linux-kernel - [tip:x86/asm] x86/asm/entry/32: Fix fallout from the R9 trick removal in the SYSCALL code

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Date:	Wed, 10 Jun 2015 00:09:31 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	bp@...en8.de, keescook@...omium.org, peterz@...radead.org,
	fweisbec@...il.com, rostedt@...dmis.org, ast@...mgrid.com,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	dvlasenk@...hat.com, oleg@...hat.com, luto@...capital.net,
	hpa@...or.com, wad@...omium.org, mingo@...nel.org
Subject: [tip:x86/asm] x86/asm/entry/32:
  Fix fallout from the R9 trick removal in the SYSCALL code

Commit-ID:  aee4b013a71666f11ffeac11ab45bb7c6e0e394d
Gitweb:     http://git.kernel.org/tip/aee4b013a71666f11ffeac11ab45bb7c6e0e394d
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Tue, 9 Jun 2015 20:54:07 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 10 Jun 2015 08:42:12 +0200

x86/asm/entry/32: Fix fallout from the R9 trick removal in the SYSCALL code

I put %ebp restoration code too late. Under strace, it is not
reached and %ebp is not restored upon return to userspace.

This is the fix. Run-tested.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Drewry <wad@...omium.org>
Link: http://lkml.kernel.org/r/1433876051-26604-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64_compat.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 2093ce6..2c44180 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -344,6 +344,7 @@ cstar_dispatch:
 	call	*ia32_sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
 1:
+	movl	RCX(%rsp), %ebp
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF
 	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -351,7 +352,6 @@ cstar_dispatch:
 
 sysretl_from_sys_call:
 	andl	$~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
-	movl	RCX(%rsp), %ebp
 	RESTORE_RSI_RDI_RDX
 	movl	RIP(%rsp), %ecx
 	movl	EFLAGS(%rsp), %r11d
--
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