tracing/perf: Add might_fault check to syscall probes

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

Cc: Michael Jeanson <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Yonghong Song <[e-mail]>
Cc: Paul E. McKenney <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: [e-mail]
Cc: Joel Fernandes <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Mathieu Desnoyers <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

include/trace/perf.h

···
 	u64 __count __attribute__((unused));				\
 	struct task_struct *__task __attribute__((unused));		\
 									\
+	might_fault();							\
 	preempt_disable_notrace();					\
 	do_perf_trace_##call(__data, args);				\
 	preempt_enable_notrace();					\

kernel/trace/trace_syscalls.c

···
 	 * 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);
···
 	 * 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);