Re: [PATCH V2 2/9] perf tools: load kernel maps before using

[Arnaldo Carvalho de Melo <acme@ghostprotocols.net>]

Em Wed, Jul 31, 2013 at 12:13:51AM +0300, Adrian Hunter escreveu:
> In order to use kernel maps to read object code, those
> maps must be adjusted to map to the dso file offset.
> Because lazy-initialization is used, that is not done
> until symbols are loaded.  However the maps are first
> used by thread__find_addr_map() before symbols are loaded.
> So this patch changes thread__find_addr() to "load" kernel
> maps before using them.

Argh, yeah, we create maps as we traverse kallsyms, right? I guess this
is there for historical reasons (i.e. it "evolved" like that), but I'm
adding a note to my TODO list to remove that mess, i.e. we should
probably do that as a separate step, i.e. the creation of kernel maps,
detached from actually loading the symbols.

For now I think your patch makes we progress, so I'll apply it.

Thanks,

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  tools/perf/builtin-inject.c     |  2 +-
>  tools/perf/builtin-script.c     |  4 ++--
>  tools/perf/tests/code-reading.c |  2 +-
>  tools/perf/util/build-id.c      |  2 +-
>  tools/perf/util/event.c         | 18 ++++++++++++++----
>  tools/perf/util/thread.h        |  2 +-
>  tools/perf/util/unwind.c        |  4 ++--
>  7 files changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index 1d8de2e..f012a98 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -206,7 +206,7 @@ static int perf_event__inject_buildid(struct perf_tool *tool,
>  	}
>  
>  	thread__find_addr_map(thread, machine, cpumode, MAP__FUNCTION,
> -			      event->ip.ip, &al);
> +			      event->ip.ip, &al, NULL);
>  
>  	if (al.map != NULL) {
>  		if (!al.map->dso->hit) {
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index 1cad370..cd616ff 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -341,10 +341,10 @@ static void print_sample_addr(union perf_event *event,
>  		return;
>  
>  	thread__find_addr_map(thread, machine, cpumode, MAP__FUNCTION,
> -			      sample->addr, &al);
> +			      sample->addr, &al, NULL);
>  	if (!al.map)
>  		thread__find_addr_map(thread, machine, cpumode, MAP__VARIABLE,
> -				      sample->addr, &al);
> +				      sample->addr, &al, NULL);
>  
>  	al.cpu = sample->cpu;
>  	al.sym = NULL;
> diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> index 7c9437d..6cd3190 100644
> --- a/tools/perf/tests/code-reading.c
> +++ b/tools/perf/tests/code-reading.c
> @@ -138,7 +138,7 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
>  	pr_debug("Reading object code for memory address: %#"PRIx64"\n", addr);
>  
>  	thread__find_addr_map(thread, machine, cpumode, MAP__FUNCTION, addr,
> -			      &al);
> +			      &al, NULL);
>  	if (!al.map || !al.map->dso) {
>  		pr_debug("thread__find_addr_map failed\n");
>  		return -1;
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index 5295625..3a0f508 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -33,7 +33,7 @@ int build_id__mark_dso_hit(struct perf_tool *tool __maybe_unused,
>  	}
>  
>  	thread__find_addr_map(thread, machine, cpumode, MAP__FUNCTION,
> -			      event->ip.ip, &al);
> +			      event->ip.ip, &al, NULL);
>  
>  	if (al.map != NULL)
>  		al.map->dso->hit = 1;
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 9541270..cc7c0c9 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -592,9 +592,10 @@ int perf_event__process(struct perf_tool *tool __maybe_unused,
>  void thread__find_addr_map(struct thread *self,
>  			   struct machine *machine, u8 cpumode,
>  			   enum map_type type, u64 addr,
> -			   struct addr_location *al)
> +			   struct addr_location *al, symbol_filter_t filter)
>  {
>  	struct map_groups *mg = &self->mg;
> +	bool load_map = false;
>  
>  	al->thread = self;
>  	al->addr = addr;
> @@ -609,11 +610,13 @@ void thread__find_addr_map(struct thread *self,
>  	if (cpumode == PERF_RECORD_MISC_KERNEL && perf_host) {
>  		al->level = 'k';
>  		mg = &machine->kmaps;
> +		load_map = true;
>  	} else if (cpumode == PERF_RECORD_MISC_USER && perf_host) {
>  		al->level = '.';
>  	} else if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL && perf_guest) {
>  		al->level = 'g';
>  		mg = &machine->kmaps;
> +		load_map = true;
>  	} else {
>  		/*
>  		 * 'u' means guest os user space.
> @@ -654,8 +657,15 @@ try_again:
>  			mg = &machine->kmaps;
>  			goto try_again;
>  		}
> -	} else
> +	} else {
> +		/*
> +		 * Kernel maps might be changed when loading symbols so loading
> +		 * must be done prior to using kernel maps.
> +		 */
> +		if (load_map)
> +			map__load(al->map, filter);
>  		al->addr = al->map->map_ip(al->map, al->addr);
> +	}
>  }
>  
>  void thread__find_addr_location(struct thread *thread, struct machine *machine,
> @@ -663,7 +673,7 @@ void thread__find_addr_location(struct thread *thread, struct machine *machine,
>  				struct addr_location *al,
>  				symbol_filter_t filter)
>  {
> -	thread__find_addr_map(thread, machine, cpumode, type, addr, al);
> +	thread__find_addr_map(thread, machine, cpumode, type, addr, al, filter);
>  	if (al->map != NULL)
>  		al->sym = map__find_symbol(al->map, al->addr, filter);
>  	else
> @@ -699,7 +709,7 @@ int perf_event__preprocess_sample(const union perf_event *event,
>  		machine__create_kernel_maps(machine);
>  
>  	thread__find_addr_map(thread, machine, cpumode, MAP__FUNCTION,
> -			      event->ip.ip, al);
> +			      event->ip.ip, al, filter);
>  	dump_printf(" ...... dso: %s\n",
>  		    al->map ? al->map->dso->long_name :
>  			al->level == 'H' ? "[hypervisor]" : "<not found>");
> diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> index 0fe1f9c..f98d1d9 100644
> --- a/tools/perf/util/thread.h
> +++ b/tools/perf/util/thread.h
> @@ -41,7 +41,7 @@ static inline struct map *thread__find_map(struct thread *self,
>  
>  void thread__find_addr_map(struct thread *thread, struct machine *machine,
>  			   u8 cpumode, enum map_type type, u64 addr,
> -			   struct addr_location *al);
> +			   struct addr_location *al, symbol_filter_t filter);
>  
>  void thread__find_addr_location(struct thread *thread, struct machine *machine,
>  				u8 cpumode, enum map_type type, u64 addr,
> diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c
> index 958723b..5bbd494 100644
> --- a/tools/perf/util/unwind.c
> +++ b/tools/perf/util/unwind.c
> @@ -272,7 +272,7 @@ static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
>  	struct addr_location al;
>  
>  	thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
> -			      MAP__FUNCTION, ip, &al);
> +			      MAP__FUNCTION, ip, &al, NULL);
>  	return al.map;
>  }
>  
> @@ -349,7 +349,7 @@ static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
>  	ssize_t size;
>  
>  	thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
> -			      MAP__FUNCTION, addr, &al);
> +			      MAP__FUNCTION, addr, &al, NULL);
>  	if (!al.map) {
>  		pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
>  		return -1;
> -- 
> 1.7.11.7