From: Adrian Hunter <[email protected]> When doing a system-wide trace with Intel PT, the jump label set up as a result of probing CLOEXEC gets reset while the trace is running. That causes an Intel PT decoding error because the object code (obtained from /proc/kcore) does not match the running code at that point. While we can't expect there never to be jump label changes, we can avoid cases that the perf tool itself creates.
The problem is avoided by first trying a cpu-wide event (pid = -1) for probing the PERF_FLAG_FD_CLOEXEC flag and falling back to an event for the current process (pid = 0). Signed-off-by: Adrian Hunter <[email protected]> Acked-by: Jiri Olsa <[email protected]> Cc: David Ahern <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Stephane Eranian <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> --- tools/perf/util/cloexec.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c index 000047cb3fee..4945aa56a017 100644 --- a/tools/perf/util/cloexec.c +++ b/tools/perf/util/cloexec.c @@ -1,3 +1,4 @@ +#include <sched.h> #include "util.h" #include "../perf.h" #include "cloexec.h" @@ -15,10 +16,23 @@ static int perf_flag_probe(void) }; int fd; int err; + int cpu; + pid_t pid = -1; - /* check cloexec flag */ - fd = sys_perf_event_open(&attr, 0, -1, -1, - PERF_FLAG_FD_CLOEXEC); + cpu = sched_getcpu(); + if (cpu < 0) + cpu = 0; + + while (1) { + /* check cloexec flag */ + fd = sys_perf_event_open(&attr, pid, cpu, -1, + PERF_FLAG_FD_CLOEXEC); + if (fd < 0 && pid == -1 && errno == EACCES) { + pid = 0; + continue; + } + break; + } err = errno; if (fd >= 0) { @@ -31,7 +45,7 @@ static int perf_flag_probe(void) err, strerror(err)); /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */ - fd = sys_perf_event_open(&attr, 0, -1, -1, 0); + fd = sys_perf_event_open(&attr, pid, cpu, -1, 0); err = errno; if (WARN_ONCE(fd < 0 && err != EBUSY, -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
