280 lines
7.2 KiB
C
280 lines
7.2 KiB
C
#include "userprog/syscall.h"
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#include "devices/shutdown.h"
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#include "devices/input.h"
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#include "filesys/filesys.h"
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#include "threads/vaddr.h"
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#include "threads/interrupt.h"
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#include "threads/thread.h"
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#include "threads/synch.h"
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#include "userprog/process.h"
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#include "userprog/pagedir.h"
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#include <stdio.h>
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#include <syscall-nr.h>
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static struct lock filesys_lock;
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struct open_file
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{
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int fd; /* File Descriptor / Identifier */
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struct file *file; /* Pointer to the associated file */
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struct hash_elem elem; /* elem for a hash table */
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};
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static void syscall_handler (struct intr_frame *);
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/* A syscall_function is a function that receives up to 3 arguments, the
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arguments to the functions are either ints or pointers taking up to 32 bits
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in size. */
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typedef uintptr_t (*syscall_function) (uintptr_t, uintptr_t, uintptr_t);
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/* System call function prototypes */
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static void syscall_halt (void);
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static void syscall_exit (int status);
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static pid_t syscall_exec (const char *cmd_line);
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static int syscall_wait (pid_t pid);
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static bool syscall_create (const char *file, unsigned initial_size);
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static bool syscall_remove (const char *file);
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static int syscall_open (const char *file);
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static int syscall_filesize (int fd);
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static int syscall_read (int fd, void *buffer, unsigned size);
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static int syscall_write (int fd, const void *buffer, unsigned size);
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static void syscall_seek (int fd, unsigned position);
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static unsigned syscall_tell (int fd);
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static void syscall_close (int fd);
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static void *validate_user_pointer (const void *ptr, size_t size);
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/* A struct defining a syscall_function pointer along with its arity. */
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typedef struct
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{
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syscall_function function; /* Function pointer. */
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int arity; /* Number of arguments of the function. */
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} syscall_arguments;
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/* A look-up table mapping numbers to system call functions with their number of
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arguments. */
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static const syscall_arguments syscall_lookup[] =
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{
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[SYS_HALT] = {(syscall_function) syscall_halt, 0},
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[SYS_EXIT] = {(syscall_function) syscall_exit, 1},
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[SYS_EXEC] = {(syscall_function) syscall_exec, 1},
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[SYS_WAIT] = {(syscall_function) syscall_wait, 1},
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[SYS_CREATE] = {(syscall_function) syscall_create, 2},
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[SYS_REMOVE] = {(syscall_function) syscall_remove, 1},
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[SYS_OPEN] = {(syscall_function) syscall_open, 1},
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[SYS_FILESIZE] = {(syscall_function) syscall_filesize, 1},
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[SYS_READ] = {(syscall_function) syscall_read, 3},
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[SYS_WRITE] = {(syscall_function) syscall_write, 3},
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[SYS_SEEK] = {(syscall_function) syscall_seek, 2},
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[SYS_TELL] = {(syscall_function) syscall_tell, 1},
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[SYS_CLOSE] = {(syscall_function) syscall_close, 1},
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};
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/* The number of syscall functions (i.e, number of elements) within the
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syscall_lookup table. */
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static const int LOOKUP_SIZE
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= sizeof (syscall_lookup) / sizeof (syscall_arguments);
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void
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syscall_init (void)
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{
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intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
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lock_init (&filesys_lock);
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}
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static void
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syscall_handler (struct intr_frame *f)
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{
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/* First, read the system call number from the stack. */
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validate_user_pointer (f->esp, 1);
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unsigned syscall_number = *(int *) f->esp;
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/* Ensures the number corresponds to a system call that can be handled. */
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if (syscall_number >= LOOKUP_SIZE)
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thread_exit ();
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syscall_arguments syscall = syscall_lookup[syscall_number];
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/* Next, read and copy the arguments from the stack pointer. */
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validate_user_pointer (f->esp + sizeof (uintptr_t),
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syscall.arity * sizeof (uintptr_t));
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uintptr_t args[3] = {0};
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for (int i=0; i < syscall.arity; i++)
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args[i] = *(uintptr_t *) (f->esp + sizeof (uintptr_t) * (i + 1));
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/* Call the function that handles this system call with the arguments. When
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there is a return value it is stored in f->eax. */
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f->eax = syscall.function (args[0], args[1], args[2]);
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}
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static void
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syscall_halt (void)
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{
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shutdown_power_off ();
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}
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static void
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syscall_exit (int status)
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{
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/* Sets exit_status of the thread to status. thread_exit () will call
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process_exit () if user programs are allowed. */
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thread_current ()->exit_status = status;
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thread_exit ();
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}
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static pid_t
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syscall_exec (const char *cmd_line)
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{
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validate_user_pointer (cmd_line, 1);
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lock_acquire (&filesys_lock);
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pid_t pid = process_execute(cmd_line);
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lock_release (&filesys_lock);
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return pid;
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}
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static int
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syscall_wait (pid_t pid)
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{
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return process_wait (pid);
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}
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static bool
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syscall_create (const char *file UNUSED, unsigned initial_size UNUSED)
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{
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validate_user_pointer (file, 1);
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lock_acquire (&filesys_lock);
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bool status = filesys_create (file, initial_size);
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lock_release (&filesys_lock);
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return status;
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}
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static bool
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syscall_remove (const char *file)
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{
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validate_user_pointer (file, 1);
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lock_acquire (&filesys_lock);
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bool status = filesys_remove (file);
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lock_release (&filesys_lock);
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return status;
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}
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static int
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syscall_open (const char *file UNUSED)
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{
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//TODO
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return 0;
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}
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static int
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syscall_filesize (int fd UNUSED)
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{
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//TODO
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return 0;
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}
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static int
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syscall_read (int fd, void *buffer, unsigned size)
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{
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/* Only console (fd = 0) or other files, not including STDOUT, (fd > 1) are
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allowed. */
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if (fd < 0 && fd != STDOUT_FILENO)
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return -1;
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validate_user_pointer (buffer, size);
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if (fd == STDIN_FILENO)
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{
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/* Reading from the console. */
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char *write_buffer = buffer;
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for (int i = 0; i < size; i++)
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write_buffer[i] = input_getc ();
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return size;
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}
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else
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{
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/* Reading from a file. */
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return 0; // TODO: Implement Write to Files
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}
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}
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static int
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syscall_write (int fd, const void *buffer, unsigned size)
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{
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/* Only console (fd = 1) or other files, not including STDIN, (fd > 1) are
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allowed. */
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if (fd <= 0)
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return 0;
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validate_user_pointer (buffer, size);
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if (fd == STDOUT_FILENO)
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{
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/* Writing to the console. */
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putbuf (buffer, size);
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return size;
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}
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else
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{
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/* Writing to a file. */
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return 0; // TODO: Implement Write to Files
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}
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}
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static void
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syscall_seek (int fd UNUSED, unsigned position UNUSED)
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{
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//TODO
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}
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static unsigned
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syscall_tell (int fd UNUSED)
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{
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//TODO
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return 0;
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}
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static void
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syscall_close (int fd UNUSED)
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{
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//TODO
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}
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unsigned
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fd_hash (const struct hash_elem *element, void *aux UNUSED)
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{
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return hash_int (hash_entry (element, struct open_file, elem)->fd);
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}
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bool
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fd_less (const struct hash_elem *a_, const struct hash_elem *b_,
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void *aux UNUSED)
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{
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struct open_file *a = hash_entry (a_, struct open_file, elem);
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struct open_file *b = hash_entry (b_, struct open_file, elem);
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return a->fd < b->fd;
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}
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/* Validates if a block of memory starting at PTR and of size SIZE bytes is
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fully contained within user virtual memory. Kills the thread (by calling
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thread_exit) if the memory is invalid. Otherwise, returns the PTR given.
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If the size is 0, the function does no checks and returns PTR.*/
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static void *
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validate_user_pointer (const void *ptr, size_t size)
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{
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if (size > 0 && (ptr == NULL ||
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!is_user_vaddr (ptr) ||
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!is_user_vaddr (ptr + size - 1) ||
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pagedir_get_page (thread_current()->pagedir, ptr) == NULL))
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thread_exit ();
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return (void *) ptr;
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}
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