[PATCH 0/3] ftrace: Introduce PERMANENT ftrace_ops flag

From: Miroslav Benes
Date: Mon Oct 07 2019 - 04:17:30 EST


Livepatch uses ftrace for redirection to new patched functions. It is
thus directly affected by ftrace sysctl knobs such as ftrace_enabled.
Setting ftrace_enabled to 0 also disables all live patched functions. It
is not a problem per se, because only administrator can set sysctl
values, but it still may be surprising.

Introduce PERMANENT ftrace_ops flag to amend this. If the
FTRACE_OPS_FL_PERMANENT is set, the tracing of the function is not
disabled. Such ftrace_ops can still be unregistered in a standard way.

The patch set passes ftrace and livepatch kselftests.

Miroslav Benes (3):
ftrace: Make test_rec_ops_needs_regs() generic
ftrace: Introduce PERMANENT ftrace_ops flag
livepatch: Use FTRACE_OPS_FL_PERMANENT

Documentation/trace/ftrace-uses.rst | 6 ++++
Documentation/trace/ftrace.rst | 2 ++
include/linux/ftrace.h | 8 +++--
kernel/livepatch/patch.c | 3 +-
kernel/trace/ftrace.c | 47 ++++++++++++++++++++++++-----
5 files changed, 55 insertions(+), 11 deletions(-)

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2.23.0