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>

diff --git a/Documentation/perf_counter/perf-report.cc b/Documentation/perf_counter/perf-report.cc
index 1727317..933a075 100644 (file)
--- 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();