Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965291AbbFJOIu (ORCPT ); Wed, 10 Jun 2015 10:08:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52350 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964909AbbFJOId (ORCPT ); Wed, 10 Jun 2015 10:08:33 -0400 Date: Wed, 10 Jun 2015 09:08:30 -0500 From: Josh Poimboeuf To: Pavel Machek Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , x86@kernel.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Len Brown , linux-pm@vger.kernel.org Subject: Re: [PATCH v5 07/10] x86/asm/acpi: Fix asmvalidate warnings for wakeup_64.S Message-ID: <20150610140830.GA25848@treble.redhat.com> References: <2817f5690aa760a601a614b738545fd60b087bbb.1433937132.git.jpoimboe@redhat.com> <20150610131914.GA25572@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150610131914.GA25572@amd> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4256 Lines: 115 On Wed, Jun 10, 2015 at 03:19:14PM +0200, Pavel Machek wrote: > Hi! > > > Fix the following asmvalidate warnings: > > > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64()+0x15: unsupported jump to outside of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64()+0x55: unsupported jump to outside of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64(): unsupported fallthrough at end of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel()+0x9a: unsupported jump to outside of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel()+0x116: unsupported jump to outside of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel(): unsupported fallthrough at end of function > > asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel(): missing FP_SAVE/RESTORE macros > > > > 1. wakeup_long64() isn't a function that can be called. It's actually > > redirected to via a return instruction in the entry code. It > > shouldn't be annotated as a callable function. Change ENDPROC -> > > PROC accordingly. > > But I see -> END. Oops! It should say -> END. > > 2. do_suspend_lowlevel() is a non-leaf callable function, so > > save/restore the frame pointer with FP_SAVE/RESTORE. > > It does not work with the frame pointer itself. Is FP_SAVE/RESTORE > still neccessary? Will you need FP_RESTORE to wakeup_long64, then? wakeup_long64 jumps to .Lresume_point, which does the FP_RESTORE. > > 3. Remove the unnecessary jump to .Lresume_point, as it just results in > > jumping to the next instruction (which is a nop because of the > > align). Otherwise asmvalidate gets confused by the jump. > > It also results in flushing the pipeline. Ok, I guess this one is unneccessary. > > > 4. Change the "jmp restore_processor_state" to a call instruction, > > because jumping outside the function's boundaries isn't allowed. Now > > restore_processor_state() will return back to do_suspend_lowlevel() > > instead of do_suspend_lowlevel()'s caller. > > > > 5. Remove superfluous rsp changes. > > Did you test the changes? Yes, I verified that it didn't break suspend/resume on my system. > Do you plan to make similar changes to wakeup_32.S? Currently, asmvalidate is x86_64 only, so I'm only fixing the 64-bit stuff right now. > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S > > index 8c35df4..7e442be 100644 > > --- a/arch/x86/kernel/acpi/wakeup_64.S > > +++ b/arch/x86/kernel/acpi/wakeup_64.S > > @@ -5,6 +5,7 @@ > > #include > > #include > > #include > > +#include > > > > # Copyright 2003 Pavel Machek , distribute under GPLv2 > > > > @@ -33,13 +34,13 @@ ENTRY(wakeup_long64) > > > > movq saved_rip, %rax > > jmp *%rax > > -ENDPROC(wakeup_long64) > > +END(wakeup_long64) > > > > This should result in no binary code changes, so that's ok with me... > > > ENTRY(do_suspend_lowlevel) > > - subq $8, %rsp > > + FP_SAVE > > xorl %eax, %eax > > call save_processor_state > > > > Are you sure? Stuff like > movq $saved_context, %rax > movq %rsp, pt_regs_sp(%rax) > > follows. And you did not modify wakeup_long64, which now receives > different value in saved_rsp. Hm, I'm looking hard, but I still don't see a problem with that code. It's saving rsp to the saved_context struct. As I mentioned above, it's ok for the wakeup_long64 path to restore the same rsp value, since it jumps to .Lresume_point which has FP_RESTORE. > > @@ -108,8 +108,9 @@ ENTRY(do_suspend_lowlevel) > > movq pt_regs_r15(%rax), %r15 > > > > xorl %eax, %eax > > - addq $8, %rsp > > - jmp restore_processor_state > > + call restore_processor_state > > + FP_RESTORE > > + ret > > ENDPROC(do_suspend_lowlevel) > > Umm. I rather liked the direct jump. Why? -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/