linux-kernel - [PATCH v3 0/3] ftrace: Introduce PERMANENT ftrace

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Date:   Wed, 16 Oct 2019 13:33:12 +0200
From:   Miroslav Benes <mbenes@...e.cz>
To:     rostedt@...dmis.org, mingo@...hat.com, jpoimboe@...hat.com,
        jikos@...nel.org, pmladek@...e.com, joe.lawrence@...hat.com
Cc:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        shuah@...nel.org, kamalesh@...ux.vnet.ibm.com,
        linux-kselftest@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH v3 0/3] ftrace: Introduce PERMANENT ftrace_ops flag

Livepatch uses ftrace for redirection to new patched functions. It means
that if ftrace is disabled, all live patched functions are disabled as
well. Toggling global 'ftrace_enabled' sysctl thus affect it directly.
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 on any ftrace ops, the tracing cannot be
disabled by disabling ftrace_enabled. Equally, a callback with the flag
set cannot be registered if ftrace_enabled is disabled.

v2->v3:
- ftrace_enabled explicitly set to true
- selftest from Joe Lawrence (I just split it to two patches)
- typo fix

v1->v2:
- different logic, proposed by Joe Lawrence

Joe Lawrence (2):
  selftests/livepatch: Make dynamic debug setup and restore generic
  selftests/livepatch: Test interaction with ftrace_enabled

Miroslav Benes (1):
  ftrace: Introduce PERMANENT ftrace_ops flag

 Documentation/trace/ftrace-uses.rst           |  8 +++
 Documentation/trace/ftrace.rst                |  4 +-
 include/linux/ftrace.h                        |  3 +
 kernel/livepatch/patch.c                      |  3 +-
 kernel/trace/ftrace.c                         | 23 ++++++-
 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../testing/selftests/livepatch/functions.sh  | 34 +++++++---
 .../selftests/livepatch/test-callbacks.sh     |  2 +-
 .../selftests/livepatch/test-ftrace.sh        | 65 +++++++++++++++++++
 .../selftests/livepatch/test-livepatch.sh     |  2 +-
 .../selftests/livepatch/test-shadow-vars.sh   |  2 +-
 11 files changed, 132 insertions(+), 17 deletions(-)
 create mode 100755 tools/testing/selftests/livepatch/test-ftrace.sh

-- 
2.23.0