On 29.04.2025 18:12, Matthieu Baerts wrote: > On 15/03/2025 14:20, Thomas Weißschuh wrote: >> -fmacro-prefix-map only affects __FILE__ and __BASE_FILE__. >> Other references, for example in debug information, are not affected. >> This makes handling of file references in the compiler outputs harder to >> use and creates problems for reproducible builds. >> >> Switch to -ffile-prefix map which affects all references. >> >> Also drop the documentation section advising manual specification of >> -fdebug-prefix-map for reproducible builds, as it is not necessary >> anymore. >> >> Suggested-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> >> Link: https://lore.kernel.org/lkml/c49cc967294f9a3a4a34f69b6a8727a6d3959ed8.camel@xxxxxxxxxxxxxxx/ >> Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> # arch/x86/ >> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx> > > Thank you for having worked on that! > > (...) > >> diff --git a/Makefile b/Makefile >> index 5c333682dc9142b1aacfe454a5c77f5923554b7d..4f920187cee658ae4d1b807fca365f6994274828 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -1067,7 +1067,7 @@ endif >> >> # change __FILE__ to the relative path to the source directory >> ifdef building_out_of_srctree >> -KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=) >> +KBUILD_CPPFLAGS += $(call cc-option,-ffile-prefix-map=$(srcroot)/=) >> KBUILD_RUSTFLAGS += --remap-path-prefix=$(srcroot)/= >> endif > > Today, I noticed that my CI for the MPTCP subsystem couldn't produce > code coverage files like before: the source files are not found. A 'git > bisect' pointed me to this patch. Reverting it seems to fix the issue. > > > My CI is building the kernel out of the source tree, in ".virtme/build". > Before and after this patch, GCOV seems to do its job properly. > Capturing GCOV data with this lcov command seems OK too: > > lcov --capture --keep-going -j "${INPUT_CPUS}" \ > --rc geninfo_unexecuted_blocks=1 \ > --include '/net/mptcp/' \ > --function-coverage --branch-coverage \ > -b "${PWD}/.virtme/build" -o kernel.lcov > > But after this patch, lcov complains some files are not found, e.g. > > ERROR: (source) unable to open > ${WORKDIR}/.virtme/build/net/mptcp/ctrl.c: No such file or directory I can confirm that the subject kernel commit breaks gcov-kernel for out-of-srctree builds by making it impossible for a consumer of GCOV data to determine the actual location of a source file without manually specifying it. Sample .gcno file content changes as seen with gcov-dump: - cwd: /home/.../build - /home/.../linux/kernel/workqueue.c:8049:19-8057:1 + cwd: /home/.../build + kernel/workqueue.c:8049:19-8057:1 > The output file is different: the path to the source file is wrong > because it points to the build dir. Instead of ... > > SF:${WORKDIR}/net/mptcp/ctrl.c > > ... now I have ... > > SF:${WORKDIR}/.virtme/build/net/mptcp/ctrl.c > > > Are there modifications needed on GCOV side to adapt to the behaviour > change introduced by this patch? Or something else needed on the > userspace side? I don't see how this could be fixed by changes in userspace nor gcov-kernel - the source tree directory information is missing from the relevant data files. -- Peter Oberparleiter Linux on IBM Z Development - IBM Germany R&D
