Commit 539287d7 authored by Zhangjin Wu's avatar Zhangjin Wu Committed by Willy Tarreau
Browse files

tools/nolibc: x86_64: shrink _start with _start_c 



move most of the _start operations to _start_c(), include the
stackprotector initialization.

Signed-off-by: default avatarZhangjin Wu <falcon@tinylab.org>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
parent 2ab44633

tools/include/nolibc/arch-x86_64.h

+6 −23
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#define _NOLIBC_ARCH_X86_64_H



#include "compiler.h"

#include "crt.h"



/* Syscalls for x86_64 :

 *   - registers are 64-bit
@@ -153,9 +154,6 @@ 
	_ret;                                                                 \

})



char **environ __attribute__((weak));

const unsigned long *_auxv __attribute__((weak));



/* startup code */

/*

 * x86-64 System V ABI mandates:
@@ -166,25 +164,10 @@ const unsigned long *_auxv __attribute__((weak)); 
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)

{

	__asm__ volatile (

#ifdef _NOLIBC_STACKPROTECTOR

		"call __stack_chk_init\n"   /* initialize stack protector                          */

#endif

		"pop %rdi\n"                /* argc   (first arg, %rdi)                            */

		"mov %rsp, %rsi\n"          /* argv[] (second arg, %rsi)                           */

		"lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx)             */

		"mov %rdx, environ\n"       /* save environ                                        */

		"xor  %ebp, %ebp\n"       /* zero the stack frame                            */

		"mov %rdx, %rax\n"          /* search for auxv (follows NULL after last env)       */

		"0:\n"

		"add $8, %rax\n"            /* search for auxv using rax, it follows the           */

		"cmp -8(%rax), %rbp\n"      /* ... NULL after last env (rbp is zero here)          */

		"jnz 0b\n"

		"mov %rax, _auxv\n"         /* save it into _auxv                                  */

		"and $-16, %rsp\n"          /* x86 ABI : esp must be 16-byte aligned before call   */

		"call main\n"               /* main() returns the status code, we'll exit with it. */

		"mov %eax, %edi\n"          /* retrieve exit code (32 bit)                         */

		"mov $60, %eax\n"           /* NR_exit == 60                                       */

		"syscall\n"                 /* really exit                                         */

		"mov  %rsp, %rdi\n"       /* save stack pointer to %rdi, as arg1 of _start_c */

		"and  $-16, %rsp\n"       /* %rsp must be 16-byte aligned before call        */

		"call _start_c\n"         /* transfer to c runtime                           */

		"hlt\n"                   /* ensure it does not return                       */

	);

	__builtin_unreachable();