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Message-Id: <26b030bd7e0d48e60350c1b325dd0668f0caf803.1688828139.git.falcon@tinylab.org>
Date: Sat, 8 Jul 2023 23:35:28 +0800
From: Zhangjin Wu <falcon@...ylab.org>
To: w@....eu
Cc: falcon@...ylab.org, arnd@...db.de, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, thomas@...ch.de
Subject: [PATCH v2 09/12] tools/nolibc: mips/crt.h: shrink _start with _start_c
move most of the _start operations to _start_c().
Also clean up the instructions in delay slots.
Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
---
tools/include/nolibc/mips/crt.h | 42 +++++++--------------------------
1 file changed, 9 insertions(+), 33 deletions(-)
diff --git a/tools/include/nolibc/mips/crt.h b/tools/include/nolibc/mips/crt.h
index 38df52d8ec16..a49632b64fdd 100644
--- a/tools/include/nolibc/mips/crt.h
+++ b/tools/include/nolibc/mips/crt.h
@@ -11,43 +11,19 @@
void __attribute__((weak, noreturn, optimize("omit-frame-pointer"))) __no_stack_protector __start(void)
{
__asm__ volatile (
- /*".set nomips16\n"*/
".set push\n"
- ".set noreorder\n"
+ ".set noreorder\n"
".option pic0\n"
#ifdef _NOLIBC_STACKPROTECTOR
- "jal __stack_chk_init\n" /* initialize stack protector */
- "nop\n" /* delayed slot */
+ "jal __stack_chk_init\n" /* initialize stack protector */
+ " nop\n" /* delayed slot */
#endif
- /*".ent __start\n"*/
- /*"__start:\n"*/
- "lw $a0,($sp)\n" /* argc was in the stack */
- "addiu $a1, $sp, 4\n" /* argv = sp + 4 */
- "sll $a2, $a0, 2\n" /* a2 = argc * 4 */
- "add $a2, $a2, $a1\n" /* envp = argv + 4*argc ... */
- "addiu $a2, $a2, 4\n" /* ... + 4 */
- "lui $a3, %hi(environ)\n" /* load environ into a3 (hi) */
- "addiu $a3, %lo(environ)\n" /* load environ into a3 (lo) */
- "sw $a2,($a3)\n" /* store envp(a2) into environ */
-
- "move $t0, $a2\n" /* iterate t0 over envp, look for NULL */
- "0:" /* do { */
- "lw $a3, ($t0)\n" /* a3=*(t0); */
- "bne $a3, $0, 0b\n" /* } while (a3); */
- "addiu $t0, $t0, 4\n" /* delayed slot: t0+=4; */
- "lui $a3, %hi(_auxv)\n" /* load _auxv into a3 (hi) */
- "addiu $a3, %lo(_auxv)\n" /* load _auxv into a3 (lo) */
- "sw $t0, ($a3)\n" /* store t0 into _auxv */
-
- "li $t0, -8\n"
- "and $sp, $sp, $t0\n" /* sp must be 8-byte aligned */
- "addiu $sp,$sp,-16\n" /* the callee expects to save a0..a3 there! */
- "jal main\n" /* main() returns the status code, we'll exit with it. */
- "nop\n" /* delayed slot */
- "move $a0, $v0\n" /* retrieve 32-bit exit code from v0 */
- "li $v0, 4001\n" /* NR_exit == 4001 */
- "syscall\n"
- /*".end __start\n"*/
+ "move $a0, $sp\n" /* save stack pointer to $a0, as arg1 of _start_c */
+ "li $t0, -8\n"
+ "and $sp, $sp, $t0\n" /* $sp must be 8-byte aligned */
+ "addiu $sp, $sp, -16\n" /* the callee expects to save a0..a3 there */
+ "jal _start_c\n" /* transfer to c runtime */
+ " nop\n" /* delayed slot */
".set pop\n"
);
__builtin_unreachable();
--
2.25.1
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