kfence: use error_report_end tracepoint

Make it possible to trace KFENCE error reporting.  A good usecase is
watching for trace events from the userspace to detect and process memory
corruption reports from the kernel.

Link: https://lkml.kernel.org/r/20210121131915.1331302-3-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/kfence/report.c

@@ -14,6 +14,7 @@
 #include <linux/seq_file.h>
 #include <linux/stacktrace.h>
 #include <linux/string.h>
+#include <trace/events/error_report.h>
 
 #include <asm/kfence.h>
 
@@ -248,6 +249,7 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r
 		show_regs(regs);
 	else
 		dump_stack_print_info(KERN_ERR);
+	trace_error_report_end(ERROR_DETECTOR_KFENCE, address);
 	pr_err("==================================================================\n");
 
 	lockdep_on();