[PATCH 3/3] kasan: use error_report_end tracepoint

[Alexander Potapenko <glider@xxxxxxxxxx>]

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

Suggested-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>

---
v3:
 - dropped error_report_start

v2:
 - change error_report_start and error_report_end prototypes
   to accept enum error_detector instead of char*
   (as suggested by Steven Rostedt)
---
 mm/kasan/report.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 234f35a84f19..87b271206163 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/sched/task_stack.h>
 #include <linux/uaccess.h>
+#include <trace/events/error_report.h>
 
 #include <asm/sections.h>
 
@@ -84,8 +85,9 @@ static void start_report(unsigned long *flags)
 	pr_err("==================================================================\n");
 }
 
-static void end_report(unsigned long *flags)
+static void end_report(unsigned long *flags, unsigned long addr)
 {
+	trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
 	pr_err("==================================================================\n");
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 	spin_unlock_irqrestore(&report_lock, *flags);
@@ -355,7 +357,7 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
 	print_address_description(object, tag);
 	pr_err("\n");
 	print_memory_metadata(object);
-	end_report(&flags);
+	end_report(&flags, (unsigned long)object);
 }
 
 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
@@ -401,7 +403,7 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 		dump_stack();
 	}
 
-	end_report(&flags);
+	end_report(&flags, addr);
 }
 
 bool kasan_report(unsigned long addr, size_t size, bool is_write,
-- 
2.30.0.296.g2bfb1c46d8-goog