From: Yonghong Song <yhs@fb.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
Bill Wendling <morbo@google.com>
Cc: "Arnaldo Carvalho de Melo" <arnaldo.melo@gmail.com>,
dwarves@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
"David Blaikie" <dblaikie@gmail.com>,
"Fāng-ruì Sòng" <maskray@google.com>,
kernel-team@fb.com, "Nick Desaulniers" <ndesaulniers@google.com>
Subject: Re: [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu()
Date: Fri, 2 Apr 2021 07:34:41 -0700 [thread overview]
Message-ID: <3f29403d-4942-e362-c98a-4e2d20a3db88@fb.com> (raw)
In-Reply-To: <YGcbp5Y+RRWzGSia@kernel.org>
On 4/2/21 6:27 AM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Apr 01, 2021 at 12:35:45PM -0700, Bill Wendling escreveu:
>> On Wed, Mar 31, 2021 at 7:58 PM Yonghong Song <yhs@fb.com> wrote:
>
>>> Function cus__merging_cu() is introduced in Commit 39227909db3c
>>> ("dwarf_loader: Permit merging all DWARF CU's for clang LTO built
>>> binary") to test whether cross-cu references may happen.
>>> The original implementation anticipates compilation flags
>>> in dwarf, but later some concerns about binary size surfaced
>>> and the decision is to scan .debug_abbrev as a faster way
>>> to check cross-cu references. 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 <morbo@google.com>
>
> 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 <yhs@fb.com>
> Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Tested-by: Bill Wendling <morbo@google.com>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Andrii Nakryiko <andrii@kernel.org>
> Cc: David Blaikie <dblaikie@gmail.com>
> Cc: Fāng-ruì Sòng <maskray@google.com>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: bpf@vger.kernel.org
> Cc: dwarves@vger.kernel.org
> Cc: kernel-team@fb.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Looks great! Thanks a lot for detailed testing log and
Suggested-by/Tested-by/Cc list!
prev parent reply other threads:[~2021-04-02 14:35 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 2:58 [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu() Yonghong Song
2021-04-01 2:58 ` [PATCH dwarves 1/2] dwarf_loader: check .debug_abbrev for cross-cu references Yonghong Song
2021-04-01 18:52 ` Nick Desaulniers
2021-04-01 19:36 ` Arnaldo
2021-04-01 20:54 ` Yonghong Song
2021-04-01 2:58 ` [PATCH dwarves 2/2] dwarf_loader: check .notes section for lto build info Yonghong Song
2021-04-01 12:59 ` [PATCH dwarves 0/2] dwarf_loader: improve cus__merging_cu() Arnaldo Carvalho de Melo
2021-04-01 18:50 ` Nick Desaulniers
2021-04-01 19:35 ` Bill Wendling
2021-04-01 20:56 ` Bill Wendling
2021-04-01 21:59 ` Yonghong Song
2021-04-02 19:44 ` Bill Wendling
2021-04-06 13:22 ` Arnaldo Carvalho de Melo
2021-04-06 13:23 ` Arnaldo Carvalho de Melo
2021-04-06 16:40 ` Arnaldo Carvalho de Melo
2021-04-06 16:55 ` Arnaldo Carvalho de Melo
2021-04-06 16:59 ` Arnaldo Carvalho de Melo
2021-04-06 17:03 ` Arnaldo Carvalho de Melo
2021-04-06 17:07 ` Arnaldo Carvalho de Melo
2021-04-06 17:25 ` Arnaldo Carvalho de Melo
2021-04-06 17:23 ` Yonghong Song
2021-04-06 17:34 ` Arnaldo Carvalho de Melo
2021-04-06 17:36 ` Arnaldo Carvalho de Melo
2021-04-06 17:48 ` Yonghong Song
2021-04-06 18:03 ` Arnaldo Carvalho de Melo
2021-04-06 18:04 ` Arnaldo Carvalho de Melo
2021-04-06 18:31 ` Nick Desaulniers
2021-04-06 18:17 ` David Blaikie
2021-04-06 18:20 ` Arnaldo Carvalho de Melo
2021-04-06 18:22 ` Fāng-ruì Sòng
2021-04-06 17:09 ` Jiri Olsa
2021-04-02 13:27 ` Arnaldo Carvalho de Melo
2021-04-02 14:34 ` Yonghong Song [this message]
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