linux-kernel - [PATCH] perf probe: Ignore vmlinux build-id when offline vmlinux and dry-run used

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Message-Id: <1485294088-17361-1-git-send-email-johunt@akamai.com>
Date:   Tue, 24 Jan 2017 16:41:28 -0500
From:   Josh Hunt <johunt@...mai.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bgregg@...flix.com, Josh Hunt <johunt@...mai.com>
Subject: [PATCH] perf probe: Ignore vmlinux build-id when offline vmlinux and dry-run used

Commit e50243bb ("perf probe: Ignore vmlinux Build-id when offline vmlinux given")
added the ability to ignore vmlinux when an offline vmlinux is passed and no
l, d, or a flag is also passed. This extends that to ignore build-id when
-n/--dry-run is used. This way we can gather probe information for offline kernels
using the method Brendan Gregg mentions in this post:
http://www.brendangregg.com/blog/2014-09-11/perf-kernel-line-tracing.html .

Ex:
 $ ./perf probe -k ./vmlinux-3.14.59 -nv 'do_sys_open=do_sys_open:7 filename:string dfd flags op'

will generate:
 do_sys_open+91 filename_string=+0(%si):string dfd=%di:s32 flags=%bx:s32 op=-60(%bp):u64

and then copy/paste this to the machine running the 3.14.59 kernel.

Signed-off-by: Josh Hunt <johunt@...mai.com>
---
 tools/perf/builtin-probe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index f87996b..e0eea723 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -616,7 +616,7 @@ static int perf_del_probe_events(struct strfilter *filter)
 	 * nor change running kernel. So if user gives offline vmlinux,
 	 * ignore its buildid.
 	 */
-	if (!strchr("lda", params.command) && symbol_conf.vmlinux_name)
+	if ((!strchr("lda", params.command) || probe_event_dry_run) && symbol_conf.vmlinux_name)
 		symbol_conf.ignore_vmlinux_buildid = true;
 
 	switch (params.command) {
-- 
1.9.1