tree a7f0330d449ab860b56b216a7da1b63ce29d3121
parent 1e6b708a1dc617478a6dede5ecd38e055f3b1e35
author Jiri Olsa <jolsa@kernel.org> 1518697595 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1527659450 +0200

perf tests: Use arch__compare_symbol_names to compare symbols

[ Upstream commit ab6e9a99345131cd8e54268d1d0dc04a33f7ed11 ]

The symbol search called by machine__find_kernel_symbol_by_name is using
internally arch__compare_symbol_names function to compare 2 symbol
names, because different archs have different ways of comparing symbols.
Mostly for skipping '.' prefixes and similar.

In test 1 when we try to find matching symbols in kallsyms and vmlinux,
by address and by symbol name. When either is found we compare the pair
symbol names  by simple strcmp, which is not good enough for reasons
explained in previous paragraph.

On powerpc this can cause lockup, because even thought we found the
pair, the compared names are different and don't match simple strcmp.
Following code path is executed, that leads to lockup:

   - we find the pair in kallsyms by sym->start
next_pair:
   - we compare the names and it fails
   - we find the pair by sym->name
   - the pair addresses match so we call goto next_pair
     because we assume the names match in this case

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 031b84c407c3 ("perf probe ppc: Enable matching against dot symbols automatically")
Link: http://lkml.kernel.org/r/20180215122635.24029-10-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>