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Subject[PATCHv3] perf build-ids: Fall back to debuginfod query if debuginfo not found
Date
From: "Frank Ch. Eigler" <fche@redhat.com>

During a perf-record, use the -ldebuginfod API to query a debuginfod
server, should the debug data not be found in the usual system
locations. If successful, the usual $HOME/.debug dir is populated.

Tested with:

$ find .
.
./ctags-debuginfo-5.8-26.fc31.x86_64.rpm
./usr
./usr/lib
./usr/lib/debug
./usr/lib/debug/.build-id
./usr/lib/debug/.build-id/ca
./usr/lib/debug/.build-id/ca/46f6ae6a0cee57d85abc1d461c49074248908d
./usr/lib/debug/.build-id/ca/46f6ae6a0cee57d85abc1d461c49074248908d.debug
./usr/lib/debug/usr
./usr/lib/debug/usr/bin
./usr/lib/debug/usr/bin/ctags-5.8-26.fc31.x86_64.debug

$ debuginfod -F .
...

$ rm -rf ~/.debug/ ; mkdir ~/.debug

$ perf record make tags
BUILD: Doing 'make -j8' parallel build
GEN tags
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.107 MB perf.data (1483 samples) ]

$ find ~/.debug | grep ctags
/home/jolsa/.debug/usr/bin/ctags
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d/elf
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d/probes

$ rm -rf ~/.debug/ ; mkdir ~/.debug

$ DEBUGINFOD_URLS=http://localhost:8002 perf record make tags
BUILD: Doing 'make -j8' parallel build
GEN tags
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.108 MB perf.data (1531 samples) ]

$ find ~/.debug | grep ctag
/home/jolsa/.debug/usr/bin/ctags
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d/debug
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d/elf
/home/jolsa/.debug/usr/bin/ctags/ca46f6ae6a0cee57d85abc1d461c49074248908d/probes

Note the 'debug' file is created in the last run.

v3:
added NO_LIBDEBUGINFOD variable
moved the libdebuginfod check to FEATURE_TESTS_EXTRA

v2: use #ifdef HAVE_DEBUGINFOD_SUPPORT guards
include feature test source file

Note that currently the debuginfo data are downloaded only on record path,
we still need add this support to perf build-id/report.. and test ;-)

Tested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Frank Ch. Eigler <fche@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/build/Makefile.feature | 3 ++-
tools/build/feature/Makefile | 4 ++++
tools/build/feature/test-libdebuginfod.c | 8 ++++++++
tools/perf/Makefile.config | 8 ++++++++
tools/perf/Makefile.perf | 2 ++
tools/perf/util/build-id.c | 19 +++++++++++++++++++
6 files changed, 43 insertions(+), 1 deletion(-)
create mode 100644 tools/build/feature/test-libdebuginfod.c

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 3e0c019ef297..8005608a2b78 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -98,7 +98,8 @@ FEATURE_TESTS_EXTRA := \
llvm \
llvm-version \
clang \
- libbpf
+ libbpf \
+ libdebuginfod

FEATURE_TESTS ?= $(FEATURE_TESTS_BASIC)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 621f528f7822..f8a4105bc376 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -26,6 +26,7 @@ FILES= \
test-libelf-gelf_getnote.bin \
test-libelf-getshdrstrndx.bin \
test-libelf-mmap.bin \
+ test-libdebuginfod.bin \
test-libnuma.bin \
test-numa_num_possible_cpus.bin \
test-libperl.bin \
@@ -156,6 +157,9 @@ $(OUTPUT)test-libelf-gelf_getnote.bin:
$(OUTPUT)test-libelf-getshdrstrndx.bin:
$(BUILD) -lelf

+$(OUTPUT)test-libdebuginfod.bin:
+ $(BUILD) -ldebuginfod
+
$(OUTPUT)test-libnuma.bin:
$(BUILD) -lnuma

diff --git a/tools/build/feature/test-libdebuginfod.c b/tools/build/feature/test-libdebuginfod.c
new file mode 100644
index 000000000000..da22548b8413
--- /dev/null
+++ b/tools/build/feature/test-libdebuginfod.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <elfutils/debuginfod.h>
+
+int main(void)
+{
+ debuginfod_client* c = debuginfod_begin();
+ return (long)c;
+}
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 12a8204d63c6..5ff7d72688b1 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -480,6 +480,14 @@ ifndef NO_LIBELF
CFLAGS += -DHAVE_ELF_GETSHDRSTRNDX_SUPPORT
endif

+ ifndef NO_LIBDEBUGINFOD
+ $(call feature_check,libdebuginfod)
+ ifeq ($(feature-libdebuginfod), 1)
+ CFLAGS += -DHAVE_DEBUGINFOD_SUPPORT
+ EXTLIBS += -ldebuginfod
+ endif
+ endif
+
ifndef NO_DWARF
ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
msg := $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled);
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index d15a311408f1..5ccb5c694640 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -118,6 +118,8 @@ include ../scripts/utilities.mak
#
# Define LIBBPF_DYNAMIC to enable libbpf dynamic linking.
#
+# Define NO_LIBDEBUGINFOD if you do not want support debuginfod
+#

# As per kernel Makefile, avoid funny character set dependencies
unexport LC_ALL
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index c076fc7fe025..31207b6e2066 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -31,6 +31,10 @@
#include "probe-file.h"
#include "strlist.h"

+#ifdef HAVE_DEBUGINFOD_SUPPORT
+#include <elfutils/debuginfod.h>
+#endif
+
#include <linux/ctype.h>
#include <linux/zalloc.h>

@@ -636,6 +640,21 @@ static char *build_id_cache__find_debug(const char *sbuild_id,
if (realname && access(realname, R_OK))
zfree(&realname);
nsinfo__mountns_exit(&nsc);
+
+#ifdef HAVE_DEBUGINFOD_SUPPORT
+ if (realname == NULL) {
+ debuginfod_client* c = debuginfod_begin();
+ if (c != NULL) {
+ int fd = debuginfod_find_debuginfo(c,
+ (const unsigned char*)sbuild_id, 0,
+ &realname);
+ if (fd >= 0)
+ close(fd); /* retaining reference by realname */
+ debuginfod_end(c);
+ }
+ }
+#endif
+
out:
free(debugfile);
return realname;
--
2.25.2
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