From: Yonghong Song <yhs@fb.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
<dwarves@vger.kernel.org>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Bill Wendling" <morbo@google.com>,
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: [PATCH dwarves 2/2] dwarf_loader: check .notes section for lto build info
Date: Wed, 31 Mar 2021 19:58:25 -0700 [thread overview]
Message-ID: <20210401025825.2254746-1-yhs@fb.com> (raw)
In-Reply-To: <20210401025815.2254256-1-yhs@fb.com>
In [1], linux introduced a note with type BUILD_COMPILER_LTO_INFO.
If this note type exist, there is no need to scan .debug_abbrev
section for cross-cu reference. With a kernel built with [1],
the cus__merging_cu() overhead is about 3us for either
lto or non-lto vmlinux.
[1] https://lore.kernel.org/bpf/20210401012406.1800957-1-yhs@fb.com/
Signed-off-by: Yonghong Song <yhs@fb.com>
---
dwarf_loader.c | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)
diff --git a/dwarf_loader.c b/dwarf_loader.c
index bd23751..026d137 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -2501,8 +2501,37 @@ static int cus__load_debug_types(struct cus *cus, struct conf_load *conf,
return 0;
}
-static bool cus__merging_cu(Dwarf *dw)
+/* Match the define in linux:include/linux/elfnote.h */
+#define LINUX_ELFNOTE_BUILD_LTO 0x101
+
+static bool cus__merging_cu(Dwarf *dw, Elf *elf)
{
+ Elf_Scn *section = NULL;
+ while ((section = elf_nextscn(elf, section)) != 0) {
+ GElf_Shdr header;
+ if (!gelf_getshdr(section, &header))
+ continue;
+
+ if (header.sh_type != SHT_NOTE)
+ continue;
+
+ Elf_Data *data = NULL;
+ while ((data = elf_getdata(section, data)) != 0) {
+ size_t name_off, desc_off, offset = 0;
+ GElf_Nhdr hdr;
+ while ((offset = gelf_getnote(data, offset, &hdr, &name_off, &desc_off)) != 0) {
+ if (hdr.n_type != LINUX_ELFNOTE_BUILD_LTO)
+ continue;
+
+ /* owner is Linux */
+ if (strcmp((char *)data->d_buf + name_off, "Linux") != 0)
+ continue;
+
+ return *(int *)(data->d_buf + desc_off) != 0;
+ }
+ }
+ }
+
Dwarf_Off off = 0, noff;
size_t cuhl;
@@ -2649,7 +2678,7 @@ static int cus__load_module(struct cus *cus, struct conf_load *conf,
}
}
- if (cus__merging_cu(dw)) {
+ if (cus__merging_cu(dw, elf)) {
res = cus__merge_and_process_cu(cus, conf, mod, dw, elf, filename,
build_id, build_id_len,
type_cu ? &type_dcu : NULL);
--
2.30.2
next prev parent reply other threads:[~2021-04-01 2:59 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 ` Yonghong Song [this message]
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
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