Re: [PATCH 2/2] perf tools: Improve EOPNOTSUPP error reporting

[He Zhe]

Oops, add some supporters from get_maintainer.pl

Zhe

On 2/23/21 4:25 PM, He Zhe wrote:
> There may be multiple reasons for EOPNOTSUPP. Sometimes we cannot determine
> which one it is.
>
> For example, when we set up uprobe with 32-bit perf and arm64 kernel on
> some hardware that does not support sampling/overflow-interrupts,
> $ perf probe -x /lib/libc.so.6 malloc
> $ perf record -e probe_libc:malloc -a ls
>
> Before this patch:
> probe_libc:malloc: PMU Hardware doesn't support sampling/overflow-interrupts. 
> Try 'perf stat'
>
> After this patch:
> probe_libc:malloc: PMU Hardware may not support sampling/overflow-interrupts. 
> Try 'perf stat'.
> Some 64-bit architectures may not support 32-bit instruction probing.
>
> Signed-off-by: He Zhe 
> ---
>  tools/perf/util/evsel.c | 18 ++
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 1bf76864c4f2..aa56511ddf60 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2697,22 +2697,24 @@ int evsel__open_strerror(struct evsel *evsel, struct 
> target *target,
>   break;
>   case EOPNOTSUPP:
>   if (evsel->core.attr.aux_output)
> - return scnprintf(msg, size,
> - "%s: PMU Hardware doesn't support 'aux_output' feature",
> + printed += scnprintf(msg + printed, size,
> + "%s: PMU Hardware may not support 'aux_output' feature.\n",
>evsel__name(evsel));
>   if (evsel->core.attr.sample_period != 0)
> - return scnprintf(msg, size,
> - "%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 
> 'perf stat'",
> + printed += scnprintf(msg + printed, size,
> + "%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 
> 'perf stat'.\n",
>evsel__name(evsel));
>   if (evsel->core.attr.precise_ip)
> - return scnprintf(msg, size, "%s",
> - "\'precise\' request may not be supported. Try removing 'p' modifier.");
> + printed += scnprintf(msg + printed, size, "%s",
> + "\'precise\' request may not be supported. Try removing 'p' 
> modifier.\n");
>  #if defined(__i386__) || defined(__x86_64__)
>   if (evsel->core.attr.type == PERF_TYPE_HARDWARE)
> - return scnprintf(msg, size, "%s",
> + printed += scnprintf(msg + printed, size, "%s",
>   "No hardware sampling interrupt available.\n");
>  #endif
> - break;
> + scnprintf(msg + printed, size, "%s",
> + "Some 64-bit architectures may not support 32-bit instruction 
> uprobe.\n");
> + return;
>   case EBUSY:
>   if (find_process("oprofiled"))
>   return scnprintf(msg, size,

[PATCH 2/2] perf tools: Improve EOPNOTSUPP error reporting

[He Zhe]

There may be multiple reasons for EOPNOTSUPP. Sometimes we cannot determine
which one it is.

For example, when we set up uprobe with 32-bit perf and arm64 kernel on
some hardware that does not support sampling/overflow-interrupts,
$ perf probe -x /lib/libc.so.6 malloc
$ perf record -e probe_libc:malloc -a ls

Before this patch:
probe_libc:malloc: PMU Hardware doesn't support sampling/overflow-interrupts. 
Try 'perf stat'

After this patch:
probe_libc:malloc: PMU Hardware may not support sampling/overflow-interrupts. 
Try 'perf stat'.
Some 64-bit architectures may not support 32-bit instruction probing.

Signed-off-by: He Zhe 
---
 tools/perf/util/evsel.c | 18 ++
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 1bf76864c4f2..aa56511ddf60 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2697,22 +2697,24 @@ int evsel__open_strerror(struct evsel *evsel, struct 
target *target,
break;
case EOPNOTSUPP:
if (evsel->core.attr.aux_output)
-   return scnprintf(msg, size,
-   "%s: PMU Hardware doesn't support 'aux_output' feature",
+   printed += scnprintf(msg + printed, size,
+   "%s: PMU Hardware may not support 'aux_output' feature.\n",
 evsel__name(evsel));
if (evsel->core.attr.sample_period != 0)
-   return scnprintf(msg, size,
-   "%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 
'perf stat'",
+   printed += scnprintf(msg + printed, size,
+   "%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 
'perf stat'.\n",
 evsel__name(evsel));
if (evsel->core.attr.precise_ip)
-   return scnprintf(msg, size, "%s",
-   "\'precise\' request may not be supported. Try removing 'p' modifier.");
+   printed += scnprintf(msg + printed, size, "%s",
+   "\'precise\' request may not be supported. Try removing 'p' 
modifier.\n");
 #if defined(__i386__) || defined(__x86_64__)
if (evsel->core.attr.type == PERF_TYPE_HARDWARE)
-   return scnprintf(msg, size, "%s",
+   printed += scnprintf(msg + printed, size, "%s",
"No hardware sampling interrupt available.\n");
 #endif
-   break;
+   scnprintf(msg + printed, size, "%s",
+   "Some 64-bit architectures may not support 32-bit instruction 
uprobe.\n");
+   return;
case EBUSY:
if (find_process("oprofiled"))
return scnprintf(msg, size,
-- 
2.17.1