[PATCH v5 0/5] Enable perf tracing for unprivileged users

[PATCH v5 0/5] Enable perf tracing for unprivileged users

[Anubhav Shelat]

Enable users to use perf-trace to trace their own processes, like strace
but without the overhead of ptrace(). Ensure that users cannot access
other users' or systemwide tracing data.

Changes in v5:
- Move event_define_fields() before directory creation. If
  event_define_fields() fails then we don't need to cleanup whatever
  dirs were created. 
- New read-only eventfs file system with the same structure as
  /sys/kernel/tracing/events/ to handle files read by unprivileged
  users.
- Allow unprivileged users to fall back to /sys/kernel/events/ when they
  cannot access /sys/kernel/tracing/events/.
- Factor out reused code into helper function that checks if a
  tracepoint should be restricted in commit 5.

Changes in v4:
- Preserve security_perf_event_open(PERF_SECURITY_KERNEL) LSM hook in
  the tp_bypass path.
- Lift the PERF_SAMPLE_IP check out of the tp_bypass path above the
  PERF_SAMPLE_RAW branch so it applies to counting and sampling. This
  also allows us to ensure PERF_SAMPLE_IP is set for uprobes.
- Block counting path for TRACE_EVENT_FL_CAP_ANY for unprivileged users
  with sysctl_perf_event_paranoid > 1.

Changes in v3:
- Don't set PERF_SAMPLE_IP for unprivileged tracepoints. This allows us
  to exclude PERF_SAMPLE_IP from kaddr_leak without weakening KASLR.
- Mount tracefs as world-traversable so users can access eventfs
  directories.

Anubhav Shelat (5):
  eventfs: define event fields before directory creation
  tracefs: add read-only eventfs filesystem at /sys/kernel/events
  perf tools: fall back to eventfs for unprivileged event discovery
  perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints
  perf: enable unprivileged syscall tracing with perf trace

 fs/tracefs/event_inode.c           |  61 ++++++++++++++++++
 fs/tracefs/inode.c                 |  95 ++++++++++++++++++++++++++-
 fs/tracefs/internal.h              |   3 +
 include/linux/trace_events.h       |   1 +
 include/linux/tracefs.h            |   4 ++
 include/uapi/linux/magic.h         |   1 +
 kernel/events/core.c               |  28 +++++++-
 kernel/trace/trace.h               |   2 +
 kernel/trace/trace_event_perf.c    |  28 +++++++-
 kernel/trace/trace_events.c        | 100 +++++++++++++++++++++++++++--
 tools/lib/api/fs/fs.c              |  10 +++
 tools/lib/api/fs/fs.h              |   1 +
 tools/lib/api/fs/tracing_path.c    |  52 +++++++++++++--
 tools/lib/api/fs/tracing_path.h    |   1 +
 tools/perf/util/evsel.c            |  14 +++-
 tools/perf/util/tp_pmu.c           |   5 +-
 tools/perf/util/trace-event-info.c |  19 +++---
 17 files changed, 395 insertions(+), 30 deletions(-)

-- 
2.54.0