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: Zhangjin Wu <falcon@tinylab.org> Signed-off-by: Willy Tarreau <w@1wt.eu>
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@ -8,6 +8,7 @@
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#define _NOLIBC_ARCH_X86_64_H
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#include "compiler.h"
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#include "crt.h"
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/* Syscalls for x86_64 :
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* - registers are 64-bit
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@ -153,9 +154,6 @@
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_ret; \
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})
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char **environ __attribute__((weak));
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const unsigned long *_auxv __attribute__((weak));
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/* startup code */
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/*
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* x86-64 System V ABI mandates:
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@ -166,26 +164,11 @@ const unsigned long *_auxv __attribute__((weak));
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void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
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{
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__asm__ volatile (
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#ifdef _NOLIBC_STACKPROTECTOR
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"call __stack_chk_init\n" /* initialize stack protector */
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#endif
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"pop %rdi\n" /* argc (first arg, %rdi) */
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"mov %rsp, %rsi\n" /* argv[] (second arg, %rsi) */
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"lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx) */
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"mov %rdx, environ\n" /* save environ */
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"xor %ebp, %ebp\n" /* zero the stack frame */
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"mov %rdx, %rax\n" /* search for auxv (follows NULL after last env) */
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"0:\n"
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"add $8, %rax\n" /* search for auxv using rax, it follows the */
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"cmp -8(%rax), %rbp\n" /* ... NULL after last env (rbp is zero here) */
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"jnz 0b\n"
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"mov %rax, _auxv\n" /* save it into _auxv */
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"and $-16, %rsp\n" /* x86 ABI : esp must be 16-byte aligned before call */
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"call main\n" /* main() returns the status code, we'll exit with it. */
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"mov %eax, %edi\n" /* retrieve exit code (32 bit) */
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"mov $60, %eax\n" /* NR_exit == 60 */
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"syscall\n" /* really exit */
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"hlt\n" /* ensure it does not return */
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"xor %ebp, %ebp\n" /* zero the stack frame */
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"mov %rsp, %rdi\n" /* save stack pointer to %rdi, as arg1 of _start_c */
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"and $-16, %rsp\n" /* %rsp must be 16-byte aligned before call */
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"call _start_c\n" /* transfer to c runtime */
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"hlt\n" /* ensure it does not return */
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);
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__builtin_unreachable();
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}
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