perf_counter tools: fix infinite loop in perf-report on zeroed event records

Bail out early if a record has zero size - we have no chance to make
reliable progress in that case. Print out the offset where this happens,
and print the number of bytes we missed out on.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 2 deletions

diff --git a/Documentation/perf_counter/perf-report.cc b/Documentation/perf_counter/perf-report.cc
index 1727317352bf..933a07544534 100644
--- a/Documentation/perf_counter/perf-report.cc
+++ b/Documentation/perf_counter/perf-report.cc
@@ -13,6 +13,7 @@
 #include <ctype.h>
 #include <time.h>
 #include <getopt.h>
+#include <assert.h>
 
 #include <sys/ioctl.h>
 #include <sys/poll.h>
@@ -226,7 +227,7 @@ void load_kallsyms(void)
         while (!feof(file)) {
                 uint64_t start;
                 char c;
-                char sym[1024];
+                char sym[1024000];
 
                 if (getline(&line, &n, file) < 0)
                         break;
@@ -416,12 +417,23 @@ more:
 
         if (head + event->header.size >= page_size * mmap_window) {
                 unsigned long shift = page_size * (head / page_size);
+                int ret;
+
+                ret = munmap(buf, page_size * mmap_window);
+                assert(ret == 0);
 
-                munmap(buf, page_size * mmap_window);
                 offset += shift;
                 head -= shift;
                 goto remap;
         }
+
+
+        if (!event->header.size) {
+                fprintf(stderr, "zero-sized event at file offset %ld\n", offset + head);
+                fprintf(stderr, "skipping %ld bytes of events.\n", stat.st_size - offset - head);
+                goto done;
+        }
+
         head += event->header.size;
 
         if (event->header.misc & PERF_EVENT_MISC_OVERFLOW) {
@@ -458,6 +470,8 @@ more:
         if (offset + head < stat.st_size)
                 goto more;
 
+done:
+
         close(input);
 
         std::map<std::string, int>::iterator hi = hist.begin();