Re: [PATCH] perf machine: Initialize srcline string member in add_location struct

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

Em Mon, Jul 19, 2021 at 04:53:32PM +0200, Michael Petlan escreveu:
> It's later supposed to be either a correct address or NULL. Without the
> initialization, it may contain an undefined value which results in the
> following segmentation fault:
> 
>   # perf top --sort comm -g --ignore-callees=do_idle

Later where? The backtrace below is unresolved, I couldn't reproduce it
here, that al variable is local to add_callchain_ip(), and is then
passed to several places where I couldn't find al->srcline being used,
can you state where it is used and causes the segfault?

- Arnaldo
 
> terminates with
> 
>   perf: Segmentation fault
>   -------- backtrace --------
>   perf(+0x417b26)[0x557794f1fb26]
>   /lib64/libc.so.6(+0x37400)[0x7f62a0194400]
>   /lib64/libc.so.6(+0x15d685)[0x7f62a02ba685]
>   /lib64/libc.so.6(__strdup+0x12)[0x7f62a01e6802]
>   perf(+0x3769d9)[0x557794e7e9d9]
>   perf(+0x376d3a)[0x557794e7ed3a]
>   perf(+0x377284)[0x557794e7f284]
>   perf(+0x3773e0)[0x557794e7f3e0]
>   perf(hist_entry_iter__add+0xc4)[0x557794e80114]
>   perf(+0x2799aa)[0x557794d819aa]
>   perf(+0x354ec8)[0x557794e5cec8]
>   perf(+0x279341)[0x557794d81341]
>   /lib64/libpthread.so.0(+0x814a)[0x7f62a27b514a]
>   /lib64/libc.so.6(clone+0x43)[0x7f62a0259dc3]
> 
> Fixes: 1fb7d06a509e ("perf report: Use srcline from callchain for hist entries")
> 
> Signed-off-by: Michael Petlan <mpetlan@redhat.com>
> Reported-by: Juri Lelli <jlelli@redhat.com>
> CC: Milian Wolff <milian.wolff@kdab.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/machine.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index da19be7da284..44e40bad0e33 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -2149,6 +2149,7 @@ static int add_callchain_ip(struct thread *thread,
>  
>  	al.filtered = 0;
>  	al.sym = NULL;
> +	al.srcline = NULL;
>  	if (!cpumode) {
>  		thread__find_cpumode_addr_location(thread, ip, &al);
>  	} else {
> -- 
> 2.18.4
> 

-- 

- Arnaldo