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Also putting a note in vmlinux >>> to indicate whether lto is enabled for built or not can >>> provide a much faster way. > >>> This patch set implemented this two approaches, first >>> checking the note (in Patch #2), if not found, then >>> check .debug_abbrev (in Patch #1). > >>> Yonghong Song (2): >>> dwarf_loader: check .debug_abbrev for cross-cu references >>> dwarf_loader: check .notes section for lto build info > >>> dwarf_loader.c | 76 ++++++++++++++++++++++++++++++++++++-------------- >>> 1 file changed, 55 insertions(+), 21 deletions(-) > >> With this series of patches, the compilation passes for me with >> ThinLTO. You may add this if you like: > >> Tested-by: Bill Wendling > > Thanks, added, and also this "Committer testing" section: > > Committer testing: > > Using a thin-LTO built vmlinux that doesn't have the > LINUX_ELFNOTE_BUILD_LTO note: > > $ readelf --notes vmlinux.clang.thin.LTO > > Displaying notes found in: .notes > Owner Data size Description > Xen 0x00000006 Unknown note type: (0x00000006) > description data: 6c 69 6e 75 78 00 > Xen 0x00000004 Unknown note type: (0x00000007) > description data: 32 2e 36 00 > Xen 0x00000008 Unknown note type: (0x00000005) > description data: 78 65 6e 2d 33 2e 30 00 > Xen 0x00000008 Unknown note type: (0x00000003) > description data: 00 00 00 80 ff ff ff ff > Xen 0x00000008 Unknown note type: (0x0000000f) > description data: 00 00 00 00 80 00 00 00 > Xen 0x00000008 NT_VERSION (version) > description data: c0 e1 33 83 ff ff ff ff > Xen 0x00000008 NT_ARCH (architecture) > description data: 00 20 00 81 ff ff ff ff > Xen 0x00000029 Unknown note type: (0x0000000a) > description data: 21 77 72 69 74 61 62 6c 65 5f 70 61 67 65 5f 74 61 62 6c 65 73 7c 70 61 65 5f 70 67 64 69 72 5f 61 62 6f 76 65 5f 34 67 62 > Xen 0x00000004 Unknown note type: (0x00000011) > description data: 01 88 00 00 > Xen 0x00000004 Unknown note type: (0x00000009) > description data: 79 65 73 00 > Xen 0x00000008 Unknown note type: (0x00000008) > description data: 67 65 6e 65 72 69 63 00 > Xen 0x00000010 Unknown note type: (0x0000000d) > description data: 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 > Xen 0x00000004 Unknown note type: (0x0000000e) > description data: 01 00 00 00 > Xen 0x00000004 Unknown note type: (0x00000010) > description data: 01 00 00 00 > Xen 0x00000008 Unknown note type: (0x0000000c) > description data: 00 00 00 00 00 80 ff ff > Xen 0x00000008 Unknown note type: (0x00000004) > description data: 00 00 00 00 00 00 00 00 > Xen 0x00000008 Unknown note type: (0x00000012) > description data: e0 02 00 01 00 00 00 00 > Linux 0x00000017 OPEN > description data: 34 2e 31 39 2e 34 2d 33 30 30 2e 66 63 32 39 2e 78 38 36 5f 36 34 00 > GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) > Build ID: 354f81317b1b3c35f3f81f8d9f04d0c8caccb09a > $ > > Then with one with the new ELF note stating that this binary was built > with LTO: > > [acme@five pahole]$ readelf --notes vmlinux.clang.thin.LTO+ELF_note > > Displaying notes found in: .notes > Owner Data size Description > Xen 0x00000006 Unknown note type: (0x00000006) > description data: 6c 69 6e 75 78 00 > Xen 0x00000004 Unknown note type: (0x00000007) > description data: 32 2e 36 00 > Xen 0x00000008 Unknown note type: (0x00000005) > description data: 78 65 6e 2d 33 2e 30 00 > Xen 0x00000008 Unknown note type: (0x00000003) > description data: 00 00 00 80 ff ff ff ff > Xen 0x00000008 Unknown note type: (0x0000000f) > description data: 00 00 00 00 80 00 00 00 > Xen 0x00000008 NT_VERSION (version) > description data: c0 e1 33 83 ff ff ff ff > Xen 0x00000008 NT_ARCH (architecture) > description data: 00 20 00 81 ff ff ff ff > Xen 0x00000029 Unknown note type: (0x0000000a) > description data: 21 77 72 69 74 61 62 6c 65 5f 70 61 67 65 5f 74 61 62 6c 65 73 7c 70 61 65 5f 70 67 64 69 72 5f 61 62 6f 76 65 5f 34 67 62 > Xen 0x00000004 Unknown note type: (0x00000011) > description data: 01 88 00 00 > Xen 0x00000004 Unknown note type: (0x00000009) > description data: 79 65 73 00 > Xen 0x00000008 Unknown note type: (0x00000008) > description data: 67 65 6e 65 72 69 63 00 > Xen 0x00000010 Unknown note type: (0x0000000d) > description data: 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 > Xen 0x00000004 Unknown note type: (0x0000000e) > description data: 01 00 00 00 > Xen 0x00000004 Unknown note type: (0x00000010) > description data: 01 00 00 00 > Xen 0x00000008 Unknown note type: (0x0000000c) > description data: 00 00 00 00 00 80 ff ff > Xen 0x00000008 Unknown note type: (0x00000004) > description data: 00 00 00 00 00 00 00 00 > Xen 0x00000008 Unknown note type: (0x00000012) > description data: e0 02 00 01 00 00 00 00 > Linux 0x00000017 OPEN > description data: 34 2e 31 39 2e 34 2d 33 30 30 2e 66 63 32 39 2e 78 38 36 5f 36 34 00 > Linux 0x00000004 func > description data: 01 00 00 00 > GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) > Build ID: aeba9ffc929acd3cd573b4d1afc8df9af4f3694d > $ > > Now to see the diff: > > $ readelf --notes vmlinux.clang.thin.LTO+ELF_note > with-note > $ readelf --notes vmlinux.clang.thin.LTO > without-note > $ diff -u without-note with-note > --- without-note 2021-04-02 10:23:57.545349084 -0300 > +++ with-note 2021-04-02 10:23:50.690196102 -0300 > @@ -37,5 +37,7 @@ > description data: e0 02 00 01 00 00 00 00 > Linux 0x00000017 OPEN > description data: 34 2e 31 39 2e 34 2d 33 30 30 2e 66 63 32 39 2e 78 38 36 5f 36 34 00 > + Linux 0x00000004 func > + description data: 01 00 00 00 > GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) > - Build ID: 354f81317b1b3c35f3f81f8d9f04d0c8caccb09a > + Build ID: aeba9ffc929acd3cd573b4d1afc8df9af4f3694d > $ > > Signed-off-by: Yonghong Song > Suggested-by: Arnaldo Carvalho de Melo > Tested-by: Arnaldo Carvalho de Melo > Tested-by: Bill Wendling > Cc: Alexei Starovoitov > Cc: Andrii Nakryiko > Cc: David Blaikie > Cc: Fāng-ruì Sòng > Cc: Nick Desaulniers > Cc: bpf@vger.kernel.org > Cc: dwarves@vger.kernel.org > Cc: kernel-team@fb.com > Signed-off-by: Arnaldo Carvalho de Melo Looks great! Thanks a lot for detailed testing log and Suggested-by/Tested-by/Cc list!