Re: [PATCH 14/25] perf symbols: Save DSO loading errno to better report errors

[Borislav Petkov]

On Tue, Mar 24, 2015 at 01:19:29PM -0300, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> 
> Before, when some problem happened while trying to load the kernel
> symtab, 'perf top' would show:
> 
>       ââWarning:ââââââââââââââââââââââââââââ
>       âThe vmlinux file can't be used.     â
>       âKernel samples will not be resolved.â
>       â                                    â
>       â                                    â
>       âPress any key...                    â
>       ââââââââââââââââââââââââââââââââââââââ
> 
> Now, it reports:
> 
>   # perf top --vmlinux /dev/null
> 
>       ââWarning:ââââââââââââââââââââââââââââââââââââââââââââ
>       âThe /tmp/passwd file can't be used: Invalid ELF fileâ
>       âKernel samples will not be resolved.                â
>       â                                                    â
>       â                                                    â
>       âPress any key...                                    â
>       ââââââââââââââââââââââââââââââââââââââââââââââââââââââ
> 
> 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@xxxxxxxxxx>
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxx>
> Cc: Don Zickus <dzickus@xxxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Stephane Eranian <eranian@xxxxxxxxxx>
> Link: http://lkml.kernel.org/n/tip-u5rb5uq63xqhkfb8uv2lxd5u@xxxxxxxxxxxxxx
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

...

> @@ -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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