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authorNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>2015-04-28 17:35:39 +0530
committerArnaldo Carvalho de Melo <acme@redhat.com>2015-05-04 12:43:46 -0300
commitd5c2e2c17ae1d630ddbceb53a264f24cc99703a4 (patch)
tree140641716e514c3f40e1002f26146cfacf91f5c0
parentc50fc0a43e33a6c3257c5cbb954cd747d7b9a680 (diff)
downloadlinux-d5c2e2c17ae1d630ddbceb53a264f24cc99703a4.tar.gz
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>
-rw-r--r--tools/perf/arch/powerpc/util/sym-handling.c8
-rw-r--r--tools/perf/util/probe-event.c8
-rw-r--r--tools/perf/util/probe-event.h1
3 files changed, 17 insertions, 0 deletions
diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
index 012a0f8098de..a1700609e145 100644
--- a/tools/perf/arch/powerpc/util/sym-handling.c
+++ b/tools/perf/arch/powerpc/util/sym-handling.c
@@ -9,6 +9,7 @@
#include "debug.h"
#include "symbol.h"
#include "map.h"
+#include "probe-event.h"
#ifdef HAVE_LIBELF_SUPPORT
bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
@@ -57,3 +58,10 @@ int arch__compare_symbol_names(const char *namea, const char *nameb)
return strcmp(namea, nameb);
}
#endif
+
+#if defined(_CALL_ELF) && _CALL_ELF == 2
+bool arch__prefers_symtab(void)
+{
+ return true;
+}
+#endif
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 291bf23a5013..4dfb412ff1f4 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2567,6 +2567,8 @@ err_out:
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 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
}
}
+ 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 d6b783447be9..52bca4bf07ca 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -135,6 +135,7 @@ extern int show_available_vars(struct perf_probe_event *pevs, int npevs,
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