On 6/20/23 8:07 AM, Nick Desaulniers wrote:
On Tue, Jun 20, 2023 at 10:53 AM Yonghong Song <yhs@xxxxxxxx> wrote:
On 6/20/23 7:38 AM, Nick Desaulniers wrote:
3. you did not run defconfig/menuconfig to have kconfig check for
DWARFv5 support.
Yes, I didn't run defconfig/menuconfig.
That doesn't mean the odd combo of clang+gas doesn't work.
Just like how using scripts/config is a hazard since it also doesn't
run kconfig and allows you to set incompatible configurations. Garbage
in; garbage out.
The kconfigs should prevent you from selecting DWARFv5 if your
toolchain combination doesn't support it; if you run kconfig.
/tmp/video-bios-59fa52.s:4: Error: file number less than one
/tmp/video-bios-59fa52.s:5: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:6: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:7: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:8: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:9: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:10: Error: junk at end of line, first
unrecognized character is `"'
/tmp/video-bios-59fa52.s:68: Error: junk at end of line, first
unrecognized character is `"'
clang: error: assembler command failed with exit code 1 (use -v to see
invocation)
make[4]: *** [/home/yhs/work/bpf-next/scripts/Makefile.build:252:
arch/x86/realmode/rm/video-bios.o] Error 1
make[4]: *** Waiting for unfinished jobs....
/tmp/wakemain-88777c.s: Assembler messages:
/tmp/wakemain-88777c.s:4: Error: junk at end of line, first unrecognized
character is `"'
/tmp/wakemain-88777c.s:4: Error: file number less than one
/tmp/wakemain-88777c.s:5: Error: junk at end of line, first unrecognized
character is `"'
/tmp/wakemain-88777c.s:6: Error: junk at end of line, first unrecognized
character is `"'
/tmp/wakemain-88777c.s:7: Error: junk at end of line, first unrecognized
character is `"'
/tmp/wakemain-88777c.s:8: Error: junk at end of line, first unrecognized
character is `"'
/tmp/wakemain-88777c.s:81: Error: junk at end of line, first
unrecognized character is `"'
/tmp/wakemain-88777c.s:312: Error: junk at end of line, first
unrecognized character is `"'
clang: error: assembler command failed with exit code 1 (use -v to see
invocation)
Potentially because of my local gnu assembler 2.30-120.el8 won't work
It's recorded in lib/Kconfig.debug that 2.35.2 is required for DWARFv5
support if you're using GAS. My machine has 2.40.
with some syntax generated by clang. Mixing clang compiler and arbitrary
gnu assembler are not a good idea (see the above example). It might
I agree, but for older branches of stable which are still supported,
we didn't quite have clang assembler support usable. We still need to
support those branches of stable.
Thanks Florent pointing out 5.10 stable kernels which have this issue.
No, all kernels have this issue, when using `LLVM=1 LLVM_IAS=0`. It's
more likely that someone is using that combination for branches of
stable that predate 4.19 (such as 4.14) but we do still try to support
that combination somewhat, even if we recommend just using `LLVM=1`.
Interop between toolchains is still important, even if "why would you
do that?"
Okay, yes, although 'LLVM=1' is recommended way to compiler clang
based kernel, users can certainly do 'LLVM=1 LLVM_IAS=0' as well
although not recommended. Then it is okay to put a bug fix in
the commit message. Just need to clarify that
- > 5.10 kernel, LLVM=1 (LLVM_IAS=0 is not the default)
is recommended but user can still have LLVM=1 LLVM_IAS=0
to trigger the issue
- <= 5.10 kernel, LLVM=1 (LLVM_IAS=0 is the default) is
recommended in which case gnu as will be used.
I am okay with backporting to old stable kernels if that is needed.
But the patch going to bpf-next should not have a bug-fix tag and
the patch commit message can be tweaked for backport to 5.10 though.
work with close-to-latest gnu assembler.
To support function name like '<fname>.isra', some llvm work will be
needed, and it may take some time.
So in my opinion, this patch is NOT a bug fix. It won't affect distro.
Whether we should backport to the old kernel, I am not sure whether it
is absolutely necessary as casual build can always remove LLVM_IAS=0 or
hack the kernel source itself.
