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Subject[PATCH 29/40] perf top: Support lookup of symbols in other mount namespaces.
Date
From: Krister Johansen <kjlx@templeofstupid.com>

The perf top command needs to unshare its fs from the helper threads in
order to successfully setns(2) during its symbol lookup. It also needs
to impelement a force flag to ignore ownership of perf-<pid>.map files.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1499305693-1599-6-git-send-email-kjlx@templeofstupid.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-top.txt | 4 ++++
tools/perf/builtin-top.c | 15 +++++++++++++++
2 files changed, 19 insertions(+)

diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index e71d63843f45..d864ea6fd367 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -237,6 +237,10 @@ Default is to monitor all CPUS.
--hierarchy::
Enable hierarchy output.

+--force::
+ Don't do ownership validation.
+
+
INTERACTIVE PROMPTING KEYS
--------------------------

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index e5a8f249077f..ee954bde7e3e 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -587,6 +587,13 @@ static void *display_thread_tui(void *arg)
.refresh = top->delay_secs,
};

+ /* In order to read symbols from other namespaces perf to needs to call
+ * setns(2). This isn't permitted if the struct_fs has multiple users.
+ * unshare(2) the fs so that we may continue to setns into namespaces
+ * that we're observing.
+ */
+ unshare(CLONE_FS);
+
perf_top__sort_new_samples(top);

/*
@@ -628,6 +635,13 @@ static void *display_thread(void *arg)
struct perf_top *top = arg;
int delay_msecs, c;

+ /* In order to read symbols from other namespaces perf to needs to call
+ * setns(2). This isn't permitted if the struct_fs has multiple users.
+ * unshare(2) the fs so that we may continue to setns into namespaces
+ * that we're observing.
+ */
+ unshare(CLONE_FS);
+
display_setup_sig();
pthread__unblock_sigwinch();
repeat:
@@ -1206,6 +1220,7 @@ int cmd_top(int argc, const char **argv)
"Show raw trace event output (do not use print fmt or plugins)"),
OPT_BOOLEAN(0, "hierarchy", &symbol_conf.report_hierarchy,
"Show entries in a hierarchy"),
+ OPT_BOOLEAN(0, "force", &symbol_conf.force, "don't complain, do it"),
OPT_END()
};
const char * const top_usage[] = {
--
2.9.4
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