Message-ID: <d3d616f3-0f0e-4ecf-bd47-f58a34dcf16b@oracle.com>
Date: Mon, 15 Dec 2025 17:00:48 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Guenter Roeck <linux@...ck-us.net>,
        "Maciej W. Rozycki"
 <macro@...am.me.uk>
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, jpoimboe@...nel.org,
        peterz@...radead.org, david.laight.linux@...il.com
Subject: Re: [PATCH v6 03/30] objtool: Disassemble code with libopcodes
 instead of running objdump


On 12/10/25 22:54, Guenter Roeck wrote:
> On 12/10/25 10:42, Guenter Roeck wrote:
> ...
>>> That's weird because the "clean" rule in tools/objtool/Makefile should remove the
>>> entire tools/objtool/feature directory:
>>>
>>> $ cat tools/objtool/Makefile
>>> ...
>>> clean: $(LIBSUBCMD)-clean
>>>      $(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
>>>      $(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
>>>      $(Q)$(RM) $(OUTPUT)arch/x86/lib/cpu-feature-names.c $(OUTPUT)fixdep
>>>      $(Q)$(RM) $(OUTPUT)arch/x86/lib/inat-tables.c $(OUTPUT)fixdep
>>>      $(Q)$(RM) -- $(OUTPUT)FEATURE-DUMP.objtool
>>>      $(Q)$(RM) -r -- $(OUTPUT)feature
>>>
>>> see $(Q)$(RM) -r -- $(OUTPUT)feature
>>>
>>
>> $ find . -name test-disassembler-init-styled*
>> ./tools/build/feature/test-disassembler-init-styled.c
>> ./tools/objtool/feature/test-disassembler-init-styled.make.output
>> ./tools/objtool/feature/test-disassembler-init-styled.d
>> $ make clean
>>    CLEAN   arch/x86/lib
>>    CLEAN   certs
>>    CLEAN   arch/x86/entry/vdso
>>    CLEAN   init
>>    CLEAN   lib/crc
>>    CLEAN   arch/x86/tools
>>    CLEAN   arch/x86/realmode/rm
>>    CLEAN   security/selinux
>>    CLEAN   usr
>>    CLEAN   .
>> $ find . -name test-disassembler-init-styled*
>> ./tools/build/feature/test-disassembler-init-styled.c
>> ./tools/objtool/feature/test-disassembler-init-styled.make.output
>> ./tools/objtool/feature/test-disassembler-init-styled.d
>> $
>>
>> "make clean" does not execute the cleanup in tools/objtool. I have to run
>> "make -C tools/objtool clean". "make mrproper" doesn't clean tools either.
>>
>> I guess that is on purpose ?
>>
>> Anyway, even "make -C tools/objtool clean" doesn't solve my problem if I build with
>> an out-of-tree toolchain. Turns out that, in this case, test-disassembler-init-styled
>> is build with binutils from the toolchain (which succeeds because its binutils
>> version is more recent). Later on, the actual build of disas.c fails because it uses
>> the system toolchain.
>>
> 
> This is actually even worse than I thought.
> 
> $ git clean -d -x -f -q
> $ make defconfig
> $ make -j40
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.c
> ./tools/objtool/feature/test-disassembler-init-styled.make.output
> ./tools/objtool/feature/test-disassembler-init-styled.d
> $ make -C tools/objtool/ clean
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.make.output
> ./tools/build/feature/test-disassembler-init-styled.c
> ./tools/build/feature/test-disassembler-init-styled.d
> $ rm -f ./tools/build/feature/test-disassembler-init-styled.make.output ./tools/build/feature/test-disassembler-init-styled.d
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.c
> $ make -C tools/objtool/ clean
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.make.output
> ./tools/build/feature/test-disassembler-init-styled.c
> ./tools/build/feature/test-disassembler-init-styled.d
> 
> Repeated with local toolchain:
> $ git clean -d -x -f -q
> $ make-x86 defconfig
> $ make-x86 -j40
>    (fails)
> $ make-x86 -C tools/objtool clean
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.c
> ./tools/objtool/feature/test-disassembler-init-styled.make.output
> ./tools/objtool/feature/test-disassembler-init-styled.bin
> ./tools/objtool/feature/test-disassembler-init-styled.d
> 
> So the "make clean" command actually (re-)creates the .bin file. Worse,
> if I now run
> 
> $ make -C tools/objtool clean
> 
> with the system toolchain, the .bin file is not removed.
> 
> $ find . -name test-disassembler-init-styled*
> ./tools/build/feature/test-disassembler-init-styled.make.output
> ./tools/build/feature/test-disassembler-init-styled.bin
> ./tools/build/feature/test-disassembler-init-styled.c
> ./tools/build/feature/test-disassembler-init-styled.d
> 
> The local toolchain used in this example is gcc 13.3.0 with binutils 2.42.
> 

I think I've found the issue. The problem is that the feature check for objtool
is also run for the "clean" target, and this creates the
tools/build/feature/test-disassembler-init-styled.* files.

The change below should fix this problem. I will prepare a patch. Note that
you will still need to run "make -C tools/objtool clean" (I don't know the
reason for  "make clean" not to cleanup tools/objtool).

Thanks,

alex.

-----

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index ad6e1ec706ce0..0c9238cacdcea 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -77,7 +77,22 @@ HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)"
  FEATURE_USER = .objtool
  FEATURE_TESTS = libbfd disassembler-init-styled
  FEATURE_DISPLAY =
+
+check_feat := 1
+NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
+ifdef MAKECMDGOALS
+ifeq ($(filter-out $(NON_CHECK_FEAT_TARGETS),$(MAKECMDGOALS)),)
+  check_feat := 0
+endif
+endif
+
+ifeq ($(check_feat),1)
+ifeq ($(FEATURES_DUMP),)
  include $(srctree)/tools/build/Makefile.feature
+else
+include $(FEATURES_DUMP)
+endif
+endif
  
  ifeq ($(feature-disassembler-init-styled), 1)
         OBJTOOL_CFLAGS += -DDISASM_INIT_STYLED

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