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SubjectRe: [PATCH 14/25] perf symbols: Save DSO loading errno to better report errors
On Tue, Mar 24, 2015 at 01:19:29PM -0300, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
>
> Before, when some problem happened while trying to load the kernel
> symtab, 'perf top' would show:
>
> ┌─Warning:───────────────────────────┐
> │The vmlinux file can't be used. │
> │Kernel samples will not be resolved.│
> │ │
> │ │
> │Press any key... │
> └────────────────────────────────────┘
>
> Now, it reports:
>
> # perf top --vmlinux /dev/null
>
> ┌─Warning:───────────────────────────────────────────┐
> │The /tmp/passwd file can't be used: Invalid ELF file│
> │Kernel samples will not be resolved. │
> │ │
> │ │
> │Press any key... │
> └────────────────────────────────────────────────────┘
>
> This is possible because we now register the reason for not being able
> to load the symtab in the dso->load_errno member, and provide a
> dso__strerror_load() routine to format this error into a strerror like
> string with a short reason for the error while loading.
>
> That can be just forwarding the dso__strerror_load() call to
> strerror_r(), or, for a separate errno range providing a custom message.
>
> Reported-by: Ingo Molnar <mingo@kernel.org>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Don Zickus <dzickus@redhat.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Stephane Eranian <eranian@google.com>
> Link: http://lkml.kernel.org/n/tip-u5rb5uq63xqhkfb8uv2lxd5u@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

...

> @@ -1137,3 +1137,36 @@ enum dso_type dso__type(struct dso *dso, struct machine *machine)
>
> return dso__type_fd(fd);
> }
> +
> +int dso__strerror_load(struct dso *dso, char *buf, size_t buflen)
> +{
> + int idx, errnum = dso->load_errno;
> + /*
> + * This must have a same ordering as the enum dso_load_errno.
> + */
> + static const char *dso_load__error_str[] = {
> + "Internal tools/perf/ library error",
> + "Invalid ELF file",
> + "Can not read build id",
> + "Mismatching build id",
> + "Decompression failure",
> + };

You could define this str array by using the dso_load_errno defines so
that they're always in sync:

static const char *dso_load__error_str[] = {
[DSO_LOAD_ERRNO__INTERNAL_ERROR - __DSO_LOAD_ERRNO__START] = "Internal tools/perf/ library error",
[DSO_LOAD_ERRNO__INVALID_ELF - __DSO_LOAD_ERRNO__START] = "Invalid ELF file",
...

and even use a small macro to hide the __DSO_LOAD_ERRNO__START thing.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


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