[for-next][PATCH 04/10] tracing/bpf: disable preemption in syscall probe

Steven Rostedt
2024-10-10T14:25:42Z

In preparation for allowing system call enter/exit instrumentation to
handle page faults, make sure that bpf can handle this change by
explicitly disabling preemption within the bpf system call tracepoint
probes to respect the current expectations within bpf tracing code.

This change does not yet allow bpf to take page faults per se within its
probe, but allows its existing probes to adapt to the upcoming change.

Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Link: https://lore.kernel.org/20241009010718.2050182-5-mathieu.desnoyers@efficios.com
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Andrii Nakryiko <andrii@kernel.org> # BPF parts
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/trace/bpf_probe.h | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index c85bbce5aaa5..fec97c93e1c9 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -53,8 +53,18 @@ __bpf_trace_##call(void *__data, proto) \
#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))

+#define __BPF_DECLARE_TRACE_SYSCALL(call, proto, args) \
+static notrace void \
+__bpf_trace_##call(void *__data, proto) \
+{ \
+ preempt_disable_notrace(); \
+ CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(__data, CAST_TO_U64(args)); \
+ preempt_enable_notrace(); \
+}
+
#undef DECLARE_EVENT_SYSCALL_CLASS
-#define DECLARE_EVENT_SYSCALL_CLASS DECLARE_EVENT_CLASS
+#define DECLARE_EVENT_SYSCALL_CLASS(call, proto, args, tstruct, assign, print) \
+ __BPF_DECLARE_TRACE_SYSCALL(call, PARAMS(proto), PARAMS(args))

/*
* This part is compiled out, it is only here as a build time check
--
2.45.2