linux-kernel - Re: [PATCH 2/2] selftests/mm: Fix a build failure on powerpc

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Message-ID: <a1d2c51c-7959-4446-81b7-bfc48ced606e@linux.ibm.com>
Date: Mon, 28 Apr 2025 22:19:28 +0530
From: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
To: "Nysal Jan K.A." <nysal@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>
Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, Kevin Brodsky <kevin.brodsky@....com>,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] selftests/mm: Fix a build failure on powerpc


On 28/04/25 6:49 pm, Nysal Jan K.A. wrote:
> The compiler is unaware of the size of code generated by the ".rept"
> assembler directive. This results in the compiler emitting branch
> instructions where the offset to branch to exceeds the maximum allowed
> value, resulting in build failures like the following:
>
>    CC       protection_keys
>    /tmp/ccypKWAE.s: Assembler messages:
>    /tmp/ccypKWAE.s:2073: Error: operand out of range (0x0000000000020158
>    is not between 0xffffffffffff8000 and 0x0000000000007ffc)
>    /tmp/ccypKWAE.s:2509: Error: operand out of range (0x0000000000020130
>    is not between 0xffffffffffff8000 and 0x0000000000007ffc)
>
> Fix the issue by manually adding nop instructions using the preprocessor.
>
> Fixes: 46036188ea1f5 ("selftests/mm: build with -O2")
> Reported-by: Madhavan Srinivasan <maddy@...ux.ibm.com>
> Signed-off-by: Nysal Jan K.A. <nysal@...ux.ibm.com>
> ---
>   tools/testing/selftests/mm/pkey-powerpc.h | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/pkey-powerpc.h b/tools/testing/selftests/mm/pkey-powerpc.h
> index d8ec906b8120..17bf2d1b0192 100644
> --- a/tools/testing/selftests/mm/pkey-powerpc.h
> +++ b/tools/testing/selftests/mm/pkey-powerpc.h
> @@ -104,8 +104,18 @@ static inline void expect_fault_on_read_execonly_key(void *p1, int pkey)
>   	return;
>   }
>   
> +#define REPEAT_8(s) s s s s s s s s
> +#define REPEAT_64(s) REPEAT_8(s) REPEAT_8(s) REPEAT_8(s) REPEAT_8(s) \
> +		     REPEAT_8(s) REPEAT_8(s) REPEAT_8(s) REPEAT_8(s)
> +#define REPEAT_512(s) REPEAT_64(s) REPEAT_64(s) REPEAT_64(s) REPEAT_64(s) \
> +		      REPEAT_64(s) REPEAT_64(s) REPEAT_64(s) REPEAT_64(s)
> +#define REPEAT_4096(s) REPEAT_512(s) REPEAT_512(s) REPEAT_512(s) REPEAT_512(s) \
> +		       REPEAT_512(s) REPEAT_512(s) REPEAT_512(s) REPEAT_512(s)
> +#define REPEAT_16384(s) REPEAT_4096(s) REPEAT_4096(s) \
> +			REPEAT_4096(s) REPEAT_4096(s)
> +
>   /* 4-byte instructions * 16384 = 64K page */
> -#define __page_o_noops() asm(".rept 16384 ; nop; .endr")
> +#define __page_o_noops() asm(REPEAT_16384("nop\n"))
>   
>   static inline void *malloc_pkey_with_mprotect_subpage(long size, int prot, u16 pkey)
>   {


Tested this patch by applying on top of mainline kernel v6.15-rc4, and 
it fixes the build issue. Hence,


Tested-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>


Without this Patch:


  CC       protection_keys
/tmp/ccG0zLKW.s: Assembler messages:
/tmp/ccG0zLKW.s:1694: Error: operand out of range (0x0000000000020138 is 
not between 0xffffffffffff8000 and 0x0000000000007ffc)
/tmp/ccG0zLKW.s:2577: Error: operand out of range (0x0000000000020110 is 
not between 0xffffffffffff8000 and 0x0000000000007ffc)
In file included from pkey_util.c:5:


With this patch:


make -j 33
/bin/sh ./check_config.sh gcc
   CC       cow
   CC       compaction_test
   CC       gup_longterm
   CC       gup_test
   CC       hmm-tests
   CC       hugetlb-madvise
   CC       hugetlb-read-hwpoison
   CC       hugetlb-soft-offline
   CC       hugepage-mmap
   CC       hugepage-mremap
   CC       hugepage-shm
   CC       hugepage-vmemmap
   CC       khugepaged
   CC       madv_populate
   CC       map_fixed_noreplace
   CC       map_hugetlb
   CC       map_populate
   CC       migration
   CC       mkdirty
   CC       mlock-random-test
   CC       mlock2-tests
   CC       mrelease_test
   CC       mremap_dontunmap
   CC       mremap_test
   CC       mseal_test
   CC       on-fault-limit
   CC       pagemap_ioctl
   CC       thuge-gen
   CC       transhuge-stress
   CC       uffd-stress
   CC       uffd-unit-tests
   CC       uffd-wp-mremap
   CC       split_huge_page_test
   CC       ksm_tests
   CC       ksm_functional_tests
   CC       hugetlb_fault_after_madv
   CC       hugetlb_madv_vs_map
   CC       mdwe_test
   CC       hugetlb_dio
   CC       droppable
   CC       guard-regions
   CC       soft-dirty
   CC       protection_keys
   CC       va_high_addr_switch
   CC       virtual_address_range
   CC       write_to_hugetlbfs
   CC [M]  page_frag_test.o
   MODPOST Module.symvers
   CC [M]  page_frag_test.mod.o
   CC [M]  .module-common.o
   LD [M]  page_frag_test.ko


Regards,

Venkat.