2022-09-29 21:12:45

by Henry Castro

Subject: [PATCH] perf: fix the probe finder location (.dwo files)

If the file object is compiled using -gsplit-dwarf,
the probe finder location will fail.

Signed-off-by: Henry Castro <[email protected]>
---
tools/perf/util/probe-finder.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 50d861a80f57..6d7c5461251d 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1161,7 +1161,8 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
struct perf_probe_point *pp = &pf->pev->point;
Dwarf_Off off, noff;
size_t cuhl;
- Dwarf_Die *diep;
+ Dwarf_Die *diep, cudie, subdie;
+ uint8_t unit_type;
int ret = 0;

off = 0;
@@ -1200,6 +1201,14 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
continue;
}

+ /* Check separate debug information file. */
+ if (dwarf_cu_info(pf->cu_die.cu, NULL, &unit_type, &cudie,
+ &subdie, NULL, NULL, NULL))
+ continue;
+
+ if (unit_type == DW_UT_skeleton)
+ pf->cu_die = subdie;
+
/* Check if target file is included. */
if (pp->file)
pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
--
2.20.1

2022-09-30 17:26:08

by Namhyung Kim

Subject: Re: [PATCH] perf: fix the probe finder location (.dwo files)

Hello,

On Thu, Sep 29, 2022 at 2:00 PM Henry Castro <[email protected]> wrote:
>
> If the file object is compiled using -gsplit-dwarf,
> the probe finder location will fail.
>
> Signed-off-by: Henry Castro <[email protected]>
> ---
> tools/perf/util/probe-finder.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 50d861a80f57..6d7c5461251d 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -1161,7 +1161,8 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
> struct perf_probe_point *pp = &pf->pev->point;
> Dwarf_Off off, noff;
> size_t cuhl;
> - Dwarf_Die *diep;
> + Dwarf_Die *diep, cudie, subdie;
> + uint8_t unit_type;
> int ret = 0;
>
> off = 0;
> @@ -1200,6 +1201,14 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
> continue;
> }
>
> + /* Check separate debug information file. */
> + if (dwarf_cu_info(pf->cu_die.cu, NULL, &unit_type, &cudie,
> + &subdie, NULL, NULL, NULL))

It seems dwarf_cu_info was introduced in elfutils 0.171 which
was released in June 2018. I hope all the test setups have
more recent versions.


> + continue;
> +
> + if (unit_type == DW_UT_skeleton)
> + pf->cu_die = subdie;

Is this DWARF5 thing? Will it handle the previous version well?
IOW wouldn't dwarf_cu_info() return fail?

Anyway I think it'd be safer to do

if (dwarf_cu_info() == 0 && unit_type == skeleton)
pf->cu_die = subdie;

Thanks,
Namhyung


> +
> /* Check if target file is included. */
> if (pp->file)
> pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
> --
> 2.20.1
>

2022-10-03 18:32:45

by Henry Castro

Subject: [PATCH v2] perf: fix the probe finder location (.dwo files)

If the file object is compiled using -gsplit-dwarf,
the probe finder location will fail.

Signed-off-by: Henry Castro <[email protected]>
---

> Anyway I think it'd be safer to do
>
> if (dwarf_cu_info() == 0 && unit_type == skeleton)
> pf->cu_die = subdie;

Thank you, I have modifed the patch :)


tools/perf/util/probe-finder.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 50d861a80f57..b27039f5f04b 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1161,7 +1161,8 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
struct perf_probe_point *pp = &pf->pev->point;
Dwarf_Off off, noff;
size_t cuhl;
- Dwarf_Die *diep;
+ Dwarf_Die *diep, cudie, subdie;
+ uint8_t unit_type;
int ret = 0;

off = 0;
@@ -1200,6 +1201,14 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
continue;
}

+#if _ELFUTILS_VERSION >= 171
+ /* Check separate debug information file. */
+ if (dwarf_cu_info(pf->cu_die.cu, NULL, &unit_type,
+ &cudie, &subdie, NULL, NULL, NULL) == 0
+ && unit_type == DW_UT_skeleton)
+ pf->cu_die = subdie;
+#endif
+
/* Check if target file is included. */
if (pp->file)
pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
--
2.20.1