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Message-Id: <0d650309e0cf79fee1a87995d3fcae083b96b150.1687976753.git.falcon@tinylab.org>
Date: Thu, 29 Jun 2023 03:01:14 +0800
From: Zhangjin Wu <falcon@...ylab.org>
To: thomas@...ch.de, w@....eu
Cc: falcon@...ylab.org, arnd@...db.de, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: [PATCH v1 08/11] tools/nolibc: mips: shrink _start with _start_c
Let's 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/arch-mips.h | 45 +++++++-------------------------
1 file changed, 9 insertions(+), 36 deletions(-)
diff --git a/tools/include/nolibc/arch-mips.h b/tools/include/nolibc/arch-mips.h
index ecf912a1938f..d0f73f03bfa1 100644
--- a/tools/include/nolibc/arch-mips.h
+++ b/tools/include/nolibc/arch-mips.h
@@ -173,50 +173,23 @@
_arg4 ? -_num : _num; \
})
-char **environ __attribute__((weak));
-const unsigned long *_auxv __attribute__((weak));
-
/* startup code, note that it's called __start on MIPS */
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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