Re: [PATCH perf/core ] perf probe: Show the error reason comes from invalid DSO

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Arnaldo, could you also apply this?

This will helps users to find the reason why perf probe failed
to open the debuginfo.

On 2015/05/12 12:40, Masami Hiramatsu wrote:
> Show the reason of error when dso__load* failed. This shows
> when user gives wrong kernel image or wrong path.
> 
> Without this, perf probe shows an obscure message.
>   ----
>   $ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
>   Failed to find path of kernel module.
>     Error: Failed to show lines.
>   ----
> 
> With this, perf shows appropriate error message.
>   ----
>   $ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
>   Failed to find the path for kernel: Mismatching build id
>     Error: Failed to show lines.
>   ----
> And
>   ----
>   $ perf probe -k /non-exist/kernel/vmlinux -L vfs_read
>   Failed to find the path for kernel: No such file or directory
>     Error: Failed to show lines.
>   ----
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> ---
>  tools/perf/util/probe-event.c |   47 +++++++++++++++++++++--------------------
>  tools/perf/util/probe-event.h |    3 ---
>  2 files changed, 24 insertions(+), 26 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index a2d8cef..a4830a6 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -201,11 +201,12 @@ static void put_target_map(struct map *map, bool user)
>  }
>  
>  
> -static struct dso *kernel_get_module_dso(const char *module)
> +static int kernel_get_module_dso(const char *module, struct dso **pdso)
>  {
>  	struct dso *dso;
>  	struct map *map;
>  	const char *vmlinux_name;
> +	int ret = 0;
>  
>  	if (module) {
>  		list_for_each_entry(dso, &host_machine->kernel_dsos.head,
> @@ -215,30 +216,21 @@ static struct dso *kernel_get_module_dso(const char *module)
>  				goto found;
>  		}
>  		pr_debug("Failed to find module %s.\n", module);
> -		return NULL;
> +		return -ENOENT;
>  	}
>  
>  	map = host_machine->vmlinux_maps[MAP__FUNCTION];
>  	dso = map->dso;
>  
>  	vmlinux_name = symbol_conf.vmlinux_name;
> -	if (vmlinux_name) {
> -		if (dso__load_vmlinux(dso, map, vmlinux_name, false, NULL) <= 0)
> -			return NULL;
> -	} else {
> -		if (dso__load_vmlinux_path(dso, map, NULL) <= 0) {
> -			pr_debug("Failed to load kernel map.\n");
> -			return NULL;
> -		}
> -	}
> +	dso->load_errno = 0;
> +	if (vmlinux_name)
> +		ret = dso__load_vmlinux(dso, map, vmlinux_name, false, NULL);
> +	else
> +		ret = dso__load_vmlinux_path(dso, map, NULL);
>  found:
> -	return dso;
> -}
> -
> -const char *kernel_get_module_path(const char *module)
> -{
> -	struct dso *dso = kernel_get_module_dso(module);
> -	return (dso) ? dso->long_name : NULL;
> +	*pdso = dso;
> +	return ret;
>  }
>  
>  static int convert_exec_to_group(const char *exec, char **result)
> @@ -390,16 +382,25 @@ static int get_alternative_line_range(struct debuginfo *dinfo,
>  static struct debuginfo *open_debuginfo(const char *module, bool silent)
>  {
>  	const char *path = module;
> -	struct debuginfo *ret;
> +	char reason[STRERR_BUFSIZE];
> +	struct debuginfo *ret = NULL;
> +	struct dso *dso = NULL;
> +	int err;
>  
>  	if (!module || !strchr(module, '/')) {
> -		path = kernel_get_module_path(module);
> -		if (!path) {
> +		err = kernel_get_module_dso(module, &dso);
> +		if (err < 0) {
> +			if (!dso || dso->load_errno == 0) {
> +				if (!strerror_r(-err, reason, STRERR_BUFSIZE))
> +					strcpy(reason, "(unknown)");
> +			} else
> +				dso__strerror_load(dso, reason, STRERR_BUFSIZE);
>  			if (!silent)
> -				pr_err("Failed to find path of %s module.\n",
> -				       module ?: "kernel");
> +				pr_err("Failed to find the path for %s: %s\n",
> +					module ?: "kernel", reason);
>  			return NULL;
>  		}
> +		path = dso->long_name;
>  	}
>  	ret = debuginfo__new(path);
>  	if (!ret && !silent) {
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index 537eb32..31db6ee 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -131,9 +131,6 @@ extern void line_range__clear(struct line_range *lr);
>  /* Initialize line range */
>  extern int line_range__init(struct line_range *lr);
>  
> -/* Internal use: Return kernel/module path */
> -extern const char *kernel_get_module_path(const char *module);
> -
>  extern int add_perf_probe_events(struct perf_probe_event *pevs, int npevs);
>  extern int del_perf_probe_events(struct strfilter *filter);
>  extern int show_perf_probe_events(struct strfilter *filter);
> 
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com