From 7b1c7048e2371c3c3544b7b62c57ee8180d4fdc5 Mon Sep 17 00:00:00 2001
From: Joshua Saxby <joshua.a.saxby@gmail.com>
Date: Tue, 3 Dec 2019 10:19:39 +0000
Subject: [PATCH] Not-quite-working implementation of write()
---
lib/kernel/stdio.h | 1 +
userprog/syscall_write.c | 23 +++++++++++++++++++++--
2 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/lib/kernel/stdio.h b/lib/kernel/stdio.h
index 3e5bae9..c7f9b39 100644
--- a/lib/kernel/stdio.h
+++ b/lib/kernel/stdio.h
@@ -1,5 +1,6 @@
#ifndef __LIB_KERNEL_STDIO_H
#define __LIB_KERNEL_STDIO_H
+#include <stddef.h>
void putbuf (const char *, size_t);
diff --git a/userprog/syscall_write.c b/userprog/syscall_write.c
index cf476a7..24e7039 100644
--- a/userprog/syscall_write.c
+++ b/userprog/syscall_write.c
@@ -3,10 +3,29 @@
*
* Authored by Joshua Saxby
*/
+#include <stdio.h>
+#include "lib/kernel/stdio.h"
#include "system_calls.h"
#include "threads/interrupt.h"
void syscall_write(struct intr_frame *f) {
- // TODO: implement me!
- (void*)0;
+ // first argument is syscall code (already handled)
+ int fd = *((int*)f->esp + 1); // file descriptor is second argument
+ void* buffer = (void*)(*((int*)f->esp + 2)); // buffer is third argument
+ unsigned size = *((unsigned*)((int*)f->esp + 3)); // size to write is fourth
+ printf("syscall_write: fd = %d\n", fd);
+ printf("syscall_write: buffer = '%s'\n", buffer);
+ printf("syscall_write: size = %u\n", size);
+ // writing to stdout or stderr (fd in {1, 2}) is a special case
+ switch (fd) {
+ case 1:
+ // case 2:
+ // TODO: split up output into reasonable-sized chunks
+ putbuf((const char*)buffer, size);
+ f->eax = size;
+ break;
+ default:
+ // XXX: unimplemented for now
+ break;
+ }
}
--
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