perf top: Support lookup of symbols in other mount namespaces.

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>

diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index e71d63843f45d493611cef226a87915427dfa0c2..d864ea6fd367efb63e1a9411f6e74e8d42ab3428 100644 (file)
--- 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 e5a8f249077fef709a03c90d896fa4e518823230..ee954bde7e3e800d308a41af7d70acc333802b67 100644 (file)
--- 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[] = {