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Message-Id: <20250316-nolibc-sp-align-v1-1-1e1fb073ca1e@weissschuh.net>
Date: Sun, 16 Mar 2025 20:46:07 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>
Cc: linux-kernel@...r.kernel.org,
Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH] tools/nolibc: drop manual stack pointer alignment
The stack pointer is already aligned by the kernel to a multiple of 16.
See STACK_ROUND() in fs/binfmt_elf.c.
The manual realignment is unnecessary, drop it.
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
MIPS is not adapted in this patch, but in [0].
[0] https://lore.kernel.org/lkml/20250225-nolibc-mips-n32-v2-2-664b47d87fa0@weissschuh.net/
---
tools/include/nolibc/arch-aarch64.h | 1 -
tools/include/nolibc/arch-arm.h | 2 --
tools/include/nolibc/arch-i386.h | 2 --
tools/include/nolibc/arch-loongarch.h | 7 -------
tools/include/nolibc/arch-powerpc.h | 2 --
tools/include/nolibc/arch-riscv.h | 1 -
tools/include/nolibc/arch-x86_64.h | 1 -
7 files changed, 16 deletions(-)
diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index 06fdef7b291a0b276948c08fdec7858f51616546..937a348da42e1b134d9736a5a0f6920df6e4709d 100644
--- a/tools/include/nolibc/arch-aarch64.h
+++ b/tools/include/nolibc/arch-aarch64.h
@@ -146,7 +146,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
{
__asm__ volatile (
"mov x0, sp\n" /* save stack pointer to x0, as arg1 of _start_c */
- "and sp, x0, -16\n" /* sp must be 16-byte aligned in the callee */
"bl _start_c\n" /* transfer to c runtime */
);
__nolibc_entrypoint_epilogue();
diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h
index 6180ff99ab43dff1751f9ac22b518382a0e917c7..1f66e7e5a444b2506150f0b4f4f11f296902b2bc 100644
--- a/tools/include/nolibc/arch-arm.h
+++ b/tools/include/nolibc/arch-arm.h
@@ -189,8 +189,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
{
__asm__ volatile (
"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 */
);
__nolibc_entrypoint_epilogue();
diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h
index ff5afc35bbd8be0876cbd9ae6361c3a07fb2d734..7c9b38e9641831b6b08432f833365b9f6a2b2f41 100644
--- a/tools/include/nolibc/arch-i386.h
+++ b/tools/include/nolibc/arch-i386.h
@@ -167,8 +167,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
__asm__ volatile (
"xor %ebp, %ebp\n" /* zero the stack frame */
"mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */
- "add $12, %esp\n" /* avoid over-estimating after the 'and' & 'sub' below */
- "and $-16, %esp\n" /* the %esp must be 16-byte aligned on 'call' */
"sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */
"push %eax\n" /* push arg1 on stack to support plain stack modes too */
"call _start_c\n" /* transfer to c runtime */
diff --git a/tools/include/nolibc/arch-loongarch.h b/tools/include/nolibc/arch-loongarch.h
index fb519545959edf44f939093e21bb73a532d9ac9b..5511705303ea908209d5a8be62722491c2987f82 100644
--- a/tools/include/nolibc/arch-loongarch.h
+++ b/tools/include/nolibc/arch-loongarch.h
@@ -142,18 +142,11 @@
_arg1; \
})
-#if __loongarch_grlen == 32
-#define LONG_BSTRINS "bstrins.w"
-#else /* __loongarch_grlen == 64 */
-#define LONG_BSTRINS "bstrins.d"
-#endif
-
/* startup code */
void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void)
{
__asm__ volatile (
"move $a0, $sp\n" /* save stack pointer to $a0, as arg1 of _start_c */
- LONG_BSTRINS " $sp, $zero, 3, 0\n" /* $sp must be 16-byte aligned */
"bl _start_c\n" /* transfer to c runtime */
);
__nolibc_entrypoint_epilogue();
diff --git a/tools/include/nolibc/arch-powerpc.h b/tools/include/nolibc/arch-powerpc.h
index ee2fdb8d601dcc0796e1fee89b7121dc7184a523..204564bbcd328ed51a804ecbbdb55d578dee132e 100644
--- a/tools/include/nolibc/arch-powerpc.h
+++ b/tools/include/nolibc/arch-powerpc.h
@@ -201,7 +201,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
__asm__ volatile (
"mr 3, 1\n" /* save stack pointer to r3, as arg1 of _start_c */
- "clrrdi 1, 1, 4\n" /* align the stack to 16 bytes */
"li 0, 0\n" /* zero the frame pointer */
"stdu 1, -32(1)\n" /* the initial stack frame */
"bl _start_c\n" /* transfer to c runtime */
@@ -209,7 +208,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
#else
__asm__ volatile (
"mr 3, 1\n" /* save stack pointer to r3, as arg1 of _start_c */
- "clrrwi 1, 1, 4\n" /* align the stack to 16 bytes */
"li 0, 0\n" /* zero the frame pointer */
"stwu 1, -16(1)\n" /* the initial stack frame */
"bl _start_c\n" /* transfer to c runtime */
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h
index 8827bf936212416f9fbc3da7428cb04664cbd702..885383a86c38b186bb6eb269e670080b36c9d982 100644
--- a/tools/include/nolibc/arch-riscv.h
+++ b/tools/include/nolibc/arch-riscv.h
@@ -148,7 +148,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
"lla gp, __global_pointer$\n"
".option pop\n"
"mv a0, sp\n" /* save stack pointer to a0, as arg1 of _start_c */
- "andi sp, a0, -16\n" /* sp must be 16-byte aligned */
"call _start_c\n" /* transfer to c runtime */
);
__nolibc_entrypoint_epilogue();
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index 1e40620a2b33da501b7e06dda2472903f7e2bfed..67305e24dbefdcd4fd1fc6fd8fdb98d74a34c2d9 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -166,7 +166,6 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _s
__asm__ volatile (
"xor %ebp, %ebp\n" /* zero the stack frame */
"mov %rsp, %rdi\n" /* save stack pointer to %rdi, as arg1 of _start_c */
- "and $-16, %rsp\n" /* %rsp must be 16-byte aligned before call */
"call _start_c\n" /* transfer to c runtime */
"hlt\n" /* ensure it does not return */
);
---
base-commit: bceb73904c855c78402dca94c82915f078f259dd
change-id: 20250228-nolibc-sp-align-935ab31724c2
Best regards,
--
Thomas Weißschuh <linux@...ssschuh.net>
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