From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752908AbbC1Iku (ORCPT ); Sat, 28 Mar 2015 04:40:50 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47976 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751232AbbC1Ikq (ORCPT ); Sat, 28 Mar 2015 04:40:46 -0400 Date: Sat, 28 Mar 2015 01:40:15 -0700 From: tip-bot for Denys Vlasenko Message-ID: Cc: rostedt@goodmis.org, fweisbec@gmail.com, bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, luto@amacapital.net, oleg@redhat.com, torvalds@linux-foundation.org, mingo@kernel.org, ast@plumgrid.com, wad@chromium.org, hpa@zytor.com, tglx@linutronix.de, keescook@chromium.org Reply-To: rostedt@goodmis.org, fweisbec@gmail.com, dvlasenk@redhat.com, bp@alien8.de, oleg@redhat.com, luto@amacapital.net, linux-kernel@vger.kernel.org, keescook@chromium.org, tglx@linutronix.de, wad@chromium.org, hpa@zytor.com, ast@plumgrid.com, mingo@kernel.org, torvalds@linux-foundation.org In-Reply-To: <1427452582-21624-3-git-send-email-dvlasenk@redhat.com> References: <1427452582-21624-3-git-send-email-dvlasenk@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/asm/entry/32: Make register zero-extension more prominent Git-Commit-ID: 4ee8ec17ba00fce4af042543771f996fb9d98d34 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4ee8ec17ba00fce4af042543771f996fb9d98d34 Gitweb: http://git.kernel.org/tip/4ee8ec17ba00fce4af042543771f996fb9d98d34 Author: Denys Vlasenko AuthorDate: Fri, 27 Mar 2015 11:36:21 +0100 Committer: Ingo Molnar CommitDate: Fri, 27 Mar 2015 12:27:57 +0100 x86/asm/entry/32: Make register zero-extension more prominent There are a couple of syscall argument zero-extension instructions in the 32-bit compat entry code, and it was mentioned that people keep trying to optimize them out, introducing bugs. Make them more visible, and add a "do not remove" comment. Signed-off-by: Denys Vlasenko Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1427452582-21624-3-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/ia32/ia32entry.S | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 7502ff0..dec8c1d 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -122,8 +122,11 @@ ENTRY(ia32_sysenter_target) movq PER_CPU_VAR(cpu_tss + TSS_sp0), %rsp ENABLE_INTERRUPTS(CLBR_NONE) + /* Zero-extending 32-bit regs, do not remove */ + movl %ebp, %ebp + movl %eax, %eax + /* Construct iret frame (ss,rsp,rflags,cs,rip) */ - movl %ebp,%ebp /* zero extension */ pushq_cfi $__USER32_DS /*CFI_REL_OFFSET ss,0*/ pushq_cfi %rbp @@ -134,7 +137,6 @@ ENTRY(ia32_sysenter_target) CFI_REGISTER rip,r10 pushq_cfi $__USER32_CS /*CFI_REL_OFFSET cs,0*/ - movl %eax, %eax /* Store thread_info->sysenter_return in rip stack slot */ pushq_cfi %r10 CFI_REL_OFFSET rip,0 @@ -329,9 +331,11 @@ ENTRY(ia32_cstar_target) movq PER_CPU_VAR(kernel_stack),%rsp ENABLE_INTERRUPTS(CLBR_NONE) + /* Zero-extending 32-bit regs, do not remove */ + movl %eax,%eax + ALLOC_PT_GPREGS_ON_STACK 6*8 /* 6*8: space for orig_ax and iret frame */ SAVE_C_REGS_EXCEPT_RCX_R891011 - movl %eax,%eax /* zero extension */ movq %rax,ORIG_RAX(%rsp) movq %rcx,RIP(%rsp) CFI_REL_OFFSET rip,RIP @@ -471,7 +475,9 @@ ENTRY(ia32_syscall) SWAPGS ENABLE_INTERRUPTS(CLBR_NONE) - movl %eax,%eax + /* Zero-extending 32-bit regs, do not remove */ + movl %eax,%eax + pushq_cfi %rax /* store orig_ax */ cld /* note the registers are not zero extended to the sf.