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tools/nolibc: i386: shrink _start with _start_c 

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

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
This commit is contained in:
Zhangjin Wu 2023-07-16 02:26:42 +08:00 committed by Willy Tarreau
parent ded8af47c2
commit 2ab446336b
1 changed files with 7 additions and 27 deletions
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34
tools/include/nolibc/arch-i386.h
View File

@ -8,6 +8,7 @@
#define _NOLIBC_ARCH_I386_H
#include "compiler.h"
#include "crt.h"
/* Syscalls for i386 :
* - mostly similar to x86_64
@ -154,9 +155,6 @@
_eax; \
})
char **environ __attribute__((weak));
const unsigned long *_auxv __attribute__((weak));
/* startup code */
/*
* i386 System V ABI mandates:
@ -167,30 +165,12 @@ 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 %eax\n" /* argc (first arg, %eax) */
"mov %esp, %ebx\n" /* argv[] (second arg, %ebx) */
"lea 4(%ebx,%eax,4),%ecx\n" /* then a NULL then envp (third arg, %ecx) */
"mov %ecx, environ\n" /* save environ */
"xor %ebp, %ebp\n" /* zero the stack frame */
"mov %ecx, %edx\n" /* search for auxv (follows NULL after last env) */
"0:\n"
"add $4, %edx\n" /* search for auxv using edx, it follows the */
"cmp -4(%edx), %ebp\n" /* ... NULL after last env (ebp is zero here) */
"jnz 0b\n"
"mov %edx, _auxv\n" /* save it into _auxv */
"and $-16, %esp\n" /* x86 ABI : esp must be 16-byte aligned before */
"sub $4, %esp\n" /* the call instruction (args are aligned) */
"push %ecx\n" /* push all registers on the stack so that we */
"push %ebx\n" /* support both regparm and plain stack modes */
"push %eax\n"
"call main\n" /* main() returns the status code in %eax */
"mov %eax, %ebx\n" /* retrieve exit code (32-bit int) */
"movl $1, %eax\n" /* NR_exit == 1 */
"int $0x80\n" /* exit now */
"hlt\n" /* ensure it does not */
"xor %ebp, %ebp\n" /* zero the stack frame */
"mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */
"and $-16, %esp\n" /* last pushed argument must be 16-byte aligned */
"push %eax\n" /* push arg1 on stack to support plain stack modes too */
"call _start_c\n" /* transfer to c runtime */
"hlt\n" /* ensure it does not return */
);
__builtin_unreachable();
}