Messages in this thread | | | Date | Tue, 6 Feb 2018 14:52:43 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 4.4 05/53] x86/asm: Use register variable to get stack pointer value |
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On Tue, Feb 06, 2018 at 02:48:45PM -0800, Matthias Kaehlcke wrote: > 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 <aryabinin@virtuozzo.com> > > > > > > > > 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, %<dst>" instructions: > > > > > > > > -mov %rsp,%rdx > > > > -sub %rdx,%rax > > > > -cmp $0x3fff,%rax > > > > -ja ffffffff810722fd <ist_begin_non_atomic+0x2d> > > > > > > > > +sub %rsp,%rax > > > > +cmp $0x3fff,%rax > > > > +ja ffffffff810722fa <ist_begin_non_atomic+0x2a> > > > > > > > > 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 <aryabinin@virtuozzo.com> > > > > Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> > > > > Cc: Andy Lutomirski <luto@kernel.org> > > > > Cc: Linus Torvalds <torvalds@linux-foundation.org> > > > > Cc: Peter Zijlstra <peterz@infradead.org> > > > > Cc: Thomas Gleixner <tglx@linutronix.de> > > > > Link: http://lkml.kernel.org/r/20170929141537.29167-1-aryabinin@virtuozzo.com > > > > Signed-off-by: Ingo Molnar <mingo@kernel.org> > > > > [dwmw2: We want ASM_CALL_CONSTRAINT for retpoline] > > > > Signed-off-by: David Woodhouse <dwmw@amazon.co.ku> > > > > Signed-off-by: Razvan Ghitulete <rga@amazon.de> > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > > > 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 > > > ^ > > > <scratch space>: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 <jpoimboe@redhat.com> > > > 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.
Great, thanks for verifying, now queued up.
greg k-h
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