perf probe ppc64le: Prefer symbol table lookup over DWARF
Use symbol table lookups by default if DWARF is not necessary, since
powerpc ABIv2 encodes local entry points in the symbol table and the
function entry address in DWARF may not be appropriate for kprobes, as
described here:
https://sourceware.org/bugzilla/show_bug.cgi?id=17638
"The DWARF address ranges deliberately include the *whole* function,
both global and local entry points."
...
"If you want to set probes on a local entry point, you should look up
the symbol in the main symbol table (not DWARF), and check the st_other
bits; they will indicate whether the function has a local entry point,
and what its offset from the global entry point is. Note that GDB does
the same when setting a breakpoint on a function entry."
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/88a10e22f4aaba2aef812824ca4b10d7beeea012.1430217967.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 291bf23..4dfb412 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2567,6 +2567,8 @@
goto out;
}
+bool __weak arch__prefers_symtab(void) { return false; }
+
static int convert_to_probe_trace_events(struct perf_probe_event *pev,
struct probe_trace_event **tevs,
int max_tevs, const char *target)
@@ -2582,6 +2584,12 @@
}
}
+ if (arch__prefers_symtab() && !perf_probe_event_need_dwarf(pev)) {
+ ret = find_probe_trace_events_from_map(pev, tevs, max_tevs, target);
+ if (ret > 0)
+ return ret; /* Found in symbol table */
+ }
+
/* Convert perf_probe_event with debuginfo */
ret = try_to_find_probe_trace_events(pev, tevs, max_tevs, target);
if (ret != 0)
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index d6b7834..52bca4b 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -135,6 +135,7 @@
struct strfilter *filter, bool externs);
extern int show_available_funcs(const char *module, struct strfilter *filter,
bool user);
+bool arch__prefers_symtab(void);
/* Maximum index number of event-name postfix */
#define MAX_EVENT_INDEX 1024