ring-buffer: Do not record in NMI if the arch does not support cmpxchg in NMI

[ Upstream commit 712292308af2265cd9b126aedfa987f10f452a33 ]

As the ring buffer recording requires cmpxchg() to work, if the
architecture does not support cmpxchg in NMI, then do not do any recording
within an NMI.

Link: https://lore.kernel.org/linux-trace-kernel/20231213175403.6fc18540@gandalf.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 901a140..f232cf5 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3649,6 +3649,12 @@ rb_reserve_next_event(struct trace_buffer *buffer,
        int nr_loops = 0;
        int add_ts_default;
 
+       /* ring buffer does cmpxchg, make sure it is safe in NMI context */
+       if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
+           (unlikely(in_nmi()))) {
+               return NULL;
+       }
+
        rb_start_commit(cpu_buffer);
        /* The commit page can not change after this */