[tip:perf/core] perf powerpc: Choose local entry point with kretprobes

["tip-bot for Naveen N. Rao" <tipbot@zytor.com>]

Commit-ID:  44ca9341f65295c56e904cce4c84f5778f5c8537
Gitweb:     http://git.kernel.org/tip/44ca9341f65295c56e904cce4c84f5778f5c8537
Author:     Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
AuthorDate: Wed, 8 Mar 2017 13:56:10 +0530
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 14 Mar 2017 15:17:39 -0300

perf powerpc: Choose local entry point with kretprobes

perf now uses an offset from _text/_stext for kretprobes if the kernel
supports it, rather than the actual function name. As such, let's choose
the LEP for powerpc ABIv2 so as to ensure the probe gets hit. Do it only
if the kernel supports specifying offsets with kretprobes.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/7445b5334673ef5404ac1d12609bad4d73d2b567.1488961018.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/arch/powerpc/util/sym-handling.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
index 1030a6e..39dbe51 100644
--- a/tools/perf/arch/powerpc/util/sym-handling.c
+++ b/tools/perf/arch/powerpc/util/sym-handling.c
@@ -10,6 +10,7 @@
 #include "symbol.h"
 #include "map.h"
 #include "probe-event.h"
+#include "probe-file.h"
 
 #ifdef HAVE_LIBELF_SUPPORT
 bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
@@ -79,13 +80,18 @@ void arch__fix_tev_from_maps(struct perf_probe_event *pev,
 	 * However, if the user specifies an offset, we fall back to using the
 	 * GEP since all userspace applications (objdump/readelf) show function
 	 * disassembly with offsets from the GEP.
-	 *
-	 * In addition, we shouldn't specify an offset for kretprobes.
 	 */
-	if (pev->point.offset || (!pev->uprobes && pev->point.retprobe) ||
-	    !map || !sym)
+	if (pev->point.offset || !map || !sym)
 		return;
 
+	/* For kretprobes, add an offset only if the kernel supports it */
+	if (!pev->uprobes && pev->point.retprobe) {
+#ifdef HAVE_LIBELF_SUPPORT
+		if (!kretprobe_offset_is_supported())
+#endif
+			return;
+	}
+
 	lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
 
 	if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)