Re: [linux-stable-rc:linux-4.4.y 1401/1774] drivers/spi/spi-s3c24xx-fiq.S:52: Error: bad instruction `subsne pc, lr, #4'

[Nick Desaulniers <ndesaulniers@google.com>]

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On Thu, Jul 1, 2021 at 3:20 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Thu, Jul 1, 2021 at 12:38 AM kernel test robot <lkp@intel.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.4.y
> > head:   38c92ba3580f0d00e57a55caf8f880aa1a0f2a50
> > commit: 10a0c6746644a4fcaf1ffe2916387e17ba059517 [1401/1774] ARM: s3c: fix fiq for clang IAS
> > config: arm-randconfig-r034-20210630 (attached as .config)
> > compiler: arm-linux-gnueabi-gcc (GCC) 7.5.0
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=10a0c6746644a4fcaf1ffe2916387e17ba059517
> >         git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> >         git fetch --no-tags linux-stable-rc linux-4.4.y
> >         git checkout 10a0c6746644a4fcaf1ffe2916387e17ba059517
> >         # save the attached .config to linux build tree
> >         mkdir build_dir
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-7.5.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash drivers/
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> >    drivers/spi/spi-s3c24xx-fiq.S: Assembler messages:
> > >> drivers/spi/spi-s3c24xx-fiq.S:52: Error: bad instruction `subsne pc,lr,#4'
> >    drivers/spi/spi-s3c24xx-fiq.S:78: Error: bad instruction `subsne pc,lr,#4'
> >    drivers/spi/spi-s3c24xx-fiq.S:102: Error: bad instruction `subsne pc,lr,#4'
>
> Ah, this must be a kernel that never got the unified assembler syntax fixes
> that this requires. It seems they went into linux-5.1 but nothing before that,
> though they may have been backported.
>
> Nick or Nathan, what is the earliest lts kernel series that you would expect
> to work with clang IAS?

5.4+ for A32.

> Should we just drop these fixes for all 4.x.y versions?

Sure, but I'm curious what is missing here that exists further
upstream?  subsne is the correct syntax, isn't it?

F5.1.249 SUB, SUBS (SP minus register)

>> If the destination register is the PC
>> The SUBS variant of the instruction performs an exception return without the use of the stack. Arm
deprecates use of this instruction.
-- 
Thanks,
~Nick Desaulniers