From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fix to get the declared file name even if it uses file index 0
in DWARF5, using custom die_get_decl_file() function.
Actually, the DWARF5 standard says file index 0 of the
DW_AT_decl_file is invalid(*), but there is a discussion and
maybe this will be updated. Anyway, the clang generates such
DWARF5 file for the linux kernel. Thus it must be handled.
Without this, the perf probe returns an error;
$ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
Debuginfo analysis failed.
Error: Failed to show lines.
With this, it can handle the case correctly;
$ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
<vfs_read@$SRC_PATH/fs/read_write.c:10>
11 ret = rw_verify_area(READ, file, pos, count);
12 if (ret)
return ret;
(* DWARF5 specification 2.14 says "The value 0 indicates that no
source file has been specified.")
(**
http://wiki.dwarfstd.org/index.php?title=DWARF5_Line_Table_File_Numbers)
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v2:
- Update description so that it is clang version of DWARF5.
---
tools/perf/util/dwarf-aux.c | 47 +++++++++++++++++++++++++++-------------
tools/perf/util/dwarf-aux.h | 3 +++
tools/perf/util/probe-finder.c | 14 ++++++------
3 files changed, 42 insertions(+), 22 deletions(-)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 216fc3d959e8..30b36b525681 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -123,7 +123,7 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, Dwarf_Addr addr,
if (die_find_realfunc(cu_die, addr, &die_mem)
&& die_entrypc(&die_mem, &faddr) == 0 &&
faddr == addr) {
- *fname = dwarf_decl_file(&die_mem);
+ *fname = die_get_decl_file(&die_mem);
dwarf_decl_line(&die_mem, lineno);
goto out;
}
@@ -486,6 +486,19 @@ static int die_get_decl_fileno(Dwarf_Die *pdie)
return -ENOENT;
}
+/* Return the file name by index */
+static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
+{
+ Dwarf_Die cu_die;
+ Dwarf_Files *files;
+
+ if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
+ dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
+ return NULL;
+
+ return dwarf_filesrc(files, idx, NULL, NULL);
+}
+
/**
* die_get_call_file - Get callsite file name of inlined function instance
* @in_die: a DIE of an inlined function instance
@@ -495,18 +508,22 @@ static int die_get_decl_fileno(Dwarf_Die *pdie)
*/
const char *die_get_call_file(Dwarf_Die *in_die)
{
- Dwarf_Die cu_die;
- Dwarf_Files *files;
- int idx;
-
- idx = die_get_call_fileno(in_die);
- if (idx < 0 || !dwarf_diecu(in_die, &cu_die, NULL, NULL) ||
- dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
- return NULL;
-
- return dwarf_filesrc(files, idx, NULL, NULL);
+ return die_get_file_name(in_die, die_get_call_fileno(in_die));
}
+/**
+ * die_get_decl_file - Find the declared file name of this DIE
+ * @dw_die: a DIE for something declared.
+ *
+ * Get declared file name of @dw_die.
+ * NOTE: Since some version of clang DWARF5 implementation incorrectly uses
+ * file index 0 for DW_AT_decl_file, die_get_decl_file() will return NULL for
+ * such cases. Use this function instead.
+ */
+const char *die_get_decl_file(Dwarf_Die *dw_die)
+{
+ return die_get_file_name(dw_die, die_get_decl_fileno(dw_die));
+}
/**
* die_find_child - Generic DIE search function in DIE tree
@@ -790,7 +807,7 @@ static int __die_walk_funclines_cb(Dwarf_Die *in_die, void *data)
}
if (addr) {
- fname = dwarf_decl_file(in_die);
+ fname = die_get_decl_file(in_die);
if (fname && dwarf_decl_line(in_die, &lineno) == 0) {
lw->retval = lw->callback(fname, lineno, addr, lw->data);
if (lw->retval != 0)
@@ -818,7 +835,7 @@ static int __die_walk_funclines(Dwarf_Die *sp_die, bool recursive,
int lineno;
/* Handle function declaration line */
- fname = dwarf_decl_file(sp_die);
+ fname = die_get_decl_file(sp_die);
if (fname && dwarf_decl_line(sp_die, &lineno) == 0 &&
die_entrypc(sp_die, &addr) == 0) {
lw.retval = callback(fname, lineno, addr, data);
@@ -873,7 +890,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
if (dwarf_tag(rt_die) != DW_TAG_compile_unit) {
cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
dwarf_decl_line(rt_die, &decl);
- decf = dwarf_decl_file(rt_die);
+ decf = die_get_decl_file(rt_die);
if (!decf) {
pr_debug2("Failed to get the declared file name of %s\n",
dwarf_diename(rt_die));
@@ -928,7 +945,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
dwarf_decl_line(&die_mem, &inl);
if (inl != decl ||
- decf != dwarf_decl_file(&die_mem))
+ decf != die_get_decl_file(&die_mem))
continue;
}
}
diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index 7ee0fa19b5c4..7ec8bc1083bb 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -50,6 +50,9 @@ int die_get_call_lineno(Dwarf_Die *in_die);
/* Get callsite file name of inlined function instance */
const char *die_get_call_file(Dwarf_Die *in_die);
+/* Get declared file name of a DIE */
+const char *die_get_decl_file(Dwarf_Die *dw_die);
+
/* Get type die */
Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 1aa8fcc41c76..54b49ce85c9f 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -763,7 +763,7 @@ static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
/* Skip if declared file name does not match */
if (fsp->file) {
- file = dwarf_decl_file(fn_die);
+ file = die_get_decl_file(fn_die);
if (!file || strcmp(fsp->file, file) != 0)
return 0;
}
@@ -1071,7 +1071,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
return DWARF_CB_OK;
/* Check declared file */
- fname = dwarf_decl_file(sp_die);
+ fname = die_get_decl_file(sp_die);
if (!fname) {
pr_warning("A function DIE doesn't have decl_line. Maybe broken DWARF?\n");
return DWARF_CB_OK;
@@ -1151,7 +1151,7 @@ static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
return DWARF_CB_OK;
if (param->file) {
- fname = dwarf_decl_file(param->sp_die);
+ fname = die_get_decl_file(param->sp_die);
if (!fname || strtailcmp(param->file, fname))
return DWARF_CB_OK;
}
@@ -1750,7 +1750,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
goto post;
}
- fname = dwarf_decl_file(&spdie);
+ fname = die_get_decl_file(&spdie);
if (addr == baseaddr) {
/* Function entry - Relative line number is 0 */
lineno = baseline;
@@ -1787,7 +1787,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
}
}
/* Verify the lineno and baseline are in a same file */
- tmp = dwarf_decl_file(&spdie);
+ tmp = die_get_decl_file(&spdie);
if (!tmp || (fname && strcmp(tmp, fname) != 0))
lineno = 0;
}
@@ -1902,13 +1902,13 @@ static int line_range_search_cb(Dwarf_Die *sp_die, void *data)
/* Check declared file */
if (lr->file) {
- fname = dwarf_decl_file(sp_die);
+ fname = die_get_decl_file(sp_die);
if (!fname || strtailcmp(lr->file, fname))
return DWARF_CB_OK;
}
if (die_match_name(sp_die, lr->function) && die_is_func_def(sp_die)) {
- lf->fname = dwarf_decl_file(sp_die);
+ lf->fname = die_get_decl_file(sp_die);
dwarf_decl_line(sp_die, &lr->offset);
pr_debug("fname: %s, lineno:%d\n", lf->fname, lr->offset);
lf->lno_s = lr->offset + lr->start;Hi, Am 01.11.22 um 14:48 schrieb Masami Hiramatsu (Google): > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > Fix to get the declared file name even if it uses file index 0 > in DWARF5, using custom die_get_decl_file() function. > this patch breaks perf probe on fedora 38. I was trying to a add a probe to systemd-logind using kernel-6.3.6-200.fc38.x86_64 with kernel-tools-6.3.3-200.fc38.x86_64. When trying to add a probe, I get the following message: # perf probe -x /usr/lib/systemd/systemd-logind --funcs="match_unit_removed" match_unit_removed Function exists and was found: # perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed A function DIE doesn't have decl_line. Maybe broken DWARF? A function DIE doesn't have decl_line. Maybe broken DWARF? Probe point 'match_unit_removed' not found. Error: Failed to add events. When reverting dc9a5d2ccd5c823cc05cafe75fcf19b682d8152c, I was able to add the probe point: # ./perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed Added new event: probe_systemd:match_unit_removed (on match_unit_removed in /usr/lib/systemd/systemd-logind) You can now use it in all perf tools, such as: perf record -e probe_systemd:match_unit_removed -aR sleep 1 Probe point is then visible with and without this commit: # perf probe -l probe_systemd:match_unit_removed (on match_unit_removed in /usr/lib/systemd/systemd-logind) # ./perf probe -l probe_systemd:match_unit_removed (on match_unit_removed@../src/login/logind-dbus.c in /usr/lib/systemd/systemd-logind) Best regards, Georg
When switching from dwarf_decl_file() to die_get_decl_file(), a regression
was introduced when having a binary where the DWARF info is split to
multiple CUs. It is not possible to add probes to certain functions.
These patches introduce a testcase which shows the current regression
and a fix for the issue
Signed-off-by: Georg Müller <georgmueller@gmx.net>
Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
---
Changes in v2:
- Add testcase
Georg Müller (2):
perf probe: add test for regression introduced by switch to
die_get_decl_file
perf probe: read DWARF files from the correct CU
.../shell/test_uprobe_from_different_cu.sh | 77 +++++++++++++++++++
tools/perf/util/dwarf-aux.c | 4 +-
2 files changed, 80 insertions(+), 1 deletion(-)
create mode 100755 tools/perf/tests/shell/test_uprobe_from_different_cu.sh
--
2.41.0
On 28.06.23 10:23, Georg Müller wrote: > When switching from dwarf_decl_file() to die_get_decl_file(), a regression > was introduced when having a binary where the DWARF info is split to > multiple CUs. It is not possible to add probes to certain functions. > > These patches introduce a testcase which shows the current regression > and a fix for the issue > > Signed-off-by: Georg Müller <georgmueller@gmx.net> > Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/ FWIW, you in both commits might want to add a Cc: stable@vger.kernel.org to ensure the fix is backported to appropriate releases (e.g. 6.4 and 6.3, if the latter doesn't go EOL earlier). Ciao, Thorsten P.S.: Some (I guess: most) maintainers prefer if patch series are startet as new threads
This patch adds a test to validate that perf probe works for binaries
where DWARF info is split into multiple CUs
Signed-off-by: Georg Müller <georgmueller@gmx.net>
Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
---
.../shell/test_uprobe_from_different_cu.sh | 77 +++++++++++++++++++
1 file changed, 77 insertions(+)
create mode 100755 tools/perf/tests/shell/test_uprobe_from_different_cu.sh
diff --git a/tools/perf/tests/shell/test_uprobe_from_different_cu.sh b/tools/perf/tests/shell/test_uprobe_from_different_cu.sh
new file mode 100755
index 000000000000..00d2e0e2e0c2
--- /dev/null
+++ b/tools/perf/tests/shell/test_uprobe_from_different_cu.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+# test perf probe of function from different CU
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+temp_dir=$(mktemp -d /tmp/perf-uprobe-different-cu-sh.XXXXXXXXXX)
+
+cleanup()
+{
+ trap - EXIT TERM INT
+ if [[ "${temp_dir}" =~ ^/tmp/perf-uprobe-different-cu-sh.*$ ]]; then
+ echo "--- Cleaning up ---"
+ perf probe -x ${temp_dir}/testfile -d foo
+ rm -f "${temp_dir}/"*
+ rmdir "${temp_dir}"
+ fi
+}
+
+trap_cleanup()
+{
+ cleanup
+ exit 1
+}
+
+trap trap_cleanup EXIT TERM INT
+
+cat > ${temp_dir}/testfile-foo.h << EOF
+struct t
+{
+ int *p;
+ int c;
+};
+
+extern int foo (int i, struct t *t);
+EOF
+
+cat > ${temp_dir}/testfile-foo.c << EOF
+#include "testfile-foo.h"
+
+int
+foo (int i, struct t *t)
+{
+ int j, res = 0;
+ for (j = 0; j < i && j < t->c; j++)
+ res += t->p[j];
+
+ return res;
+}
+EOF
+
+cat > ${temp_dir}/testfile-main.c << EOF
+#include "testfile-foo.h"
+
+static struct t g;
+
+int
+main (int argc, char **argv)
+{
+ int i;
+ int j[argc];
+ g.c = argc;
+ g.p = j;
+ for (i = 0; i < argc; i++)
+ j[i] = (int) argv[i][0];
+ return foo (3, &g);
+}
+EOF
+
+gcc -g -Og -flto -c ${temp_dir}/testfile-foo.c -o ${temp_dir}/testfile-foo.o
+gcc -g -Og -c ${temp_dir}/testfile-main.c -o ${temp_dir}/testfile-main.o
+gcc -g -Og -o ${temp_dir}/testfile ${temp_dir}/testfile-foo.o ${temp_dir}/testfile-main.o
+
+perf probe -x ${temp_dir}/testfile --funcs foo
+perf probe -x ${temp_dir}/testfile foo
+
+cleanup
--
2.41.0On Wed, Jun 28, 2023 at 1:25 AM Georg Müller <georgmueller@gmx.net> wrote:
>
> This patch adds a test to validate that perf probe works for binaries
> where DWARF info is split into multiple CUs
>
> Signed-off-by: Georg Müller <georgmueller@gmx.net>
> Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
> ---
> .../shell/test_uprobe_from_different_cu.sh | 77 +++++++++++++++++++
> 1 file changed, 77 insertions(+)
> create mode 100755 tools/perf/tests/shell/test_uprobe_from_different_cu.sh
>
> diff --git a/tools/perf/tests/shell/test_uprobe_from_different_cu.sh b/tools/perf/tests/shell/test_uprobe_from_different_cu.sh
> new file mode 100755
> index 000000000000..00d2e0e2e0c2
> --- /dev/null
> +++ b/tools/perf/tests/shell/test_uprobe_from_different_cu.sh
> @@ -0,0 +1,77 @@
> +#!/bin/bash
> +# test perf probe of function from different CU
> +# SPDX-License-Identifier: GPL-2.0
> +
> +set -e
> +
> +temp_dir=$(mktemp -d /tmp/perf-uprobe-different-cu-sh.XXXXXXXXXX)
> +
> +cleanup()
> +{
> + trap - EXIT TERM INT
> + if [[ "${temp_dir}" =~ ^/tmp/perf-uprobe-different-cu-sh.*$ ]]; then
> + echo "--- Cleaning up ---"
> + perf probe -x ${temp_dir}/testfile -d foo
> + rm -f "${temp_dir}/"*
> + rmdir "${temp_dir}"
> + fi
> +}
> +
> +trap_cleanup()
> +{
> + cleanup
> + exit 1
> +}
> +
> +trap trap_cleanup EXIT TERM INT
> +
> +cat > ${temp_dir}/testfile-foo.h << EOF
> +struct t
> +{
> + int *p;
> + int c;
> +};
> +
> +extern int foo (int i, struct t *t);
> +EOF
> +
> +cat > ${temp_dir}/testfile-foo.c << EOF
> +#include "testfile-foo.h"
> +
> +int
> +foo (int i, struct t *t)
> +{
> + int j, res = 0;
> + for (j = 0; j < i && j < t->c; j++)
> + res += t->p[j];
> +
> + return res;
> +}
> +EOF
> +
> +cat > ${temp_dir}/testfile-main.c << EOF
> +#include "testfile-foo.h"
> +
> +static struct t g;
> +
> +int
> +main (int argc, char **argv)
> +{
> + int i;
> + int j[argc];
> + g.c = argc;
> + g.p = j;
> + for (i = 0; i < argc; i++)
> + j[i] = (int) argv[i][0];
> + return foo (3, &g);
> +}
> +EOF
> +
> +gcc -g -Og -flto -c ${temp_dir}/testfile-foo.c -o ${temp_dir}/testfile-foo.o
> +gcc -g -Og -c ${temp_dir}/testfile-main.c -o ${temp_dir}/testfile-main.o
> +gcc -g -Og -o ${temp_dir}/testfile ${temp_dir}/testfile-foo.o ${temp_dir}/testfile-main.o
Thanks for the test Georg! By directly relying on gcc this test fails
for me in some constrained environments, like containers. I think
there should be a skip if gcc isn't present. A different option is to
just build the test code into the perf binary itself as a test
workload:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/workloads?h=perf-tools-next
Wdyt? Thanks,
Ian
> +
> +perf probe -x ${temp_dir}/testfile --funcs foo
> +perf probe -x ${temp_dir}/testfile foo
> +
> +cleanup
> --
> 2.41.0
>
Am 27.07.23 um 19:45 schrieb Ian Rogers: > On Wed, Jun 28, 2023 at 1:25 AM Georg Müller <georgmueller@gmx.net> wrote: > > Thanks for the test Georg! By directly relying on gcc this test fails > for me in some constrained environments, like containers. I think > there should be a skip if gcc isn't present. A different option is to > just build the test code into the perf binary itself as a test > workload: > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/workloads?h=perf-tools-next > > Wdyt? Thanks, > Ian > I prepare a commit which checks for gcc and skips the test in this case. I think building thi test code into the perf binary itself is not an option here, since the test relies on a special setup of using -flto for one of the compilation units. There is also a cleanup issue if anything fails. This will be included in the patch as well. Best regards, Georg
After switching from dwarf_decl_file() to die_get_decl_file(), it is not
possible to add probes for certain functions:
$ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed
A function DIE doesn't have decl_line. Maybe broken DWARF?
A function DIE doesn't have decl_line. Maybe broken DWARF?
Probe point 'match_unit_removed' not found.
Error: Failed to add events.
The problem is that die_get_decl_file() uses the wrong CU to search for
the file. elfutils commit e1db5cdc9f has some good explanation for this:
dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
attribute. This means the attribute might come from a different DIE
in a different CU. If so, we need to use the CU associated with the
attribute, not the original DIE, to resolve the file name.
This patch uses the same source of information as elfutils: use attribute
DW_AT_decl_file and use this CU to search for the file.
Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5")
Signed-off-by: Georg Müller <georgmueller@gmx.net>
Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
---
tools/perf/util/dwarf-aux.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index b07414409771..137b3ed9897b 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
{
Dwarf_Die cu_die;
Dwarf_Files *files;
+ Dwarf_Attribute attr_mem;
- if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
+ if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
+ !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
return NULL;
--
2.41.0Hi all,
I have found a solution for this bug and will post a patch later today.
Am 09.06.23 um 14:21 schrieb Georg Müller:
>
> Am 01.11.22 um 14:48 schrieb Masami Hiramatsu (Google):
>> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>>
>> Fix to get the declared file name even if it uses file index 0
>> in DWARF5, using custom die_get_decl_file() function.
>>
>
> this patch breaks perf probe on fedora 38.
>
The problem is that die_get_file_name() uses the wrong cu_die.
I was pointed to the solution by reading elfutils commit e1db5cdc9:
dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
attribute. This means the attribute might come from a different DIE
in a different CU. If so, we need to use the CU associated with the
attribute, not the original DIE, to resolve the file name.
The correct cu_die has to be obtained via
dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem)
and then cu_die from the cu from attr_mem (dwarf_cu_die(attr_mem.cu, &cu_die, ...)
to obtain it) has to be used.
Best regards,
Georg
[CCing the regression list, as it should be in the loop for regressions: https://docs.kernel.org/admin-guide/reporting-regressions.html] [TLDR: I'm adding this report to the list of tracked Linux kernel regressions; the text you find below is based on a few templates paragraphs you might have encountered already in similar form. See link in footer if these mails annoy you.] On 09.06.23 14:21, Georg Müller wrote: > > Am 01.11.22 um 14:48 schrieb Masami Hiramatsu (Google): >> From: Masami Hiramatsu (Google) <mhiramat@kernel.org> >> >> Fix to get the declared file name even if it uses file index 0 >> in DWARF5, using custom die_get_decl_file() function. >> > > this patch breaks perf probe on fedora 38. > > I was trying to a add a probe to systemd-logind using > kernel-6.3.6-200.fc38.x86_64 with kernel-tools-6.3.3-200.fc38.x86_64. > > When trying to add a probe, I get the following message: > > # perf probe -x /usr/lib/systemd/systemd-logind > --funcs="match_unit_removed" > match_unit_removed > > Function exists and was found: > > # perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed > A function DIE doesn't have decl_line. Maybe broken DWARF? > A function DIE doesn't have decl_line. Maybe broken DWARF? > Probe point 'match_unit_removed' not found. > Error: Failed to add events. > > When reverting dc9a5d2ccd5c823cc05cafe75fcf19b682d8152c, I was able to > add the probe point: > > # ./perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed > Added new event: > probe_systemd:match_unit_removed (on match_unit_removed in > /usr/lib/systemd/systemd-logind) > > You can now use it in all perf tools, such as: > > perf record -e probe_systemd:match_unit_removed -aR sleep 1 > > > Probe point is then visible with and without this commit: > > # perf probe -l > probe_systemd:match_unit_removed (on match_unit_removed in > /usr/lib/systemd/systemd-logind) > # ./perf probe -l > probe_systemd:match_unit_removed (on > match_unit_removed@../src/login/logind-dbus.c in > /usr/lib/systemd/systemd-logind) Thanks for the report. To be sure the issue doesn't fall through the cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression tracking bot: #regzbot ^introduced dc9a5d2ccd5c823cc05cafe75fcf19b682d8152c #regzbot title tools/perf: adding a specific probe suddenly fails #regzbot ignore-activity This isn't a regression? This issue or a fix for it are already discussed somewhere else? It was fixed already? You want to clarify when the regression started to happen? Or point out I got the title or something else totally wrong? Then just reply and tell me -- ideally while also telling regzbot about it, as explained by the page listed in the footer of this mail. Developers: When fixing the issue, remember to add 'Link:' tags pointing to the report (the parent of this mail). See page linked in footer for details. Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr That page also explains what to do if mails like this annoy you.
[TLDR: This mail in primarily relevant for Linux kernel regression tracking. See link in footer if these mails annoy you.] On 15.06.23 13:42, Linux regression tracking #adding (Thorsten Leemhuis) wrote: > On 09.06.23 14:21, Georg Müller wrote: >> >> Am 01.11.22 um 14:48 schrieb Masami Hiramatsu (Google): >>> From: Masami Hiramatsu (Google) <mhiramat@kernel.org> >>> >>> Fix to get the declared file name even if it uses file index 0 >>> in DWARF5, using custom die_get_decl_file() function. >> >> this patch breaks perf probe on fedora 38. #regzbot fix: c66e1c68c13b87250 #regzbot ignore-activity Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr That page also explains what to do if mails like this annoy you.
After switching from dwarf_decl_file() to die_get_decl_file(), it is not
possible to add probes for certain functions of certain binaries:
$ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed
A function DIE doesn't have decl_line. Maybe broken DWARF?
A function DIE doesn't have decl_line. Maybe broken DWARF?
Probe point 'match_unit_removed' not found.
Error: Failed to add events.
The problem is that die_get_decl_file() uses the wrong CU to search for
the file. elfutils commit e1db5cdc9f has some good explanation for this:
dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
attribute. This means the attribute might come from a different DIE
in a different CU. If so, we need to use the CU associated with the
attribute, not the original DIE, to resolve the file name.
This patch uses the same source of information as elfutils: use attribute
DW_AT_decl_file and use this CU to search for the file.
Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5")
Signed-off-by: Georg Müller <georgmueller@gmx.net>
Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
---
tools/perf/util/dwarf-aux.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index b07414409771..137b3ed9897b 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
{
Dwarf_Die cu_die;
Dwarf_Files *files;
+ Dwarf_Attribute attr_mem;
- if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
+ if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
+ !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
return NULL;
--
2.41.0Em Thu, Jun 15, 2023 at 10:01:37PM +0200, Georg Müller escreveu:
> After switching from dwarf_decl_file() to die_get_decl_file(), it is not
> possible to add probes for certain functions of certain binaries:
>
> $ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed
> A function DIE doesn't have decl_line. Maybe broken DWARF?
> A function DIE doesn't have decl_line. Maybe broken DWARF?
> Probe point 'match_unit_removed' not found.
> Error: Failed to add events.
>
> The problem is that die_get_decl_file() uses the wrong CU to search for
> the file. elfutils commit e1db5cdc9f has some good explanation for this:
>
> dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
> attribute. This means the attribute might come from a different DIE
> in a different CU. If so, we need to use the CU associated with the
> attribute, not the original DIE, to resolve the file name.
>
> This patch uses the same source of information as elfutils: use attribute
> DW_AT_decl_file and use this CU to search for the file.
Thanks, applied to the perf-tools branch, that will be submitted for
Linux v6.5.
- Arnaldo
> Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5")
> Signed-off-by: Georg Müller <georgmueller@gmx.net>
> Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
> ---
> tools/perf/util/dwarf-aux.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index b07414409771..137b3ed9897b 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
> {
> Dwarf_Die cu_die;
> Dwarf_Files *files;
> + Dwarf_Attribute attr_mem;
>
> - if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
> + if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
> + !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
> dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
> return NULL;
>
> --
> 2.41.0
>
--
- Arnaldo
On Tue, 11 Jul 2023 09:57:45 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> Em Thu, Jun 15, 2023 at 10:01:37PM +0200, Georg Müller escreveu:
> > After switching from dwarf_decl_file() to die_get_decl_file(), it is not
> > possible to add probes for certain functions of certain binaries:
> >
> > $ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed
> > A function DIE doesn't have decl_line. Maybe broken DWARF?
> > A function DIE doesn't have decl_line. Maybe broken DWARF?
> > Probe point 'match_unit_removed' not found.
> > Error: Failed to add events.
> >
> > The problem is that die_get_decl_file() uses the wrong CU to search for
> > the file. elfutils commit e1db5cdc9f has some good explanation for this:
> >
> > dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
> > attribute. This means the attribute might come from a different DIE
> > in a different CU. If so, we need to use the CU associated with the
> > attribute, not the original DIE, to resolve the file name.
> >
> > This patch uses the same source of information as elfutils: use attribute
> > DW_AT_decl_file and use this CU to search for the file.
>
> Thanks, applied to the perf-tools branch, that will be submitted for
> Linux v6.5.
Thanks Arnaldo and Georg,
It sounds perfect reason why that happened. I didn't expect the case that
the attribute comes from another CU...
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> - Arnaldo
>
> > Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5")
> > Signed-off-by: Georg Müller <georgmueller@gmx.net>
> > Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
> > ---
> > tools/perf/util/dwarf-aux.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> > index b07414409771..137b3ed9897b 100644
> > --- a/tools/perf/util/dwarf-aux.c
> > +++ b/tools/perf/util/dwarf-aux.c
> > @@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
> > {
> > Dwarf_Die cu_die;
> > Dwarf_Files *files;
> > + Dwarf_Attribute attr_mem;
> >
> > - if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
> > + if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
> > + !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
> > dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
> > return NULL;
> >
> > --
> > 2.41.0
> >
>
> --
>
> - Arnaldo
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
Em Tue, Jul 11, 2023 at 10:20:00PM +0900, Masami Hiramatsu escreveu: > On Tue, 11 Jul 2023 09:57:45 -0300 Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > > Em Thu, Jun 15, 2023 at 10:01:37PM +0200, Georg Müller escreveu: > > > The problem is that die_get_decl_file() uses the wrong CU to search for > > > the file. elfutils commit e1db5cdc9f has some good explanation for this: > > > > > > dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file > > > attribute. This means the attribute might come from a different DIE > > > in a different CU. If so, we need to use the CU associated with the > > > attribute, not the original DIE, to resolve the file name. > > > > > > This patch uses the same source of information as elfutils: use attribute > > > DW_AT_decl_file and use this CU to search for the file. > > > > Thanks, applied to the perf-tools branch, that will be submitted for > > Linux v6.5. > Thanks Arnaldo and Georg, > It sounds perfect reason why that happened. I didn't expect the case that > the attribute comes from another CU... > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thanks, added it to the cset. - Arnaldo
Hi,
Am 15.06.23 um 22:01 schrieb Georg Müller:
> After switching from dwarf_decl_file() to die_get_decl_file(), it is not
> possible to add probes for certain functions of certain binaries:
>
> $ perf probe -x /usr/lib/systemd/systemd-logind match_unit_removed
> A function DIE doesn't have decl_line. Maybe broken DWARF?
> A function DIE doesn't have decl_line. Maybe broken DWARF?
> Probe point 'match_unit_removed' not found.
> Error: Failed to add events.
>
> The problem is that die_get_decl_file() uses the wrong CU to search for
> the file. elfutils commit e1db5cdc9f has some good explanation for this:
>
> dwarf_decl_file uses dwarf_attr_integrate to get the DW_AT_decl_file
> attribute. This means the attribute might come from a different DIE
> in a different CU. If so, we need to use the CU associated with the
> attribute, not the original DIE, to resolve the file name.
>
> This patch uses the same source of information as elfutils: use attribute
> DW_AT_decl_file and use this CU to search for the file.
>
> Fixes: dc9a5d2ccd5c ("perf probe: Fix to get declared file name from clang DWARF5")
> Signed-off-by: Georg Müller <georgmueller@gmx.net>
> Link: https://lore.kernel.org/r/5a00d5a5-7be7-ef8a-4044-9a16249fff25@gmx.net/
> ---
> tools/perf/util/dwarf-aux.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index b07414409771..137b3ed9897b 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -478,8 +478,10 @@ static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
> {
> Dwarf_Die cu_die;
> Dwarf_Files *files;
> + Dwarf_Attribute attr_mem;
>
> - if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
> + if (idx < 0 || !dwarf_attr_integrate(dw_die, DW_AT_decl_file, &attr_mem) ||
> + !dwarf_cu_die(attr_mem.cu, &cu_die, NULL, NULL, NULL, NULL, NULL, NULL) ||
> dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
> return NULL;
>
> --
> 2.41.0
>
Just a question regarding the patch:
Should I also add a testcase to show the issue or is this enough? It can be
reproduced quite simple with two .c files and one .h file, the same test as the
one added in elfutils with commit e1db5cdc9f, compiled with the same three steps
as in the comment of the shell script, but without "-flto":
https://sourceware.org/git/?p=elfutils.git;a=commitdiff;h=e1db5cdc9f230f8de4df1a0f38dca69b283ee57a
Best regards,
Georg
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