4.9-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Olsa jolsa@kernel.org
[ 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 --- tools/perf/tests/vmlinux-kallsyms.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/tools/perf/tests/vmlinux-kallsyms.c +++ b/tools/perf/tests/vmlinux-kallsyms.c @@ -123,7 +123,7 @@ int test__vmlinux_matches_kallsyms(int s
if (pair && UM(pair->start) == mem_start) { next_pair: - if (strcmp(sym->name, pair->name) == 0) { + if (arch__compare_symbol_names(sym->name, pair->name) == 0) { /* * kallsyms don't have the symbol end, so we * set that by using the next symbol start - 1,