linux-kernel - [PATCH 2/3 RESEND] x86, acpi: On S3 failure, just fall through

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Message-Id: <1435954115-1800-2-git-send-email-dvlasenk@redhat.com>
Date:	Fri,  3 Jul 2015 22:08:34 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>, Pavel Machek <pavel@....cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/3 RESEND] x86, acpi: On S3 failure, just fall through

Th "jmp" deleted by this patch in fact compiles to "jmp to next insn",
since ".p2align 4,,7" happens to not do any alignment -
aligning to 2^4 would require more than 7 bytes of padding:

000000b0 <do_suspend_lowlevel>:
  b0:   e8 fc ff ff ff          call   <save_processor_state>
  b5:   e8 8d ff ff ff          call   47 <save_registers>
  ba:   6a 03                   push   $0x3
  bc:   e8 fc ff ff ff          call   <x86_acpi_enter_sleep_state>
  c1:   83 c4 04                add    $0x4,%esp
  c4:   eb 00                   jmp    c6 <ret_point>   <============ THIS
000000c6 <ret_point>:
  c6:   e8 c4 ff ff ff          call   8f <restore_registers>

Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Pavel Machek <pavel@....cz>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.kernel.org
---
 arch/x86/kernel/acpi/wakeup_32.S | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S
index eef2bd3..5fec9b0 100644
--- a/arch/x86/kernel/acpi/wakeup_32.S
+++ b/arch/x86/kernel/acpi/wakeup_32.S
@@ -68,11 +68,8 @@ ENTRY(do_suspend_lowlevel)
 	pushl	$3
 	call	x86_acpi_enter_sleep_state
 	addl	$4, %esp
+# If S3 fails, we simply fall through to S3 wakeup code:
 
-#	In case of S3 failure, we'll emerge here.  Jump
-# 	to ret_point to recover
-	jmp	ret_point
-	.p2align 4,,7
 ret_point:
 	call	restore_registers
 	call	restore_processor_state
-- 
1.8.1.4

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