On 06/11/2018 04:10 PM, Sandipan Das wrote:
> For some cases, the callchain provided by the kernel may be
> empty. So, the callchain ip filtering code will cause a crash
> if we do not check whether the struct ip_callchain pointer is
> NULL before accessing any members.
>
> This can be observed on a powerpc64le system running Fedora 27
> as shown below.
>
> # perf record -b -e cycles:u ls
>
> Before applying this patch:
>
> # perf report --branch-history
>
> perf: Segmentation fault
> -------- backtrace --------
> perf[0x1027615c]
> linux-vdso64.so.1(__kernel_sigtramp_rt64+0x0)[0x7fff856304d8]
> perf(arch_skip_callchain_idx+0x44)[0x10257c58]
> perf[0x1017f2e4]
> perf(thread__resolve_callchain+0x124)[0x1017ff5c]
> perf(sample__resolve_callchain+0xf0)[0x10172788]
> ...
>
> After applying this patch:
>
> # perf report --branch-history
>
> Samples: 25 of event 'cycles:u', Event count (approx.): 2306870
> Overhead Source:Line Symbol Shared Object
> + 11.60% _init+35736 [.] _init ls
> + 9.84% strcoll_l.c:137 [.] __strcoll_l libc-2.26.so
> + 9.16% memcpy.S:175 [.] __memcpy_power7 libc-2.26.so
> + 9.01% gconv_charset.h:54 [.] _nl_find_locale libc-2.26.so
> + 8.87% dl-addr.c:52 [.] _dl_addr libc-2.26.so
> + 8.83% _init+236 [.] _init ls
> ...
>
> Reported-by: Ravi Bangoria <ravi.bango...@linux.ibm.com>
> Signed-off-by: Sandipan Das <sandi...@linux.ibm.com>
Acked-by: Ravi Bangoria <ravi.bango...@linux.ibm.com>
