syscall.c

#include "include.h"


long _syscall(long number, ...) 
{
    va_list args;
    va_start(args, number);

    unsigned long arg1 = va_arg(args, unsigned long);
    unsigned long arg2 = va_arg(args, unsigned long);
    unsigned long arg3 = va_arg(args, unsigned long);
    unsigned long arg4 = va_arg(args, unsigned long);
    unsigned long arg5 = va_arg(args, unsigned long);
    unsigned long arg6 = va_arg(args, unsigned long);

    va_end(args);

    long ret;

    __asm__ volatile 
	(
        "mov %1, %%rax \n"
        "mov %2, %%rdi \n"
        "mov %3, %%rsi \n"
        "mov %4, %%rdx \n"
        "mov %5, %%r10 \n"
        "mov %6, %%r8  \n"
        "mov %7, %%r9  \n"
        "syscall        \n"
        "mov %%rax, %0  \n"
        : "=r" (ret)
        : "r" (number),
          "r" (arg1),
          "r" (arg2),
          "r" (arg3),
          "r" (arg4),
          "r" (arg5),
          "r" (arg6)
        : "%rax", "%rdi", "%rsi", "%rdx", "%r10", "%r8", "%r9", "memory"
    );

    if (ret < 0) 
        return ret;

    return ret;
}


#ifdef TINY_ALLOC

__attribute__((deprecated("This function is deprecated. Use mmap instead.")))
void* _sbrk(intptr_t increment) 
{
	static uintptr_t current_brk = 0;
	uintptr_t new_brk;
	void* result;

	if (current_brk == 0) 
	{
		result = (void*)_syscall(SYS_brk, 0);
		current_brk = (uintptr_t)result;
		if (current_brk == (uintptr_t)-1) 
		{
			errno = ENOMEM;
			return (void*)-1;
		}
	}

	new_brk = current_brk + increment;
	result = (void*)_syscall(SYS_brk, new_brk);
	if ((uintptr_t)result == (uintptr_t)-1) 
	{
		errno = ENOMEM;
		return (void*)-1;
	}

	void* old_brk = (void*)current_brk;
	current_brk = new_brk;

	return old_brk;
}
#endif