Re: [PATCH v2 1/4] perf-probe: Avoid setting probes on same address on same event

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Fri, Jul 10, 2020 at 10:11:04PM +0900, Masami Hiramatsu escreveu:
> There is a case that the several same-name symbols points
> same address. In that case, perf probe returns an error.
> 
> E.g.
> 
>   perf probe -x /lib64/libc-2.30.so -v -a "memcpy arg1=%di"
>   probe-definition(0): memcpy arg1=%di
>   symbol:memcpy file:(null) line:0 offset:0 return:0 lazy:(null)
>   parsing arg: arg1=%di into name:arg1 %di
>   1 arguments
>   symbol:setjmp file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:longjmp file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:longjmp_target file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:lll_lock_wait_private file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_arena_max file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_arena_test file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_tunable_tcache_max_bytes file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_tunable_tcache_count file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_tunable_tcache_unsorted_limit file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_trim_threshold file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_top_pad file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_mmap_threshold file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_mmap_max file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_perturb file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_mxfast file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_heap_new file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_arena_reuse_free_list file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_arena_reuse file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_arena_reuse_wait file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_arena_new file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_arena_retry file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_sbrk_less file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_heap_free file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_heap_less file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_tcache_double_free file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_heap_more file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_sbrk_more file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_malloc_retry file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_memalign_retry file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt_free_dyn_thresholds file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_realloc_retry file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_calloc_retry file:(null) line:0 offset:0 return:0 lazy:(null)
>   symbol:memory_mallopt file:(null) line:0 offset:0 return:0 lazy:(null)
>   Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.30.so.debug
>   Try to find probe point from debuginfo.
>   Opening /sys/kernel/debug/tracing//README write=0
>   Failed to find the location of the '%di' variable at this address.
>    Perhaps it has been optimized out.
>    Use -V with the --range option to show '%di' location range.
>   An error occurred in debuginfo analysis (-2).
>   Trying to use symbols.
>   Opening /sys/kernel/debug/tracing//uprobe_events write=1
>   Writing event: p:probe_libc/memcpy /usr/lib64/libc-2.30.so:0x914c0 arg1=%di
>   Writing event: p:probe_libc/memcpy /usr/lib64/libc-2.30.so:0x914c0 arg1=%di
>   Failed to write event: File exists
>     Error: Failed to add events. Reason: File exists (Code: -17)
> 
> You can see the perf tried to write completely same probe definition
> twice, which caused an error.
> 
> To fix this issue, check the symbol list and drop duplicated
> symbols (which has same symbol name and address) from it.
> 
> With this patch;
> 
>   # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di"
>   Failed to find the location of the '%di' variable at this address.
>    Perhaps it has been optimized out.
>    Use -V with the --range option to show '%di' location range.
>   Added new events:
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
>     probe_libc:memcpy    (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di)
> 
>   You can now use it in all perf tools, such as:
> 
>   	perf record -e probe_libc:memcpy -aR sleep 1
> 
> 
> Reported-by: Andi Kleen <andi@firstfloor.org>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
>  Changes in V2
>   - Change "find" word to "Found".
> ---
>  tools/perf/util/probe-event.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index df713a5d1e26..8cd1224e5f4c 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2968,6 +2968,16 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  	for (j = 0; j < num_matched_functions; j++) {
>  		sym = syms[j];
>  
> +		/* There can be duplicated symbols in the map */
> +		for (i = 0; i < j; i++)
> +			if (sym->start == syms[i]->start) {
> +				pr_debug("Found duplicated symbol %s @ %lx\n",
> +					 sym->name, sym->start);
> +				break;
> +			}

Breaks 32-bit builds with:

  CC       /tmp/build/perf/util/demangle-java.o
In file included from util/probe-event.c:27:
util/probe-event.c: In function 'find_probe_trace_events_from_map':
util/probe-event.c:2978:14: error: format '%lx' expects argument of type 'long unsigned int', but argument 5 has type 'u64' {aka 'long long unsigned int'} [-Werror=format=]
     pr_debug("Found duplicated symbol %s @ %lx\n",
              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
util/debug.h:17:21: note: in definition of macro 'pr_fmt'
 #define pr_fmt(fmt) fmt
                     ^~~
util/probe-event.c:2978:5: note: in expansion of macro 'pr_debug'
     pr_debug("Found duplicated symbol %s @ %lx\n",
     ^~~~~~~~
  CC       /tmp/build/perf/util/demangle-rust.o


I'll change this to use PRIx64.

- Arnaldo

> +		if (i != j)
> +			continue;
> +
>  		tev = (*tevs) + ret;
>  		tp = &tev->point;
>  		if (ret == num_matched_functions) {
> 

-- 

- Arnaldo