From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1517957327; cv=none; d=google.com; s=arc-20160816; b=Nku81mN9fTggpffBrRHha0imDTAnQqKDsBGE3XCuXcQzbQ7/bngLABfsQ77z0Qi52/ dEbPmglVFbKYk4PfkaaUN/5WZYPZtOqbAUHJP9Qy8Psf6HMgE2KymxzxCg4fCjkduJcK rCexH9q7j5J9P4grbAohOxTz+cOgKTzzcuPmbseQv2AX2w3QiW7ZqehiaIvjc6aq1As3 vXe3+jYnTRwlic9qt4SlvbswTofJHzGB1vyUSxGb11VknnwEOINA3+j/MGE1ar4QckEu nq6orXkJWlM6xSntvqMWfCviVCwSXEFJWnrDZk1viQiDqqaQCXJd83i2XD3ILgQuPLiN T5sA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature :arc-authentication-results; bh=kj4gruxTcwEzQcZ4OkDZjboWslHQyU+jq//Oh3wCf8Y=; b=Rxumn4uuYQ3MLTbl+fWlPclyG7SnjSBISmpROLnPZGMav9tlWkDw9LquZlcV7FXc/p bAx0mgsjriLk+9l7zP+ga95T4Kn/ShttULnaMZMoSbKjtFSLOwt+i2m2gsFUHcwiuJDR LqWcLJybOczW4u4BD343ZNjWNHJ5GTeJiKT3w8LO64N1J5gWOHJGfd2blrWblQbE5ALA vCqysc80Ert+qJg8MmMqlDzN4mLCIY/qS+ozs38fPj+DKEGrwtPLb6QWV3CkGIc0wPUS jAtMILHUutJBFD0/yE8Vb+x1No4EG9bhw8/AzxFGBYY6qbihaUvnjPnJ1o5kHQ83FU3Y L3tA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=NrJC1naj; spf=pass (google.com: domain of mka@chromium.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=mka@chromium.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Authentication-Results: mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=NrJC1naj; spf=pass (google.com: domain of mka@chromium.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=mka@chromium.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org X-Google-Smtp-Source: AH8x225/Hx2WGNpLmMFuJU2mV7gvTYJHISpS2rgvqxGdTqYLKZjVaSv7QtyGbozvzdWQE8O0LZlQDQ== Date: Tue, 6 Feb 2018 14:48:45 -0800 From: Matthias Kaehlcke To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Andrey Ryabinin , Josh Poimboeuf , Andy Lutomirski , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , David Woodhouse , Razvan Ghitulete , Guenter Roeck , Nick Desaulniers , Greg Hackmann Subject: Re: [PATCH 4.4 05/53] x86/asm: Use register variable to get stack pointer value Message-ID: <20180206224845.GA116483@google.com> References: <20180122083910.299610926@linuxfoundation.org> <20180122083910.527513802@linuxfoundation.org> <20180206215941.GA99249@google.com> <20180206223706.GC23990@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180206223706.GC23990@kroah.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcSW1wb3J0YW50Ig==?= X-GMAIL-THRID: =?utf-8?q?1590281391571990781?= X-GMAIL-MSGID: =?utf-8?q?1591693622219146736?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: El Tue, Feb 06, 2018 at 02:37:06PM -0800 Greg Kroah-Hartman ha dit: > On Tue, Feb 06, 2018 at 01:59:41PM -0800, Matthias Kaehlcke wrote: > > Hi Greg, > > > > El Mon, Jan 22, 2018 at 09:39:57AM +0100 Greg Kroah-Hartman ha dit: > > > > > 4.4-stable review patch. If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Andrey Ryabinin > > > > > > commit 196bd485ee4f03ce4c690bfcf38138abfcd0a4bc upstream. > > > > > > Currently we use current_stack_pointer() function to get the value > > > of the stack pointer register. Since commit: > > > > > > f5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang") > > > > > > ... we have a stack register variable declared. It can be used instead of > > > current_stack_pointer() function which allows to optimize away some > > > excessive "mov %rsp, %" instructions: > > > > > > -mov %rsp,%rdx > > > -sub %rdx,%rax > > > -cmp $0x3fff,%rax > > > -ja ffffffff810722fd > > > > > > +sub %rsp,%rax > > > +cmp $0x3fff,%rax > > > +ja ffffffff810722fa > > > > > > Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer > > > and use it instead of the removed function. > > > > > > Signed-off-by: Andrey Ryabinin > > > Reviewed-by: Josh Poimboeuf > > > Cc: Andy Lutomirski > > > Cc: Linus Torvalds > > > Cc: Peter Zijlstra > > > Cc: Thomas Gleixner > > > Link: http://lkml.kernel.org/r/20170929141537.29167-1-aryabinin@virtuozzo.com > > > Signed-off-by: Ingo Molnar > > > [dwmw2: We want ASM_CALL_CONSTRAINT for retpoline] > > > Signed-off-by: David Woodhouse > > > Signed-off-by: Razvan Ghitulete > > > Signed-off-by: Greg Kroah-Hartman > > > > We recently merged this patch to the Chrome OS kernel tree and it > > broke our x86 builds with clang: > > > > arch/x86/include/asm/asm.h:116:50: error: register 'rsp' unsuitable for global register variables on this target > > register unsigned long current_stack_pointer asm(_ASM_SP); > > ^ > > arch/x86/include/asm/asm.h:41:18: note: expanded from macro '_ASM_SP' > > #define _ASM_SP __ASM_REG(sp) > > ^ > > arch/x86/include/asm/asm.h:24:32: note: expanded from macro '__ASM_REG' > > #define __ASM_REG(reg) __ASM_SEL_RAW(e##reg, r##reg) > > ^ > > arch/x86/include/asm/asm.h:19:29: note: expanded from macro '__ASM_SEL_RAW' > > # define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(b) > > ^ > > arch/x86/include/asm/asm.h:10:32: note: expanded from macro '__ASM_FORM_RAW' > > # define __ASM_FORM_RAW(x) #x > > ^ > > :4:1: note: expanded from here > > "rsp" > > ^ > > 1 error generated. > > > > > > This can be fixed by also integrating the following patch: > > > > commit 520a13c530aeb5f63e011d668c42db1af19ed349 > > Author: Josh Poimboeuf > > Date: Thu Sep 28 16:58:26 2017 -0500 > > > > x86/asm: Fix inline asm call constraints for GCC 4.4 > > > > > > Admittedly a v4.4 kernel built with clang + LTS merges is a very > > special case and we can fix this in Chrome OS by integrating the above > > patch locally. Still it would be good to get it into stable to avoid > > others from running into this, especially since the fix is very > > simple. > > > > Actually I just noticed that the patch also isn't in v4.9, which could > > extend the number of affected 'users' significantly, so I think we > > almost certainly want Josh's patch in stable. > > That patch doesn't apply cleanly to the 4.4.y or 4.9.y trees anymore. > It seems that only one hunk of it is really needed, the #ifndef change, > right? If so, I'll be glad to apply that portion. Indeed, only the #ifndef change is needed. Thanks! m.