From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753606AbbDBOhH (ORCPT ); Thu, 2 Apr 2015 10:37:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42956 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753057AbbDBOhB (ORCPT ); Thu, 2 Apr 2015 10:37:01 -0400 From: Denys Vlasenko To: Ingo Molnar Cc: Denys Vlasenko , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/9] x86/asm/entry/64: do not SAVE_EXTRA_REGS in stub_sigreturn Date: Thu, 2 Apr 2015 16:36:12 +0200 Message-Id: <1427985378-4287-3-git-send-email-dvlasenk@redhat.com> In-Reply-To: <1427985378-4287-1-git-send-email-dvlasenk@redhat.com> References: <1427985378-4287-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org stub_sigreturn ignores old values of pt_regs->REG for all general-purpose registers, it sets them to values saved on userspace signal stack. Which is hardly surprising - it would be a bug if it would use pt_regs->REG. sigreturn must restore all registers. Therefore, SAVE_EXTRA_REGS in it ought to be redundant. It is a leftover from the time SAVE_EXTRA_REGS wasn't only saving registers, but it also was extending stack to "full" pt_regs. Delete this SAVE_EXTRA_REGS. Run-tested. Signed-off-by: Denys Vlasenko CC: Linus Torvalds CC: Steven Rostedt CC: Ingo Molnar CC: Borislav Petkov CC: "H. Peter Anvin" CC: Andy Lutomirski CC: Oleg Nesterov CC: Frederic Weisbecker CC: Alexei Starovoitov CC: Will Drewry CC: Kees Cook CC: x86@kernel.org CC: linux-kernel@vger.kernel.org --- arch/x86/kernel/entry_64.S | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index ec51598..1cf245d 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -447,7 +447,12 @@ ENTRY(stub_rt_sigreturn) CFI_STARTPROC addq $8, %rsp DEFAULT_FRAME 0 - SAVE_EXTRA_REGS + /* + * Despite RESTORE_EXTRA_REGS in return_from_stub, + * no need to SAVE_EXTRA_REGS here: + * sys_rt_sigreturn overwrites all general purpose pt_regs->REGs + * on stack, for RESTORE_{EXTRA,C}_REGS to pick them up. + */ call sys_rt_sigreturn jmp return_from_stub CFI_ENDPROC @@ -458,7 +463,7 @@ ENTRY(stub_x32_rt_sigreturn) CFI_STARTPROC addq $8, %rsp DEFAULT_FRAME 0 - SAVE_EXTRA_REGS + /* No need to SAVE_EXTRA_REGS */ call sys32_x32_rt_sigreturn jmp return_from_stub CFI_ENDPROC -- 1.8.1.4