Working on libc

lib/libc/SConscript

@@ -12,7 +12,8 @@ src_common = [
 ]
 
 src_amd64 = [
-    "amd64/syscall.S"
+    "amd64/entry.S",
+    "amd64/syscall.S",
 ]
 
 if (env["ARCH"] == "amd64"):

lib/libc/amd64/entry.S

@@ -0,0 +1,14 @@
+
+#
+# Program entry point
+#
+
+.text
+
+.globl _start
+_start:
+    call main
+    movq %rax, %rdi
+    call SystemExit
+    int $3
+

lib/libc/exit.c

@@ -4,15 +4,41 @@
 
 #include <syscall.h>
 
+struct atexit_cb {
+    struct atexit_cb *next;
+    void (*cb)(void);
+};
+
+static uint64_t _atexit_count = 0;
+static struct atexit_cb _atexits[32]; // POSIX requires at least 32 atexit functions
+static struct atexit_cb *_atexit_last = NULL;
+
 int
 atexit(void (*function)(void))
 {
+    if (_atexit_count < 32) {
+	struct atexit_cb *prev = _atexit_last;
+
+	_atexits[_atexit_count].cb = function;
+	_atexits[_atexit_count].next = prev;
+
+	_atexit_last = &_atexits[_atexit_count];
+	_atexit_count++;
+    } else {
+	// XXX: Support malloc
+	return -1;
+    }
+
+    return 0;
 }
 
 void
 exit(int status)
 {
-    //
+    while (_atexit_last != NULL) {
+	(_atexit_last->cb)();
+	_atexit_last = _atexit_last->next;
+    }
 
     SystemExit(status);
 

lib/libc/syscall.c

@@ -37,10 +37,27 @@ SystemMemUnmap(void *addr, uint64_t len)
     return syscall(SYSCALL_MUNMAP, addr, len);
 }
 
-
 int
 SystemMemProtect(void *addr, uint64_t len, int flags)
 {
     return syscall(SYSCALL_MPROTECT, addr, len, flags);
 }
 
+int
+SystemRead(uint64_t fd, void *addr, uint64_t off, uint64_t length)
+{
+    return syscall(SYSCALL_READ, fd, addr, off, length);
+}
+
+int
+SystemWrite(uint64_t fd, void *addr, uint64_t off, uint64_t length)
+{
+    return syscall(SYSCALL_WRITE, fd, addr, off, length);
+}
+
+int
+SystemFlush(uint64_t fd)
+{
+    return syscall(SYSCALL_FLUSH, fd);
+}
+