On Tue, May 24, 2022 at 06:59:50PM +0000, Christophe Leroy wrote:


Le 24/05/2022 à 20:02, Peter Zijlstra a écrit :

On Tue, May 24, 2022 at 08:01:39PM +0200, Peter Zijlstra wrote:

On Tue, May 24, 2022 at 03:17:45PM +0200, Christophe Leroy wrote:

From: Sathvika Vasireddy <sv@linux.ibm.com>

This patch makes sure objtool runs only on the object files
that have ftrace enabled, instead of running on all the object
files.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
  scripts/Makefile.build | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2e0c3f9c1459..06ceffd92921 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -258,8 +258,8 @@ else
  # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
  # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
  
-$(obj)/%.o: objtool-enabled = $(if $(filter-out y%, \
-	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
+$(obj)/%.o: objtool-enabled = $(and $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y),        \
+        $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),y),y)

I think this breaks x86, quite a bit of files have ftrace disabled but
very much must run objtool anyway.

Also; since the Changelog gives 0 clue as to what problem it's trying to
solve, I can't suggest anything.

I asked Sathvika on the previous series, see 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220523175548.922671-3-sv@linux.ibm.com/

He says it is to solve the problem I reported at 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220318105140.43914-4-sv@linux.ibm.com/#2861128

So on x86 we have:

arch/x86/entry/vdso/Makefile:OBJECT_FILES_NON_STANDARD       := y

to kill objtool for the whole of the VDSO. When we run objtool on
vmlinux it isn't a problem, because the VDSO ends up as a data section
through linker scripts.
