libc

commit 80fbc61891a63b385eabf6d73085d363a33d439b
parent 1016044500a65dc921a61d8e330dd9baa9bc217e
Author: evenfri <evenfri@noreply.codeberg.org>
Date:   Thu, 23 Jul 2026 19:45:55 +0200

feat: close, open, read syscalls stack_chk (#1)

Co-authored-by: evenfri <evenfri256@gmail.com>
Reviewed-on: https://codeberg.org/evenfri/libc/pulls/1

Diffstat:
A
close.c
 | 
19
+++++++++++++++++++
M
libc.h
 | 
12
++++++++++++
M
mkfile
 | 
4
++++
A
open.c
 | 
19
+++++++++++++++++++
A
read.c
 | 
19
+++++++++++++++++++
A
stack_chk.c
 | 
14
++++++++++++++
M
start.s
 | 
2
++
M
wrapers/cc
 | 
9
++++++++-

8 files changed, 97 insertions(+), 1 deletion(-)
diff --git a/close.c b/close.c
@@ -0,0 +1,19 @@
+/*
+ * close.c — close system call
+ * Copyright (C) 2026. All rights reserved.
+ */
+
+#include "libc.h"
+
+int close(int fd) {
+  long ret;
+
+  asm volatile (
+    "syscall"
+    : "=a"(ret)
+    : "a"(sys_close), "D"(fd)
+    : "rcx", "r11", "memory"
+  );
+
+  return ret;
+}
diff --git a/libc.h b/libc.h
@@ -18,12 +18,24 @@ typedef long ssize_t;
 #define stdout 1
 #define stderr 2
 
+/* open flags */
+#define o_rdonly 00
+#define o_wronly 01
+#define o_rdwr 02
+#define o_creat 0100
+
 /* syscall numbers */
+#define sys_read 0
 #define sys_write 1
+#define sys_open 2
+#define sys_close 3
 #define sys_exit 60
 
 /* function prototypes */
+ssize_t read(int fd, void *buf, size_t count);
 ssize_t write(int fd, const void *buf, size_t count);
+int open(const char *filename, int flags, int mode);
+int close(int fd);
 void _exit(int status);
 void exit(int status);
 
diff --git a/mkfile b/mkfile
@@ -8,8 +8,12 @@ lib = libc.a
 ofiles =  start.$o \
           _exit.$o \
           exit.$o \
+          read.$o \
           write.$o \
+          open.$o \
+          close.$o \
           strlen.$o \
+          stack_chk.$o \
 
 hfiles =  libc.h \
 
diff --git a/open.c b/open.c
@@ -0,0 +1,19 @@
+/*
+ * open.c — open system call
+ * Copyright (C) 2026. All rights reserved.
+ */
+
+#include "libc.h"
+
+int open(const char *filename, int flags, int mode) {
+  long ret;
+
+  asm volatile (
+    "syscall"
+    : "=a"(ret)
+    : "a"(sys_open), "D"(filename), "S"(flags), "d"(mode)
+    : "rcx", "r11", "memory"
+  );
+
+  return ret;
+}
diff --git a/read.c b/read.c
@@ -0,0 +1,19 @@
+/*
+ * read.c — read system call
+ * Copyright (C) 2026. All rights reserved.
+ */
+
+#include "libc.h"
+
+ssize_t read(int fd, void *buf, size_t count) {
+  long ret;
+
+  asm volatile (
+    "syscall"
+    : "=a"(ret)
+    : "a"(sys_read), "D"(fd), "S"(buf), "d"(count)
+    : "rcx", "r11", "memory"
+  );
+
+  return ret;
+}
diff --git a/stack_chk.c b/stack_chk.c
@@ -0,0 +1,14 @@
+/*
+ * stack_chk.c — stack smashing protection stub
+ * Copyright (C) 2026. All rights reserved.
+ */
+
+#include "libc.h"
+
+/* stack canary guard word */
+unsigned long __stack_chk_guard = 0x5900f50fa0a3f200UL;
+
+void __stack_chk_fail(void) {
+  write(stderr, "err: stack smashing detected\n", 29);
+  _exit(127);
+}
diff --git a/start.s b/start.s
@@ -9,6 +9,8 @@ _start:
 
   lea rdx, [rsi + rdi*8 + 8] 
 
+  sub rsp, 8
+
   call main
 
   # exit(rax)
diff --git a/wrapers/cc b/wrapers/cc
@@ -1,4 +1,11 @@
 #!/bin/sh
 
 INC=$(cc -print-file-name=include)
-exec cc -nostdlib -nostdinc -ffreestanding -fno-builtin -isystem "$INC" "$@"
+exec cc -fstack-protector-all \
+  -mstack-protector-guard=global \
+  -nostdlib \
+  -nostdinc \
+  -ffreestanding \
+  -fno-builtin \
+  -isystem "$INC" \
+  "$@"