Re: [next-20260313] kernel build fails with “ar: unrecognized option '--thin'”

Mon Mar 16 20:48:50 AEDT 2026

On 16/03/26 11:41 am, Venkat Rao Bagalkote wrote:
> Greetings!!
>
>
> I am seeing a repeatable build failure in current mainline when 
> generating vmlinux.a.
>
> The build stops with an error from ar regarding the --thin option.
>
> This issue is seen on IBM Power11 System.
>
> Attached is the .config file.
>
> Also, I see couple of build warnings, before the build fails.
> Note: These warnings and build failure are not see on 20260312 build.
>
>
> Warnings:
>
> In file included from ./include/linux/seqlock.h:20,
>                  from ./include/linux/mmzone.h:17,
>                  from ./include/linux/gfp.h:7,
>                  from ./include/linux/umh.h:4,
>                  from ./include/linux/kmod.h:9,
>                  from ./include/linux/module.h:18,
>                  from drivers/char/nvram.c:34:
> drivers/char/nvram.c:56:21: warning: ‘nvram_mutex’ defined but not 
> used [-Wunused-variable]
>    56 | static DEFINE_MUTEX(nvram_mutex);
>       |                     ^~~~~~~~~~~
> ./include/linux/mutex.h:87:22: note: in definition of macro 
> ‘DEFINE_MUTEX’
>    87 |         struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
>
>
> Below are the failure logs.
>
>
> ar: unrecognized option '--thin'
> Usage: ar [emulation options] [-]{dmpqrstx}[abcDfilMNoOPsSTuvV] 
> [--plugin <name>] [member-name] [count] archive-file file...
>        ar -M [<mri-script]
>  commands:
>   d            - delete file(s) from the archive
>   m[ab]        - move file(s) in the archive
>   p            - print file(s) found in the archive
>   q[f]         - quick append file(s) to the archive
>   r[ab][f][u]  - replace existing or insert new file(s) into the archive
>   s            - act as ranlib
>   t[O][v]      - display contents of the archive
>   x[o]         - extract file(s) from the archive
>  command specific modifiers:
>   [a]          - put file(s) after [member-name]
>   [b]          - put file(s) before [member-name] (same as [i])
>   [D]          - use zero for timestamps and uids/gids
>   [U]          - use actual timestamps and uids/gids (default)
>   [N]          - use instance [count] of name
>   [f]          - truncate inserted file names
>   [P]          - use full path names when matching
>   [o]          - preserve original dates
>   [O]          - display offsets of files in the archive
>   [u]          - only replace files that are newer than current 
> archive contents
>  generic modifiers:
>   [c]          - do not warn if the library had to be created
>   [s]          - create an archive index (cf. ranlib)
>   [S]          - do not build a symbol table
>   [T]          - make a thin archive
>   [v]          - be verbose
>   [V]          - display the version number
>   @<file>      - read options from <file>
>   --target=BFDNAME - specify the target object format as BFDNAME
>   --output=DIRNAME - specify the output directory for extraction 
> operations
>  optional:
>   --plugin <p> - load the specified plugin
>  emulation options:
>   No emulation specific options
> ar: supported targets: elf64-powerpcle elf64-powerpc elf32-powerpcle 
> elf32-powerpc aixcoff-rs6000 aixcoff64-rs6000 aix5coff64-rs6000 
> elf64-little elf64-big elf32-little elf32-big ppcboot elf32-spu 
> pe-x86-64 pei-x86-64 pe-bigobj-x86-64 elf64-x86-64 elf64-l1om 
> elf64-k1om pe-i386 pei-i386 elf32-i386 elf32-iamcu elf64-bpfle 
> elf64-bpfbe srec symbolsrec verilog tekhex binary ihex plugin
> make[2]: *** [scripts/Makefile.vmlinux_a:22: built-in-fixup.a] Error 1
> make[1]: *** [/root/linux-next/Makefile:1278: vmlinux_a] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
>
>

Git bisect is pointing to below commit as first bad commit.

4519221849f26a3b0c0dc45b9914a0f9cdc00740 is the first bad commit
commit 4519221849f26a3b0c0dc45b9914a0f9cdc00740 (HEAD)
Author: Masahiro Yamada <masahiroy at kernel.org>
Date:   Tue Oct 28 18:28:21 2025 +0000

     kbuild: move vmlinux.a build rule to scripts/Makefile.vmlinux_a

     Move the build rule for vmlinux.a to a separate file in preparation
     for supporting distributed builds with Clang ThinLTO.

     Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
     Tested-by: Rong Xu <xur at google.com>
     Reviewed-by: Nathan Chancellor <nathan at kernel.org>
     Tested-by: Nathan Chancellor <nathan at kernel.org>
     Link: https://patch.msgid.link/20251028182822.3210436-2-xur@google.com
     Signed-off-by: Nicolas Schier <nsc at kernel.org>

  Makefile                   | 16 ++++++----------
  scripts/Makefile.vmlinux_a | 46 
++++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 52 insertions(+), 10 deletions(-)
  create mode 100644 scripts/Makefile.vmlinux_a

Git bisect log:

git bisect log
git bisect start
# status: waiting for both good and bad commits
# bad: [b84a0ebe421ca56995ff78b66307667b62b3a900] Add linux-next 
specific files for 20260313
git bisect bad b84a0ebe421ca56995ff78b66307667b62b3a900
# status: waiting for good commit(s), bad commit known
# good: [1f318b96cc84d7c2ab792fcc0bfd42a7ca890681] Linux 7.0-rc3
git bisect good 1f318b96cc84d7c2ab792fcc0bfd42a7ca890681
# bad: [ddc6cc7f66af99528c8a827d4ba835fb650b6446] Merge branch 'main' of 
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect bad ddc6cc7f66af99528c8a827d4ba835fb650b6446
# bad: [06da2b04b5f2f11952969e813d8dd8f0c7617b79] Merge branch 
'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux.git
git bisect bad 06da2b04b5f2f11952969e813d8dd8f0c7617b79
# good: [85689b69dad24170252dc5be8238de2388e68871] Merge branch 
'rust-analyzer-next' of https://github.com/Rust-for-Linux/linux.git
git bisect good 85689b69dad24170252dc5be8238de2388e68871
# bad: [5457bcbc73733c7268108a2acfc35c6505f3cbf3] Merge branch 
'for-next/core' of 
https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
git bisect bad 5457bcbc73733c7268108a2acfc35c6505f3cbf3
# good: [5473c1ee6462a5d3543c2b4c7dc6f1aac71eb082] userfaultfd: 
introduce mfill_copy_folio_locked() helper
git bisect good 5473c1ee6462a5d3543c2b4c7dc6f1aac71eb082
# good: [d1b4433308592363d133a788f0443d5d63872bdd] CREDITS: simplify the 
end-of-file alphabetical order comment
git bisect good d1b4433308592363d133a788f0443d5d63872bdd
# good: [ff28b3bb65c3eafeece9334b908e62c492f341e5] mm/damon/core: allow 
quota goals set zero effective size quota
git bisect good ff28b3bb65c3eafeece9334b908e62c492f341e5
# bad: [4f6ad15007039f296611ee76dad9f6ed071e63fb] Merge branch 
'kbuild-for-next' of 
https://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux.git
git bisect bad 4f6ad15007039f296611ee76dad9f6ed071e63fb
# good: [07bc816c63b94e83dbe311d84b0278e54f6b83db] Merge branch 
'mm-unstable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect good 07bc816c63b94e83dbe311d84b0278e54f6b83db
# good: [aad94ba683adc6ff7ff4e29ae48184b42782dd97] kbuild: uapi: provide 
stub includes for some libc headers
git bisect good aad94ba683adc6ff7ff4e29ae48184b42782dd97
# good: [0d3fccf68d9873a3c824fb70be0dbb2c4642aa90] kbuild: Use 
'-fms-anonymous-structs' if it is available
git bisect good 0d3fccf68d9873a3c824fb70be0dbb2c4642aa90
# bad: [8e786d89efce381609bd7fb9e8d6c52429e8b753] kbuild: distributed 
build support for Clang ThinLTO
git bisect bad 8e786d89efce381609bd7fb9e8d6c52429e8b753
# bad: [4519221849f26a3b0c0dc45b9914a0f9cdc00740] kbuild: move vmlinux.a 
build rule to scripts/Makefile.vmlinux_a
git bisect bad 4519221849f26a3b0c0dc45b9914a0f9cdc00740
# first bad commit: [4519221849f26a3b0c0dc45b9914a0f9cdc00740] kbuild: 
move vmlinux.a build rule to scripts/Makefile.vmlinux_a

Regards,

Venkat.

>
> If you happen to fix this issue, please add below tag.
>
>
> Reported-by: Venkat Rao Bagalkote <venkat88 at linux.ibm.com>
>
>
> Regards,
>
> Venkat.