C userspace programs

ulib/syscall/syscall.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+uint64_t syscall(uint64_t num, uint64_t arg1, uint64_t arg2,
+    uint64_t arg3, uint64_t arg4, uint64_t arg5, uint64_t arg6) {
+  uint64_t ret = 0;
+  asm volatile (
+    "mov %[SYSNUM], %%rax\n"
+    "mov %[ARG1], %%rdi\n"
+    "mov %[ARG2], %%rsi\n"
+    "mov %[ARG3], %%rdx\n"
+    "mov %[ARG4], %%r10\n"
+    "mov %[ARG5], %%r8\n"
+    "mov %[ARG6], %%r9\n"
+    "int $0x80\n"
+    "mov %%rax, %[RESULT]\n"
+    : [RESULT]"=r"(ret)
+    : [SYSNUM]"r"(num),
+      [ARG1]"r"(arg1),
+      [ARG2]"r"(arg2),
+      [ARG3]"r"(arg3),
+      [ARG4]"r"(arg4),
+      [ARG5]"r"(arg5),
+      [ARG6]"r"(arg6)
+    : "%rax", "%rdi", "%rsi", "%rdx", "%r10", "%r8", "%r9", "memory"
+  );
+  return ret;
+}