Re: [tip:core/rseq 25/39] include/linux/rseq_entry.h:132:3: error: invalid operand for instruction

Nathan Chancellor
2025-11-25T23:18:39Z

On Tue, Nov 25, 2025 at 08:38:40AM +0100, Christophe Leroy (CS GROUP) wrote:
>
>
> Le 24/11/2025 à 20:15, Thomas Gleixner a écrit :
> > On Tue, Nov 25 2025 at 01:37, kernel test robot wrote:
> > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core/rseq
> > > head: 21782b3a5cd40892cb2995aa1ec3e74dd1112f1d
> > > commit: abc850e7616c91ebaa3f5ba3617ab0a104d45039 [25/39] rseq: Provide and use rseq_update_user_cs()
> > > config: powerpc-randconfig-002-20251124 (https://download.01.org/0day-ci/archive/20251125/202511250134.i0Jm8d7I-lkp@intel.com/config)
> > > compiler: clang version 16.0.6 (https://github.com/llvm/llvm-project 7cbf1a2591520c2491aa35339f227775f4d3adf6)
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251125/202511250134.i0Jm8d7I-lkp@intel.com/reproduce)
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202511250134.i0Jm8d7I-lkp@intel.com/
> > >
> > > All errors (new ones prefixed by >>):
> > >
> > > In file included from kernel/rseq.c:75:
> > > > > include/linux/rseq_entry.h:132:3: error: invalid operand for instruction
> > > unsafe_get_user(start_ip, &ucs->start_ip, efault);
> > > ^
> > > include/linux/uaccess.h:606:2: note: expanded from macro 'unsafe_get_user'
> > > arch_unsafe_get_user(x, ptr, local_label); \
> > > ^
> > > arch/powerpc/include/asm/uaccess.h:458:2: note: expanded from macro 'arch_unsafe_get_user'
> > > __get_user_size_goto(__gu_val, __gu_addr, sizeof(*(p)), e); \
> > > ^
> > > arch/powerpc/include/asm/uaccess.h:282:2: note: expanded from macro '__get_user_size_goto'
> > > __get_user_size_allowed(x, ptr, size, __gus_retval); \
> > > ^
> > > arch/powerpc/include/asm/uaccess.h:273:10: note: expanded from macro '__get_user_size_allowed'
> > > case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \
> > > ^
> > > arch/powerpc/include/asm/uaccess.h:256:4: note: expanded from macro '__get_user_asm2'
> > > " li %1+1,0\n" \
> > > ^
> > > <inline asm>:7:5: note: instantiated into assembly here
> > > li 31+1,0
> >
> > Definitely not a problem of tip core/rseq. It just ends up in
> > __get_user_asm2() and then the compiler gets unhappy about the PowerPC
> > inline assembly for whatever reason.
>
> I see it is a CLANG build.
>
> CLANG might be less flexible, can you test with following change ?

That avoids the error for me. I notice that this does not reproduce
beyond clang-16 for me so I am going to bisect LLVM to see what fixes
this error.

> diff --git a/arch/powerpc/include/asm/uaccess.h
> b/arch/powerpc/include/asm/uaccess.h
> index 4f5a46a77fa2..33d5f7ade254 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -253,7 +253,7 @@ __gus_failed: \
> ".section .fixup,\"ax\"\n" \
> "4: li %0,%3\n" \
> " li %1,0\n" \
> - " li %1+1,0\n" \
> + " li %L1,0\n" \
> " b 3b\n" \
> ".previous\n" \
> EX_TABLE(1b, 4b) \
>
>
> Thanks
> Christophe