* [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
@ 2025-02-20 18:55 Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 1/3] tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT Stephen Brennan
` (3 more replies)
0 siblings, 4 replies; 10+ messages in thread
From: Stephen Brennan @ 2025-02-20 18:55 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Arnaldo Carvalho de Melo,
Namhyung Kim
Cc: Stephen Brennan, Liang, Kan, Mark Rutland, Athira Rajeev,
Jiri Olsa, linux-kernel, Alexander Shishkin, James Clark,
Chaitanya S Prakash, Ian Rogers, linux-perf-users, Adrian Hunter,
Andi Kleen
Hello all,
This series adds the ability to read symbols from the ".gnu_debugdata" section,
an LZMA-compressed embedded ELF file which is supposed to contain additional ELF
symbols. This is something that Fedora implemented (as "MiniDebuginfo" [1]).
There are more details in v1. I've tested it with binaries that have
.gnu_debugdata, and I've also ensured that the build & runtime work when LZMA is
disabled.
[1]: https://fedoraproject.org/wiki/Features/MiniDebugInfo
Changes since v1:
* Reuses the existing LZMA decompression helpers, rather than implementing a
new LZMA decompression loop. This does involve creating a temporary file, but
I think that actually makes things cleaner, since now the symsrc has a file
descriptor to close, rather than adding a new pointer that needs freeing.
* I did also remove the pr_debug() for the case where there is no
".gnu_debugdata" section. That's not really an error worth logging, that's
just normal operation.
* I added a pr_debug() for the case where we successfully load .gnu_debugdata
so that it's easier to determine whether it gets used in tests.
v1: https://lore.kernel.org/linux-perf-users/20250213190542.3249050-1-stephen.s.brennan@oracle.com/
Stephen Brennan (3):
tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT
tools: perf: add LZMA decompression from FILE
tools: perf: support .gnu_debugdata for symbols
tools/perf/util/compress.h | 20 +++++++
tools/perf/util/dso.c | 2 +
tools/perf/util/dso.h | 1 +
tools/perf/util/lzma.c | 29 ++++++----
tools/perf/util/symbol-elf.c | 106 ++++++++++++++++++++++++++++++++++-
tools/perf/util/symbol.c | 2 +
6 files changed, 147 insertions(+), 13 deletions(-)
--
2.43.5
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v2 1/3] tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT
2025-02-20 18:55 [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Stephen Brennan
@ 2025-02-20 18:55 ` Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 2/3] tools: perf: add LZMA decompression from FILE Stephen Brennan
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Stephen Brennan @ 2025-02-20 18:55 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra,
Namhyung Kim
Cc: Stephen Brennan, Liang, Kan, Mark Rutland, Athira Rajeev,
Jiri Olsa, linux-kernel, Alexander Shishkin, James Clark,
Chaitanya S Prakash, Ian Rogers, linux-perf-users, Adrian Hunter,
Andi Kleen
This allows us to use them without needing to ifdef the calling code.
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
tools/perf/util/compress.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/tools/perf/util/compress.h b/tools/perf/util/compress.h
index b29109cd36095..a7650353c6622 100644
--- a/tools/perf/util/compress.h
+++ b/tools/perf/util/compress.h
@@ -5,6 +5,7 @@
#include <stdbool.h>
#include <stddef.h>
#include <sys/types.h>
+#include <linux/compiler.h>
#ifdef HAVE_ZSTD_SUPPORT
#include <zstd.h>
#endif
@@ -17,6 +18,17 @@ bool gzip_is_compressed(const char *input);
#ifdef HAVE_LZMA_SUPPORT
int lzma_decompress_to_file(const char *input, int output_fd);
bool lzma_is_compressed(const char *input);
+#else
+static inline
+int lzma_decompress_to_file(const char *input __maybe_unused,
+ int output_fd __maybe_unused)
+{
+ return -1;
+}
+static inline int lzma_is_compressed(const char *input __maybe_unused)
+{
+ return false;
+}
#endif
struct zstd_data {
--
2.43.5
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH v2 2/3] tools: perf: add LZMA decompression from FILE
2025-02-20 18:55 [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 1/3] tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT Stephen Brennan
@ 2025-02-20 18:55 ` Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 3/3] tools: perf: support .gnu_debugdata for symbols Stephen Brennan
2025-02-26 22:06 ` [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Namhyung Kim
3 siblings, 0 replies; 10+ messages in thread
From: Stephen Brennan @ 2025-02-20 18:55 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra,
Namhyung Kim
Cc: Stephen Brennan, Liang, Kan, Mark Rutland, Athira Rajeev,
Jiri Olsa, linux-kernel, Alexander Shishkin, James Clark,
Chaitanya S Prakash, Ian Rogers, linux-perf-users, Adrian Hunter,
Andi Kleen
Internally lzma_decompress_to_file() creates a FILE from the filename.
Add an API that takes an existing FILE directly. This allows
decompressing already-open files and even buffers opened by fmemopen().
It is necessary for supporting .gnu_debugdata in the next patch.
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
tools/perf/util/compress.h | 8 ++++++++
tools/perf/util/lzma.c | 29 ++++++++++++++++++-----------
2 files changed, 26 insertions(+), 11 deletions(-)
diff --git a/tools/perf/util/compress.h b/tools/perf/util/compress.h
index a7650353c6622..6cfecfca16f24 100644
--- a/tools/perf/util/compress.h
+++ b/tools/perf/util/compress.h
@@ -4,6 +4,7 @@
#include <stdbool.h>
#include <stddef.h>
+#include <stdio.h>
#include <sys/types.h>
#include <linux/compiler.h>
#ifdef HAVE_ZSTD_SUPPORT
@@ -16,10 +17,17 @@ bool gzip_is_compressed(const char *input);
#endif
#ifdef HAVE_LZMA_SUPPORT
+int lzma_decompress_stream_to_file(FILE *input, int output_fd);
int lzma_decompress_to_file(const char *input, int output_fd);
bool lzma_is_compressed(const char *input);
#else
static inline
+int lzma_decompress_stream_to_file(FILE *input __maybe_unused,
+ int output_fd __maybe_unused)
+{
+ return -1;
+}
+static inline
int lzma_decompress_to_file(const char *input __maybe_unused,
int output_fd __maybe_unused)
{
diff --git a/tools/perf/util/lzma.c b/tools/perf/util/lzma.c
index af9a97612f9df..bbcd2ffcf4bd1 100644
--- a/tools/perf/util/lzma.c
+++ b/tools/perf/util/lzma.c
@@ -32,7 +32,7 @@ static const char *lzma_strerror(lzma_ret ret)
}
}
-int lzma_decompress_to_file(const char *input, int output_fd)
+int lzma_decompress_stream_to_file(FILE *infile, int output_fd)
{
lzma_action action = LZMA_RUN;
lzma_stream strm = LZMA_STREAM_INIT;
@@ -41,18 +41,11 @@ int lzma_decompress_to_file(const char *input, int output_fd)
u8 buf_in[BUFSIZE];
u8 buf_out[BUFSIZE];
- FILE *infile;
-
- infile = fopen(input, "rb");
- if (!infile) {
- pr_debug("lzma: fopen failed on %s: '%s'\n", input, strerror(errno));
- return -1;
- }
ret = lzma_stream_decoder(&strm, UINT64_MAX, LZMA_CONCATENATED);
if (ret != LZMA_OK) {
pr_debug("lzma: lzma_stream_decoder failed %s (%d)\n", lzma_strerror(ret), ret);
- goto err_fclose;
+ return err;
}
strm.next_in = NULL;
@@ -100,11 +93,25 @@ int lzma_decompress_to_file(const char *input, int output_fd)
err = 0;
err_lzma_end:
lzma_end(&strm);
-err_fclose:
- fclose(infile);
return err;
}
+int lzma_decompress_to_file(const char *input, int output_fd)
+{
+ FILE *infile;
+ int ret;
+
+ infile = fopen(input, "rb");
+ if (!infile) {
+ pr_debug("lzma: fopen failed on %s: '%s'\n", input, strerror(errno));
+ return -1;
+ }
+
+ ret = lzma_decompress_stream_to_file(infile, output_fd);
+ fclose(infile);
+ return ret;
+}
+
bool lzma_is_compressed(const char *input)
{
int fd = open(input, O_RDONLY);
--
2.43.5
^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH v2 3/3] tools: perf: support .gnu_debugdata for symbols
2025-02-20 18:55 [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 1/3] tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 2/3] tools: perf: add LZMA decompression from FILE Stephen Brennan
@ 2025-02-20 18:55 ` Stephen Brennan
2025-02-26 22:06 ` [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Namhyung Kim
3 siblings, 0 replies; 10+ messages in thread
From: Stephen Brennan @ 2025-02-20 18:55 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra,
Namhyung Kim
Cc: Stephen Brennan, Liang, Kan, Mark Rutland, Athira Rajeev,
Jiri Olsa, linux-kernel, Alexander Shishkin, James Clark,
Chaitanya S Prakash, Ian Rogers, linux-perf-users, Adrian Hunter,
Andi Kleen
Fedora introduced a "MiniDebuginfo" feature, in which an LZMA-compressed
ELF file is placed inside a section named ".gnu_debugdata". This file
contains nothing but a symbol table, which can be used to supplement the
.dynsym section which only contains required symbols for runtime.
It is supported by GDB for stack traces, but it should be useful for
tracing as well. Implement support for loading symbols from
.gnu_debugdata.
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
tools/perf/util/dso.c | 2 +
tools/perf/util/dso.h | 1 +
tools/perf/util/symbol-elf.c | 106 ++++++++++++++++++++++++++++++++++-
tools/perf/util/symbol.c | 2 +
4 files changed, 109 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 5c6e85fdae0de..67c21999628d4 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -93,6 +93,7 @@ bool dso__is_object_file(const struct dso *dso)
case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO:
case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO:
case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:
+ case DSO_BINARY_TYPE__GNU_DEBUGDATA:
case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:
case DSO_BINARY_TYPE__GUEST_KMODULE:
case DSO_BINARY_TYPE__GUEST_KMODULE_COMP:
@@ -224,6 +225,7 @@ int dso__read_binary_type_filename(const struct dso *dso,
case DSO_BINARY_TYPE__VMLINUX:
case DSO_BINARY_TYPE__GUEST_VMLINUX:
case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:
+ case DSO_BINARY_TYPE__GNU_DEBUGDATA:
__symbol__join_symfs(filename, size, dso__long_name(dso));
break;
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index bb8e8f444054d..84d5aac666aa1 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -33,6 +33,7 @@ enum dso_binary_type {
DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,
DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO,
DSO_BINARY_TYPE__BUILDID_DEBUGINFO,
+ DSO_BINARY_TYPE__GNU_DEBUGDATA,
DSO_BINARY_TYPE__SYSTEM_PATH_DSO,
DSO_BINARY_TYPE__GUEST_KMODULE,
DSO_BINARY_TYPE__GUEST_KMODULE_COMP,
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 66fd1249660a3..3fa92697c457b 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -7,6 +7,7 @@
#include <unistd.h>
#include <inttypes.h>
+#include "compress.h"
#include "dso.h"
#include "map.h"
#include "maps.h"
@@ -1228,6 +1229,81 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
ehdr.e_type == ET_DYN;
}
+static Elf *read_gnu_debugdata(struct dso *dso, Elf *elf, const char *name, int *fd_ret)
+{
+ Elf *elf_embedded;
+ GElf_Ehdr ehdr;
+ GElf_Shdr shdr;
+ Elf_Scn *scn;
+ Elf_Data *scn_data;
+ FILE *wrapped;
+ size_t shndx;
+ char temp_filename[] = "/tmp/perf.gnu_debugdata.elf.XXXXXX";
+ int ret, temp_fd;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ pr_debug("%s: cannot read %s ELF file.\n", __func__, name);
+ *dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;
+ return NULL;
+ }
+
+ scn = elf_section_by_name(elf, &ehdr, &shdr, ".gnu_debugdata", &shndx);
+ if (!scn) {
+ *dso__load_errno(dso) = -ENOENT;
+ return NULL;
+ }
+
+ if (shdr.sh_type == SHT_NOBITS) {
+ pr_debug("%s: .gnu_debugdata of ELF file %s has no data.\n", __func__, name);
+ *dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;
+ return NULL;
+ }
+
+ scn_data = elf_rawdata(scn, NULL);
+ if (!scn_data) {
+ pr_debug("%s: error reading .gnu_debugdata of %s: %s\n", __func__,
+ name, elf_errmsg(-1));
+ *dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;
+ return NULL;
+ }
+
+ wrapped = fmemopen(scn_data->d_buf, scn_data->d_size, "r");
+ if (!wrapped) {
+ pr_debug("%s: fmemopen: %s\n", __func__, strerror(errno));
+ *dso__load_errno(dso) = -errno;
+ return NULL;
+ }
+
+ temp_fd = mkstemp(temp_filename);
+ if (temp_fd < 0) {
+ pr_debug("%s: mkstemp: %s\n", __func__, strerror(errno));
+ *dso__load_errno(dso) = -errno;
+ fclose(wrapped);
+ return NULL;
+ }
+ unlink(temp_filename);
+
+ ret = lzma_decompress_stream_to_file(wrapped, temp_fd);
+ fclose(wrapped);
+ if (ret < 0) {
+ *dso__load_errno(dso) = -errno;
+ close(temp_fd);
+ return NULL;
+ }
+
+ elf_embedded = elf_begin(temp_fd, PERF_ELF_C_READ_MMAP, NULL);
+ if (!elf_embedded) {
+ pr_debug("%s: error reading .gnu_debugdata of %s: %s\n", __func__,
+ name, elf_errmsg(-1));
+ *dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;
+ close(temp_fd);
+ return NULL;
+ }
+ pr_debug("%s: using .gnu_debugdata of %s\n", __func__, name);
+ *fd_ret = temp_fd;
+ return elf_embedded;
+}
+
int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
enum dso_binary_type type)
{
@@ -1256,6 +1332,19 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
goto out_close;
}
+ if (type == DSO_BINARY_TYPE__GNU_DEBUGDATA) {
+ int new_fd;
+ Elf *embedded = read_gnu_debugdata(dso, elf, name, &new_fd);
+
+ if (!embedded)
+ goto out_close;
+
+ elf_end(elf);
+ close(fd);
+ fd = new_fd;
+ elf = embedded;
+ }
+
if (gelf_getehdr(elf, &ehdr) == NULL) {
*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;
pr_debug("%s: cannot get elf header.\n", __func__);
@@ -1854,10 +1943,23 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
kmodule, 1);
if (err < 0)
return err;
- err += nr;
+ nr += err;
}
- return err;
+ /*
+ * The .gnu_debugdata is a special situation: it contains a symbol
+ * table, but the runtime file may also contain dynsym entries which are
+ * not present there. We need to load both.
+ */
+ if (syms_ss->type == DSO_BINARY_TYPE__GNU_DEBUGDATA && runtime_ss->dynsym) {
+ err = dso__load_sym_internal(dso, map, runtime_ss, runtime_ss,
+ kmodule, 1);
+ if (err < 0)
+ return err;
+ nr += err;
+ }
+
+ return nr;
}
static int elf_read_maps(Elf *elf, bool exe, mapfn_t mapfn, void *data)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 49b08adc6ee34..a0767762d4d73 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -84,6 +84,7 @@ static enum dso_binary_type binary_type_symtab[] = {
DSO_BINARY_TYPE__FEDORA_DEBUGINFO,
DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,
DSO_BINARY_TYPE__BUILDID_DEBUGINFO,
+ DSO_BINARY_TYPE__GNU_DEBUGDATA,
DSO_BINARY_TYPE__SYSTEM_PATH_DSO,
DSO_BINARY_TYPE__GUEST_KMODULE,
DSO_BINARY_TYPE__GUEST_KMODULE_COMP,
@@ -1716,6 +1717,7 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO:
case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:
case DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO:
+ case DSO_BINARY_TYPE__GNU_DEBUGDATA:
return !kmod && dso__kernel(dso) == DSO_SPACE__USER;
case DSO_BINARY_TYPE__KALLSYMS:
--
2.43.5
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-02-20 18:55 [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Stephen Brennan
` (2 preceding siblings ...)
2025-02-20 18:55 ` [PATCH v2 3/3] tools: perf: support .gnu_debugdata for symbols Stephen Brennan
@ 2025-02-26 22:06 ` Namhyung Kim
2025-03-07 20:10 ` Arnaldo Carvalho de Melo
3 siblings, 1 reply; 10+ messages in thread
From: Namhyung Kim @ 2025-02-26 22:06 UTC (permalink / raw)
To: Stephen Brennan
Cc: Ingo Molnar, Peter Zijlstra, Arnaldo Carvalho de Melo, Liang, Kan,
Mark Rutland, Athira Rajeev, Jiri Olsa, linux-kernel,
Alexander Shishkin, James Clark, Chaitanya S Prakash, Ian Rogers,
linux-perf-users, Adrian Hunter, Andi Kleen
On Thu, Feb 20, 2025 at 10:55:08AM -0800, Stephen Brennan wrote:
> Hello all,
>
> This series adds the ability to read symbols from the ".gnu_debugdata" section,
> an LZMA-compressed embedded ELF file which is supposed to contain additional ELF
> symbols. This is something that Fedora implemented (as "MiniDebuginfo" [1]).
> There are more details in v1. I've tested it with binaries that have
> .gnu_debugdata, and I've also ensured that the build & runtime work when LZMA is
> disabled.
>
> [1]: https://fedoraproject.org/wiki/Features/MiniDebugInfo
>
> Changes since v1:
> * Reuses the existing LZMA decompression helpers, rather than implementing a
> new LZMA decompression loop. This does involve creating a temporary file, but
> I think that actually makes things cleaner, since now the symsrc has a file
> descriptor to close, rather than adding a new pointer that needs freeing.
> * I did also remove the pr_debug() for the case where there is no
> ".gnu_debugdata" section. That's not really an error worth logging, that's
> just normal operation.
> * I added a pr_debug() for the case where we successfully load .gnu_debugdata
> so that it's easier to determine whether it gets used in tests.
Thanks, it'd be nice if anyone with a Fedora box could test this.
Thanks,
Namhyung
>
> v1: https://lore.kernel.org/linux-perf-users/20250213190542.3249050-1-stephen.s.brennan@oracle.com/
>
> Stephen Brennan (3):
> tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT
> tools: perf: add LZMA decompression from FILE
> tools: perf: support .gnu_debugdata for symbols
>
> tools/perf/util/compress.h | 20 +++++++
> tools/perf/util/dso.c | 2 +
> tools/perf/util/dso.h | 1 +
> tools/perf/util/lzma.c | 29 ++++++----
> tools/perf/util/symbol-elf.c | 106 ++++++++++++++++++++++++++++++++++-
> tools/perf/util/symbol.c | 2 +
> 6 files changed, 147 insertions(+), 13 deletions(-)
>
> --
> 2.43.5
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-02-26 22:06 ` [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Namhyung Kim
@ 2025-03-07 20:10 ` Arnaldo Carvalho de Melo
2025-03-07 20:18 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-03-07 20:10 UTC (permalink / raw)
To: Namhyung Kim
Cc: Stephen Brennan, Ingo Molnar, Peter Zijlstra, Liang, Kan,
Mark Rutland, Athira Rajeev, Jiri Olsa, linux-kernel,
Alexander Shishkin, James Clark, Chaitanya S Prakash, Ian Rogers,
linux-perf-users, Adrian Hunter, Andi Kleen
On Wed, Feb 26, 2025 at 02:06:28PM -0800, Namhyung Kim wrote:
> On Thu, Feb 20, 2025 at 10:55:08AM -0800, Stephen Brennan wrote:
> > Hello all,
> >
> > This series adds the ability to read symbols from the ".gnu_debugdata" section,
> > an LZMA-compressed embedded ELF file which is supposed to contain additional ELF
> > symbols. This is something that Fedora implemented (as "MiniDebuginfo" [1]).
> > There are more details in v1. I've tested it with binaries that have
> > .gnu_debugdata, and I've also ensured that the build & runtime work when LZMA is
> > disabled.
> >
> > [1]: https://fedoraproject.org/wiki/Features/MiniDebugInfo
> >
> > Changes since v1:
> > * Reuses the existing LZMA decompression helpers, rather than implementing a
> > new LZMA decompression loop. This does involve creating a temporary file, but
> > I think that actually makes things cleaner, since now the symsrc has a file
> > descriptor to close, rather than adding a new pointer that needs freeing.
> > * I did also remove the pr_debug() for the case where there is no
> > ".gnu_debugdata" section. That's not really an error worth logging, that's
> > just normal operation.
> > * I added a pr_debug() for the case where we successfully load .gnu_debugdata
> > so that it's easier to determine whether it gets used in tests.
>
> Thanks, it'd be nice if anyone with a Fedora box could test this.
I'm trying to go thru this, testing with/without LZMA so that we can
show the difference in symbol resolution, etc, but I've now stumbled on
something that predates this, namely trying to build with NO_LZMA=1
isn't disabling it:
⬢ [acme@toolbox perf-tools-next]$ rm -rf /tmp/build/$(basename $PWD)/ ; mkdir /tmp/build/$(basename $PWD)/ ; make NO_LZMA=1 O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin
make: Entering directory '/home/acme/git/perf-tools-next/tools/perf'
BUILD: Doing 'make -j28' parallel build
Auto-detecting system features:
... libdw: [ on ]
... glibc: [ on ]
... libbfd: [ on ]
... libbfd-buildid: [ on ]
... libelf: [ on ]
... libnuma: [ on ]
... numa_num_possible_cpus: [ on ]
... libperl: [ on ]
... libpython: [ on ]
... libcrypto: [ on ]
... libunwind: [ on ]
... libcapstone: [ on ]
... llvm-perf: [ on ]
... zlib: [ on ]
... lzma: [ on ]
<SNIP>
⬢ [acme@toolbox perf-tools-next]$ ldd ~/bin/perf | grep lzma
liblzma.so.5 => /lib64/liblzma.so.5 (0x00007f77ac879000)
⬢ [acme@toolbox perf-tools-next]$
my hunch is that some other feature needs lzma support and ignores the
explicit NO_LZMA=1 on the make command line when it should really be
disabling whatever features needs it, not overriding the cmd line
request.
I'm trying to investigate.
- Arnaldo
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-03-07 20:10 ` Arnaldo Carvalho de Melo
@ 2025-03-07 20:18 ` Arnaldo Carvalho de Melo
2025-03-07 20:46 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-03-07 20:18 UTC (permalink / raw)
To: Namhyung Kim
Cc: Stephen Brennan, Ingo Molnar, Peter Zijlstra, Liang, Kan,
Mark Rutland, Athira Rajeev, Jiri Olsa, linux-kernel,
Alexander Shishkin, James Clark, Chaitanya S Prakash, Ian Rogers,
linux-perf-users, Adrian Hunter, Andi Kleen
On Fri, Mar 07, 2025 at 05:10:55PM -0300, Arnaldo Carvalho de Melo wrote:
> On Wed, Feb 26, 2025 at 02:06:28PM -0800, Namhyung Kim wrote:
> > On Thu, Feb 20, 2025 at 10:55:08AM -0800, Stephen Brennan wrote:
> > > This series adds the ability to read symbols from the ".gnu_debugdata" section,
> > > an LZMA-compressed embedded ELF file which is supposed to contain additional ELF
> > > symbols. This is something that Fedora implemented (as "MiniDebuginfo" [1]).
> > > There are more details in v1. I've tested it with binaries that have
> > > .gnu_debugdata, and I've also ensured that the build & runtime work when LZMA is
> > > disabled.
> > > [1]: https://fedoraproject.org/wiki/Features/MiniDebugInfo
> > > Changes since v1:
> > > * Reuses the existing LZMA decompression helpers, rather than implementing a
> > > new LZMA decompression loop. This does involve creating a temporary file, but
> > > I think that actually makes things cleaner, since now the symsrc has a file
> > > descriptor to close, rather than adding a new pointer that needs freeing.
> > > * I did also remove the pr_debug() for the case where there is no
> > > ".gnu_debugdata" section. That's not really an error worth logging, that's
> > > just normal operation.
> > > * I added a pr_debug() for the case where we successfully load .gnu_debugdata
> > > so that it's easier to determine whether it gets used in tests.
> >
> > Thanks, it'd be nice if anyone with a Fedora box could test this.
>
> I'm trying to go thru this, testing with/without LZMA so that we can
> show the difference in symbol resolution, etc, but I've now stumbled on
> something that predates this, namely trying to build with NO_LZMA=1
> isn't disabling it:
> ⬢ [acme@toolbox perf-tools-next]$ rm -rf /tmp/build/$(basename $PWD)/ ; mkdir /tmp/build/$(basename $PWD)/ ; make NO_LZMA=1 O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin
> make: Entering directory '/home/acme/git/perf-tools-next/tools/perf'
> BUILD: Doing 'make -j28' parallel build
>
> Auto-detecting system features:
> ... libdw: [ on ]
> ... glibc: [ on ]
> ... libbfd: [ on ]
> ... libbfd-buildid: [ on ]
> ... libelf: [ on ]
> ... libnuma: [ on ]
> ... numa_num_possible_cpus: [ on ]
> ... libperl: [ on ]
> ... libpython: [ on ]
> ... libcrypto: [ on ]
> ... libunwind: [ on ]
> ... libcapstone: [ on ]
> ... llvm-perf: [ on ]
> ... zlib: [ on ]
> ... lzma: [ on ]
> <SNIP>
>
>
> ⬢ [acme@toolbox perf-tools-next]$ ldd ~/bin/perf | grep lzma
> liblzma.so.5 => /lib64/liblzma.so.5 (0x00007f77ac879000)
> ⬢ [acme@toolbox perf-tools-next]$
>
> my hunch is that some other feature needs lzma support and ignores the
> explicit NO_LZMA=1 on the make command line when it should really be
> disabling whatever features needs it, not overriding the cmd line
> request.
>
> I'm trying to investigate.
Its an interesting case, as this patch says, elfutils now depends on
liblzma, so:
⬢ [acme@toolbox perf-tools-next]$ rpm -qa | grep xz
xz-libs-5.4.6-3.fc40.x86_64
xz-5.4.6-3.fc40.x86_64
xz-devel-5.4.6-3.fc40.x86_64
⬢ [acme@toolbox perf-tools-next]$ rpm -e xz-devel
error: Failed dependencies:
pkgconfig(liblzma) is needed by (installed) elfutils-devel-0.192-9.fc40.x86_64
pkgconfig(liblzma) is needed by (installed) libxml2-devel-2.12.9-1.fc40.x86_64
xz-devel(x86-64) is needed by (installed) libxml2-devel-2.12.9-1.fc40.x86_64
⬢ [acme@toolbox perf-tools-next]$
The NO_LZMA code in the perf build system should at this point either be
deleted, as elfutils is so critical for perf, or mean that outside of
elfutils, perf should make no use of lzma, which seems odd even with
some potentially marginal value.
So for testing this series I'll have to collect data before these
patches get applied, making sure we collect samples from symbols in
binaries with a MiniDebuginfo section, do a perf report, see them as
being not resolved after making sure we don't have its debuginfo files
installed and zapping whatever local debuginfo cache we have
(debuginfod, perfs, etc), apply the patches and then see if it gets more
symbols resolved by looking at the .gnu_debugdata section.
Ok, doing that now.
- Arnaldo
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-03-07 20:18 ` Arnaldo Carvalho de Melo
@ 2025-03-07 20:46 ` Arnaldo Carvalho de Melo
2025-03-07 22:33 ` Stephen Brennan
0 siblings, 1 reply; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-03-07 20:46 UTC (permalink / raw)
To: Stephen Brennan, Namhyung Kim
Cc: Ingo Molnar, Peter Zijlstra, Liang, Kan, Mark Rutland,
Athira Rajeev, Jiri Olsa, linux-kernel, Alexander Shishkin,
James Clark, Chaitanya S Prakash, Ian Rogers, linux-perf-users,
Adrian Hunter, Andi Kleen
On Fri, Mar 07, 2025 at 05:18:36PM -0300, Arnaldo Carvalho de Melo wrote:
> The NO_LZMA code in the perf build system should at this point either be
> deleted, as elfutils is so critical for perf, or mean that outside of
> elfutils, perf should make no use of lzma, which seems odd even with
> some potentially marginal value.
> So for testing this series I'll have to collect data before these
> patches get applied, making sure we collect samples from symbols in
> binaries with a MiniDebuginfo section, do a perf report, see them as
> being not resolved after making sure we don't have its debuginfo files
> installed and zapping whatever local debuginfo cache we have
> (debuginfod, perfs, etc), apply the patches and then see if it gets more
> symbols resolved by looking at the .gnu_debugdata section.
>
> Ok, doing that now.
Works:
⬢ [acme@toolbox perf-tools-next]$ taskset -c 0 perf record -e cpu_core/cycles/P find . > /dev/null
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.011 MB perf.data (163 samples) ]
⬢ [acme@toolbox perf-tools-next]$ perf report --stdio > before
⬢ [acme@toolbox perf-tools-next]$
Apply the patches and:
⬢ [acme@toolbox perf-tools-next]$ perf report --stdio > after
⬢ [acme@toolbox perf-tools-next]$ diff -u before after
--- before 2025-03-07 17:33:15.113447391 -0300
+++ after 2025-03-07 17:33:39.291525994 -0300
@@ -9,88 +9,56 @@
# Overhead Command Shared Object Symbol
# ........ ....... .................... ..................................
#
+ 8.72% find find [.] consider_visiting
7.90% find libc.so.6 [.] __GI___readdir64
7.44% find libc.so.6 [.] _int_malloc
+ 7.06% find find [.] find
+ 6.20% find find [.] fts_build.constprop.0
6.18% find libc.so.6 [.] __memmove_avx_unaligned_erms
+ 4.36% find find [.] pred_print
4.14% find libc.so.6 [.] __printf_buffer
3.65% find libc.so.6 [.] __strlen_avx2
3.35% find libc.so.6 [.] malloc
- 2.65% find find [.] 0x000000000000b498
+ 2.85% find find [.] fts_alloc
2.51% find libc.so.6 [.] __vfprintf_internal
2.45% find libc.so.6 [.] __fprintf_chk
- 2.45% find find [.] 0x00000000000089e3
2.33% find libc.so.6 [.] __printf_buffer_write
2.13% find libc.so.6 [.] _int_free_merge_chunk
1.88% find libc.so.6 [.] __printf_buffer_flush_to_file
- 1.87% find find [.] 0x000000000000bf8e
1.79% find libc.so.6 [.] _int_free
1.64% find libc.so.6 [.] msort_with_tmp.part.0
1.63% find find [.] free@plt
- 1.34% find find [.] 0x000000000000c214
- 1.30% find find [.] 0x000000000001ea34
- 1.27% find find [.] 0x000000000001ea96
+ 1.29% find find [.] fts_safe_changedir.lto_priv.0
1.26% find [unknown] [k] 0xffffffffad4001c8
1.25% find libc.so.6 [.] __libc_fcntl64
1.23% find libc.so.6 [.] _int_free_create_chunk
- 1.22% find find [.] 0x000000000000bfb9
- 1.22% find find [.] 0x000000000000bbde
- 1.22% find find [.] 0x000000000000b4a2
- 1.20% find find [.] 0x0000000000006918
+ 1.20% find find [.] pred_and
1.16% find libc.so.6 [.] __fcntl64_nocancel_adjusted
+ 1.15% find find [.] AD_hash
1.12% find libc.so.6 [.] cfree@GLIBC_2.2.5
1.05% find libc.so.6 [.] __strchrnul_ifunc@plt
1.03% find libc.so.6 [.] __libc_openat64
1.01% find libc.so.6 [.] __strchrnul_avx2
- 0.69% find find [.] 0x0000000000008a0e
- 0.68% find find [.] 0x000000000000b553
- 0.67% find find [.] 0x000000000001ea63
- 0.67% find find [.] 0x0000000000006869
- 0.65% find find [.] 0x0000000000019e82
- 0.65% find find [.] 0x000000000000bbc5
- 0.65% find find [.] 0x000000000001117e
- 0.64% find find [.] 0x0000000000019fc6
- 0.64% find find [.] 0x000000000001111c
- 0.63% find find [.] 0x0000000000008a19
- 0.63% find find [.] 0x0000000000018b3d
- 0.63% find find [.] 0x000000000000b61e
+ 0.97% find find [.] leave_dir.lto_priv.0
+ 0.67% find find [.] apply_predicate
+ 0.63% find find [.] cwd_advance_fd.lto_priv.0
0.63% find libc.so.6 [.] __GI___fstatat64
- 0.63% find find [.] 0x000000000001f0de
0.63% find libc.so.6 [.] __fstat64
- 0.63% find find [.] 0x000000000001edfb
- 0.62% find find [.] 0x000000000001113f
- 0.61% find find [.] 0x000000000000c223
- 0.61% find find [.] 0x000000000000c06b
- 0.61% find find [.] 0x000000000000fd90
- 0.61% find find [.] 0x0000000000018d98
- 0.60% find find [.] 0x0000000000017cfa
- 0.60% find find [.] 0x000000000001e990
- 0.60% find find [.] 0x000000000000b657
+ 0.60% find find [.] rpl_fcntl
0.59% find find [.] malloc@plt
- 0.59% find find [.] 0x000000000000c099
- 0.59% find find [.] 0x00000000000089d9
0.58% find ld-linux-x86-64.so.2 [.] _dl_process_pt_gnu_property
0.57% find libc.so.6 [.] unlink_chunk.isra.0
- 0.56% find find [.] 0x000000000001ea4e
- 0.56% find find [.] 0x000000000000b64b
0.56% find libc.so.6 [.] malloc@plt
- 0.54% find find [.] 0x00000000000110e6
- 0.54% find find [.] 0x000000000001ead0
- 0.54% find find [.] 0x000000000000fdc7
- 0.53% find find [.] 0x000000000000fd8a
- 0.52% find find [.] 0x0000000000011e07
- 0.52% find find [.] 0x000000000000b6a8
- 0.48% find find [.] 0x0000000000012463
+ 0.54% find find [.] fts_compare_ino
+ 0.52% find find [.] hash_find_entry
+ 0.48% find find [.] fts_sort
0.47% find libc.so.6 [.] __printf_buffer_to_file_switch
0.42% find libc.so.6 [.] alloc_perturb
- 0.42% find find [.] 0x000000000000bfc2
- 0.41% find find [.] 0x0000000000011179
- 0.40% find find [.] 0x000000000000c234
- 0.36% find find [.] 0x0000000000018cc0
0.14% find ld-linux-x86-64.so.2 [.] _dl_sysdep_parse_arguments
0.01% find ld-linux-x86-64.so.2 [.] _dl_start
0.00% find ld-linux-x86-64.so.2 [.] _start
#
-# (Tip: Create an archive with symtabs to analyse on other machine: perf archive)
+# (Tip: To see callchains in a more compact form: perf report -g folded)
#
⬢ [acme@toolbox perf-tools-next]$
⬢ [acme@toolbox perf-tools-next]$ find ~/.debug/ -name af3f04d1b31abc9e5ce8428110e424fd980a37
⬢ [acme@toolbox perf-tools-next]$ find ~/.cache/ -name af3f04d1b31abc9e5ce8428110e424fd980a37
⬢ [acme@toolbox perf-tools-next]$
⬢ [acme@toolbox perf-tools-next]$ rpm -qf /bin/find
findutils-4.9.0-9.fc40.x86_64
⬢ [acme@toolbox perf-tools-next]$ rpm -q findutils-debuginfo
package findutils-debuginfo is not installed
⬢ [acme@toolbox perf-tools-next]$
And /bin/find has only unresolved symbols in its symtabs:
⬢ [acme@toolbox perf-tools-next]$ readelf -sW /bin/find | grep -w FUNC | wc -l
145
⬢ [acme@toolbox perf-tools-next]$ readelf -sW /bin/find | grep -w FUNC | grep -vw UND
⬢ [acme@toolbox perf-tools-next]$
⬢ [acme@toolbox perf-tools-next]$ readelf -SW /bin/find | grep SYM
[ 7] .dynsym DYNSYM 00000000000004a0 0004a0 000ed0 18 A 8 1 8
[ 9] .gnu.version VERSYM 00000000000019a0 0019a0 00013c 02 A 7 0 2
⬢ [acme@toolbox perf-tools-next]$
And that matches eu-readelf output, almost the same (UND => UNDEF):
⬢ [acme@toolbox perf-tools-next]$ eu-readelf -s /bin/find | grep -w FUNC | wc -l
145
⬢ [acme@toolbox perf-tools-next]$
⬢ [acme@toolbox perf-tools-next]$ eu-readelf -s /bin/find | grep -w FUNC | grep -vw UNDEF
⬢ [acme@toolbox perf-tools-next]$
It has a way to use that section tho:
⬢ [acme@toolbox perf-tools-next]$ man eu-readelf | grep -A2 -- --elf-section
[--elf-section [section] ]
[-w|
--debug-dump[=line,=decodedline,=info,=info+,=abbrev,=pubnames,=aranges,=macro,=frames,=str,=loc,=ranges,=gdb_index,=addr]]
--
--elf-section [section]
Use the named SECTION (default .gnu_debugdata) as (compressed) ELF input data
⬢ [acme@toolbox perf-tools-next]$
⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | wc -l
339
⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | head
1: 00000000000056d0 35 FUNC LOCAL DEFAULT 17 entry_hashfunc
2: 0000000000005700 34 FUNC LOCAL DEFAULT 17 entry_comparator
3: 0000000000005920 121 FUNC LOCAL DEFAULT 17 subtree_has_side_effects
4: 00000000000059a0 992 FUNC LOCAL DEFAULT 17 worst_cost.part.0
5: 0000000000005d80 449 FUNC LOCAL DEFAULT 17 traverse_tree
6: 0000000000005f50 73 FUNC LOCAL DEFAULT 17 undangle_file_pointers
7: 0000000000005fa0 72 FUNC LOCAL DEFAULT 17 looks_like_expression
8: 0000000000006030 303 FUNC LOCAL DEFAULT 17 get_fts_info_name
9: 0000000000006190 35 FUNC LOCAL DEFAULT 17 inside_dir.part.0
10: 0000000000006330 451 FUNC LOCAL DEFAULT 17 pred_sanity_check
⬢ [acme@toolbox perf-tools-next]$
So there we can find the new entries, such as the top one in the example
profile session above:
⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | grep -w consider_visiting
48: 000000000000b460 2544 FUNC LOCAL DEFAULT 17 consider_visiting
⬢ [acme@toolbox perf-tools-next]$
And trat address matches the resolution perf did with your patches:
⬢ [acme@toolbox perf-tools-next]$ perf report -v --stdio |& head
build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
⬢ [acme@toolbox perf-tools-next]$ perf report -v --stdio |& head -20
build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 163 of event 'cpu_core/cycles/Pu'
# Event count (approx.): 68126524
#
# Overhead Command Shared Object Symbol
# ........ ....... ............................... .......................................................
#
8.72% find /usr/bin/find 0xb498
7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
⬢ [acme@toolbox perf-tools-next]$
The only strange thing was not having it resolved in the -v case, which
I think its because you added a new type of DSO but didn't update the
code that does the 'perf report -v' verbose case?
I ran out of time, have to go AFK now, can you please take a look,
Stephen?
DSO_BINARY_TYPE__GNU_DEBUGDATA should be handled at...
int dso__read_binary_type_filename(const struct dso *dso,
enum dso_binary_type type,
char *root_dir, char *filename, size_t size)
But you have it there, ok, I'll try to continue later.
Other than that the patch looks great and makes use of this new mini
symtab, excellent!
- Arnaldo
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-03-07 20:46 ` Arnaldo Carvalho de Melo
@ 2025-03-07 22:33 ` Stephen Brennan
2025-03-10 15:21 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 10+ messages in thread
From: Stephen Brennan @ 2025-03-07 22:33 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Namhyung Kim
Cc: Ingo Molnar, Peter Zijlstra, Liang, Kan, Mark Rutland,
Athira Rajeev, Jiri Olsa, linux-kernel, Alexander Shishkin,
James Clark, Chaitanya S Prakash, Ian Rogers, linux-perf-users,
Adrian Hunter, Andi Kleen
Arnaldo Carvalho de Melo <acme@kernel.org> writes:
> On Fri, Mar 07, 2025 at 05:18:36PM -0300, Arnaldo Carvalho de Melo wrote:
[...]
> It has a way to use that section tho:
>
> ⬢ [acme@toolbox perf-tools-next]$ man eu-readelf | grep -A2 -- --elf-section
> [--elf-section [section] ]
> [-w|
> --debug-dump[=line,=decodedline,=info,=info+,=abbrev,=pubnames,=aranges,=macro,=frames,=str,=loc,=ranges,=gdb_index,=addr]]
> --
> --elf-section [section]
> Use the named SECTION (default .gnu_debugdata) as (compressed) ELF input data
>
> ⬢ [acme@toolbox perf-tools-next]$
>
> ⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | wc -l
> 339
> ⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | head
> 1: 00000000000056d0 35 FUNC LOCAL DEFAULT 17 entry_hashfunc
> 2: 0000000000005700 34 FUNC LOCAL DEFAULT 17 entry_comparator
> 3: 0000000000005920 121 FUNC LOCAL DEFAULT 17 subtree_has_side_effects
> 4: 00000000000059a0 992 FUNC LOCAL DEFAULT 17 worst_cost.part.0
> 5: 0000000000005d80 449 FUNC LOCAL DEFAULT 17 traverse_tree
> 6: 0000000000005f50 73 FUNC LOCAL DEFAULT 17 undangle_file_pointers
> 7: 0000000000005fa0 72 FUNC LOCAL DEFAULT 17 looks_like_expression
> 8: 0000000000006030 303 FUNC LOCAL DEFAULT 17 get_fts_info_name
> 9: 0000000000006190 35 FUNC LOCAL DEFAULT 17 inside_dir.part.0
> 10: 0000000000006330 451 FUNC LOCAL DEFAULT 17 pred_sanity_check
> ⬢ [acme@toolbox perf-tools-next]$
Wow, thank you for teaching me that!
I had been using:
gdb /usr/bin/bash --batch -ex 'maint print msymbols'
Because I knew GDB had support for .gnu_debugdata. But the --elf-section
argument to eu-readelf is much more useful.
> So there we can find the new entries, such as the top one in the example
> profile session above:
>
> ⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | grep -w consider_visiting
> 48: 000000000000b460 2544 FUNC LOCAL DEFAULT 17 consider_visiting
> ⬢ [acme@toolbox perf-tools-next]$
>
> And trat address matches the resolution perf did with your patches:
>
> ⬢ [acme@toolbox perf-tools-next]$ perf report -v --stdio |& head
> build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
> build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
> build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
> build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
> build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
> # To display the perf.data header info, please use --header/--header-only options.
> #
> #
> # Total Lost Samples: 0
> ⬢ [acme@toolbox perf-tools-next]$ perf report -v --stdio |& head -20
> build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
> build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
> build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
> build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
> build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
> # To display the perf.data header info, please use --header/--header-only options.
> #
> #
> # Total Lost Samples: 0
> #
> # Samples: 163 of event 'cpu_core/cycles/Pu'
> # Event count (approx.): 68126524
> #
> # Overhead Command Shared Object Symbol
> # ........ ....... ............................... .......................................................
> #
> 8.72% find /usr/bin/find 0xb498
> 7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
> 7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
> ⬢ [acme@toolbox perf-tools-next]$
>
> The only strange thing was not having it resolved in the -v case, which
> I think its because you added a new type of DSO but didn't update the
> code that does the 'perf report -v' verbose case?
>
> I ran out of time, have to go AFK now, can you please take a look,
> Stephen?
Thanks for the catch. I double checked all the places where
DSO_BINARY_TYPE constants are enumerated, and it turns out I missed
adding an entry to
char dso__symtab_origin(const struct dso *dso) ...
I assume that the array defaulted to '\0' which terminated the string
too early for this line. Oops!
Most of the letters I would associate with ".gnu_debugdata" are
taken (namely, g/G for GNU, m/M for MiniDebugInfo, d/D for
debugdata...). So 'n', for the second letter of GNU, is my selection
unless you feel differently. With that change, the table is fixed for
"perf report -v". Here it is running against my test data focusing on a
symbol only found in .gnu_debugdata of bash:
$ ./perf report -v --stdio -i ~/repos/UEK6/perf.data 2>&1 | egrep yy_readline_get\|gnu_debugdata
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/bash
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sed
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/date
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sqlite3
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sleep
0.20% 0.00% bash /usr/bin/bash 0x55fdc4509dbe n [.] yy_readline_get
I'll update the patch accordingly.
> DSO_BINARY_TYPE__GNU_DEBUGDATA should be handled at...
>
> int dso__read_binary_type_filename(const struct dso *dso,
> enum dso_binary_type type,
> char *root_dir, char *filename, size_t size)
>
> But you have it there, ok, I'll try to continue later.
>
> Other than that the patch looks great and makes use of this new mini
> symtab, excellent!
And thank you for your testing!
> - Arnaldo
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf
2025-03-07 22:33 ` Stephen Brennan
@ 2025-03-10 15:21 ` Arnaldo Carvalho de Melo
0 siblings, 0 replies; 10+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-03-10 15:21 UTC (permalink / raw)
To: Stephen Brennan
Cc: Namhyung Kim, Ingo Molnar, Peter Zijlstra, Liang, Kan,
Mark Rutland, Athira Rajeev, Jiri Olsa, linux-kernel,
Alexander Shishkin, James Clark, Chaitanya S Prakash, Ian Rogers,
linux-perf-users, Adrian Hunter, Andi Kleen
On Fri, Mar 07, 2025 at 02:33:01PM -0800, Stephen Brennan wrote:
> Arnaldo Carvalho de Melo <acme@kernel.org> writes:
> > On Fri, Mar 07, 2025 at 05:18:36PM -0300, Arnaldo Carvalho de Melo wrote:
> [...]
> > It has a way to use that section tho:
> > ⬢ [acme@toolbox perf-tools-next]$ man eu-readelf | grep -A2 -- --elf-section
> > [--elf-section [section] ]
> > [-w|
> > --debug-dump[=line,=decodedline,=info,=info+,=abbrev,=pubnames,=aranges,=macro,=frames,=str,=loc,=ranges,=gdb_index,=addr]]
> > --
> > --elf-section [section]
> > Use the named SECTION (default .gnu_debugdata) as (compressed) ELF input data
> > ⬢ [acme@toolbox perf-tools-next]$
> > ⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | wc -l
> > 339
> > ⬢ [acme@toolbox perf-tools-next]$ eu-readelf --elf-section -s /bin/find | grep -w FUNC | grep -vw UNDEF | head
> > 1: 00000000000056d0 35 FUNC LOCAL DEFAULT 17 entry_hashfunc
> > 2: 0000000000005700 34 FUNC LOCAL DEFAULT 17 entry_comparator
> > 3: 0000000000005920 121 FUNC LOCAL DEFAULT 17 subtree_has_side_effects
> > 4: 00000000000059a0 992 FUNC LOCAL DEFAULT 17 worst_cost.part.0
> > 5: 0000000000005d80 449 FUNC LOCAL DEFAULT 17 traverse_tree
> > 6: 0000000000005f50 73 FUNC LOCAL DEFAULT 17 undangle_file_pointers
> > 7: 0000000000005fa0 72 FUNC LOCAL DEFAULT 17 looks_like_expression
> > 8: 0000000000006030 303 FUNC LOCAL DEFAULT 17 get_fts_info_name
> > 9: 0000000000006190 35 FUNC LOCAL DEFAULT 17 inside_dir.part.0
> > 10: 0000000000006330 451 FUNC LOCAL DEFAULT 17 pred_sanity_check
> > ⬢ [acme@toolbox perf-tools-next]$
> Wow, thank you for teaching me that!
> I had been using:
> gdb /usr/bin/bash --batch -ex 'maint print msymbols'
> Because I knew GDB had support for .gnu_debugdata. But the --elf-section
> argument to eu-readelf is much more useful.
That was a nice assumption and it did the work for you :-)
I thought that the elfutils guys would add something to eu-readelf for
them to dump the compressed data in human readable for, looked at the
man page and voila!
<SNIP>
> > # Overhead Command Shared Object Symbol
> > # ........ ....... ............................... .......................................................
> > #
> > 8.72% find /usr/bin/find 0xb498
> > 7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
> > 7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
> > ⬢ [acme@toolbox perf-tools-next]$
> > The only strange thing was not having it resolved in the -v case, which
> > I think its because you added a new type of DSO but didn't update the
> > code that does the 'perf report -v' verbose case?
> > I ran out of time, have to go AFK now, can you please take a look,
> > Stephen?
> Thanks for the catch. I double checked all the places where
> DSO_BINARY_TYPE constants are enumerated, and it turns out I missed
> adding an entry to
> char dso__symtab_origin(const struct dso *dso) ...
>
> I assume that the array defaulted to '\0' which terminated the string
> too early for this line. Oops!
>
> Most of the letters I would associate with ".gnu_debugdata" are
> taken (namely, g/G for GNU, m/M for MiniDebugInfo, d/D for
> debugdata...). So 'n', for the second letter of GNU, is my selection
> unless you feel differently. With that change, the table is fixed for
> "perf report -v". Here it is running against my test data focusing on a
> symbol only found in .gnu_debugdata of bash:
>
> $ ./perf report -v --stdio -i ~/repos/UEK6/perf.data 2>&1 | egrep yy_readline_get\|gnu_debugdata
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/bash
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> unwind: yy_readline_get:ip = 0x55fdc4509dbe (0x33dbe)
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sed
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/date
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sqlite3
> read_gnu_debugdata: using .gnu_debugdata of /usr/bin/sleep
> 0.20% 0.00% bash /usr/bin/bash 0x55fdc4509dbe n [.] yy_readline_get
>
> I'll update the patch accordingly.
I just tested it, works as expected:
⬢ [acme@toolbox perf-tools-next]$ perf report -v --stdio |& head -20
build id event received for [vdso]: a2184b81fbbc08eff401d16259eca8ad5f9d8988 [20]
build id event received for /usr/bin/find: 3faf3f04d1b31abc9e5ce8428110e424fd980a37 [20]
build id event received for /usr/lib64/ld-linux-x86-64.so.2: 765f7ab0f3569ffe98de85864a0cedda9b686994 [20]
build id event received for /usr/lib64/libc.so.6: c8c3fa52aaee3f5d73b6fd862e39e9d4c010b6ba [20]
build id event received for [kernel.kallsyms]: c3fbb7df4dfb94762b1648bc65e4363e50f45585 [20]
read_gnu_debugdata: using .gnu_debugdata of /usr/bin/find
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 163 of event 'cpu_core/cycles/Pu'
# Event count (approx.): 68126524
#
# Overhead Command Shared Object Symbol
# ........ ....... ............................... .......................................................
#
8.72% find /usr/bin/find 0xb498 n [.] consider_visiting
7.90% find /usr/lib64/libc.so.6 0xe51e0 B [.] __GI___readdir64
7.44% find /usr/lib64/libc.so.6 0xa77cd B [.] _int_malloc
⬢ [acme@toolbox perf-tools-next]$
I'll reply to the v3 thread with my Tested-by.
Thanks!
- Arnaldo
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2025-03-10 15:21 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-02-20 18:55 [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 1/3] tools: perf: add dummy functions for !HAVE_LZMA_SUPPORT Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 2/3] tools: perf: add LZMA decompression from FILE Stephen Brennan
2025-02-20 18:55 ` [PATCH v2 3/3] tools: perf: support .gnu_debugdata for symbols Stephen Brennan
2025-02-26 22:06 ` [PATCH v2 0/3] Support .gnu_debugdata for symbols in perf Namhyung Kim
2025-03-07 20:10 ` Arnaldo Carvalho de Melo
2025-03-07 20:18 ` Arnaldo Carvalho de Melo
2025-03-07 20:46 ` Arnaldo Carvalho de Melo
2025-03-07 22:33 ` Stephen Brennan
2025-03-10 15:21 ` Arnaldo Carvalho de Melo
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