Refactor the instruction tracing subsystem. #168
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qwattash
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Sep 29, 2021
arichardson
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Sep 29, 2021
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- Rename cpu_log_instr_info to cpu_log_entry.
The -dfilter qemu option has ad-hoc support within TCG instruction tracing, this generalizes the trace filtering to an arbitrary per-CPU set of functions that can filter the trace entry based on any parameter. Note that for now filters are assumed to be stateless.
Each trace format is moved to a separate file for implementation.
This backend is intended to capture statistics from the instructions instead of dumping the whole instruction stream. Note that this is disabled by default in the configuration as it adds a dependency on libboost.
- Add cheri-perfetto submodule for tracing. - Plumb the perfetto tracing backend in the build system - Add initialization code that registers the tracing categories and starts the tracing service at startup - Add skeleton for the perfetto tracing backend glue code
- Add command line option to select filters to use. - Make sure that the filters from command line are applied to the CPUs at initialization. - Add filter to only emit entries containing events.
For each CPU we create 2 tracks: one for control events (e.g. tracing
start/stop) and another for log events on that CPU.
Currently we emit instructions and stats events on the CPU track.
- Replace the stats backend with a tracing category in the perfetto backend
- Add new CLI options to control the perfetto backend behaviour:
1. --cheri-trace-perfetto-categories comma-separated list of categories to
enable.
2. --cheri-trace-perfetto-logfile log file to use for the perfetto binary
trace. We do not use the common qemu logfile to avoid accidental pollution
and passing the qemu file descriptor is painful due to having to lock the
logfile via RCU.
- Add hook at qemu shutdown to make sure we flush the log buffers, if the
tracing backend supports this.
Flush TrackEvent data source when we receive a FLUSH event in the instruction logging subsystem. This helps making sure that we do not have lost events when running multiple tests on qemu.
Remove the event variant that bypasses log enable. This is useless as switching on/off tracing around the event is feasible and the event is rare enough that it is not a performance issue.
Add NOP that guests can use to create and increment/decrement counters. The counters are emitted into the perfetto trace stream as normal perfetto counter tracks.
These are still not hooked to the guest NOPs.
Replace the stats implementation with a new one based on the cheri-perfetto interval tracks. The stats implementation tracks basic block icount and hits, along with branches. Now there are multiple categories for each different statistic instead of a grouped one.
This works around the inability to use bytes fields in perfetto track event messages.
This was essentially unused, and can be replicated during initialization.
Add two counters to measure instruction count when tracing is enabled/disabled.
Only maintain the branch and basic block hit histograms when the corresponding trace categories are enabled.
This should not be needed because we have flags marking TBs whenever they contain instruction tracing instrumentation.
This is broken by recent liburing versions.
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Add disas_one_strbuf() to disassemble one instruction to an existing string buffer. Add disas_one_str() to disassemble one instruction to a dynamically allocated string.
- Conditionally compile cvtrace - This is done because some of these backends emit binary data that is logically incompatible with the standard qemu output file. The downside is the we need to handle our own locking if we want to support multiple CPUs.
This should help to inform log backends for management purposes.
This is better than instr_info as it reflects its use.
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Add tracing backend based on the google perfetto tracing framework.
Add the ability to aggregate statistics within qemu and emit them as part of the perfetto backend.
Add support for generic events associated to instructions.
Add better support for trace filters for each log entry.