Messages in this thread Patch in this message | | | From | Paul Clarke <> | Subject | [PATCH v3] Allow user probes on versioned symbols | Date | Fri, 31 Mar 2017 11:06:16 -0500 |
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Symbol versioning, as in glibc, results in symbols being defined as: <real symbol>@[@]<version> (Note that "@@" identifies a default symbol, if the symbol name is repeated.)
perf is currently unable to deal with this, and is unable to create user probes at such symbols: -- $ nm /lib/powerpc64le-linux-gnu/libpthread.so.0 | grep pthread_create 0000000000008d30 t __pthread_create_2_1 0000000000008d30 T pthread_create@@GLIBC_2.17 $ /usr/bin/sudo perf probe -v -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create probe-definition(0): pthread_create symbol:pthread_create file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Open Debuginfo file: /usr/lib/debug/lib/powerpc64le-linux-gnu/libpthread-2.19.so Try to find probe point from debuginfo. Probe point 'pthread_create' not found. Error: Failed to add events. Reason: No such file or directory (Code: -2) --
One is not able to specify the fully versioned symbol, either, due to syntactic conflicts with other uses of "@" by perf: -- $ /usr/bin/sudo perf probe -v -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create@@GLIBC_2.17 probe-definition(0): pthread_create@@GLIBC_2.17 Semantic error :SRC@SRC is not allowed. 0 arguments Error: Command Parse Error. Reason: Invalid argument (Code: -22) --
The attached patch ignores versioning for default symbols, thus allowing probes to be created for these symbols: -- $ /usr/bin/sudo ./perf probe -x /lib/powerpc64le-linux-gnu/libpthread.so.0 pthread_create Added new event: probe_libpthread:pthread_create (on pthread_create in /lib/powerpc64le-linux-gnu/libpthread-2.19.so)
You can now use it in all perf tools, such as:
perf record -e probe_libpthread:pthread_create -aR sleep 1
$ /usr/bin/sudo ./perf record -e probe_libpthread:pthread_create -aR ./test 2 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.052 MB perf.data (2 samples) ] $ /usr/bin/sudo ./perf script test 2915 [000] 19124.260729: probe_libpthread:pthread_create: (3fff99248d38) test 2916 [000] 19124.260962: probe_libpthread:pthread_create: (3fff99248d38) $ /usr/bin/sudo ./perf probe --del=probe_libpthread:pthread_create Removed event: probe_libpthread:pthread_create --
Signed-off-by: Paul A. Clarke <pc@us.ibm.com> --- v3: - code style fixes per David Ahern
v2: - move logic from arch__compare_symbol_names to new map__compare_symbol_names - call through from map__compare_symbol_names to arch__compare_symbol_names - redirect uses of arch__compare_symbol_names - send patch to LKML
tools/perf/util/auxtrace.c | 2 +- tools/perf/util/map.c | 23 +++++++++++++++++++++++ tools/perf/util/map.h | 3 ++- tools/perf/util/symbol.c | 4 ++-- 4 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c index c5a6e0b1..f3511a6 100644 --- a/tools/perf/util/auxtrace.c +++ b/tools/perf/util/auxtrace.c @@ -1875,7 +1875,7 @@ static bool dso_sym_match(struct symbol *sym, const char *name, int *cnt, int idx) { /* Same name, and global or the n'th found or any */ - return !arch__compare_symbol_names(name, sym->name) && + return !map__compare_symbol_names(name, sym->name) && ((!idx && sym->binding == STB_GLOBAL) || (idx > 0 && ++*cnt == idx) || idx < 0); diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c index 4f9a71c..26a3e87 100644 --- a/tools/perf/util/map.c +++ b/tools/perf/util/map.c @@ -330,6 +330,29 @@ int __weak arch__compare_symbol_names(const char *namea, const char *nameb) return strcmp(namea, nameb); } +int map__compare_symbol_names(const char *namea, const char *nameb) +{ + int rc; + const char *namea_versioning, *nameb_versioning; + + namea_versioning = strstr(namea,"@@"); + if (namea_versioning) + namea = strndup(namea,namea_versioning-namea); + + nameb_versioning = strstr(nameb,"@@"); + if (nameb_versioning) + nameb = strndup(nameb,nameb_versioning-nameb); + + rc = arch__compare_symbol_names(namea, nameb); + + if (namea_versioning) + free((void *)namea); + if (nameb_versioning) + free((void *)nameb); + + return rc; +} + struct symbol *map__find_symbol(struct map *map, u64 addr) { if (map__load(map) < 0) diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h index abdacf8..aaad64d 100644 --- a/tools/perf/util/map.h +++ b/tools/perf/util/map.h @@ -130,13 +130,14 @@ struct thread; */ #define __map__for_each_symbol_by_name(map, sym_name, pos) \ for (pos = map__find_symbol_by_name(map, sym_name); \ - pos && arch__compare_symbol_names(pos->name, sym_name) == 0; \ + pos && map__compare_symbol_names(pos->name, sym_name) == 0; \ pos = symbol__next_by_name(pos)) #define map__for_each_symbol_by_name(map, sym_name, pos) \ __map__for_each_symbol_by_name(map, sym_name, (pos)) int arch__compare_symbol_names(const char *namea, const char *nameb); +int map__compare_symbol_names(const char *namea, const char *nameb); void map__init(struct map *map, enum map_type type, u64 start, u64 end, u64 pgoff, struct dso *dso); struct map *map__new(struct machine *machine, u64 start, u64 len, diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index dc93940..4fb9d275 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -411,7 +411,7 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols, int cmp; s = rb_entry(n, struct symbol_name_rb_node, rb_node); - cmp = arch__compare_symbol_names(name, s->sym.name); + cmp = map__compare_symbol_names(name, s->sym.name); if (cmp < 0) n = n->rb_left; @@ -429,7 +429,7 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols, struct symbol_name_rb_node *tmp; tmp = rb_entry(n, struct symbol_name_rb_node, rb_node); - if (arch__compare_symbol_names(tmp->sym.name, s->sym.name)) + if (map__compare_symbol_names(tmp->sym.name, s->sym.name)) break; s = tmp; -- 2.1.4 Regards, PC
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