linux-kernel - [tip:perf/core] perf probe: Ignore vmlinux buildid if offline kernel is given

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Message-ID: <tip-428aff82e92a29da0e4276623180f9a98f2d5b16@git.kernel.org>
Date:   Mon, 5 Sep 2016 06:22:57 -0700
From:   tip-bot for Masami Hiramatsu <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org, mingo@...nel.org,
        acme@...hat.com, jolsa@...hat.com, hpa@...or.com,
        peterz@...radead.org, mhiramat@...nel.org
Subject: [tip:perf/core] perf probe: Ignore vmlinux buildid if offline
 kernel is given

Commit-ID:  428aff82e92a29da0e4276623180f9a98f2d5b16
Gitweb:     http://git.kernel.org/tip/428aff82e92a29da0e4276623180f9a98f2d5b16
Author:     Masami Hiramatsu <mhiramat@...nel.org>
AuthorDate: Fri, 26 Aug 2016 01:24:42 +0900
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 1 Sep 2016 09:44:14 -0300

perf probe: Ignore vmlinux buildid if offline kernel is given

Ignore the buildid of running kernel when both of --definition and
--vmlinux is given because that kernel should be off-line.

This also skips post-processing of kprobe event for relocating symbol
and checking blacklist, because it can not be done on off-line kernel.

E.g. without this fix perf shows an error as below
  ----
  $ perf probe --vmlinux=./vmlinux-arm --definition do_sys_open
  ./vmlinux-arm with build id 7a1f76dd56e9c4da707cd3d6333f50748141434b not found, continuing without symbols
  Failed to find symbol do_sys_open in kernel
    Error: Failed to add events.
  ----
with this fix, we can get the definition
  ----
  $ perf probe --vmlinux=./vmlinux-arm --definition do_sys_open
  p:probe/do_sys_open do_sys_open+0
  ----

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/147214228193.23638.12581984840822162131.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/Documentation/perf-probe.txt |  2 ++
 tools/perf/builtin-probe.c              | 10 +++++++++-
 tools/perf/util/probe-event.c           |  4 ++++
 tools/perf/util/symbol-elf.c            |  2 +-
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 56db4d4..e6c9902 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -36,6 +36,8 @@ OPTIONS
 -k::
 --vmlinux=PATH::
 	Specify vmlinux path which has debuginfo (Dwarf binary).
+	Only when using this with --definition, you can give an offline
+	vmlinux file.
 
 -m::
 --module=MODNAME|PATH::
diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 7a3d8c4..b4220cd 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -654,8 +654,16 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
 			return ret;
 		}
 		break;
-	case 'a':
 	case 'D':
+		/*
+		 * If user gives offline vmlinux, ignore buildid, since
+		 * --definition doesn't change running kernel.
+		 */
+		if (symbol_conf.vmlinux_name)
+			symbol_conf.ignore_vmlinux_buildid = true;
+		/* fall through */
+	case 'a':
+
 		/* Ensure the last given target is used */
 		if (params.target && !params.target_used) {
 			pr_err("  Error: -x/-m must follow the probe definitions.\n");
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 4a49cb8..8a1e9e6 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -674,6 +674,10 @@ post_process_kernel_probe_trace_events(struct probe_trace_event *tevs,
 	char *tmp;
 	int i, skipped = 0;
 
+	/* Skip post process if the target is an offline kernel */
+	if (symbol_conf.ignore_vmlinux_buildid)
+		return 0;
+
 	reloc_sym = kernel_get_ref_reloc_sym();
 	if (!reloc_sym) {
 		pr_warning("Relocated base symbol is not found!\n");
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index fbe31ef..e680371 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -732,7 +732,7 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
 	}
 
 	/* Always reject images with a mismatched build-id: */
-	if (dso->has_build_id) {
+	if (dso->has_build_id && !symbol_conf.ignore_vmlinux_buildid) {
 		u8 build_id[BUILD_ID_SIZE];
 
 		if (elf_read_build_id(elf, build_id, BUILD_ID_SIZE) < 0) {