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authorAndrii Nakryiko <andrii@kernel.org>2024-04-18 12:09:08 -0700
committerMasami Hiramatsu (Google) <mhiramat@kernel.org>2024-05-01 23:18:48 +0900
commitb0e28a4b5becea84ae6fca5cbd8a6b80a134e223 (patch)
tree436194932eee40c5eced2d6019b6d28287ffaf7a /kernel/trace
parent0dc715295d4143d1659879f7f50ad4e9a6f6a99c (diff)
ftrace: make extra rcu_is_watching() validation check optional
Introduce CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING config option to control whether ftrace low-level code performs additional rcu_is_watching()-based validation logic in an attempt to catch noinstr violations. This check is expected to never be true and is mostly useful for low-level validation of ftrace subsystem invariants. For most users it should probably be kept disabled to eliminate unnecessary runtime overhead. This improves BPF multi-kretprobe (relying on ftrace and rethook infrastructure) runtime throughput by 2%, according to BPF benchmarks ([0]). [0] https://lore.kernel.org/bpf/CAEf4BzauQ2WKMjZdc9s0rBWa01BYbgwHN6aNDXQSHYia47pQ-w@mail.gmail.com/ Link: https://lore.kernel.org/all/20240418190909.704286-1-andrii@kernel.org/ Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Paul E. McKenney <paulmck@kernel.org> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/Kconfig13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 47345bf1d4a9..d093e16d01c1 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -974,6 +974,19 @@ config FTRACE_RECORD_RECURSION_SIZE
This file can be reset, but the limit can not change in
size at runtime.
+config FTRACE_VALIDATE_RCU_IS_WATCHING
+ bool "Validate RCU is on during ftrace execution"
+ depends on FUNCTION_TRACER
+ depends on ARCH_WANTS_NO_INSTR
+ help
+ All callbacks that attach to the function tracing have some sort of
+ protection against recursion. This option is only to verify that
+ ftrace (and other users of ftrace_test_recursion_trylock()) are not
+ called outside of RCU, as if they are, it can cause a race. But it
+ also has a noticeable overhead when enabled.
+
+ If unsure, say N
+
config RING_BUFFER_RECORD_RECURSION
bool "Record functions that recurse in the ring buffer"
depends on FTRACE_RECORD_RECURSION