linux-kernel - [tip:x86/asm] x86/asm/entry/32: Reinstate clearing of pt

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Date:	Mon, 8 Jun 2015 15:24:35 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	oleg@...hat.com, ast@...mgrid.com, keescook@...omium.org,
	peterz@...radead.org, torvalds@...ux-foundation.org,
	fweisbec@...il.com, hpa@...or.com, rostedt@...dmis.org,
	akpm@...ux-foundation.org, wad@...omium.org, bp@...en8.de,
	linux-kernel@...r.kernel.org, luto@...capital.net,
	dvlasenk@...hat.com, mingo@...nel.org, tglx@...utronix.de
Subject: [tip:x86/asm] x86/asm/entry/32: Reinstate clearing of pt_regs->
 r8..r11 on EFAULT path

Commit-ID:  eb47854415825a69b1c578e7487da571227ba25a
Gitweb:     http://git.kernel.org/tip/eb47854415825a69b1c578e7487da571227ba25a
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Sun, 7 Jun 2015 20:24:30 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 8 Jun 2015 23:43:37 +0200

x86/asm/entry/32: Reinstate clearing of pt_regs->r8..r11 on EFAULT path

I broke this recently when I changed pt_regs->r8..r11 clearing
logic in INT 80 code path.

There is a branch from SYSENTER/SYSCALL code to INT 80 code:
if we fail to retrieve arg6, we return EFAULT. Before this
patch, in this case we don't clear pt_regs->r8..r11.

This patch fixes this. The resulting code is smaller and
simpler.

While at it, remove incorrect comment about syscall dispatching
CALL insn: it does not use RIP-relative addressing form (the
comment was meant to be "TODO: make this rip-relative", and
morphed since then, dropping "TODO").

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/1433701470-28800-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64_compat.S | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 59840e3..5757dde 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -413,9 +413,7 @@ END(entry_SYSCALL_compat)
 
 ia32_badarg:
 	ASM_CLAC
-	movq	$-EFAULT, %rax
-	jmp	ia32_sysret
-
+	movq	$-EFAULT, RAX(%rsp)
 ia32_ret_from_sys_call:
 	xorl	%eax, %eax		/* Do not leak kernel information */
 	movq	%rax, R11(%rsp)
@@ -486,9 +484,7 @@ ia32_do_call:
 	cmpq	$(IA32_NR_syscalls-1), %rax
 	ja	1f
 
-	call	*ia32_sys_call_table(, %rax, 8) /* RIP relative */
-
-ia32_sysret:
+	call	*ia32_sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
 1:
 	jmp	int_ret_from_sys_call
--
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