linux-kernel - Re: [PATCH v2] perf machine: Fix load kernel symbol with '-k' option

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Message-ID: <20180309205600.GB16890@krava>
Date:   Fri, 9 Mar 2018 21:56:00 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH v2] perf machine: Fix load kernel symbol with '-k' option

On Fri, Mar 09, 2018 at 02:05:23PM +0800, Leo Yan wrote:
> On Hikey arm64 octa A53 platform, when use command './perf report -v
> -k vmlinux --stdio' it outputs below error info, and it skips to load
> kernel symbol and doesn't print symbol for event:
> Failed to open [kernel.kallsyms]_text, continuing without symbols.
> 
> The regression is introduced by commit ("8c7f1bb37b29 perf machine: Move
> kernel mmap name into struct machine"), which changes the logic for
> machine mmap_name by removing function machine__mmap_name() and always
> use 'machine->mmap_name'.  Comparing difference between
> machine__mmap_name() and 'machine->mmap_name', the later one includes
> the string for specified kernel vmlinux string with option '-k' in
> command, but the old function machine__mmap_name() ignores vmlinux
> path string.  As result, event's mmap file name doesn't match with
> machine mmap file name anymore and it skips to load kernel symbol from
> vmlinux file.
> 
> To resolve this issue, this patch adds extra checking for
> 'symbol_conf.vmlinux_name', when it has been set string so we can know
> it includes vmlinux path string specified for option '-k'. For this
> case it sets 'is_kernel_mmap' to true and run into flow to load kernel
> symbol from vmlinux.
> 
> This patch has been verified with two commands: './perf report -v
> -k vmlinux --stdio' and './perf script -v -F cpu,event,ip,sym,symoff
> -k vmlinux'.
> 
> Suggested-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/machine.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 12b7427..3125871 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1299,9 +1299,18 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
>  	else
>  		kernel_type = DSO_TYPE_GUEST_KERNEL;
>  
> -	is_kernel_mmap = memcmp(event->mmap.filename,
> -				machine->mmap_name,
> -				strlen(machine->mmap_name) - 1) == 0;
> +	/*
> +	 * When symbol_conf.vmlinux_name is not NULL, it includes the specified
> +	 * kernel vmlinux path with option '-k'.  So set 'is_kernel_mmap' to
> +	 * true for creating machine symbol map.
> +	 */
> +	if (symbol_conf.vmlinux_name)
> +		is_kernel_mmap = true;
> +	else
> +		is_kernel_mmap = memcmp(event->mmap.filename,
> +					machine->mmap_name,
> +					strlen(machine->mmap_name) - 1) == 0;
> +
>  	if (event->mmap.filename[0] == '/' ||
>  	    (!is_kernel_mmap && event->mmap.filename[0] == '[')) {
>  		map = machine__findnew_module_map(machine, event->mmap.start,

right, the mmap gets confused with the vmlinux path, but I wonder
the fix should be not to include symbol_conf.vmlinux_name in the
mmap_name like below.. untested

thanks,
jirka


---
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 43fbbee409ec..f0cb72022177 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -51,15 +51,9 @@ static void machine__threads_init(struct machine *machine)
 static int machine__set_mmap_name(struct machine *machine)
 {
 	if (machine__is_host(machine)) {
-		if (symbol_conf.vmlinux_name)
-			machine->mmap_name = strdup(symbol_conf.vmlinux_name);
-		else
-			machine->mmap_name = strdup("[kernel.kallsyms]");
+		machine->mmap_name = strdup("[kernel.kallsyms]");
 	} else if (machine__is_default_guest(machine)) {
-		if (symbol_conf.default_guest_vmlinux_name)
-			machine->mmap_name = strdup(symbol_conf.default_guest_vmlinux_name);
-		else
-			machine->mmap_name = strdup("[guest.kernel.kallsyms]");
+		machine->mmap_name = strdup("[guest.kernel.kallsyms]");
 	} else {
 		if (asprintf(&machine->mmap_name, "[guest.kernel.kallsyms.%d]",
 			 machine->pid) < 0)
@@ -794,9 +788,15 @@ static struct dso *machine__get_kernel(struct machine *machine)
 	struct dso *kernel;
 
 	if (machine__is_host(machine)) {
+		if (symbol_conf.vmlinux_name)
+			vmlinux_name = symbol_conf.vmlinux_name;
+
 		kernel = machine__findnew_kernel(machine, vmlinux_name,
 						 "[kernel]", DSO_TYPE_KERNEL);
 	} else {
+		if (symbol_conf.default_guest_vmlinux_name)
+			vmlinux_name = symbol_conf.default_guest_vmlinux_name;
+
 		kernel = machine__findnew_kernel(machine, vmlinux_name,
 						 "[guest.kernel]",
 						 DSO_TYPE_GUEST_KERNEL);