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@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250316-nolibc-sp-align-v1-1-1e1fb073ca1e@weissschuh.net

7 files changed, 0 insertions, 16 deletions

diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index 06fdef7b291a..937a348da42e 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 6180ff99ab43..1f66e7e5a444 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 ff5afc35bbd8..7c9b38e96418 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 fb519545959e..5511705303ea 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 ee2fdb8d601d..204564bbcd32 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 8827bf936212..885383a86c38 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 1e40620a2b33..67305e24dbef 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                       */
 	);