[PATCH v3 1/3] perf dso: Use libbfd to read build_id and .gnu_debuglink section

* [PATCH v3 1/3] perf dso: Use libbfd to read build_id and .gnu_debuglink section
@ 2020-08-21 16:52 Remi Bernon
  2020-08-21 16:52 ` [PATCH v3 2/3] perf symbols: Try reading the symbol table with libbfd Remi Bernon
                   ` (3 more replies)
  0 siblings, 4 replies; 8+ messages in thread
From: Remi Bernon @ 2020-08-21 16:52 UTC (permalink / raw)
  To: linux-kernel
  Cc: Remi Bernon, Alexander Shishkin, Arnaldo Carvalho de Melo,
	Ingo Molnar, Jiri Olsa, Mark Rutland, Namhyung Kim,
	Peter Zijlstra, Jacek Caban

Wine generates PE binaries for most of its modules and perf is unable
to parse these files to get build_id or .gnu_debuglink section.

Using libbfd when available, instead of libelf, makes it possible to
resolve debug file location regardless of the dso binary format.

Signed-off-by: Remi Bernon <rbernon@codeweavers.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jacek Caban <jacek@codeweavers.com>
---

v3: Rebase and small changes to PATCH 2/3 and and PATCH 3/3.

 tools/perf/util/symbol-elf.c | 80 ++++++++++++++++++++++++++++++++++--
 1 file changed, 77 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 8cc4b0059fb0..f7432c4a4154 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -50,6 +50,10 @@ typedef Elf64_Nhdr GElf_Nhdr;
 #define DMGL_ANSI        (1 << 1)       /* Include const, volatile, etc */
 #endif
 
+#ifdef HAVE_LIBBFD_SUPPORT
+#define PACKAGE 'perf'
+#include <bfd.h>
+#else
 #ifdef HAVE_CPLUS_DEMANGLE_SUPPORT
 extern char *cplus_demangle(const char *, int);
 
@@ -65,9 +69,7 @@ static inline char *bfd_demangle(void __maybe_unused *v,
 {
 	return NULL;
 }
-#else
-#define PACKAGE 'perf'
-#include <bfd.h>
+#endif
 #endif
 #endif
 
@@ -530,6 +532,36 @@ static int elf_read_build_id(Elf *elf, void *bf, size_t size)
 	return err;
 }
 
+#ifdef HAVE_LIBBFD_SUPPORT
+
+int filename__read_build_id(const char *filename, void *bf, size_t size)
+{
+	int err = -1;
+	bfd *abfd;
+
+	abfd = bfd_openr(filename, NULL);
+	if (!abfd)
+		return -1;
+
+	if (!bfd_check_format(abfd, bfd_object)) {
+		pr_debug2("%s: cannot read %s bfd file.\n", __func__, filename);
+		goto out_close;
+	}
+
+	if (!abfd->build_id || abfd->build_id->size > size)
+		goto out_close;
+
+	memcpy(bf, abfd->build_id->data, abfd->build_id->size);
+	memset(bf + abfd->build_id->size, 0, size - abfd->build_id->size);
+	err = abfd->build_id->size;
+
+out_close:
+	bfd_close(abfd);
+	return err;
+}
+
+#else
+
 int filename__read_build_id(const char *filename, void *bf, size_t size)
 {
 	int fd, err = -1;
@@ -557,6 +589,8 @@ int filename__read_build_id(const char *filename, void *bf, size_t size)
 	return err;
 }
 
+#endif
+
 int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
 {
 	int fd, err = -1;
@@ -608,6 +642,44 @@ int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
 	return err;
 }
 
+#ifdef HAVE_LIBBFD_SUPPORT
+
+int filename__read_debuglink(const char *filename, char *debuglink,
+			     size_t size)
+{
+	int err = -1;
+	asection *section;
+	bfd *abfd;
+
+	abfd = bfd_openr(filename, NULL);
+	if (!abfd)
+		return -1;
+
+	if (!bfd_check_format(abfd, bfd_object)) {
+		pr_debug2("%s: cannot read %s bfd file.\n", __func__, filename);
+		goto out_close;
+	}
+
+	section = bfd_get_section_by_name(abfd, ".gnu_debuglink");
+	if (!section)
+		goto out_close;
+
+	if (section->size > size)
+		goto out_close;
+
+	if (!bfd_get_section_contents(abfd, section, debuglink, 0,
+				      section->size))
+		goto out_close;
+
+	err = 0;
+
+out_close:
+	bfd_close(abfd);
+	return err;
+}
+
+#else
+
 int filename__read_debuglink(const char *filename, char *debuglink,
 			     size_t size)
 {
@@ -660,6 +732,8 @@ int filename__read_debuglink(const char *filename, char *debuglink,
 	return err;
 }
 
+#endif
+
 static int dso__swap_init(struct dso *dso, unsigned char eidata)
 {
 	static unsigned int const endian = 1;
-- 
2.28.0


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