x86: Make sure esp is aligned when delivering signal.

While here, use STACK_ALIGNBYTES consistently for the alignment mask
(or STACK_ALIGNBYTES32 in amd64 for the compat32 alignment mask).

PR kern/59327: user stack pointer is not aligned properly

Author: riastradh

sys/arch/amd64/amd64/machdep.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: machdep.c,v 1.373 2025/03/17 11:39:02 riastradh Exp $	*/
+/*	$NetBSD: machdep.c,v 1.374 2025/04/24 23:51:03 riastradh Exp $	*/
 
 /*
  * Copyright (c) 1996, 1997, 1998, 2000, 2006, 2007, 2008, 2011
@@ -110,7 +110,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.373 2025/03/17 11:39:02 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.374 2025/04/24 23:51:03 riastradh Exp $");
 
 #include "opt_modular.h"
 #include "opt_user_ldt.h"
@@ -612,7 +612,8 @@ sendsig_siginfo(const ksiginfo_t *ksi, const sigset_t *mask)
 
 	sp -= sizeof(struct sigframe_siginfo);
 	/* Round down the stackpointer to a multiple of 16 for the ABI. */
-	fp = (struct sigframe_siginfo *)(((unsigned long)sp & ~15) - 8);
+	fp = (struct sigframe_siginfo *)(((unsigned long)sp &
+		~STACK_ALIGNBYTES) - 8);
 
 	memset(&frame, 0, sizeof(frame));
 	frame.sf_ra = (uint64_t)ps->sa_sigdesc[sig].sd_tramp;

sys/arch/amd64/amd64/netbsd32_machdep.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: netbsd32_machdep.c,v 1.141 2022/08/20 23:49:31 riastradh Exp $	*/
+/*	$NetBSD: netbsd32_machdep.c,v 1.142 2025/04/24 23:51:03 riastradh Exp $	*/
 
 /*
  * Copyright (c) 2001 Wasabi Systems, Inc.
@@ -36,7 +36,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.141 2022/08/20 23:49:31 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.142 2025/04/24 23:51:03 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_compat_netbsd.h"
@@ -233,6 +233,8 @@ netbsd32_sendsig_siginfo(const ksiginfo_t *ksi, const sigset_t *mask)
 		fp = (struct netbsd32_sigframe_siginfo *)tf->tf_rsp;
 
 	fp--;
+	fp = (struct netbsd32_sigframe_siginfo *)((uintptr_t)fp &
+	    ~STACK_ALIGNBYTES32);
 
 	/* Build stack frame for signal trampoline. */
 	switch (ps->sa_sigdesc[sig].sd_vers) {

sys/arch/amd64/include/param.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: param.h,v 1.40 2025/04/24 09:58:26 kre Exp $	*/
+/*	$NetBSD: param.h,v 1.41 2025/04/24 23:51:03 riastradh Exp $	*/
 
 #ifdef __x86_64__
 
@@ -31,6 +31,7 @@
  * (2) rtld in glibc >= 2.23 for Linux/x86_64 requires it.
  */
 #define STACK_ALIGNBYTES	(16 - 1)
+#define	STACK_ALIGNBYTES32	(4 - 1)
 
 #define ALIGNBYTES32		(sizeof(int) - 1)
 #define ALIGN32(p)		(((u_long)(p) + ALIGNBYTES32) &~ALIGNBYTES32)

sys/arch/i386/i386/machdep.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: machdep.c,v 1.845 2025/03/17 11:39:02 riastradh Exp $	*/
+/*	$NetBSD: machdep.c,v 1.846 2025/04/24 23:51:03 riastradh Exp $	*/
 
 /*
  * Copyright (c) 1996, 1997, 1998, 2000, 2004, 2006, 2008, 2009, 2017
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.845 2025/03/17 11:39:02 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.846 2025/04/24 23:51:03 riastradh Exp $");
 
 #include "opt_beep.h"
 #include "opt_compat_freebsd.h"
@@ -676,6 +676,7 @@ sendsig_siginfo(const ksiginfo_t *ksi, const sigset_t *mask)
 	KASSERT(mutex_owned(p->p_lock));
 
 	fp--;
+	fp = (struct sigframe_siginfo *)((uintptr_t)fp & ~STACK_ALIGNBYTES);
 
 	memset(&frame, 0, sizeof(frame));
 	frame.sf_ra = (int)ps->sa_sigdesc[sig].sd_tramp;

tests/kernel/t_signal_and_sp.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: t_signal_and_sp.c,v 1.12 2025/04/24 17:00:25 riastradh Exp $	*/
+/*	$NetBSD: t_signal_and_sp.c,v 1.13 2025/04/24 23:51:03 riastradh Exp $	*/
 
 /*
  * Copyright (c) 2024 The NetBSD Foundation, Inc.
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: t_signal_and_sp.c,v 1.12 2025/04/24 17:00:25 riastradh Exp $");
+__RCSID("$NetBSD: t_signal_and_sp.c,v 1.13 2025/04/24 23:51:03 riastradh Exp $");
 
 #include <sys/wait.h>
 
@@ -431,7 +431,7 @@ ATF_TC_BODY(signalsp_sigaltstack, tc)
 	fprintf(stderr, "stack @ [%p, %p)\n",
 	    stack, stack + SIGSTKSZ + STACK_ALIGNBYTES);
 
-#if defined __alpha__ || defined __i386__ || defined __mips__
+#if defined __alpha__ || defined __mips__
 	atf_tc_expect_fail("PR kern/59327:"
 	    " user stack pointer is not aligned properly");
 #endif
@@ -575,7 +575,7 @@ ATF_TC_BODY(misaligned_sp_and_signal, tc)
 	sa.sa_handler = &signalsphandler;
 	RL(sigaction(SIGALRM, &sa, NULL));
 
-#if defined __alpha__ || defined __i386__ || defined __mips__
+#if defined __alpha__ || defined __mips__
 	atf_tc_expect_fail("PR kern/58149:"
 	    " Cannot return from a signal handler"
 	    " if SP was misaligned when the signal arrived");