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tools/nolibc: arm: shrink _start with _start_c

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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 02:24:29 +08:00 committed by Willy Tarreau
parent 06f2a62c81
commit 61f9880721
1 changed files with 5 additions and 39 deletions
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44
tools/include/nolibc/arch-arm.h
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@ -8,6 +8,7 @@
#define _NOLIBC_ARCH_ARM_H
#include "compiler.h"
#include "crt.h"
/* Syscalls for ARM in ARM or Thumb modes :
* - registers are 32-bit
@ -183,49 +184,14 @@
_arg1; \
})
char **environ __attribute__((weak));
const unsigned long *_auxv __attribute__((weak));
/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
__asm__ volatile (
#ifdef _NOLIBC_STACKPROTECTOR
"bl __stack_chk_init\n" /* initialize stack protector */
#endif
"pop {%r0}\n" /* argc was in the stack */
"mov %r1, %sp\n" /* argv = sp */
"add %r2, %r0, $1\n" /* envp = (argc + 1) ... */
"lsl %r2, %r2, $2\n" /* * 4 ... */
"add %r2, %r2, %r1\n" /* + argv */
"ldr %r3, 1f\n" /* r3 = &environ (see below) */
"str %r2, [r3]\n" /* store envp into environ */
"mov r4, r2\n" /* search for auxv (follows NULL after last env) */
"0:\n"
"mov r5, r4\n" /* r5 = r4 */
"add r4, r4, #4\n" /* r4 += 4 */
"ldr r5,[r5]\n" /* r5 = *r5 = *(r4-4) */
"cmp r5, #0\n" /* and stop at NULL after last env */
"bne 0b\n"
"ldr %r3, 2f\n" /* r3 = &_auxv (low bits) */
"str r4, [r3]\n" /* store r4 into _auxv */
"mov %r3, $8\n" /* AAPCS : sp must be 8-byte aligned in the */
"neg %r3, %r3\n" /* callee, and bl doesn't push (lr=pc) */
"and %r3, %r3, %r1\n" /* so we do sp = r1(=sp) & r3(=-8); */
"mov %sp, %r3\n"
"bl main\n" /* main() returns the status code, we'll exit with it. */
"movs r7, $1\n" /* NR_exit == 1 */
"svc $0x00\n"
".align 2\n" /* below are the pointers to a few variables */
"1:\n"
".word environ\n"
"2:\n"
".word _auxv\n"
"mov %r0, sp\n" /* save stack pointer to %r0, as arg1 of _start_c */
"and ip, %r0, #-8\n" /* sp must be 8-byte aligned in the callee */
"mov sp, ip\n"
"bl _start_c\n" /* transfer to c runtime */
);
__builtin_unreachable();
}