linux-kernel - [tip:core/signals] signals/sigaltstack, x86/signals: Unify the x86 sigaltstack check with other architectures

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Date:	Tue, 3 May 2016 00:49:40 -0700
From:	tip-bot for Stas Sergeev <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	akpm@...ux-foundation.org, brgerst@...il.com, hpa@...or.com,
	bp@...en8.de, shuahkh@....samsung.com, tglx@...utronix.de,
	mingo@...nel.org, richard@....at, luto@...capital.net,
	stsp@...t.ru, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, xemul@...allels.com,
	viro@...iv.linux.org.uk, bp@...e.de, oleg@...hat.com,
	peterz@...radead.org, dvlasenk@...hat.com
Subject: [tip:core/signals] signals/sigaltstack, x86/signals: Unify the x86
 sigaltstack check with other architectures

Commit-ID:  0b4521e8cf1f582da3045ea460427ac2f741578f
Gitweb:     http://git.kernel.org/tip/0b4521e8cf1f582da3045ea460427ac2f741578f
Author:     Stas Sergeev <stsp@...t.ru>
AuthorDate: Thu, 14 Apr 2016 23:20:02 +0300
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 3 May 2016 08:37:58 +0200

signals/sigaltstack, x86/signals: Unify the x86 sigaltstack check with other architectures

Currently x86's get_sigframe() checks for "current->sas_ss_size"
to determine whether there is a need to switch to sigaltstack.
The common practice used by all other arches is to check for
sas_ss_flags(sp) == 0

This patch makes the code consistent with other architectures.

The slight complexity of the patch is added by the optimization on
!sigstack check that was requested by Andy Lutomirski: sas_ss_flags(sp)==0
already implies that we are not on a sigstack, so the code is shuffled
to avoid the duplicate checking.

This patch should have no user-visible impact.

Signed-off-by: Stas Sergeev <stsp@...t.ru>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Richard Weinberger <richard@....at>
Cc: Shuah Khan <shuahkh@....samsung.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-api@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Link: http://lkml.kernel.org/r/1460665206-13646-2-git-send-email-stsp@list.ru
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/signal.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 548ddf7..3e84ef1 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -248,18 +248,17 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 	if (config_enabled(CONFIG_X86_64))
 		sp -= 128;
 
-	if (!onsigstack) {
-		/* This is the X/Open sanctioned signal stack switching.  */
-		if (ka->sa.sa_flags & SA_ONSTACK) {
-			if (current->sas_ss_size)
-				sp = current->sas_ss_sp + current->sas_ss_size;
-		} else if (config_enabled(CONFIG_X86_32) &&
-			   (regs->ss & 0xffff) != __USER_DS &&
-			   !(ka->sa.sa_flags & SA_RESTORER) &&
-			   ka->sa.sa_restorer) {
-				/* This is the legacy signal stack switching. */
-				sp = (unsigned long) ka->sa.sa_restorer;
-		}
+	/* This is the X/Open sanctioned signal stack switching.  */
+	if (ka->sa.sa_flags & SA_ONSTACK) {
+		if (sas_ss_flags(sp) == 0)
+			sp = current->sas_ss_sp + current->sas_ss_size;
+	} else if (config_enabled(CONFIG_X86_32) &&
+		   !onsigstack &&
+		   (regs->ss & 0xffff) != __USER_DS &&
+		   !(ka->sa.sa_flags & SA_RESTORER) &&
+		   ka->sa.sa_restorer) {
+		/* This is the legacy signal stack switching. */
+		sp = (unsigned long) ka->sa.sa_restorer;
 	}
 
 	if (fpu->fpstate_active) {