selftests/bpf: Disable ASAN instrumentation for mmap()'ed memory read

AddressSanitizer assumes that all memory dereferences are done against memory
allocated by sanitizer's malloc()/free() code and not touched by anyone else.
Seems like this doesn't hold for perf buffer memory. Disable instrumentation
on perf buffer callback function.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429012111.277390-10-andriin@fb.com

tools/testing/selftests/bpf/prog_tests/perf_buffer.c

@@ -6,6 +6,11 @@
 #include <test_progs.h>
 #include "bpf/libbpf_internal.h"
 
+/* AddressSanitizer sometimes crashes due to data dereference below, due to
+ * this being mmap()'ed memory. Disable instrumentation with
+ * no_sanitize_address attribute
+ */
+__attribute__((no_sanitize_address))
 static void on_sample(void *ctx, int cpu, void *data, __u32 size)
 {
 	int cpu_data = *(int *)data, duration = 0;