include "tests/lib.h"
-#include "tests/main.h"
-
-void
-test_main (void)
-{
-  char stack_obj[4096];
-  memset (stack_obj, 'a', sizeof stack_obj);
-  memset (stack_obj+10, '\0', 1);
-  msg ("buffer: %s", stack_obj);
-}

src/tests/userprog/overflow-stack.ck

@@ -1,14 +0,0 @@
-# -*- perl -*-
-use strict;
-use warnings;
-use tests::tests;
-check_expected (IGNORE_USER_FAULTS => 1, [<<'EOF',<<'EOF']);
-(overflow-stack) begin
-overflow-stack: exit(-1)
-EOF
-(overflow-stack) begin
-(overflow-stack) buffer: aaaaaaaaaa
-(overflow-stack) end
-overflow-stack: exit(0)
-EOF
-pass;

src/tests/userprog/read-bad-buf.c

@@ -1,17 +0,0 @@
-/* Passes a buffer to the read system call that starts in valid memory, but runs into kernel space.
-   The process must be terminated with -1 exit code.
-*/
-
-#include <syscall.h>
-#include "tests/lib.h"
-#include "tests/main.h"
-
-void
-test_main (void)
-{
-  int handle;
-  CHECK ((handle = open ("sample.txt")) > 1, "open \"sample.txt\"");
-
-  read (handle, (char *) 0xbfffffe0, 100);
-  fail ("should not have survived read()");
-}

src/tests/userprog/read-bad-buf.ck

@@ -1,10 +0,0 @@
-# -*- perl -*-
-use strict;
-use warnings;
-use tests::tests;
-check_expected (IGNORE_KERNEL_FAULTS => 1, [<<'EOF']);
-(read-bad-buf) begin
-(read-bad-buf) open "sample.txt"
-read-bad-buf: exit(-1)
-EOF
-pass;

src/tests/userprog/read-bad-ptr.ck

@@ -2,7 +2,12 @@
 use strict;
 use warnings;
 use tests::tests;
-check_expected ([<<'EOF']);
+check_expected ([<<'EOF', <<'EOF']);
+(read-bad-ptr) begin
+(read-bad-ptr) open "sample.txt"
+(read-bad-ptr) end
+read-bad-ptr: exit(0)
+EOF
 (read-bad-ptr) begin
 (read-bad-ptr) open "sample.txt"
 read-bad-ptr: exit(-1)

src/tests/userprog/write-bad-buf.c

@@ -1,17 +0,0 @@
-/* Passes a buffer to the write system call that starts in valid memory, but runs into kernel space.
-   The process must be terminated with -1 exit code.
-*/
-
-#include <syscall.h>
-#include "tests/lib.h"
-#include "tests/main.h"
-
-void
-test_main (void)
-{
-  int handle;
-  CHECK ((handle = open ("sample.txt")) > 1, "open \"sample.txt\"");
-
-  write (handle, (char *) 0xbffffff0, 32);
-  fail ("should have exited with -1");
-}

src/tests/userprog/write-bad-buf.ck

@@ -1,10 +0,0 @@
-# -*- perl -*-
-use strict;
-use warnings;
-use tests::tests;
-check_expected (IGNORE_KERNEL_FAULTS => 1, [<<'EOF']);
-(write-bad-buf) begin
-(write-bad-buf) open "sample.txt"
-write-bad-buf: exit(-1)
-EOF
-pass;

src/tests/userprog/write-bad-ptr.ck

@@ -2,7 +2,12 @@
 use strict;
 use warnings;
 use tests::tests;
-check_expected ([<<'EOF']);
+check_expected ([<<'EOF', <<'EOF']);
+(write-bad-ptr) begin
+(write-bad-ptr) open "sample.txt"
+(write-bad-ptr) end
+write-bad-ptr: exit(0)
+EOF
 (write-bad-ptr) begin
 (write-bad-ptr) open "sample.txt"
 write-bad-ptr: exit(-1)

src/threads/fixed-point.h

@@ -3,40 +3,37 @@
 #define FIXED_POINT_H
 
 typedef struct
-  {
-    int32_t raw;
-  } fp32_t;
+{
+  int32_t raw;
+} fp32_t;
 
 /* Fixed Point Arithmetic bit count constants */
 #define NUM_FRAC_BITS 14
 #define NUM_INT_BITS (31 - NUM_FRAC_BITS)
-#define CONVERSION_FACTOR (1 << NUM_FRAC_BITS) /* f = 2^q, (2^14) */
+#define CONVERSION_CONST (1 << NUM_FRAC_BITS) /* f = 2^q, (2^20) */
 
 /* Fixed Point Arithmetic conversion operations */
 /* Converts an integer n to a fixed point number */
 inline fp32_t
-fp_from_int (int32_t n)
+int_to_fp (int32_t n)
 {
-  return (fp32_t){ n * CONVERSION_FACTOR };
+  return (fp32_t){ n * CONVERSION_CONST };
 }
 
-/* Handles conversion of fixed point to integer,
-   with truncation */
+/* Handles conversion of fixed point to integer. First version truncates, second one rounds */
 inline int32_t
 fp_floor (fp32_t x)
 {
-  return x.raw / CONVERSION_FACTOR;
+  return x.raw / CONVERSION_CONST;
 }
 
-/* Handles conversion of fixed point to integer,
-   with rounding */
 inline int32_t
 fp_round (fp32_t x)
 {
   if (x.raw >= 0)
-    return (x.raw + CONVERSION_FACTOR / 2) / CONVERSION_FACTOR;
+    return (x.raw + CONVERSION_CONST / 2) / CONVERSION_CONST;
   else
-    return (x.raw - CONVERSION_FACTOR / 2) / CONVERSION_FACTOR;
+    return (x.raw - CONVERSION_CONST / 2) / CONVERSION_CONST;
 }
 
 /* Add two fixed points */
@@ -53,20 +50,32 @@ fp_sub (fp32_t x, fp32_t y)
   return (fp32_t){ x.raw - y.raw };
 }
 
+/* Add fixed point to integer */
+inline fp32_t
+fp_add_int (fp32_t x, int32_t n)
+{
+  return (fp32_t){ x.raw + n * CONVERSION_CONST };
+}
 
+/* Subtract integer from fixed point */
+inline fp32_t
+fp_sub_int (fp32_t x, int32_t n)
+{
+  return (fp32_t){ x.raw - n * CONVERSION_CONST };
+}
 
 /* Multiple two fixed points */
 inline fp32_t
 fp_mul (fp32_t x, fp32_t y)
 {
-  return (fp32_t){ ((int64_t)x.raw) * y.raw / CONVERSION_FACTOR };
+  return (fp32_t){ ((int64_t)x.raw) * y.raw / CONVERSION_CONST };
 }
 
 /* Divide two fixed points */
 inline fp32_t
 fp_div (fp32_t x, fp32_t y)
 {
-  return (fp32_t){ ((int64_t)x.raw) * CONVERSION_FACTOR / y.raw };
+  return (fp32_t){ ((int64_t)x.raw) * CONVERSION_CONST / y.raw };
 }
 
 /* Multiply fixed point and integer */
@@ -83,18 +92,4 @@ fp_div_int (fp32_t x, int32_t n)
   return (fp32_t){ x.raw / n };
 }
 
-/* Add fixed point to integer */
-inline fp32_t
-fp_add_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw + n * CONVERSION_FACTOR };
-}
-
-/* Subtract integer from fixed point */
-inline fp32_t
-fp_sub_int (fp32_t x, int32_t n)
-{
-  return (fp32_t){ x.raw - n * CONVERSION_FACTOR };
-}
-
 #endif //FIXED_POINT_H

src/threads/init.c

@@ -32,7 +32,6 @@
 #include "tests/threads/tests.h"
 #endif
 #ifdef VM
-#include "vm/frame.h"
 #include "devices/swap.h"
 #endif
 #ifdef FILESYS
@@ -102,9 +101,6 @@ main (void)
   palloc_init (user_page_limit);
   malloc_init ();
   paging_init ();
-#ifdef VM
-  frame_init ();
-#endif
 
   /* Segmentation. */
 #ifdef USERPROG

src/threads/synch.c

@@ -32,10 +32,6 @@
 #include "threads/interrupt.h"
 #include "threads/thread.h"
 
-static bool
-priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED);
-
 /* Initializes semaphore SEMA to VALUE.  A semaphore is a
    nonnegative integer along with two atomic operators for
    manipulating it:
@@ -113,33 +109,15 @@ void
 sema_up (struct semaphore *sema) 
 {
   enum intr_level old_level;
-  bool thread_unblocked = false; /* Flag to track if any thread was woken up. */
 
   ASSERT (sema != NULL);
 
   old_level = intr_disable ();
   if (!list_empty (&sema->waiters)) 
-    {
-      /* Enforces wake-up of the highest priority thread waiting for the
-         semaphore. */
-      struct list_elem *e = list_max (&sema->waiters, priority_less, NULL);
-      list_remove (e);
-      thread_unblock (list_entry (e, struct thread, elem));
-      thread_unblocked = true;
-    }
+    thread_unblock (list_entry (list_pop_front (&sema->waiters),
+                                struct thread, elem));
   sema->value++;
   intr_set_level (old_level);
-
-  /* Yields the CPU in case the thread that has been woken up has a higher
-     priority that the current running thread, including the case when called
-     within an interrupt handler. */
-  if (thread_unblocked)
-    {
-      if (intr_context ())
-        intr_yield_on_return ();
-      else
-        thread_yield ();
-    }
 }
 
 static void sema_test_helper (void *sema_);
@@ -203,48 +181,6 @@ lock_init (struct lock *lock)
   sema_init (&lock->semaphore, 1);
 }
 
-/* Current thread donates its priority to donee, iteratively
-   propagating the donation in the case of chains in the wait-for graph.
-   Also keeps track of the donation by updating the donors list. Expects
-   interrupts to be disabled. */
-static void
-donate_priority (struct thread *donee) {
-  ASSERT (intr_get_level () == INTR_OFF);
-
-  struct thread *donor = thread_current ();
-  list_remove (&donor->donor_elem);
-  list_push_back (&donee->donors_list, &donor->donor_elem);
-  
-  while (donee != NULL)
-    {
-      /* Stop propagation of donation once a donee is reached that has
-         a higher effective priority (as its donees can't have less
-         priority than that being donated). */
-      if (donor->priority <= donee->priority)
-          break;
-
-      /* Also stop propagation of donation once a donee is reached with
-         no donees of its own (sink node in WFG). */
-      if (donee->waiting_lock == NULL)
-        {
-          /* Only the sink node of the WFG isn't waiting for a lock and
-             could be on the ready list. Thus, as its priority changed,
-             it must be reinserted into the list. */
-          enum intr_level old_level = intr_disable ();
-          donee->priority = donor->priority;
-          ready_list_reinsert (donee);
-          intr_set_level (old_level);
-          
-          donee = NULL;
-        }
-      else
-        {
-          donee->priority = donor->priority;
-          donee = donee->waiting_lock->holder;
-        }
-    }
-}
-
 /* Acquires LOCK, sleeping until it becomes available if
    necessary.  The lock must not already be held by the current
    thread.
@@ -260,20 +196,8 @@ lock_acquire (struct lock *lock)
   ASSERT (!intr_context ());
   ASSERT (!lock_held_by_current_thread (lock));
 
-  struct thread *t = thread_current ();
-  ASSERT (t->waiting_lock == NULL);
-
-  enum intr_level old_level = intr_disable ();
-  if (lock->holder != NULL)
-    {
-      t->waiting_lock = lock;
-      donate_priority (lock->holder);
-    }
-  intr_set_level (old_level);
-
   sema_down (&lock->semaphore);
   lock->holder = thread_current ();
-  t->waiting_lock = NULL;
 }
 
 /* Tries to acquires LOCK and returns true if successful or false
@@ -307,53 +231,9 @@ lock_release (struct lock *lock)
   ASSERT (lock != NULL);
   ASSERT (lock_held_by_current_thread (lock));
 
-  struct thread *current_thread = thread_current ();
-  struct thread *max_donor = NULL;
-
-  struct list orphan_list;
-  list_init (&orphan_list);
-
-  enum intr_level old_level = intr_disable ();
-  /* Loop through current thread's donors, removing the ones waiting for the
-     lock being released and keeping track of them (within orphan_list).
-     Also identifies the highest priority donor thread among them. */
-  struct list_elem *tail = list_tail (&current_thread->donors_list);
-  struct list_elem *e = list_begin (&current_thread->donors_list);
-  while (e != tail)
-    {
-      struct thread *donor = list_entry (e, struct thread, donor_elem);
-      struct list_elem *next = list_next (e);
-
-      /* Excludes donors that aren't waiting for the lock being released,
-         and tracks the rest. */
-      if (donor->waiting_lock == lock)
-        {
-          list_remove (e);
-          list_push_back (&orphan_list, e);
-
-          /* Identify highest priority donor. */
-          if (max_donor == NULL || donor->priority > max_donor->priority)
-            max_donor = donor;
-        }
-
-      e = next;
-    }
-
-  /* If there exists a maximum donor thread waiting for this lock to be
-     released, transfer the remaining orphaned donors to its donor list. */
-  if (max_donor != NULL)
-    {
-      while (!list_empty (&orphan_list))
-        list_push_back (&max_donor->donors_list, list_pop_front (&orphan_list));
-    }
-
-  intr_set_level (old_level);
-  /* Removal of donors to this thread may change its effective priority,
-     so recalculate. */
-  thread_recalculate_priority ();
-
   lock->holder = NULL;
   sema_up (&lock->semaphore);
+  thread_yield ();
 }
 
 /* Returns true if the current thread holds LOCK, false
@@ -374,49 +254,6 @@ struct semaphore_elem
     struct semaphore semaphore;         /* This semaphore. */
   };
 
-/* Function that compares the two threads associated with the provided
-   pointers to their 'elem' member. Returns true if the thread associated
-   with a_ has a lower priority than that of b_. */
-static bool
-priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
-{
-  struct thread *a = list_entry (a_, struct thread, elem);
-  struct thread *b = list_entry (b_, struct thread, elem);
-
-  return a->priority < b->priority;
-}
-
-/* Function that compares the two *semaphores* associated with the provided
-   list_elem structures. [i.e., takes list_elem of semaphore_elem, and]
-   Returns true if the thread associated with the semaphore associated with a_
-   has a higher priority than that of b_.
-
-    If aux is provided, then it is a pointer to an integer representing the
-    priority of the first semaphore. This is useful when the thread has not been
-    sema'd down yet. */
-static bool
-sema_priority_more(const struct list_elem *a, const struct list_elem *b,
-                   void *inserting_telem)
-{
-  struct list_elem *te_a, *te_b;
-  
-  te_b = list_front (
-    &list_entry (b, struct semaphore_elem, elem)->semaphore.waiters);
-
-  if (inserting_telem == NULL)
-    {
-      te_a = list_front (
-        &list_entry (a, struct semaphore_elem, elem)->semaphore.waiters);
-    }
-  else
-    {
-      te_a = inserting_telem;
-    }
-
-  return priority_more (te_a, te_b, NULL);
-}
-
 /* Initializes condition variable COND.  A condition variable
    allows one piece of code to signal a condition and cooperating
    code to receive the signal and act upon it. */
@@ -481,13 +318,8 @@ cond_signal (struct condition *cond, struct lock *lock UNUSED)
   ASSERT (lock_held_by_current_thread (lock));
 
   if (!list_empty (&cond->waiters)) 
-    {
-      /* Enforce wake-up of highest priority thread within the singleton 
-         semaphores waiting for condvar. */
-      struct list_elem *e = list_min (&cond->waiters, sema_priority_more, NULL);
-      list_remove (e);
-      sema_up (&list_entry (e, struct semaphore_elem, elem)->semaphore);
-    }
+    sema_up (&list_entry (list_pop_front (&cond->waiters),
+                          struct semaphore_elem, elem)->semaphore);
 }
 
 /* Wakes up all threads, if any, waiting on COND (protected by

src/threads/thread.c

@@ -1,6 +1,5 @@
 #include "threads/thread.h"
 #include <debug.h>
-#include <hash.h>
 #include <stddef.h>
 #include <random.h>
 #include <stdio.h>
@@ -10,14 +9,12 @@
 #include "threads/flags.h"
 #include "threads/interrupt.h"
 #include "threads/intr-stubs.h"
-#include "threads/malloc.h"
 #include "threads/palloc.h"
 #include "threads/switch.h"
 #include "threads/synch.h"
 #include "threads/vaddr.h"
 #ifdef USERPROG
 #include "userprog/process.h"
-#include "userprog/syscall.h"
 #endif
 
 /* Random value for struct thread's `magic' member.
@@ -58,7 +55,6 @@ static fp32_t load_avg = { 0 }; /* System load average. */
 
 /* Scheduling. */
 #define TIME_SLICE 4            /* # of timer ticks to give each thread. */
-#define PRI_UPDATE_FREQ 4       /* # of timer ticks to update priorities. */
 static unsigned thread_ticks;   /* # of timer ticks since last yield. */
 
 /* If false (default), use round-robin scheduler.
@@ -71,23 +67,17 @@ static void kernel_thread (thread_func *, void *aux);
 static void idle (void *aux UNUSED);
 static struct thread *running_thread (void);
 static struct thread *next_thread_to_run (void);
-static bool init_process_result (struct thread *t);
 static void init_thread (struct thread *, const char *name, int nice,
                          int priority, fp32_t recent_cpu);
 static bool is_thread (struct thread *) UNUSED;
 static void *alloc_frame (struct thread *, size_t size);
 static int calculate_bsd_priority (fp32_t recent_cpu, int nice);
-static void update_recent_cpu (struct thread *t, void *aux UNUSED);
-static void recalculate_priority (struct thread *t);
+static void thread_update_recent_cpu (struct thread *t, void *aux UNUSED);
+static bool thread_priority_less (const struct list_elem *a,
+                                  const struct list_elem *b, void *aux UNUSED);
 static void schedule (void);
 void thread_schedule_tail (struct thread *prev);
 static tid_t allocate_tid (void);
-static bool donor_priority_less (const struct list_elem *a_,
-                                 const struct list_elem *b_, void *aux UNUSED);
-static unsigned process_result_hash (const struct hash_elem *e,
-                                     void *aux UNUSED);
-static bool process_result_less (const struct hash_elem *a,
-                                 const struct hash_elem *b, void *aux UNUSED);
 
 /* Initializes the threading system by transforming the code
    that's currently running into a thread.  This can't work in
@@ -118,7 +108,6 @@ thread_init (void)
                initial_thread_recent_cpu);
   initial_thread->status = THREAD_RUNNING;
   initial_thread->tid = allocate_tid ();
-  initial_thread->result = NULL; /* Main thread cannot be waited for. */
 }
 
 /* Starts preemptive thread scheduling by enabling interrupts.
@@ -126,13 +115,6 @@ thread_init (void)
 void
 thread_start (void) 
 {
-  /* Malloc has been initalised, we can allocate the child results table
-     for the main thread. */
-  struct thread *t = thread_current ();
-  if (!hash_init (&t->child_results, process_result_hash, process_result_less,
-                  t))
-    PANIC ("Failed to initialise child results table for main thread.");
-
   /* Create the idle thread. */
   struct semaphore idle_started;
   sema_init (&idle_started, 0);
@@ -175,31 +157,24 @@ thread_tick (void)
 
   /* Update system load_avg and all threads recent_cpu every second. */
   int64_t ticks = timer_ticks ();
-  if (thread_mlfqs)
+  if (thread_mlfqs && (ticks % TIMER_FREQ == 0))
     {
+      size_t ready = threads_ready ();
       if (t != idle_thread)
-          t->recent_cpu = fp_add_int (t->recent_cpu, 1);
+        ready++;
+      fp32_t old_coeff = fp_mul (fp_div_int (int_to_fp (59), 60), load_avg);
+      fp32_t new_coeff = fp_div_int (int_to_fp (ready), 60);
+      load_avg = fp_add (old_coeff, new_coeff);
 
-      if (ticks % TIMER_FREQ == 0)
-        {
-          size_t ready = threads_ready ();
-          if (t != idle_thread)
-            ready++;
-          fp32_t old_coeff = fp_div_int (fp_mul_int (load_avg, 59), 60);
-          fp32_t new_coeff = fp_div_int (fp_from_int (ready), 60);
-          load_avg = fp_add (old_coeff, new_coeff);
+      thread_foreach (thread_update_recent_cpu, NULL);
+    }
 
-          thread_foreach (update_recent_cpu, NULL);
-          /* Priorities have been updated, need to re-sort. */
-          list_sort (&ready_list, priority_more, NULL);
-        }
-
-      /* Recent cpu was updated, update priority. */
-      if (t != idle_thread && ticks % PRI_UPDATE_FREQ == 0)
-        {
-          t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-          recalculate_priority (t);
-        }
+  /* Update current thread's recent_cpu. */
+  if (thread_mlfqs && (t != idle_thread))
+    {
+      t->recent_cpu = fp_add_int (t->recent_cpu, 1);
+      if (ticks % 4 == 0) // recent_cpu was updated, update priority.
+        t->priority = calculate_bsd_priority (t->recent_cpu, t->nice);
     }
 
   /* Enforce preemption. */
@@ -249,28 +224,9 @@ thread_create (const char *name, int priority,
     return TID_ERROR;
 
   /* Initialize thread. */
-  struct thread *parent_thread = thread_current ();
-  init_thread (t, name, parent_thread->nice, priority, parent_thread->recent_cpu);
+  struct thread *pt = thread_current ();
+  init_thread (t, name, pt->nice, priority, pt->recent_cpu);
   tid = t->tid = allocate_tid ();
-  if (!init_process_result (t))
-    {
-      palloc_free_page (t);
-      return TID_ERROR;
-    }
-
-#ifdef USERPROG
-  /* Initialize the thread's file descriptor table. */
-  t->fd_counter = MINIMUM_USER_FD;
-
-  if (!hash_init (&t->open_files, fd_hash, fd_less, NULL)
-      || !hash_init (&t->child_results, process_result_hash,
-                     process_result_less, t))
-    {
-      palloc_free_page (t);
-      free (t->result);
-      return TID_ERROR;
-    }
-#endif
 
   /* Prepare thread for first run by initializing its stack.
      Do this atomically so intermediate values for the 'stack' 
@@ -294,16 +250,9 @@ thread_create (const char *name, int priority,
 
   intr_set_level (old_level);
 
-  hash_insert (&parent_thread->child_results, &t->result->elem);
-
   /* Add to run queue. */
   thread_unblock (t);
 
-  /* Yield if the newly created thread has higher priority than the current
-     thread. */
-  if (t->priority > thread_get_priority ())
-    thread_yield ();
-
   return tid;
 }
 
@@ -340,10 +289,10 @@ thread_unblock (struct thread *t)
 
   old_level = intr_disable ();
   ASSERT (t->status == THREAD_BLOCKED);
-
-  /* Insert the thread back into the ready list in priority order. */
-  list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
-
+  if (thread_mlfqs)
+    list_insert_ordered (&ready_list, &t->elem, thread_priority_less, NULL);
+  else
+    list_push_back (&ready_list, &t->elem);
   t->status = THREAD_READY;
   intr_set_level (old_level);
 }
@@ -396,9 +345,7 @@ thread_exit (void)
      and schedule another process.  That process will destroy us
      when it calls thread_schedule_tail(). */
   intr_disable ();
-  struct thread *t = thread_current ();
-  list_remove (&t->allelem);
-  list_remove (&t->donor_elem);
+  list_remove (&thread_current()->allelem);
   thread_current ()->status = THREAD_DYING;
   schedule ();
   NOT_REACHED ();
@@ -415,13 +362,14 @@ thread_yield (void)
   ASSERT (!intr_context ());
 
   old_level = intr_disable ();
-
   if (cur != idle_thread)
     {
-      /* Insert the thread back into the ready list in priority order. */
-      list_insert_ordered (&ready_list, &cur->elem, priority_more, NULL);
+      if (thread_mlfqs)
+        list_insert_ordered (&ready_list, &cur->elem, thread_priority_less,
+                             NULL);
+      else
+        list_push_back (&ready_list, &cur->elem);
     }
-
   cur->status = THREAD_READY;
   schedule ();
   intr_set_level (old_level);
@@ -444,68 +392,25 @@ thread_foreach (thread_action_func *func, void *aux)
     }
 }
 
-/* Function that compares the two threads associated with the provided
-   pointers to their 'elem' member. Returns true if the thread associated
-   with a_ has a higher priority than that of b_. */
-bool
-priority_more (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
-{
-  struct thread *a = list_entry (a_, struct thread, elem);
-  struct thread *b = list_entry (b_, struct thread, elem);
-
-  return a->priority > b->priority;
-
-}
-
-/* Function that compares the two threads associated with the provided
-   pointers to their 'donor_elem' member. Returns true if the thread associated
-   with a_ has a lower priority than that of b_. */
-static bool
-donor_priority_less (const struct list_elem *a_, const struct list_elem *b_,
-               void *aux UNUSED)
-{
-  struct thread *a = list_entry (a_, struct thread, donor_elem);
-  struct thread *b = list_entry (b_, struct thread, donor_elem);
-
-  return a->priority < b->priority;
-}
-
-/* Sets the current thread's base priority to new_base_priority.
-   Updates the current thread's effective priority if necessary. */
+/* Sets the current thread's priority to NEW_PRIORITY. */
 void
-thread_set_priority (int new_base_priority)
+thread_set_priority (int new_priority) 
 {
-
   if (thread_mlfqs)
     return;
-
-  ASSERT (new_base_priority >= PRI_MIN);
-  ASSERT (new_base_priority <= PRI_MAX);
-
-  struct thread *t = thread_current ();
-
-  /* If the base priority is unchanged, do nothing. */
-  if (new_base_priority == t->base_priority)
-    return;
-
-  t->base_priority = new_base_priority;
-  recalculate_priority (t);
-
-  thread_yield ();
+  thread_current ()->priority = new_priority;
 }
 
-/* Returns the current thread's effective priority. */
+/* Returns the current thread's priority. */
 int
 thread_get_priority (void) 
 {
   return thread_current ()->priority;
 }
 
-
 /* Updates recent_cpu for a thread. */
 static void
-update_recent_cpu (struct thread *t, void *aux UNUSED)
+thread_update_recent_cpu (struct thread *t, void *aux UNUSED)
 {
   fp32_t curr_recent_cpu = t->recent_cpu;
   fp32_t dbl_load_avg = fp_mul_int (load_avg, 2);
@@ -514,38 +419,7 @@ update_recent_cpu (struct thread *t, void *aux UNUSED)
   t->recent_cpu
       = fp_add_int (fp_mul (recent_cpu_coeff, curr_recent_cpu), t->nice);
   // recent_cpu was updated, update priority.
-  t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-  recalculate_priority (t);
-}
-
-/* Recalculates the effective priority of the current thread. */
-void
-thread_recalculate_priority (void)
-{
-  struct thread *t = thread_current ();
-  recalculate_priority (t);
-}
-
-static void
-recalculate_priority (struct thread *t)
-{
-  enum intr_level old_level = intr_disable ();
-  t->priority = t->base_priority;
-
-  /* If there are no donors to the current thread, then the effective
-     priority is just the base priority. */
-  if (!list_empty (&t->donors_list))
-    {
-      int max_donated_priority =
-        list_entry (list_max (&t->donors_list, donor_priority_less, NULL),
-                    struct thread, donor_elem)->priority;
-
-      /* The effective priority is the max donated priority if this is
-         higher than the base priority. */
-      if (max_donated_priority > t->priority)
-        t->priority = max_donated_priority;
-    }
-  intr_set_level (old_level);
+  t->priority = calculate_bsd_priority (t->recent_cpu, t->nice);
 }
 
 /* Sets the current thread's nice value to NICE. */
@@ -556,11 +430,10 @@ thread_set_nice (int nice)
 
   struct thread *t = thread_current ();
   t->nice = nice;
-  t->base_priority = calculate_bsd_priority (t->recent_cpu, t->nice);
-  recalculate_priority (t);
+  int priority = calculate_bsd_priority (t->recent_cpu, t->nice);
   struct thread *next_t
       = list_entry (list_begin (&ready_list), struct thread, elem);
-  if (t->priority < next_t->priority)
+  if (priority < next_t->priority)
     thread_yield ();
 }
 
@@ -585,22 +458,6 @@ thread_get_recent_cpu (void)
   return fp_round (fp_mul_int (thread_current ()->recent_cpu, 100));
 }
 
-/* Reinsert thread t into the ready list at its correct position
-   in descending order of priority. Used when this thread's priority
-   may have changed. Must be called with interrupts disabled. */
-void
-ready_list_reinsert (struct thread *t)
-{
-  ASSERT (intr_get_level () == INTR_OFF);
-
-  /* If the thread isn't ready to run, do nothing. */
-  if (t->status != THREAD_READY)
-    return;
-
-  list_remove (&t->elem);
-  list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
-}
-
 /* Idle thread.  Executes when no other thread is ready to run.
 
    The idle thread is initially put on the ready list by
@@ -671,21 +528,6 @@ is_thread (struct thread *t)
   return t != NULL && t->magic == THREAD_MAGIC;
 }
 
-/* Allocate and initialise a process result for given thread. */
-static bool
-init_process_result (struct thread *t)
-{
-  struct process_result *result = malloc (sizeof (struct process_result));
-  if (result == NULL)
-    return false;
-  result->tid = t->tid;
-  result->exit_status = -1;
-  lock_init (&result->lock);
-  sema_init (&result->sema, 0);
-  t->result = result;
-  return true;
-}
-
 /* Does basic initialization of T as a blocked thread named
    NAME. */
 static void
@@ -702,17 +544,11 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->status = THREAD_BLOCKED;
   strlcpy (t->name, name, sizeof t->name);
   t->stack = (uint8_t *) t + PGSIZE;
-  t->magic = THREAD_MAGIC;
-
-  t->base_priority
+  t->priority
       = thread_mlfqs ? calculate_bsd_priority (recent_cpu, nice) : priority;
-  list_init (&t->donors_list);
-  list_push_back (&t->donors_list, &t->donor_elem);
-  t->waiting_lock = NULL;
-
   t->nice = nice;
   t->recent_cpu = recent_cpu;
-  t->priority = t->base_priority;
+  t->magic = THREAD_MAGIC;
 
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);
@@ -796,9 +632,6 @@ thread_schedule_tail (struct thread *prev)
 static int
 calculate_bsd_priority (fp32_t recent_cpu, int nice)
 {
-
-  ASSERT (thread_mlfqs);
-
   int priority = PRI_MAX - (fp_round (recent_cpu) / 4) - (nice * 2);
   if (priority < PRI_MIN)
     return PRI_MIN;
@@ -807,8 +640,18 @@ calculate_bsd_priority (fp32_t recent_cpu, int nice)
   return priority;
 }
 
-/* Schedules a new process.  At entry, interrupts must be off and
-   the running process's state must have been changed from
+/* Returns true if thread a's priority is strictly greater than
+   thread b's priority. */
+static bool
+thread_priority_less (const struct list_elem *a, const struct list_elem *b,
+                      void *aux UNUSED)
+{
+  struct thread *ta = list_entry (a, struct thread, elem);
+  struct thread *tb = list_entry (b, struct thread, elem);
+  return ta->priority > tb->priority;
+}
+
+/* ss's state must have been changed from
    running to some other state.  This function finds another
    thread to run and switches to it.
 
@@ -844,29 +687,6 @@ allocate_tid (void)
   return tid;
 }
 
-/* Hashing function needed for child_results table.
-   Returns hash of process_result's TID. */
-static unsigned
-process_result_hash (const struct hash_elem *e, void *aux UNUSED)
-{
-  const struct process_result *result
-      = hash_entry (e, struct process_result, elem);
-  return hash_int (result->tid);
-}
-
-/* Comparator function needed for child_results table.
-   Returns less than comparison on process_results' TIDs. */
-static bool
-process_result_less (const struct hash_elem *a_, const struct hash_elem *b_,
-                     void *aux UNUSED)
-{
-  const struct process_result *a
-      = hash_entry (a_, struct process_result, elem);
-  const struct process_result *b
-      = hash_entry (b_, struct process_result, elem);
-  return a->tid < b->tid;
-}
-
 /* Offset of `stack' member within `struct thread'.
    Used by switch.S, which can't figure it out on its own. */
 uint32_t thread_stack_ofs = offsetof (struct thread, stack);

src/threads/thread.h

@@ -2,11 +2,8 @@
 #define THREADS_THREAD_H
 
 #include <debug.h>
-#include <hash.h>
 #include <list.h>
 #include <stdint.h>
-#include <stdbool.h>
-#include "threads/synch.h"
 #include "threads/fixed-point.h"
 
 /* States in a thread's life cycle. */
@@ -32,21 +29,6 @@ typedef int tid_t;
 #define NICE_DEFAULT 0 /* Default niceness. */
 #define NICE_MAX 20    /* Highest niceness. */
 
-/* File Descriptors. */
-#define MINIMUM_USER_FD 2 /* Minimum file descriptor for user programs. */
-
-/* A process result, synchronised between parent and child. */
-struct process_result
-{
-  tid_t tid;             /* The tid of the child process. */
-  int exit_status;       /* The exit status of the child process. Initially set
-                            to -1, then to exit_status when child dies. */
-  struct lock lock;      /* Lock the exit_status and sema. */
-  struct semaphore sema; /* Semaphore to signal the parent that the exit_status
-                            has been set. */
-  struct hash_elem elem; /* Hash element for the parent's children map. */
-};
-
 /* A kernel thread or user process.
 
    Each thread structure is stored in its own 4 kB page.  The
@@ -113,34 +95,16 @@ struct thread
     int priority;                       /* Priority. */
     struct list_elem allelem;           /* List element for all threads list. */
 
-    /* Donation Related */
-    int base_priority;                  /* Base priority of the thread. */
-    struct list donors_list;            /* List of threads that have donated
-                                           to this thread. */
-    struct lock *waiting_lock;          /* The lock that the current thread is
-                                           waiting for. */
-    struct list_elem donor_elem;        /* List element so that thread can be
-                                           enlisted in other donors list. */
+    /* Shared between thread.c and synch.c. */
+    struct list_elem elem;              /* List element. */
 
     /* MLFQS items */
     int nice;                           /* Nice value for this thread */
     fp32_t recent_cpu;                  /* Amount of time this process received */
 
-    /* Process wait properties. */
-    struct process_result *result;      /* Result of the process. */
-    struct hash child_results;          /* Map of children's of this thread
-                                           TID to process result. */
-    struct file *exec_file;             /* Thread's currently running file */
-
-    /* Shared between thread.c and synch.c. */
-    struct list_elem elem;              /* List element. */
-
 #ifdef USERPROG
     /* Owned by userprog/process.c. */
     uint32_t *pagedir;                  /* Page directory. */
-    unsigned int fd_counter;            /* File descriptor counter for thread's
-                                           open files. */
-    struct hash open_files;             /* Hash Table of FD -> Struct File. */
 #endif
 
     /* Owned by thread.c. */
@@ -176,17 +140,12 @@ void thread_yield (void);
 typedef void thread_action_func (struct thread *t, void *aux);
 void thread_foreach (thread_action_func *, void *);
 
-bool priority_more (const struct list_elem *a_, const struct list_elem *b_,
-                    void *aux UNUSED);
 int thread_get_priority (void);
 void thread_set_priority (int);
-void thread_recalculate_priority (void);
 
 int thread_get_nice (void);
 void thread_set_nice (int);
 int thread_get_recent_cpu (void);
 int thread_get_load_avg (void);
 
-void ready_list_reinsert (struct thread *t);
-
 #endif /* threads/thread.h */

src/userprog/process.c

@@ -1,15 +1,12 @@
 #include "userprog/process.h"
 #include <debug.h>
-#include <hash.h>
 #include <inttypes.h>
-#include <list.h>
 #include <round.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "userprog/gdt.h"
 #include "userprog/pagedir.h"
-#include "userprog/syscall.h"
 #include "userprog/tss.h"
 #include "filesys/directory.h"
 #include "filesys/file.h"
@@ -17,172 +14,57 @@
 #include "threads/flags.h"
 #include "threads/init.h"
 #include "threads/interrupt.h"
-#include "threads/synch.h"
 #include "threads/palloc.h"
-#include "threads/malloc.h"
 #include "threads/thread.h"
 #include "threads/vaddr.h"
-#include "threads/synch.h"
-#include "devices/timer.h"
-#ifdef VM
-#include "vm/frame.h"
-#endif
-
-/* Defines the native number of bytes processed by the processor
-   (for the purposes of alignment). */
-#define WORD_SIZE 4
-
-/* Defines non-negative integer division wherein the result is always rounded
-   up. */
-#define DIV_CEIL(x, y) ((x + (y - 1)) / y)
-
-/* Keeps track of the position of pointers to user program arguments
-   within a linked list. */
-struct arg_elem
-  {
-    char* arg;
-    struct list_elem elem;
-  };
-
-/* Holds the data required to be passed from a kernel thread to a thread
-   that executes process_start for the purpose of starting a user process. */
-struct process_start_data
-  {
-    char *cmd_saveptr; /* Value pointed to by 'saveptr' argument used by
-                          successive calls to strtok_r to split 'cmd' into
-                          tokens while maintaining state. */
-    char file_name[FNAME_MAX_LEN + 1]; /* Name of the file of the process to
-                                      be started. */
-    bool success; /* Indicates whether the process was successfully loaded. */
-    struct semaphore loaded; /* Semaphore used to signal that the process has
-                                finished attempting to load. */
-  };
 
 static thread_func start_process NO_RETURN;
-static void destruct_process_result (struct hash_elem *e, void *aux UNUSED);
 static bool load (const char *cmdline, void (**eip) (void), void **esp);
 
-/* Starts a new thread running a user program executed via
-   CMD.  The new thread may be scheduled (and may even exit)
+/* Starts a new thread running a user program loaded from
+   FILENAME.  The new thread may be scheduled (and may even exit)
    before process_execute() returns.  Returns the new process's
    thread id, or TID_ERROR if the thread cannot be created. */
 tid_t
-process_execute (const char *cmd) 
+process_execute (const char *file_name) 
 {
-  char *cmd_copy;
+  char *fn_copy;
   tid_t tid;
-  struct process_start_data data;
 
-  /* Make a copy of command.
+  /* Make a copy of FILE_NAME.
      Otherwise there's a race between the caller and load(). */
-  cmd_copy = palloc_get_page (0);
-  if (cmd_copy == NULL)
+  fn_copy = palloc_get_page (0);
+  if (fn_copy == NULL)
     return TID_ERROR;
+  strlcpy (fn_copy, file_name, PGSIZE);
 
-  /* Imposing implicit limit that the command line arguments
-    including the user program name fit within a single page. */
-  strlcpy (cmd_copy, cmd, PGSIZE);
-
-  /* Retrieve first argument of command, which is the file name
-     of the process. */
-  char *file_name = strtok_r (cmd_copy, " ", &data.cmd_saveptr);
-
-  /* Validates that the current file to be executed can be opened/exists. */
-  lock_acquire (&filesys_lock);
-  struct file *file = filesys_open (file_name);
-  lock_release (&filesys_lock);
-  if (file == NULL)
-    return TID_ERROR;
-
-  /* Create a new thread to execute the command, by initializing
-     it running the function 'start_process' with the appropriate
-     arguments. For details of arguments, see 'start_process'. */
-  strlcpy (data.file_name, file_name, FNAME_MAX_LEN + 1);
-  sema_init (&data.loaded, 0);
-  data.success = false;
-
-  tid = thread_create (file_name, PRI_DEFAULT, start_process, &data);
-
-  /* Wait until process file has finished attempting to load via the child
-     thread before reporting success of starting execution. */
-  if (tid != TID_ERROR)
-    {
-      sema_down (&data.loaded);
-      if (!data.success)
-        tid = TID_ERROR;
-    }
-
-  palloc_free_page (cmd_copy);
+  /* Create a new thread to execute FILE_NAME. */
+  tid = thread_create (file_name, PRI_DEFAULT, start_process, fn_copy);
+  if (tid == TID_ERROR)
+    palloc_free_page (fn_copy); 
   return tid;
 }
 
-static void *get_usr_kpage (enum palloc_flags flags);
-static void free_usr_kpage (void *kpage);
-static bool install_page (void *upage, void *kpage, bool writable);
-
-static bool process_init_stack (char *cmd_saveptr, void **esp, char *file_name);
-static void *push_to_stack (void **esp, void *data, size_t data_size);
-#define push_var_to_stack(esp, var) (push_to_stack (esp, &var, sizeof (var)))
-
-/* Make the current thread execute 'cmd', passing in a copy of the
-   command string used for processing, the saveptr used by strtok_r
-   (in order to further tokenize the same command and retrieve its
-   arguments), the name of the file being executed, and a semaphore that
-   calls sema_up to indicate that the 'success' variable passed to it
-   has been updated to indicate whether the process file loading succeeded. 
-   This involves loading the specified file and calling its main () function
-   with the specified command arguments. */
+/* A thread function that loads a user process and starts it
+   running. */
 static void
-start_process (void *proc_start_data)
+start_process (void *file_name_)
 {
+  char *file_name = file_name_;
   struct intr_frame if_;
-  struct process_start_data *data = proc_start_data;
+  bool success;
 
   /* Initialize interrupt frame and load executable. */
   memset (&if_, 0, sizeof if_);
   if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
   if_.cs = SEL_UCSEG;
   if_.eflags = FLAG_IF | FLAG_MBS;
+  success = load (file_name, &if_.eip, &if_.esp);
 
-  /* Acquire the file system lock to prevent race conditions. */
-  lock_acquire (&filesys_lock);
-
-  struct file *exec_file = filesys_open (data->file_name);
-  if (exec_file == NULL)
-    {
-      /* If the executable file cannot be opened, free resources and quit. */
-      lock_release (&filesys_lock);
-      sema_up (&data->loaded);
-      thread_exit ();
-    }
-
-  /* Deny write to the executable file to prevent writing to it and release the
-     file system lock. */
-  file_deny_write (exec_file);
-  lock_release (&filesys_lock);
-
-  thread_current ()->exec_file = exec_file;
-
-  /* Load the ELF executable file, and store the success of the operation in
-     the 'success' variable in data. */
-  data->success = load (data->file_name, &if_.eip, &if_.esp);
-
-  /* If load was sucessful, initialize user process stack and free page used
- to store the command that executed the process. */
-  if (data->success)
-    {
-      data->success =
-        process_init_stack (data->cmd_saveptr, &if_.esp, data->file_name);
-    }
-
-  /* Signal that the process has finished attempting to load. */
-  bool success = data->success;
-  sema_up (&data->loaded);
-  
-  /* If the load was unsuccessful or if it was but the stack initialization
-     failed, exit the thread. */
+  /* If load failed, quit. */
+  palloc_free_page (file_name);
   if (!success) 
-      thread_exit ();
+    thread_exit ();
 
   /* Start the user process by simulating a return from an
      interrupt, implemented by intr_exit (in
@@ -194,123 +76,6 @@ start_process (void *proc_start_data)
   NOT_REACHED ();
 }
 
-/* Helper function that initializes the stack of a newly created 
-   user process. Returns true if successful, false otherwise. */
-static bool
-process_init_stack (char *cmd_saveptr, void **esp, char *file_name)
-  {
-    ASSERT (cmd_saveptr != NULL);
-    ASSERT (esp != NULL);
-    ASSERT (file_name != NULL);
-
-    /* Load command line argument *data* to user process stack.
-       This can't cause overflow due to enforcing that the size of
-       command line input must fit in a page. Also keep track
-       of pointers to the argument data within a linked list. */
-    struct list arg_list;
-    list_init (&arg_list);
-
-    char *arg = file_name;
-    int arg_count = 0;
-    while (arg != NULL)
-      {
-        /* filename has already been validated to be a safe-to-access string,
-           so we can safely use strlen here. Filename has already been
-           split from the command line arguments. */
-        push_to_stack (esp, arg, (strlen (arg) + 1) * sizeof (char));
-
-        /* Try to allocate memory for the argument pointer. */
-        struct arg_elem *arg_elem = malloc (sizeof (struct arg_elem));
-        if (arg_elem == NULL)
-          {
-            printf("ERROR: Couldn't allocate argument pointer memory for %s!\n",
-                   thread_current ()->name);
-            return false;
-          }
-
-        /* Store the argument pointer in the linked list. */
-        arg_elem->arg = *esp;
-        list_push_front (&arg_list, &arg_elem->elem);
-
-        /* Increment the argument count and get the next argument. */
-        arg_count++;
-        arg = strtok_r (NULL, " ", &cmd_saveptr);
-      }
-
-    /* Calculate the remaining number of bytes that need to be written
-       to the user process stack in order to check for possible overflow. */
-    size_t align_size = ((unsigned int) *esp % WORD_SIZE) * sizeof (uint8_t);
-    size_t argv_data_size = (arg_count + 1) * sizeof (char *);
-    size_t argv_size = sizeof (char **);
-    size_t argc_size = sizeof (int);
-    size_t return_addr_size = sizeof (void *);
-    size_t remaining_size = align_size + argv_data_size + argv_size + argc_size
-                            + return_addr_size;
-
-    /* If pushing the rest of the data required for the stack would cause
-       overflow, allocate as many extra pages as needed to the user process
-       contiguously in the virtual address space below the initial page. */
-    int overflow_bytes = (PHYS_BASE - *esp) + remaining_size - PGSIZE;
-    if (overflow_bytes > 0)
-      {
-        /* Calculate the number of pages needed to allocate. */
-        int pages_needed = DIV_CEIL (overflow_bytes, PGSIZE);
-
-        /* Allocate the pages and map them to the user process. */
-        for (int i = 1; i < pages_needed + 1; i++)
-          {
-            uint8_t *kpage = get_usr_kpage (PAL_ZERO);
-            if (!install_page (((uint8_t *) PHYS_BASE) - PGSIZE * (i + 1),
-                               kpage, true))
-              return false;
-          }
-      }
-
-    /* Align stack pointer to word size before pushing argv elements for
-       performance. */
-    *esp -= align_size;
-    
-    /* Push a null pointer sentinel inside argv. */
-    char *null_sentinel = NULL;
-    push_var_to_stack (esp, null_sentinel); 
-
-    /* Push pointers to process arguments from argument linked list */
-    struct list_elem *e = list_begin (&arg_list);
-    struct list_elem *tail = list_tail (&arg_list);
-    while (e != tail)
-      {
-        struct arg_elem *arg_elem = list_entry (e, struct arg_elem, elem);
-        
-        push_var_to_stack(esp, arg_elem->arg);
-        
-        e = list_next (e);
-        free (arg_elem);
-      }
-
-    /* Push pointer to the start of argv array. */
-    char **argv = *esp;
-    push_var_to_stack(esp, argv);
-
-    /* Push the number of arguments to the stack. */
-    push_var_to_stack(esp, arg_count);
-
-    /* Push fake return address (null pointer). */
-    push_var_to_stack (esp, null_sentinel); 
-
-    return true;
- }
-
-/* Helper function that pushes the first 'data_size' bytes stored
-   in the address '*data' into the stack given a pointer to the
-   stack pointer '**esp'. */
-static void *
-push_to_stack (void **esp, void *data, size_t data_size)
-{
-  *esp -= data_size;
-  memcpy (*esp, data, data_size);
-  return *esp;
-}
-
 /* Waits for thread TID to die and returns its exit status. 
  * If it was terminated by the kernel (i.e. killed due to an exception), 
  * returns -1.  
@@ -321,37 +86,9 @@ push_to_stack (void **esp, void *data, size_t data_size)
  * This function will be implemented in task 2.
  * For now, it does nothing. */
 int
-process_wait (tid_t child_tid)
+process_wait (tid_t child_tid UNUSED) 
 {
-  struct thread *t = thread_current ();
-  struct process_result fake_result;
-  fake_result.tid = child_tid;
-  struct hash_elem *e = hash_find (&t->child_results, &fake_result.elem);
-  if (e == NULL)
-    return -1;
-
-  struct process_result *child_result
-      = hash_entry (e, struct process_result, elem);
-  /* Wait for child to die. */
-  sema_down (&child_result->sema);
-
-  /* We need lock release in process_exit, so we need to acquire (and possibly
-     wait) for it here to ensure we don't free the lock memory before it is
-     released in process_exit. */
-  lock_acquire (&child_result->lock);
-  /* To prevent waiting for child twice, remove it from the table.
-     No need to use lock since this is the only thread with access to
-     the struct process_result now. */
-  hash_delete (&t->child_results, &child_result->elem);
-
-  /* Get the exit status of the child */
-  int exit_status = child_result->exit_status;
-
-  /* Release the lock */
-  lock_release (&child_result->lock);
-  /* Result no-longer used by parent, nor child. Deallocate it. */
-  free (child_result);
-  return exit_status;
+  return -1;
 }
 
 /* Free the current process's resources. */
@@ -361,28 +98,6 @@ process_exit (void)
   struct thread *cur = thread_current ();
   uint32_t *pd;
 
-  /* Clean up all open files */
-  hash_destroy (&cur->open_files, fd_cleanup);
-
-  /* Close the executable file, implicitly allowing it to be written to. */
-  if (cur->exec_file != NULL)
-    {
-      /* Acquire the file system lock to prevent race conditions. */
-      lock_acquire (&filesys_lock);
-      file_close (cur->exec_file);
-      lock_release (&filesys_lock);
-    }
-
-  if (cur->result != NULL)
-    {
-      printf ("%s: exit(%d)\n", cur->name, cur->result->exit_status);
-      /* Update own process result. */
-      destruct_process_result (&cur->result->elem, cur);
-    }
-
-  /* Free child process results or signal parent's death. */
-  hash_destroy (&cur->child_results, destruct_process_result);
-
   /* Destroy the current process's page directory and switch back
      to the kernel-only page directory. */
   pd = cur->pagedir;
@@ -401,28 +116,6 @@ process_exit (void)
     }
 }
 
-/* Destruct a process_result, with multi-thread awareness.
-   If the other thread is running, simply signals death. Otherwise
-   frees the result. */
-static void
-destruct_process_result (struct hash_elem *e, void *aux UNUSED)
-{
-  struct process_result *result = hash_entry (e, struct process_result, elem);
-  lock_acquire (&result->lock);
-  /* Other thread has died (and was not waited for). Free the result. */
-  if (sema_try_down (&result->sema))
-    {
-      lock_release (&result->lock);
-      free (result);
-    }
-  /* Other thread is still alive, signal via sema that parent has died. */
-  else
-    {
-      sema_up (&result->sema);
-      lock_release (&result->lock);
-    }
-}
-
 /* Sets up the CPU for running user code in the current
    thread.
    This function is called on every context switch. */
@@ -521,7 +214,6 @@ load (const char *file_name, void (**eip) (void), void **esp)
   off_t file_ofs;
   bool success = false;
   int i;
-  lock_acquire (&filesys_lock);
 
   /* Allocate and activate page directory. */
   t->pagedir = pagedir_create ();
@@ -621,12 +313,13 @@ load (const char *file_name, void (**eip) (void), void **esp)
  done:
   /* We arrive here whether the load is successful or not. */
   file_close (file);
-  lock_release (&filesys_lock);
   return success;
 }
 
 /* load() helpers. */
 
+static bool install_page (void *upage, void *kpage, bool writable);
+
 /* Checks whether PHDR describes a valid, loadable segment in
    FILE and returns true if so, false otherwise. */
 static bool
@@ -710,7 +403,7 @@ load_segment (struct file *file, off_t ofs, uint8_t *upage,
       if (kpage == NULL){
         
         /* Get a new page of memory. */
-        kpage = get_usr_kpage (0);
+        kpage = palloc_get_page (PAL_USER);
         if (kpage == NULL){
           return false;
         }
@@ -718,7 +411,7 @@ load_segment (struct file *file, off_t ofs, uint8_t *upage,
         /* Add the page to the process's address space. */
         if (!install_page (upage, kpage, writable)) 
         {
-          free_usr_kpage (kpage);
+          palloc_free_page (kpage);
           return false; 
         }     
         
@@ -753,44 +446,18 @@ setup_stack (void **esp)
   uint8_t *kpage;
   bool success = false;
 
-  kpage = get_usr_kpage (PAL_ZERO);
+  kpage = palloc_get_page (PAL_USER | PAL_ZERO);
   if (kpage != NULL) 
     {
       success = install_page (((uint8_t *) PHYS_BASE) - PGSIZE, kpage, true);
       if (success)
         *esp = PHYS_BASE;
       else
-        free_usr_kpage (kpage);
+        palloc_free_page (kpage);
     }
   return success;
 }
 
-/* Claims a page from the user pool and returns its kernel address,
-   updating the frame table if VM is enabled. */
-static void *
-get_usr_kpage (enum palloc_flags flags)
-{
-  void *page;
-#ifdef VM
-  page = frame_alloc (flags);
-#else
-  page = palloc_get_page (flags | PAL_USER);
-#endif
-  return page;
-}
-
-/* Frees a page belonging to a user process given its kernel address,
-   updating the frame table if VM is enabled. */
-static void
-free_usr_kpage (void *kpage)
-{
-#ifdef VM
-  frame_free (kpage);
-#else
-  palloc_free_page (kpage);
-#endif
-}
-
 /* Adds a mapping from user virtual address UPAGE to kernel
    virtual address KPAGE to the page table.
    If WRITABLE is true, the user process may modify the page;

src/userprog/syscall.c

@@ -1,513 +1,20 @@
 #include "userprog/syscall.h"
-#include "devices/shutdown.h"
-#include "devices/input.h"
-#include "filesys/file.h"
-#include "filesys/filesys.h"
-#include "threads/vaddr.h"
-#include "threads/interrupt.h"
-#include "threads/malloc.h"
-#include "threads/thread.h"
-#include "threads/synch.h"
-#include "userprog/process.h"
-#include "userprog/pagedir.h"
 #include <stdio.h>
 #include <syscall-nr.h>
-
-#define MAX_SYSCALL_ARGS 3
-#define EXIT_FAILURE -1
-
-struct open_file
-  {
-    int fd;                     /* File Descriptor / Identifier */
-    struct file *file;          /* Pointer to the associated file */
-    struct hash_elem elem;      /* elem for a hash table */
-  };
+#include "threads/interrupt.h"
+#include "threads/thread.h"
 
 static void syscall_handler (struct intr_frame *);
 
-/* A syscall_function is a function that receives up to 3 arguments, the
-   arguments to the functions are either ints or pointers taking up to 32 bits
-   in size. */
-typedef uintptr_t (*syscall_function) (uintptr_t, uintptr_t, uintptr_t);
-
-/* System call function prototypes */
-static void syscall_halt (void);
-static void syscall_exit (int status);
-static pid_t syscall_exec (const char *cmd_line);
-static int syscall_wait (pid_t pid);
-static bool syscall_create (const char *file, unsigned initial_size);
-static bool syscall_remove (const char *file);
-static int syscall_open (const char *file);
-static int syscall_filesize (int fd);
-static int syscall_read (int fd, void *buffer, unsigned size);
-static int syscall_write (int fd, const void *buffer, unsigned size);
-static void syscall_seek (int fd, unsigned position);
-static unsigned syscall_tell (int fd);
-static void syscall_close (int fd);
-
-static struct open_file *fd_get_file (int fd);
-static void validate_user_pointer (const void *start, size_t size);
-static void validate_user_string (const char *str);
-
-/* A struct defining a syscall_function pointer along with its arity. */
-struct syscall_arguments
-  {
-    syscall_function function;    /* Function pointer. */
-    int arity;                    /* Number of arguments of the function. */
-  };
-
-/* A look-up table mapping numbers to system call functions with their number of
-   arguments. */
-static const struct syscall_arguments syscall_lookup[] =
-{
-  [SYS_HALT] = {(syscall_function) syscall_halt, 0},
-  [SYS_EXIT] = {(syscall_function) syscall_exit, 1},
-  [SYS_EXEC] = {(syscall_function) syscall_exec, 1},
-  [SYS_WAIT] = {(syscall_function) syscall_wait, 1},
-  [SYS_CREATE] = {(syscall_function) syscall_create, 2},
-  [SYS_REMOVE] = {(syscall_function) syscall_remove, 1},
-  [SYS_OPEN] = {(syscall_function) syscall_open, 1},
-  [SYS_FILESIZE] = {(syscall_function) syscall_filesize, 1},
-  [SYS_READ] = {(syscall_function) syscall_read, 3},
-  [SYS_WRITE] = {(syscall_function) syscall_write, 3},
-  [SYS_SEEK] = {(syscall_function) syscall_seek, 2},
-  [SYS_TELL] = {(syscall_function) syscall_tell, 1},
-  [SYS_CLOSE] = {(syscall_function) syscall_close, 1},
-};
-
-/* The number of syscall functions (i.e, number of elements) within the
-   syscall_lookup table. */
-static const int LOOKUP_SIZE
-  = sizeof (syscall_lookup) / sizeof (struct syscall_arguments);
-
-/* Initialises the syscall handling system, as well as a global lock to
-   synchronise all file access between processes. */
 void
 syscall_init (void) 
 {
   intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
-  lock_init (&filesys_lock);
-}
-
-/* Function that takes an interrupt frame containing a syscall and its args.
-   Validates the arguments and pointers before calling the relevant
-   high-level system call function, storing its output (if any) in f->eax */
-static void
-syscall_handler (struct intr_frame *f)
-{
-  /* First, read the system call number from the stack. */
-  validate_user_pointer (f->esp, sizeof (uintptr_t));
-  uintptr_t syscall_number = *(int *) f->esp;
-
-  /* Ensures the number corresponds to a system call that can be handled. */
-  if (syscall_number >= LOOKUP_SIZE)
-    syscall_exit (EXIT_FAILURE);
-
-  struct syscall_arguments syscall = syscall_lookup[syscall_number];
-
-  /* Next, read and copy the arguments from the stack pointer. */
-  validate_user_pointer (f->esp + sizeof (uintptr_t),
-                         syscall.arity * sizeof (uintptr_t));
-
-  uintptr_t args[MAX_SYSCALL_ARGS] = {0};
-  for (int i = 0; i < syscall.arity && i < MAX_SYSCALL_ARGS; i++)
-    args[i] = *(uintptr_t *) (f->esp + sizeof (uintptr_t) * (i + 1));
-
-  /* Call the function that handles this system call with the arguments. When
-     there is a return value it is stored in f->eax. */
-  f->eax = syscall.function (args[0], args[1], args[2]);
-}
-
-/* Called upon a "halt" syscall, resulting in a complete shutdown of the
-   process, via shutdown_power_off (); */
-static void
-syscall_halt (void)
-{
-  shutdown_power_off ();
 }
 
 static void
-syscall_exit (int status)
+syscall_handler (struct intr_frame *f UNUSED) 
 {
-  /* Sets exit_status of the thread to status. thread_exit () will call
-     process_exit () if user programs are allowed. */
-  thread_current ()->result->exit_status = status;
+  printf ("system call!\n");
   thread_exit ();
 }
-
-/* Executes a given command with the relevant args, by calling process_execute.
-   Returns PID for the process that is running the CMD_LINE. */
-static pid_t
-syscall_exec (const char *cmd_line)
-{
-  /* Validate the user string before executing the process. */
-  validate_user_string (cmd_line);
-
-  return process_execute (cmd_line); /* Returns the PID of the new process */
-}
-
-/* Handles the syscall of wait. Effectively a wrapper for process_wait as the
-   necessary validation and such all happens in process_wait anyway. */
-static int
-syscall_wait (pid_t pid)
-{
-  return process_wait (pid); /* Returns the exit status of the waited process */
-}
-
-/* Handles the syscall for file creation. First validates the user file
-   pointer. Acquires the file system lock to prevent synchronisation issues,
-   and then uses FILESYS_CREATE to create the file, returning the same status */
-static bool
-syscall_create (const char *file, unsigned initial_size)
-{
-  /* Validate the user string before creating the file. */
-  validate_user_string (file);
-
-  /* Acquire the file system lock to prevent race conditions. */
-  lock_acquire (&filesys_lock);
-  bool status = filesys_create (file, initial_size);
-  lock_release (&filesys_lock);
-
-  /* Return the status of the file creation. */
-  return status;
-}
-
-/* Handles the syscall for file removal. First validates the user file pointer.
-   Acquires the file system lock to prevent synchronisation issues, and then
-   uses FILESYS_REMOVE to remove the file, returning the same success status */
-static bool
-syscall_remove (const char *file)
-{
-  /* Validate the user string before removing the file. */
-  validate_user_string (file);
-
-  /* Acquire the file system lock to prevent race conditions. */
-  lock_acquire (&filesys_lock);
-  bool status = filesys_remove (file);
-  lock_release (&filesys_lock);
-
-  /* Return the status of the file removal. */
-  return status;
-}
-
-/* Handles the syscall for opening a file connection. First, validates the file
-   pointer. Then it acquires a lock for the file system, in order to open the
-   connection without synchronisation issues. It then maps a new fd to this file
-   in the hash table before returning the fd. */
-static int
-syscall_open (const char *file)
-{
-  /* Validate the user string before opening the file. */
-  validate_user_string (file);
-
-  /* Acquire the file system lock to prevent race conditions. */
-  lock_acquire (&filesys_lock);
-  struct file *ptr = filesys_open (file);
-  lock_release (&filesys_lock);
-
-  /* If the file could not be opened, return failure. */
-  if (ptr == NULL)
-    return EXIT_FAILURE;
-
-  /* Allocate space for a struct representing a mapping from an FD to a struct
-     file. */
-  struct open_file *file_info
-    = (struct open_file*) malloc (sizeof (struct open_file));
-  if (file_info == NULL)
-    {
-      /* If we could not allocate memory for the file_info struct, close the
-         file and return failure. */
-      file_close (ptr);
-      return EXIT_FAILURE;
-    }
-
-  /* Populate the above struct, with a unique FD and the current open file */
-  file_info->fd = thread_current ()->fd_counter++;
-  file_info->file = ptr;
-
-  /* Add the new FD->file mapping to the hashtable for the current thread */
-  hash_insert (&thread_current ()->open_files, &file_info->elem);
-
-  /* Return the new FD */
-  return file_info->fd;
-}
-
-/* Handles the syscall for getting a file's size. Converts a provided FD into
-   the asssociated file struct. Acquire the lock for the filesystem and use
-   FILE_LENGTH to calculate the length for return. */
-static int
-syscall_filesize (int fd)
-{
-  /* Try to get the file from the FD. If it does not exist, return failure. */
-  struct open_file *file_info = fd_get_file (fd);
-  if (file_info == NULL)
-      return EXIT_FAILURE;
-
-  /* Acquire the file system lock to prevent any race conditions. */
-  lock_acquire (&filesys_lock);
-  int bytes = file_length (file_info->file);
-  lock_release (&filesys_lock);
-
-  /* Return the number of bytes in the file. */
-  return bytes;
-}
-
-/* Handles the syscall for reading SIZE bytes from a file referenced by FD.
-   If the FD references the console, use input_getc (), otherwise convert the
-   FD to its associated file struct, acquire the filesystem lock, read up to
-   SIZE bytes and then return the number of bytes read.*/
-static int
-syscall_read (int fd, void *buffer, unsigned size)
-{
-  /* Only console (fd = 0) or other files, not including STDOUT, (fd > 1) are
-     allowed. */
-  if (fd < STDIN_FILENO || fd == STDOUT_FILENO)
-    return EXIT_FAILURE;
-
-  /* Validate the user buffer for the provided size before reading. */
-  validate_user_pointer (buffer, size);
-
-  if (fd == STDIN_FILENO)
-    {
-      /* Reading from the console. */
-      char *write_buffer = buffer;
-      for (unsigned i = 0; i < size; i++)
-        write_buffer[i] = input_getc ();
-
-      /* In case of console, read is always (eventually) successful. So return
-         the size for the number of bytes read. */
-      return size;
-    }
-  else
-    {
-      /* Reading from a file. */
-      /* Find the file from the FD. If it does not exist, return failure. */
-      struct open_file *file_info = fd_get_file (fd);
-      if (file_info == NULL)
-        return EXIT_FAILURE;
-
-      /* Acquire the file system lock to prevent race-conditions. */
-      lock_acquire (&filesys_lock);
-      int bytes_written = file_read (file_info->file, buffer, size);
-      lock_release (&filesys_lock);
-
-      /* Return the number of bytes read. */
-      return bytes_written;
-    }
-}
-
-/* Handles the syscall for writing SIZE bytes to a file referenced by FD.
-   If the FD references the console, use put_buf (), otherwise convert the
-   FD to its associated file struct, acquire the filesystem lock, write up to
-   SIZE bytes and then return the number of bytes written.*/
-static int
-syscall_write (int fd, const void *buffer, unsigned size)
-{
-  /* Only console (fd = 1) or other files, not including STDIN, (fd > 1) are
-     allowed. */
-  if (fd <= 0)
-    return 0;
-
-  /* Validate the user buffer for the provided size before writing. */
-  validate_user_pointer (buffer, size);
-
-  if (fd == STDOUT_FILENO)
-    {
-      /* Writing to the console. */
-      putbuf (buffer, size);
-
-      /* In case of console, write is always successful. So return the size for
-         the number of bytes written. */
-      return size;
-    }
-  else
-    {
-      /* Writing to a file. */
-      /* Find the file from the FD. If it does not exist, return failure. */
-      struct open_file *file_info = fd_get_file (fd);
-      if (file_info == NULL)
-        return 0;
-
-      /* Acquire the file system lock to prevent race conditions. */
-      lock_acquire (&filesys_lock);
-      int bytes = file_write (file_info->file, buffer, size);
-      lock_release (&filesys_lock);
-
-      /* Return the number of bytes written. */
-      return bytes;
-    }
-}
-
-/* Handles the syscall for seeking to POSITION bytes in a file referenced by
-   FD. Converts the FD to its associated file struct, acquires the filesystem
-   lock and then uses file_seek to adjust the cursor to a specific position in
-   the file.*/
-static void
-syscall_seek (int fd, unsigned position)
-{
-  /* Find the file from the FD. If it does not exist, do nothing. */
-  struct open_file *file_info = fd_get_file (fd);
-  if (file_info != NULL)
-    file_seek (file_info->file, position);
-}
-
-/* Handles the syscall for returning the next byte in a file referenced by
-   FD. Converts the FD to its associated file struct, acquires the filesystem
-   lock and then uses file_tell to read the next byte.*/
-static unsigned
-syscall_tell (int fd)
-{
-  /* Find the file from the FD. If it does not exist, return 0. */
-  struct open_file *file_info = fd_get_file (fd);
-  if (file_info == NULL)
-    return 0;
-
-  unsigned pos = file_tell (file_info->file);
-
-  /* Return the current position in the file. */
-  return pos;
-}
-
-/* Handles the syscall for closing a connection to a file. Converts the FD to
-   its associated file struct. If it exists, it removes it from the hash table,
-   acquires the filesystem lock, and uses file_close to close the connection.*/
-static void
-syscall_close (int fd)
-{
-  /* Find the file from the FD. If it does not exist, do nothing. */
-  struct open_file *file_info = fd_get_file (fd);
-  if (file_info != NULL)
-    {
-      /* File exists */
-      /* First, remove the file from the hash table of open files. */
-      hash_delete (&thread_current ()->open_files, &file_info->elem);
-
-      /* Then, close the file, acquiring the file system lock to prevent race
-         conditions. */
-      lock_acquire (&filesys_lock);
-      file_close (file_info->file);
-      lock_release (&filesys_lock);
-
-      /* Free the memory allocated for the file_info struct. */
-      free (file_info);
-    }
-}
-
-/* Hashing function needed for the open_file table. Returns a hash for an entry,
-   based on its FD. */
-unsigned
-fd_hash (const struct hash_elem *element, void *aux UNUSED)
-{
-  /* We use the FD as the hash value. This is because the FD is incremented
-     sequentially and is therefore unique for each file. It positively affects
-     the performance of the hash table: 1. It is unique so no need to call
-     expensive hash functions. 2. It being sequential means that the hash table
-     is more likely to be weight balanced. */
-  return hash_entry (element, struct open_file, elem)->fd;
-}
-
-/* Comparator function for the open_file table. Compares two entries based on
-   the FDs. */
-bool
-fd_less (const struct hash_elem *a_, const struct hash_elem *b_,
-        void *aux UNUSED)
-{
-  struct open_file *a = hash_entry (a_, struct open_file, elem);
-  struct open_file *b = hash_entry (b_, struct open_file, elem);
-
-  return a->fd < b->fd;
-}
-
-/* Function to clean up an open file entry. Closes the file and frees the
-   associated memory. */
-void
-fd_cleanup (struct hash_elem *e, void *aux UNUSED)
-{
-  struct open_file *file_info = hash_entry (e, struct open_file, elem);
-
-  lock_acquire (&filesys_lock);
-  file_close (file_info->file);
-  lock_release (&filesys_lock);
-
-  free (file_info);
-}
-
-/* Gets a file from its descriptor (FD number). If there is no file with the fd
-   FD it returns NULL. */
-static struct open_file *
-fd_get_file (int fd)
-{
-  /* We have to set up a fake open_file in order to be able to search the hash
-     table. See hash.h. */
-  struct open_file fake_file_info;
-  fake_file_info.fd = fd;
-
-  struct hash_elem *e
-    = hash_find (&thread_current ()->open_files, &fake_file_info.elem);
-
-  if (e == NULL)
-      return NULL;
-
-  return hash_entry (e, struct open_file, elem);
-}
-
-/* Validates if a block of memory starting at START and of size SIZE bytes is
-   fully contained within user virtual memory. Kills the thread (by exiting with
-   failure) if the memory is invalid. Otherwise, returns (nothing) normally.
-   If the size is 0, the function does no checks and returns the given ptr. */
-static void
-validate_user_pointer (const void *start, size_t size)
-{
-  /* If the size is 0, we do not need to check anything. */
-  if (size == 0)
-    return;
-
-  const void *end = start + size - 1;
-
-  /* Check if the start and end pointers are valid user virtual addresses. */
-  if (start == NULL || !is_user_vaddr (start) || !is_user_vaddr (end))
-    syscall_exit (EXIT_FAILURE);
-
-  /* We now need to check if the entire memory block is mapped to physical
-     memory by the page table. */
-  for (const void *ptr = pg_round_down (start); ptr <= end; ptr += PGSIZE)
-    if (pagedir_get_page (thread_current ()->pagedir, ptr) == NULL)
-      syscall_exit (EXIT_FAILURE);
-}
-
-/* Validates if a string is fully contained within user virtual memory. Kills
-   the thread (by exiting with failure) if the memory is invalid. Otherwise,
-   returns (nothing) normally. */
-static void
-validate_user_string (const char *str)
-{
-  /* Check if the string pointer is a valid user virtual address. */
-  if (str == NULL || !is_user_vaddr (str))
-    syscall_exit (EXIT_FAILURE);
-
-  /* Calculate the offset of the string within the (first) page. */
-  size_t offset = (uintptr_t) str % PGSIZE;
-
-  /* We move page by page, checking if the page is mapped to physical memory. */
-  for (;;)
-  {
-    void *page = pg_round_down (str);
-
-    /* If we reach addresses that are not mapped to physical memory before the
-       end of the string, the thread is terminated. */
-    if (!is_user_vaddr(page) ||
-        pagedir_get_page (thread_current ()->pagedir, page) == NULL)
-      syscall_exit (EXIT_FAILURE);
-
-    while (offset < PGSIZE)
-      {
-        if (*str == '\0')
-          return; /* We reached the end of the string without issues. */
-
-        str++;
-        offset++;
-      }
-
-    offset = 0; /* Next page will start at the beginning. */
-  }
-}

src/userprog/syscall.h

@@ -1,17 +1,6 @@
 #ifndef USERPROG_SYSCALL_H
 #define USERPROG_SYSCALL_H
 
-#include <hash.h>
-#include "threads/synch.h"
-
-typedef int pid_t;
-
-struct lock filesys_lock;
-
 void syscall_init (void);
 
-unsigned fd_hash (const struct hash_elem *element, void *aux);
-bool fd_less (const struct hash_elem *a, const struct hash_elem *b, void *aux);
-void fd_cleanup (struct hash_elem *e, void *aux);
-
 #endif /* userprog/syscall.h */

src/vm/frame.c

@@ -1,137 +0,0 @@
-#include <debug.h>
-#include <hash.h>
-#include <list.h>
-
-#include "frame.h"
-#include "threads/malloc.h"
-#include "threads/synch.h"
-
-/* Hash table that maps every active frame's kernel virtual address
-   to its corresponding 'frame_metadata'.*/
-struct hash frame_table;
-
-/* Linked list of frame_metadata whose pages are predicted to currently
-   be in the working set of a process. They are not considered for
-   eviction, but are considered for demotion to the 'inactive' list. */
-struct list active_list;
-
-/* Linked list of frame_metadata whose pages are predicted to leave the
-   working set of their processes soon, so are considered for eviction.
-   Pages are considered for eviction from the tail end, and are initially
-   demoted to 'inactive' at the head. */
-struct list inactive_list;
-
-/* Synchronisation variables. */
-/* Ensures mutual exclusion to accessing the 'head' and first element of
-   'inactive_list', which is accessed every time a frame is allocated. */
-struct lock inactive_head_lock;
-
-struct frame_metadata
-  {
-     void *frame;  /* The kernel virtual address holding the frame. */
-     struct hash_elem hash_elem;  /* Tracks the position of the frame metadata
-                                     within 'frame_table', whose key is the 
-                                     kernel virtual address of the frame. */
-     struct list_elem list_elem;  /* Tracks the position of the frame metadata
-                                     in either the 'active' or 'inactive' list,
-                                     so a victim can be chosen for eviction. */
-  };
-
-hash_hash_func frame_metadata_hash;
-hash_less_func frame_metadata_less;
-
-/* Initialize the frame system by initializing the frame (hash) table with
-   the frame_metadata hashing and comparison functions, as well as initializing
-   the active & inactive lists. Also initializes the system's synchronisation
-   primitives. */
-void
-frame_init (void)
-{
-  hash_init (&frame_table, frame_metadata_hash, frame_metadata_less, NULL);
-  list_init (&active_list);
-  list_init (&inactive_list);
-
-  lock_init (&inactive_head_lock);
-}
-
-/* Attempt to allocate a frame for a user process, either by direct
-   allocation of a user page if there is sufficient RAM, or by
-   evicting a currently active page if memory allocated for user
-   processes is fulled and storing it in swap. If swap is full in
-   the former case, panic the kernel. */
-void *
-frame_alloc (enum palloc_flags flags)
-{
-  flags |= PAL_USER;
-
-  void *frame = palloc_get_page (flags);
-  if (frame == NULL)
-    {
-      /* TODO: Find victim page to replace, and swap it with this new page. */
-      return NULL;
-    }
-
-  struct frame_metadata *frame_metadata =
-    malloc (sizeof (struct frame_metadata));
-  frame_metadata->frame = frame;
-
-  /* Newly faulted pages begin at the head of the inactive list. */
-  lock_acquire (&inactive_head_lock);
-  list_push_front (&inactive_list, &frame_metadata->list_elem);
-  lock_release (&inactive_head_lock);
-
-  /* Finally, insert frame metadata within the frame table, with the key as its
-     allocated kernel address. */
-  hash_replace (&frame_table, &frame_metadata->hash_elem);
-
-  return frame;
-}
-
-/* Attempt to deallocate a frame for a user process by removing it from the
-   frame table as well as active/inactive list, and freeing the underlying
-   page memory. Panics if the frame isn't active in memory. */
-void
-frame_free (void *frame)
-  {
-    struct frame_metadata key_metadata;
-    key_metadata.frame = frame;
-
-    struct hash_elem *e =
-      hash_delete (&frame_table, &key_metadata.hash_elem);
-    if (e == NULL) PANIC ("Attempted to free a frame without a corresponding "
-                          "kernel address!\n");
-
-    struct frame_metadata *frame_metadata =
-      hash_entry (e, struct frame_metadata, hash_elem);
-    
-    list_remove (&frame_metadata->list_elem);
-    free (frame_metadata);
-    palloc_free_page (frame);
-  }
-
-/* Hash function for frame metadata, used for storing entries in the
-   frame table. */
-unsigned
-frame_metadata_hash (const struct hash_elem *e, void *aux UNUSED)
-  {
-    struct frame_metadata *frame_metadata = 
-      hash_entry (e, struct frame_metadata, hash_elem);
-
-    return hash_bytes (&frame_metadata->frame, sizeof (frame_metadata->frame));
-  }
-
-/* 'less_func' comparison function for frame metadata, used for comparing 
-   the keys of the frame table. Returns true iff the kernel virtual address
-   of the first frame is less than that of the second frame. */
-bool
-frame_metadata_less (const struct hash_elem *a_, const struct hash_elem *b_,
-                     void *aux UNUSED)
-  {
-    struct frame_metadata *a =
-      hash_entry (a_, struct frame_metadata, hash_elem);
-    struct frame_metadata *b =
-      hash_entry (b_, struct frame_metadata, hash_elem);
-
-    return a->frame < b->frame;
-  }
-

src/vm/frame.h

@@ -1,10 +0,0 @@
-#ifndef VM_FRAME_H
-#define VM_FRAME_H
-
-#include "threads/palloc.h"
-
-void frame_init (void);
-void *frame_alloc (enum palloc_flags);
-void frame_free (void *frame);
-
-#endif /* vm/frame.h */