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perf symbols: Allow user probes on versioned symbols

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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)
  --

This 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
  --

Committer note:

Change the variable storing the result of strlen() to 'int', to fix the build
on debian:experimental-x-mipsel, fedora:24-x-ARC-uClibc, ubuntu:16.04-x-arm,
etc:

  util/symbol.c: In function 'symbol__match_symbol_name':
  util/symbol.c:422:11: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     if (len < versioning - name)
             ^

Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/c2b18d9c-17f8-9285-4868-f58b6359ccac@us.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Paul Clarke 2017-04-25 13:15:49 -05:00 committed by Arnaldo Carvalho de Melo
parent b843f62ad9
commit d80406453a
5 changed files with 74 additions and 20 deletions
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12
tools/perf/arch/powerpc/util/sym-handling.c
View file

@ -52,6 +52,18 @@ int arch__compare_symbol_names(const char *namea, const char *nameb)
return strcmp(namea, nameb);
}
int arch__compare_symbol_names_n(const char *namea, const char *nameb,
unsigned int n)
{
/* Skip over initial dot */
if (*namea == '.')
namea++;
if (*nameb == '.')
nameb++;
return strncmp(namea, nameb, n);
}
#endif
#if defined(_CALL_ELF) && _CALL_ELF == 2

5
tools/perf/util/map.c
View file

@ -325,11 +325,6 @@ int map__load(struct map *map)
return 0;
}
int __weak arch__compare_symbol_names(const char *namea, const char *nameb)
{
return strcmp(namea, nameb);
}
struct symbol *map__find_symbol(struct map *map, u64 addr)
{
if (map__load(map) < 0)

5
tools/perf/util/map.h
View file

@ -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 && \
!symbol__match_symbol_name(pos->name, sym_name, \
SYMBOL_TAG_INCLUDE__DEFAULT_ONLY); \
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);
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,

61
tools/perf/util/symbol.c
View file

@ -90,6 +90,17 @@ static int prefix_underscores_count(const char *str)
return tail - str;
}
int __weak arch__compare_symbol_names(const char *namea, const char *nameb)
{
return strcmp(namea, nameb);
}
int __weak arch__compare_symbol_names_n(const char *namea, const char *nameb,
unsigned int n)
{
return strncmp(namea, nameb, n);
}
int __weak arch__choose_best_symbol(struct symbol *syma,
struct symbol *symb __maybe_unused)
{
@ -399,8 +410,26 @@ static void symbols__sort_by_name(struct rb_root *symbols,
}
}
int symbol__match_symbol_name(const char *name, const char *str,
enum symbol_tag_include includes)
{
const char *versioning;
if (includes == SYMBOL_TAG_INCLUDE__DEFAULT_ONLY &&
(versioning = strstr(name, "@@"))) {
int len = strlen(str);
if (len < versioning - name)
len = versioning - name;
return arch__compare_symbol_names_n(name, str, len);
} else
return arch__compare_symbol_names(name, str);
}
static struct symbol *symbols__find_by_name(struct rb_root *symbols,
const char *name)
const char *name,
enum symbol_tag_include includes)
{
struct rb_node *n;
struct symbol_name_rb_node *s = NULL;
@ -414,11 +443,11 @@ 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 = symbol__match_symbol_name(s->sym.name, name, includes);
if (cmp < 0)
if (cmp > 0)
n = n->rb_left;
else if (cmp > 0)
else if (cmp < 0)
n = n->rb_right;
else
break;
@ -427,16 +456,17 @@ static struct symbol *symbols__find_by_name(struct rb_root *symbols,
if (n == NULL)
return NULL;
/* return first symbol that has same name (if any) */
for (n = rb_prev(n); n; n = rb_prev(n)) {
struct symbol_name_rb_node *tmp;
if (includes != SYMBOL_TAG_INCLUDE__DEFAULT_ONLY)
/* return first symbol that has same name (if any) */
for (n = rb_prev(n); n; n = rb_prev(n)) {
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))
break;
tmp = rb_entry(n, struct symbol_name_rb_node, rb_node);
if (arch__compare_symbol_names(tmp->sym.name, s->sym.name))
break;
s = tmp;
}
s = tmp;
}
return &s->sym;
}
@ -503,7 +533,12 @@ struct symbol *symbol__next_by_name(struct symbol *sym)
struct symbol *dso__find_symbol_by_name(struct dso *dso, enum map_type type,
const char *name)
{
return symbols__find_by_name(&dso->symbol_names[type], name);
struct symbol *s = symbols__find_by_name(&dso->symbol_names[type], name,
SYMBOL_TAG_INCLUDE__NONE);
if (!s)
s = symbols__find_by_name(&dso->symbol_names[type], name,
SYMBOL_TAG_INCLUDE__DEFAULT_ONLY);
return s;
}
void dso__sort_by_name(struct dso *dso, enum map_type type)

11
tools/perf/util/symbol.h
View file

@ -348,8 +348,19 @@ void arch__sym_update(struct symbol *s, GElf_Sym *sym);
#define SYMBOL_A 0
#define SYMBOL_B 1
int arch__compare_symbol_names(const char *namea, const char *nameb);
int arch__compare_symbol_names_n(const char *namea, const char *nameb,
unsigned int n);
int arch__choose_best_symbol(struct symbol *syma, struct symbol *symb);
enum symbol_tag_include {
SYMBOL_TAG_INCLUDE__NONE = 0,
SYMBOL_TAG_INCLUDE__DEFAULT_ONLY
};
int symbol__match_symbol_name(const char *namea, const char *nameb,
enum symbol_tag_include includes);
/* structure containing an SDT note's info */
struct sdt_note {
char *name; /* name of the note*/