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SubjectRe: linux-next: Tree for March 8 (BROKEN: arch/x86/kernel/entry_32.S? Debian's binutils/as?)
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On Wed, Mar 9, 2011 at 12:51 AM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * H.J. Lu <hjl.tools@gmail.com> wrote:
>
>> On Tue, Mar 8, 2011 at 12:33 PM, Sedat Dilek <sedat.dilek@googlemail.com> wrote:
>> > On Tue, Mar 8, 2011 at 9:25 PM, Alexander van Heukelum
>> > <heukelum@fastmail.fm> wrote:
>> >> On Tue, 08 Mar 2011 18:53 +0100, "Sedat Dilek" <sedat.dilek@googlemail.com> wrote:
>> >>> On Tue, Mar 8, 2011 at 6:27 PM, Alexander van Heukelum
>> >>> <heukelum@fastmail.fm> wrote:
>> >>> > On Tue, 08 Mar 2011 16:42 +0100, "Sedat Dilek" <sedat.dilek@googlemail.com> wrote:
>> >>> >> On 3/8/11, Sedat Dilek <sedat.dilek@googlemail.com> wrote:
>> >>> >> > On 3/8/11, H.J. Lu <hjl.tools@gmail.com> wrote:
>> >>> >> >> On Tue, Mar 8, 2011 at 2:44 AM, Sedat Dilek <sedat.dilek@googlemail.com>
>> >>> >> >> wrote:
>> >>> >> >>> Hi,
>> >>> >> >>>
>> >>> >> >>> my build of linux-next (next-20110308, the same with the one from
>> >>> >> >>> yesterday) is broken.
>> >>> >> >>> (I translated the German output.)
>> >>> >> >>>
>> >>> >> >>> [ build.log ]
>> >>> >> >>>  AS      arch/x86/kernel/entry_32.o
>> >>> >> >>> /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/entry_32.S:
>> >>> >> >>> Assembler messages:
>> >>> >> >>> /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/entry_32.S:1421:
>> >>> >> >>> Error: .size expression does not evaluate to a constant
>> >>> >> >>> make[6]: *** [arch/x86/kernel/entry_32.o] Fehler 1 (Error 1)
>> >>> >> >>> make[5]: *** [arch/x86/kernel] Fehler 2 (Error 2)
>> >>> >> >>> make[4]: *** [arch/x86] Fehler 2 (Error 2)
>> >>> >> >>> make[4]: *** Warte auf noch nicht beendete Prozesse... (Waiting for
>> >>> >> >>> unfinished jobs...)
>> >>> >> >>>
>> >>> >> >>
>> >>> >> >> This is a kernel bug.  Please use the latest binutils from CVS.
>> >>> >> >> It will tell you which symbol causes this.
>> >>> >> >>
>> >>> >> >>
>> >>> >> >> --
>> >>> >> >> H.J.
>> >>> >> >>
>> >>> >> >
>> >>> >> > Yeah, I have cherry-picked these two upstream commits before you have
>> >>> >> > mentionned it...
>> >>> >> >
>> >>> >> > 0001-Mention-symbol-name-in-non-constant-.size-expression.patch
>> >>> >> >        (Cherry-picked from commit b9521fc0be7945fc842ce1197e241a023378125d)
>> >>> >> > 0002-Revert-the-last-change-on-gas-elf-bad-size.err.patch
>> >>> >> >        (Cherry-picked from commit cbd141bb69f791de7ea1581abe7afb34f0c61288)
>> >>> >> >
>> >>> >> > ... and have built with them a new binutils Debian package.
>> >>> >> >
>> >>> >> > The error looks now like this (sorry for the German output):
>> >>> >> > ...
>> >>> >> >   AS      arch/x86/kernel/entry_32.o
>> >>> >> > /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/entry_32.S:
>> >>> >> > Assembler messages:
>> >>> >> > /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/entry_32.S:1421:
>> >>> >> > Error: .size expression with symbol `apf_page_fault' does not evaluate
>> >>> >> > to a constant
>> >>> >> > make[6]: *** [arch/x86/kernel/entry_32.o] Fehler 1
>> >>> >> > make[5]: *** [arch/x86/kernel] Fehler 2
>> >>> >> > make[5]: *** Warte auf noch nicht beendete Prozesse...
>> >>> >> >
>> >>> >> > Anyway, before more riddling around it would be very helpful to have a
>> >>> >> > clear pointer if there is a fix around... That building, testing and
>> >>> >> > installing took me now several hours.
>> >>> >> > And... yeah, backports to 2.21-branch appreciated.
>> >>> >> >
>> >>> >> > - Sedat -
>> >>> >> >
>> >>> >>
>> >>> >> After a quick look into the source, it seems attached patch fixes the
>> >>> >> issue.
>> >>> >> Is that OK?
>> >>> >
>> >>> > Hi Sedat,
>> >>> >
>> >>> > The patch ( https://lkml.org/lkml/2011/3/8/203 ) is ok, feel free to add
>> >>> > Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
>> >>> >
>> >>> > Better description might be something like:
>> >>> >
>> >>> > i386: Fix mismatched ENTRY/END pair.
>> >>> >
>> >>> > Under CONFIG_KVM_GUEST=y, the following part of entry_32.S causes a compile failure.
>> >>> >
>> >>> > 1409 #ifdef CONFIG_KVM_GUEST
>> >>> > 1410 ENTRY(async_page_fault)
>> >>> > 1411         RING0_EC_FRAME
>> >>> > 1412         pushl $do_async_page_fault
>> >>> > 1413         CFI_ADJUST_CFA_OFFSET 4
>> >>> > 1414         jmp error_code
>> >>> > 1415         CFI_ENDPROC
>> >>> > 1416 END(apf_page_fault)
>> >>> > 1417 #endif
>> >>> >
>> >>> > Replace apf_page_fault with async_page_fault, as intended.
>> >>> >
>> >>> > Greetings,
>> >>> >    Alexander
>> >>> >
>> >>> >> - Sedat -
>> >>> >>
>> >>> >> Email had 1 attachment:
>> >>> >> + 0001-x86-Fix-build-failure-with-binutils-as-from-upstream.patch
>> >>> >>   1k (text/x-patch)
>> >>> >
>> >>>
>> >>> As I said, quick view on the code, quick fix :-).
>> >>>
>> >>> Your description is definitive more meaningful.
>> >>> I can refresh my patch and add your ACK.
>> >>>
>> >>> Anyway, I continued after dinner and with the above patch I ran into
>> >>> the next problem:
>> >>> [ build.log ]
>> >>> ...
>> >>>   AS      arch/x86/kernel/acpi/wakeup_rm.o
>> >>> /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/acpi/wakeup_rm.S:
>> >>> Assembler messages:
>> >>> /home/sd/src/linux-2.6/linux-2.6.38-rc7/debian/build/source_i386_none/arch/x86/kernel/acpi/wakeup_rm.S:12:
>> >>> Error: .size expression with symbol `wakeup_code_start' does not
>> >>> evaluate to a constant
>> >>
>> >> No idea what's wrong there. But my version of wakeup_rm.S has only 10 lines...
>> >>
>> >>     1  /*
>> >>     2   * Wrapper script for the realmode binary as a transport object
>> >>     3   * before copying to low memory.
>> >>     4   */
>> >>     5          .section ".rodata","a"
>> >>     6          .globl  wakeup_code_start, wakeup_code_end
>> >>     7  wakeup_code_start:
>> >>     8          .incbin "arch/x86/kernel/acpi/realmode/wakeup.bin"
>> >>     9  wakeup_code_end:
>> >>    10          .size   wakeup_code_start, .-wakeup_code_start
>> >>
>> >> And it compiles just fine.
>> >> The fix for entry_32.S is valid, though, and necessary for mainline.
>> >>
>> >> Greetings,
>> >>    Alexander
>> >>
>> >>> I am unsure how to fix that and open for feedback.
>> >>>
>> >>> - Sedat -
>> >>>
>> >>
>> >
>> > The file in linux-next (next-20110308) looks different (the above code
>> > looks more logical to me)
>> >
>> > [ arch/x86/kernel/acpi/wakeup_rm.S ]
>> >
>> > /*
>> >  * Wrapper script for the realmode binary as a transport object
>> >  * before copying to low memory.
>> >  */
>> > #include <asm/page_types.h>
>> >
>> >        .section ".x86_trampoline","a"
>> >        .balign PAGE_SIZE
>> >        .globl  acpi_wakeup_code
>> > acpi_wakeup_code:
>> >        .incbin "arch/x86/kernel/acpi/realmode/wakeup.bin"
>> >        .size   wakeup_code_start, .-wakeup_code_start
>> >
>>
>> Those are simply wrong.  2.6.38-rc8 is OK.
>
> 2.6.37-rc8 is not OK: for example commit 631bc4878220932fe67fc46fc7cf7cccdb1ec597 is
> already upstream and if you enable KVM you see a broken kernel build with new
> binutils. This is from 2.6.38-rc8:
>
>  #ifdef CONFIG_KVM_GUEST
>  ENTRY(async_page_fault)
>        RING0_EC_FRAME
>        pushl $do_async_page_fault
>        CFI_ADJUST_CFA_OFFSET 4
>        jmp error_code
>        CFI_ENDPROC
>  END(apf_page_fault)
>  #endif
>
> Yes, the .size directive not matching up is technically a bug, but it was not
> checked by binutils before, for *years* - and you cannot just flip a switch and
> break who knows how much code.
>
> You need to at least emit a warning for some time to give people a *chance* to fix
> bugs - not just stuff an incompatible binutils down their throat and break the
> kernel build for thousands of commits and break bisection.

If kernel doesn't use/need symbol size, don't put it in assembly code.

> This binutils change is breaking numerous upstream kernel builds (and is making
> bisection with new binutils impossible) for no particular good reason: binutils was
> capable to figure out the symbol name before this change.
>

That is totally false. The old assembler just generates incorrect size and
It couldn't read the programmer's mind to find the correct symbol name.


--
H.J.
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