linux_amd64_main.c

// libc-free platform layer for x86-64 Linux
// This is free and unencumbered software released into the public domain.
#include "u-config.c"

#define SYS_close 3
#define SYS_exit  60
#define SYS_mmap  9
#define SYS_open  2
#define SYS_read  0
#define SYS_write 1

#include "linux_noarch.c"

asm (
    "        .globl _start\n"
    "_start: mov   %rsp, %rdi\n"
    "        call  entrypoint\n"
);

static long syscall1(long n, long a)
{
    long r;
    asm volatile (
        "syscall"
        : "=a"(r)
        : "a"(n), "D"(a)
        : "rcx", "r11", "memory"
    );
    return r;
}

static long syscall2(long n, long a, long b)
{
    long r;
    asm volatile (
        "syscall"
        : "=a"(r)
        : "a"(n), "D"(a), "S"(b)
        : "rcx", "r11", "memory"
    );
    return r;
}

static long syscall3(long n, long a, long b, long c)
{
    long r;
    asm volatile (
        "syscall"
        : "=a"(r)
        : "a"(n), "D"(a), "S"(b), "d"(c)
        : "rcx", "r11", "memory"
    );
    return r;
}

static long syscall6(long n, long a, long b, long c, long d, long e, long f)
{
    long r;
    register long r10 asm("r10") = d;
    register long r8  asm("r8")  = e;
    register long r9  asm("r9")  = f;
    asm volatile (
        "syscall"
        : "=a"(r)
        : "a"(n), "D"(a), "S"(b), "d"(c), "r"(r10), "r"(r8), "r"(r9)
        : "rcx", "r11", "memory"
    );
    return r;
}