[PATCH resend 6/8] tracing/ftrace: Add might_fault check to syscall probes

[Mathieu Desnoyers]

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.desnoy...@efficios.com>
Acked-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Cc: Michael Jeanson <mjean...@efficios.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Masami Hiramatsu <mhira...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Alexei Starovoitov <a...@kernel.org>
Cc: Yonghong Song <y...@fb.com>
Cc: Paul E. McKenney <paul...@kernel.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Andrii Nakryiko <andrii.nakry...@gmail.com>
Cc: b...@vger.kernel.org
Cc: Joel Fernandes <j...@joelfernandes.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 a3d8ac00793e..0430890cbb42 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