Add the ability to specify a DSO in the /tmp/perf-<PID>.map file. The DSO should be the first line in the file and readable by the running user. If a valid DSO is found all other contents of the file will be ignored. This allows things like callchain unwinding with DWARF to work.
Suggested-by: Wang Nan <wangn...@huawei.com> Signed-off-by: Josh Hunt <joh...@akamai.com> --- We have an application which uses huge pages for its text section, but still needs the ability to do callchain unwinding with DWARF. We use the perf-<PID>.map file setup to do symbol resolution and that works great, but callchain unwinding fails. A few months ago I mentioned this to Wang Nan and he suggested a way around this problem could be to specify the path of the DSO in the map file. The attached patch is my initial hack at this. Running with this patch I can now get full callchain unwinding with DWARF. FWIW LBR + map file works with callchains, but unfortunately there are some cases where we still need DWARF. I submitted an RFC as an earlier draft: https://lkml.org/lkml/2018/4/24/1070 v2: 1. Rebase RFC patch to git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core 2. Update jit-interface.txt as per Arnaldo's request tools/perf/Documentation/jit-interface.txt | 8 +++++--- tools/perf/util/map.c | 32 ++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+), 3 deletions(-) diff --git a/tools/perf/Documentation/jit-interface.txt b/tools/perf/Documentation/jit-interface.txt index a8656f564915..8a25b979802f 100644 --- a/tools/perf/Documentation/jit-interface.txt +++ b/tools/perf/Documentation/jit-interface.txt @@ -3,13 +3,15 @@ by a JIT. The JIT has to write a /tmp/perf-%d.map (%d = pid of process) file -This is a text file. +This is a text file and can have one of the following formats: -Each line has the following format, fields separated with spaces: +1) Each line has the following format, fields separated with spaces: START SIZE symbolname START and SIZE are hex numbers without 0x. symbolname is the rest of the line, so it could contain special characters. -The ownership of the file has to match the process. +2) A single line with the full pathname of the DSO to use. + +For both formats, the ownership of the file has to match the process. diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c index c8fe836e4c3c..da3050b18e34 100644 --- a/tools/perf/util/map.c +++ b/tools/perf/util/map.c @@ -139,6 +139,31 @@ void map__init(struct map *map, u64 start, u64 end, u64 pgoff, struct dso *dso) refcount_set(&map->refcnt, 1); } +static bool replace_anon(char *mapfilename) +{ + FILE *file = NULL; + bool ret = false; + + file = fopen(mapfilename, "r"); + if (file != NULL) { + char *line = NULL; + size_t line_len, linesz=0; + + line_len = getline(&line, &linesz, file); + if (line_len > 0) { + line[line_len-1] = '\0'; /* null terminate */ + if (!access(line, R_OK)) { + strlcpy(mapfilename, line, line_len); + ret = true; + } + } + free(line); + fclose(file); + } + + return ret; +} + struct map *map__new(struct machine *machine, u64 start, u64 len, u64 pgoff, u32 d_maj, u32 d_min, u64 ino, u64 ino_gen, u32 prot, u32 flags, char *filename, @@ -170,6 +195,13 @@ struct map *map__new(struct machine *machine, u64 start, u64 len, snprintf(newfilename, sizeof(newfilename), "/tmp/perf-%d.map", nsi->pid); filename = newfilename; + /* + * Check to see if map file references DSO to use, if so, use it. + */ + if (anon && replace_anon(newfilename)) { + anon = 0; + filename = newfilename; + } } if (android) { -- 1.9.1
