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ftrace: Preserve kprobe events during trace-cmd reset

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FtraceCollector.reset() executes 'trace-cmd reset ..' command which
clears all kprobes. This breaks tracing existing kprobe events (if any).
Thus, save kprobe events before trace-cmd reset and restore them after
the reset operation.

For the context, I want to trace an ordinary function in kernel (e.g.,
"echo 'p do_sys_open' > /sys/kernel/tracing/kprobe_events"). However,
FtraceCollector.reset() destroys kprobes, too. Preserving existing
kprobes allows me to use FtraceCollector class as is.

Signed-off-by: Metin Kaya <metin.kaya@arm.com>
This commit is contained in:
Metin Kaya 2024-09-23 12:52:37 +01:00 committed by Marc Bonnici
parent 8773c10424
commit d4d9c92ae9
1 changed files with 9 additions and 1 deletions
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10
devlib/collector/ftrace.py
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@ -107,7 +107,8 @@ class FtraceCollector(CollectorBase):
self.function_profile_file = self.target.path.join(self.tracing_path, 'function_profile_enabled')
self.marker_file = self.target.path.join(self.tracing_path, 'trace_marker')
self.ftrace_filter_file = self.target.path.join(self.tracing_path, 'set_ftrace_filter')
self.available_tracers_file = self.target.path.join(self.tracing_path, 'available_tracers')
self.available_tracers_file = self.target.path.join(self.tracing_path, 'available_tracers')
self.kprobe_events = self.target.path.join(self.tracing_path, 'kprobe_events')
self.host_binary = which('trace-cmd')
self.kernelshark = which('kernelshark')
@ -240,6 +241,9 @@ class FtraceCollector(CollectorBase):
return self.target.read_value(self.available_functions_file).splitlines()
def reset(self):
# Save kprobe events
kprobe_events = self.target.read_value(self.kprobe_events)
self.target.execute('{} reset -B devlib'.format(self.target_binary),
as_root=True, timeout=TIMEOUT)
@ -256,6 +260,10 @@ class FtraceCollector(CollectorBase):
if self.functions:
self.target.write_value(self.function_profile_file, 0, verify=False)
# Restore kprobe events
self.target.write_value(self.kprobe_events, kprobe_events)
self._reset_needed = False
@asyncf