[PATCH] nolibc: optimise _start() on x86_64
From: Alexey Dobriyan
Date: Sat Dec 02 2023 - 07:45:22 EST
Just jump into _start_c, it is not going to return anyway.
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---
Also, kernel clears all registers before starting process,
I'm not sure why
xor ebp, ebp
was added.
tools/include/nolibc/arch-x86_64.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -167,8 +167,7 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
"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 */
+ "jmp _start_c\n" /* transfer to c runtime */
);
__builtin_unreachable();
}