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SubjectRe: [PATCH v2 4/5] perf-probe: Find versioned symbols from map
On Fri, 8 Dec 2017 12:08:41 +0100
Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> wrote:

> On 12/07/2017 08:21 AM, Masami Hiramatsu wrote:
> > Find versioned symbols correctly from map.
> > Commit d80406453ad4 ("perf symbols: Allow user probes on
> > versioned symbols") allows user to find default versioned
> > symbols (with "@@") in map. However, it did not enable
> > normal versioned symbol (with "@") for perf-probe.
> > E.g.
> >
> > =====
> > # ./perf probe -x /lib64/libc-2.25.so malloc_get_state
> > Failed to find symbol malloc_get_state in /usr/lib64/libc-2.25.so
> > Error: Failed to add events.
> > =====
> >
> > This solves above issue by improving perf-probe symbol
> > search function, as below.
> >
> > =====
> > # ./perf probe -x /lib64/libc-2.25.so malloc_get_state
> > Added new event:
> > probe_libc:malloc_get_state (on malloc_get_state in /usr/lib64/libc-2.25.so)
> >
> > You can now use it in all perf tools, such as:
> >
> > perf record -e probe_libc:malloc_get_state -aR sleep 1
> >
> > # ./perf probe -l
> > probe_libc:malloc_get_state (on malloc_get_state@GLIBC_2.2.5 in /usr/lib64/libc-2.25.so)
> > =====
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> > tools/perf/arch/powerpc/util/sym-handling.c | 8 ++++++++
> > tools/perf/util/probe-event.c | 16 +++++++++++++++-
> > tools/perf/util/symbol.c | 5 +++++
> > tools/perf/util/symbol.h | 1 +
> > 4 files changed, 29 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
> > index 9c4e23d8c8ce..a3613c8d97b6 100644
> > --- a/tools/perf/arch/powerpc/util/sym-handling.c
> > +++ b/tools/perf/arch/powerpc/util/sym-handling.c
> > @@ -64,6 +64,14 @@ int arch__compare_symbol_names_n(const char *namea, const char *nameb,
> >
> > return strncmp(namea, nameb, n);
> > }
> > +
> > +const char *arch__normalize_symbol_name(const char *name)
> > +{
> > + /* Skip over initial dot */
> > + if (*name == '.')
> > + name++;
> > + return name;
> > +}
> > #endif
> >
> > #if defined(_CALL_ELF) && _CALL_ELF == 2
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 959c4d2ef455..94acc5846e2a 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -2801,16 +2801,30 @@ static int find_probe_functions(struct map *map, char *name,
> > int found = 0;
> > struct symbol *sym;
> > struct rb_node *tmp;
> > + const char *norm, *ver;
> > + char *buf = NULL;
> >
> > if (map__load(map) < 0)
> > return 0;
> >
> > map__for_each_symbol(map, sym, tmp) {
> > - if (strglobmatch(sym->name, name)) {
> > + norm = arch__normalize_symbol_name(sym->name);
>
> The weak default function arch__normalize_symbol_name() simply returns
> its parameter, so norm can be a NULL ptr when parameter sym->name is a
> NULL pointer.
> However when sym->name is a NULL pointer (or can be one) then the
> Powerpc version of arch__normalize_symbol_name() dereferences a NULL
> ptr (by checking the symbol's first character is a '.').

Oops, right!
Thank you for pointing out. :)

>
> > + if (!norm)
> > + continue;
> > +
> > + /* We don't care about default symbol or not */
> > + ver = strchr(norm, '@');
> > + if (ver) {
> > + buf = strndup(norm, ver - norm);
> > + norm = buf;
>
> if strndup() returns a NULL pointer (due to lack of memory)
> then variable norm is a NULL ptr and strglobmatch() --> __match_glob()
> derefenences that NULL pointer (1. parameter).

Ah, right. easy miss...

OK, I'll update.

Thank you,

>
> > + }
> > + if (strglobmatch(norm, name)) {
> > found++;
> > if (syms && found < probe_conf.max_probes)
> > syms[found - 1] = sym;
> > }
> > + if (buf)
> > + zfree(&buf);
> > }
> >
> > return found;
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index 1b67a8639dfe..cc065d4bfafc 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -94,6 +94,11 @@ static int prefix_underscores_count(const char *str)
> > return tail - str;
> > }
> >
> > +const char * __weak arch__normalize_symbol_name(const char *name)
> > +{
> > + return name;
> > +}
> > +
> > int __weak arch__compare_symbol_names(const char *namea, const char *nameb)
> > {
> > return strcmp(namea, nameb);
> > diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> > index a4f0075b4e5c..0563f33c1eb3 100644
> > --- a/tools/perf/util/symbol.h
> > +++ b/tools/perf/util/symbol.h
> > @@ -349,6 +349,7 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr);
> > void arch__sym_update(struct symbol *s, GElf_Sym *sym);
> > #endif
> >
> > +const char *arch__normalize_symbol_name(const char *name);
> > #define SYMBOL_A 0
> > #define SYMBOL_B 1
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
>
> --
> Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
> --
> Vorsitzende des Aufsichtsrats: Martina Koederitz
> Geschäftsführung: Dirk Wittkopp
> Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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