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Message-Id: <5cdded9a3bd45b035ab25cba1996745d7009f02e.1689444638.git.falcon@tinylab.org>
Date: Sun, 16 Jul 2023 02:24:29 +0800
From: Zhangjin Wu <falcon@...ylab.org>
To: w@....eu
Cc: arnd@...db.de, falcon@...ylab.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, thomas@...ch.de
Subject: [PATCH v4 07/18] tools/nolibc: arm: shrink _start with _start_c
move most of the _start operations to _start_c(), include the
stackprotector initialization.
Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
---
tools/include/nolibc/arch-arm.h | 44 ++++-----------------------------
1 file changed, 5 insertions(+), 39 deletions(-)
diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h
index a06dad789a22..cae4afa7c1c7 100644
--- a/tools/include/nolibc/arch-arm.h
+++ b/tools/include/nolibc/arch-arm.h
@@ -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();
}
--
2.25.1
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