Commit 61f98807 authored by Zhangjin Wu's avatar Zhangjin Wu Committed by Willy Tarreau
Browse files

tools/nolibc: arm: shrink _start with _start_c 



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

Signed-off-by: default avatarZhangjin Wu <falcon@tinylab.org>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
parent 06f2a62c

tools/include/nolibc/arch-arm.h

+5 −39
Original line number Diff line number Diff line
@@ -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();

}