From 18694d7b629bdb13ced060f78ce897ac614c6ab0 Mon Sep 17 00:00:00 2001
From: EDiasAlberto <proxamon1@gmail.com>
Date: Fri, 8 Nov 2024 16:25:49 +0000
Subject: [PATCH] Implement file reading syscall and fix fd validation w/ S.

---
 src/userprog/syscall.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index f0aaf47..9a42214 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -211,7 +211,7 @@ syscall_read (int fd, void *buffer, unsigned size)
 {
   /* Only console (fd = 0) or other files, not including STDOUT, (fd > 1) are
      allowed. */
-  if (fd < 0 && fd != STDOUT_FILENO)
+  if (fd < 0 || fd == STDOUT_FILENO)
     return -1;
 
   validate_user_pointer (buffer, size);
@@ -228,7 +228,14 @@ syscall_read (int fd, void *buffer, unsigned size)
   else
     {
       /* Reading from a file. */
-      return 0; // TODO: Implement Write to Files
+      struct open_file *file_info = fd_get_file (fd);
+      if (file_info == NULL)
+        return -1;
+
+      lock_acquire (&filesys_lock);
+      int bytes_written = file_read (file_info->file, buffer, size);
+      lock_release (&filesys_lock);
+      return bytes_written;
     }
 }