Missing operand for tlbie instruction on Power7

On 10/2/15, Laura Abbott <labbott@redhat.com> wrote:
> Hi,
>
> We received a report (https://bugzilla.redhat.com/show_bug.cgi?id=1267395)
> of bad assembly
> when compiling on powerpc with little endian
>
> [labbott@labbott-redhat-machine linux_upstream]$ make ARCH=powerpc
> CROSS_COMPILE=powerpc64-linux-gnu-
>    CHK     include/config/kernel.release
>    CHK     include/generated/uapi/linux/version.h
>    CHK     include/generated/utsrelease.h
>    CHK     include/generated/bounds.h
>    CHK     include/generated/timeconst.h
>    CHK     include/generated/asm-offsets.h
>    CALL    scripts/checksyscalls.sh
>    CHK     include/generated/compile.h
>    CALL    arch/powerpc/kernel/systbl_chk.sh
>    AS      arch/powerpc/kernel/swsusp_asm64.o
> arch/powerpc/kernel/swsusp_asm64.S: Assembler messages:
> arch/powerpc/kernel/swsusp_asm64.S:188: Error: missing operand
> scripts/Makefile.build:294: recipe for target
> 'arch/powerpc/kernel/swsusp_asm64.o' failed
> make[1]: *** [arch/powerpc/kernel/swsusp_asm64.o] Error 1
> Makefile:941: recipe for target 'arch/powerpc/kernel' failed
> make: *** [arch/powerpc/kernel] Error 2
>
> This problem started happening after a binutils update:
>
> [labbott@labbott-redhat-machine linux_upstream]$ powerpc64-linux-gnu-as
> --version
> GNU assembler version 2.25.1-1.fc22
> Copyright (C) 2014 Free Software Foundation, Inc.
> This program is free software; you may redistribute it under the terms of
> the GNU General Public License version 3 or later.
> This program has absolutely no warranty.
> This assembler was configured for a target of `powerpc64-linux-gnu'.
> [labbott@labbott-redhat-machine linux_upstream]$
>
> After some discussion with the binutils folks, it turns out that the tlbie
> instruction actually requires another operand and binutils was updated to
> check for this https://sourceware.org/ml/binutils/2015-05/msg00133.html .
>
> The code sequence in arch/powerpc/include/asm/ppc_asm.h now needs to be
> updated:
>
> #if !defined(CONFIG_4xx) && !defined(CONFIG_8xx)
> #define tlbia                                   \
>          li      r4,1024;                        \
>          mtctr   r4;                             \
>          lis     r4,KERNELBASE@h;                \
> 0:      tlbie   r4;                             \
>          addi    r4,r4,0x1000;                   \
>          bdnz    0b
> #endif
>
> I don't know enough ppc assembly to properly fix this but I can test.

Could you please test the patch attached?



>
> Thanks,
> Laura
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev

On Fri, 2015-10-02 at 22:03 +0300, Denis Kirjanov wrote:
> arch/powerpc/kernel/swsusp_asm64.S: Assembler messages:
>> arch/powerpc/kernel/swsusp_asm64.S:188: Error: missing operand
>> scripts/Makefile.build:294: recipe for target
>> 'arch/powerpc/kernel/swsusp_asm64.o' failed
>> make[1]: *** [arch/powerpc/kernel/swsusp_asm64.o] Error 1
>> Makefile:941: recipe for target 'arch/powerpc/kernel' failed
>> make: *** [arch/powerpc/kernel] Error 2
[snip]
>> I don't know enough ppc assembly to properly fix this but I can test.
> 
> Could you please test the patch attached?
[snip]
> -0:     tlbie   r4;                             \
> +0:     tlbie   r4, 0;                          \

This isn't correct.  With POWER7 and later (which this compile
is, since it's on LE), the tlbie instruction takes two register
operands:

    tlbie RB, RS

The tlbie instruction on pre POWER7 cpus had one required register
operand (RB) and an optional second L operand, where if you omitted
it, it was the same as using "0":

    tlbie RB, L

This is a POWER7 and later build, so your change which adds the "0"
above is really adding r0 for RS.  The new tlbie instruction doesn't
treat r0 specially, so you'll be using whatever random bits which
happen to be in r0 which I don't think that is what you want.


Peter