day 4

lib.h

@@ -1,11 +1,30 @@
 #pragma once
-#include <stdlib.h>
+#include <stddef.h>
 #include <stdcountof.h>
-#include <sys/syscall.h>
-#include <unistd.h>
 #include <stdint.h>
 #include <string.h>
 
+#define SYS_write 1
+#define SYS_exit_group 231
+
+#define STDOUT_FILENO 1
+
+static
+void write(uint64_t fileno, void *buffer, size_t len) {
+    uint64_t a,d;
+    asm volatile("syscall"
+        :"=a"(a),"=d"(d):"a"(SYS_write),"D"(fileno),"S"(buffer),"d"(len):"memory");
+}
+
+[[noreturn]] static
+void exit_group(uint64_t code) {
+    asm volatile(
+        "syscall\n"
+        "ud2"
+        ::"a"(SYS_exit_group),"D"(code));
+    for (;;);
+}
+
 #define xstr(s) str(s)
 #define str(s) #s
 
@@ -13,7 +32,7 @@ typedef uint64_t bcdint;
 
 static
 void printns(size_t len, unsigned char chars[len]) {
-    syscall(SYS_write, STDOUT_FILENO, chars, len);
+    write(STDOUT_FILENO, chars, len);
 }
 
 static 
@@ -29,12 +48,12 @@ void printptr(uintptr_t v) {
         }
         v >>= 4;
     }
-    syscall(SYS_write, STDOUT_FILENO, p, countof(buf));
+    write(STDOUT_FILENO, p, countof(buf));
 }
 
 static
 void print_many_char(size_t len, char chars[len]) {
-    syscall(SYS_write, STDOUT_FILENO, chars, len);
+    write(STDOUT_FILENO, chars, len);
 }
 
 #define print(string) print_many_char(sizeof(string)-1, string)
@@ -54,7 +73,7 @@ void printd(unsigned long v) {
         v /= 10;
         count++;
     }
-    syscall(SYS_write, STDOUT_FILENO, p, count);
+    write(STDOUT_FILENO, p, count);
 }
 
 static
@@ -76,7 +95,7 @@ void printh(unsigned long v) {
         v >>= 4;
         count++;
     }
-    syscall(SYS_write, STDOUT_FILENO, p, count);
+    write(STDOUT_FILENO, p, count);
 }
 
 static
@@ -95,7 +114,7 @@ void print_hex_char(unsigned char v) {
         buf[1] = 'A' - 0xA + (v & 0x0F);
     }
 
-    syscall(SYS_write, STDOUT_FILENO, buf, sizeof(buf));
+    write(STDOUT_FILENO, buf, sizeof(buf));
 }
 
 static
@@ -125,11 +144,11 @@ bcdint grabbcd(unsigned char *s, unsigned char **end) {
 }
 
 static
-unsigned grabnum(const char *s, const char **end) {
-    unsigned r = 0;
+unsigned long grabnum(unsigned char *s, unsigned char **end) {
+    unsigned long r = 0;
     for (; *s >= '0' && *s <= '9'; s++)
         r = r * 10 + (*s - '0');
-    *end = s;
+    if (end) *end = s;
     return r;
 }