| From foo@baz Mon Dec 18 15:03:25 CET 2017 |
| From: Daniel Borkmann <daniel@iogearbox.net> |
| Date: Wed, 15 Mar 2017 22:53:37 +0100 |
| Subject: perf symbols: Fix symbols__fixup_end heuristic for corner cases |
| |
| From: Daniel Borkmann <daniel@iogearbox.net> |
| |
| |
| [ Upstream commit e7ede72a6d40cb3a30c087142d79381ca8a31dab ] |
| |
| The current symbols__fixup_end() heuristic for the last entry in the rb |
| tree is suboptimal as it leads to not being able to recognize the symbol |
| in the call graph in a couple of corner cases, for example: |
| |
| i) If the symbol has a start address (f.e. exposed via kallsyms) |
| that is at a page boundary, then the roundup(curr->start, 4096) |
| for the last entry will result in curr->start == curr->end with |
| a symbol length of zero. |
| |
| ii) If the symbol has a start address that is shortly before a page |
| boundary, then also here, curr->end - curr->start will just be |
| very few bytes, where it's unrealistic that we could perform a |
| match against. |
| |
| Instead, change the heuristic to roundup(curr->start, 4096) + 4096, so |
| that we can catch such corner cases and have a better chance to find |
| that specific symbol. It's still just best effort as the real end of the |
| symbol is unknown to us (and could even be at a larger offset than the |
| current range), but better than the current situation. |
| |
| Alexei reported that he recently run into case i) with a JITed eBPF |
| program (these are all page aligned) as the last symbol which wasn't |
| properly shown in the call graph (while other eBPF program symbols in |
| the rb tree were displayed correctly). Since this is a generic issue, |
| lets try to improve the heuristic a bit. |
| |
| Reported-and-Tested-by: Alexei Starovoitov <ast@kernel.org> |
| Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> |
| Fixes: 2e538c4a1847 ("perf tools: Improve kernel/modules symbol lookup") |
| Link: http://lkml.kernel.org/r/bb5c80d27743be6f12afc68405f1956a330e1bc9.1489614365.git.daniel@iogearbox.net |
| Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
| Signed-off-by: Sasha Levin <alexander.levin@verizon.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| tools/perf/util/symbol.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/tools/perf/util/symbol.c |
| +++ b/tools/perf/util/symbol.c |
| @@ -191,7 +191,7 @@ void symbols__fixup_end(struct rb_root * |
| |
| /* Last entry */ |
| if (curr->end == curr->start) |
| - curr->end = roundup(curr->start, 4096); |
| + curr->end = roundup(curr->start, 4096) + 4096; |
| } |
| |
| void __map_groups__fixup_end(struct map_groups *mg, enum map_type type) |