Re: [linux-next:master 3665/11714] {standard input}:2644: Error: pcrel offset for branch to .LS0015 too far (0x3e)

[Feng Tang <feng.tang@intel.com>]

Add linux-csky list and originally cced people and replace the linux-mm
with linux-kbuild list, which match the discussion better and avoid
email noise for mm people.

On Tue, Jun 22, 2021 at 05:48:18PM +0800, Tang, Feng wrote:
> On Tue, Jun 22, 2021 at 09:49:05AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   889bab4c367a0ef58208fd80fafa74bb6e2dca26
> > commit: cf536e185869d4815d506e777bcca6edd9966a6e [3665/11714] Makefile: extend 32B aligned debug option to 64B aligned
> > config: csky-randconfig-c024-20210622 (attached as .config)
> > compiler: csky-linux-gcc (GCC) 9.3.0
> > 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/next/linux-next.git/commit/?id=cf536e185869d4815d506e777bcca6edd9966a6e
> >         git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> >         git fetch --no-tags linux-next master
> >         git checkout cf536e185869d4815d506e777bcca6edd9966a6e
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=csky 

> Thanks for the report. 
> 
> I just reproduced the issue locally, with similar log:
> 
>   CC      drivers/target/target_core_sbc.o
> {standard input}: Assembler messages:
> {standard input}:2644: Error: pcrel offset for branch to .LS0015 too far (0x3e)
> {standard input}:2653: Error: pcrel offset for branch to .LS0015 too far (0x34)
> {standard input}:2659: Error: pcrel offset for branch to .LS0015 too far (0x2c)
> make[2]: *** [scripts/Makefile.build:272: drivers/target/target_core_sbc.o] Error 1
> m
> 
> And when I changed the function align option from 64 to 32, the
> compilation did pass, so this looks to be related with the alignment
> option.
> 
> I'm not very familiar with compiler, and will try to check more.

I did some check and found the error info comes from the assembler
for 'csky' in binutils' gas/config/tc-csky.c, and I could hardly
dive deeper into the code as limited by my knowledge.


> I know it works on x86_64, but don't know how about other
> architectures, and if 'csky' is the only not working one, one
> workaround I can think of is to add kconfig dependency for !csky 

I reused the 0day's reproduce process, and tried on arm64, powerpc64,
and arc, the kernel compilation all succeeded. So maybe we can
add some dependency for this debug option like:

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3cf48998a374..eb035b31657f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -415,7 +415,8 @@ config SECTION_MISMATCH_WARN_ONLY
 	  If unsure, say Y.
 
 config DEBUG_FORCE_FUNCTION_ALIGN_64B
-	bool "Force all function address 64B aligned" if EXPERT
+	bool "Force all function address 64B aligned"
+	depends on EXPERT && (X86_64 || ARM64 || PPC32 || PPC64 || ARC)
 	help
 	  There are cases that a commit from one domain changes the function
 	  address alignment of other domains, and cause magic performance

Any comments? thanks!

- Feng

> Thanks,
> Feng
> 
>