linux-kernel - [PATCH v2 5/7] tracing/ftrace: Add might

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Message-Id: <20241004011201.1681962-6-mathieu.desnoyers@efficios.com>
Date: Thu,  3 Oct 2024 21:11:59 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Yonghong Song <yhs@...com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	bpf@...r.kernel.org,
	Joel Fernandes <joel@...lfernandes.org>,
	linux-trace-kernel@...r.kernel.org,
	Michael Jeanson <mjeanson@...icios.com>
Subject: [PATCH v2 5/7] tracing/ftrace: Add might_fault check to syscall probes

Add a might_fault() check to validate that the ftrace sys_enter/sys_exit
probe callbacks are indeed called from a context where page faults can
be handled.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Cc: Michael Jeanson <mjeanson@...icios.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: bpf@...r.kernel.org
Cc: Joel Fernandes <joel@...lfernandes.org>
---
 include/trace/trace_events.h  | 1 +
 kernel/trace/trace_syscalls.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 0228d9ed94a3..e0d4850b0d77 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -446,6 +446,7 @@ __DECLARE_EVENT_CLASS(call, PARAMS(proto), PARAMS(args), PARAMS(tstruct), \
 static notrace void							\
 trace_event_raw_event_##call(void *__data, proto)			\
 {									\
+	might_fault();							\
 	guard(preempt_notrace)();					\
 	do_trace_event_raw_event_##call(__data, args);			\
 }
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index edcfa47446c7..89d7e4c57b5b 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -303,6 +303,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 	 * Syscall probe called with preemption enabled, but the ring
 	 * buffer and per-cpu data require preemption to be disabled.
 	 */
+	might_fault();
 	guard(preempt_notrace)();
 
 	syscall_nr = trace_get_syscall_nr(current, regs);
@@ -348,6 +349,7 @@ static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 	 * Syscall probe called with preemption enabled, but the ring
 	 * buffer and per-cpu data require preemption to be disabled.
 	 */
+	might_fault();
 	guard(preempt_notrace)();
 
 	syscall_nr = trace_get_syscall_nr(current, regs);
-- 
2.39.2