Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-10-23 05:30:55 +00:00
Code Issues Packages Projects Releases Wiki Activity

tools/nolibc: x86_64: shrink _start with _start_c

Browse Source 
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 02:27:49 +08:00 committed by Willy Tarreau
parent 2ab446336b
commit 539287d751
1 changed files with 6 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
tools/include/nolibc/arch-x86_64.h
View File

@ -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:
@ -166,26 +164,11 @@ 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 */
"hlt\n" /* ensure it does not return */
"xor %ebp, %ebp\n" /* zero the stack frame */
"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();
}