dump_all_pmcs: Add a try_harder option

1 files changed, 36 insertions, 1 deletions

diff --git a/dump_all_pmcs.c b/dump_all_pmcs.c
index be7a043..8f0c943 100644
--- a/dump_all_pmcs.c
+++ b/dump_all_pmcs.c
@@ -9,6 +9,9 @@
 #include <signal.h>
 #include <string.h>
 #include <err.h>
+#include <linux/perf_event.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
 
 static volatile sig_atomic_t got_sigbus = 0;
 
@@ -58,8 +61,40 @@ __attribute__((noinline, noclone)) static void do_rdpmc(unsigned int ecx)
 	printf("PMC 0x%08X: 0x%08X%08X\n", ecx, edx, eax);
 }
 
-int main()
+static int perf_event_open(struct perf_event_attr *hw_event, pid_t pid,
+			   int cpu, int group_fd, unsigned long flags)
 {
+           return syscall(__NR_perf_event_open, hw_event, pid, cpu,
+                          group_fd, flags);
+}
+
+static void* map_one(void)
+{
+	struct perf_event_attr pe;
+	int fd;
+
+	memset(&pe, 0, sizeof(struct perf_event_attr));
+	pe.type = PERF_TYPE_HARDWARE;
+	pe.size = sizeof(struct perf_event_attr);
+	pe.config = PERF_COUNT_HW_INSTRUCTIONS;
+	pe.disabled = 0;
+	pe.exclude_kernel = 1;
+	pe.exclude_hv = 1;
+
+	fd = perf_event_open(&pe, getpid(), -1, -1, 0);
+	if (fd == -1)
+		err(1, "perf_event_open");
+
+	return mmap(NULL, 4096, PROT_READ, MAP_SHARED, fd, 0);
+}
+
+int main(int argc, char **argv)
+{
+	if (argc == 2 && !strcmp(argv[1], "try_harder")) {
+		map_one();
+		munmap(map_one(), 4096);
+	}
+
 	sethandler(SIGSEGV, sigsegv, 0);
 
 	for (unsigned int i = 0; i < 4096; i++)