1 files changed, 62 insertions, 0 deletions
diff --git a/tools/kcovtrace/kcovtrace.c b/tools/kcovtrace/kcovtrace.c
new file mode 100644
index 000000000..2d6188c2c
--- /dev/null
+++ b/tools/kcovtrace/kcovtrace.c
@@ -0,0 +1,62 @@
+// Copyright 2017 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// kcovtrace is like strace but show kernel coverage collected with KCOV.
+// It is very simplistic at this point and does not support multithreaded processes, etc.
+// It can be used to understand, for example, exact location where kernel bails out
+// with an error for a particular syscall.
+
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define KCOV_INIT_TRACE _IOR('c', 1, unsigned long)
+#define KCOV_ENABLE _IO('c', 100)
+#define KCOV_DISABLE _IO('c', 101)
+#define COVER_SIZE (16 << 20)
+
+int main(int argc, char** argv, char** envp)
+{
+	int fd, pid, status;
+	unsigned long *cover, n, i;
+
+	if (argc == 1)
+		fprintf(stderr, "usage: kcovtrace program [args...]\n"), exit(1);
+	fd = open("/sys/kernel/debug/kcov", O_RDWR);
+	if (fd == -1)
+		perror("open"), exit(1);
+	if (ioctl(fd, KCOV_INIT_TRACE, COVER_SIZE))
+		perror("ioctl"), exit(1);
+	cover = (unsigned long*)mmap(NULL, COVER_SIZE * sizeof(unsigned long),
+				     PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if ((void*)cover == MAP_FAILED)
+		perror("mmap"), exit(1);
+	pid = fork();
+	if (pid < 0)
+		perror("fork"), exit(1);
+	if (pid == 0) {
+		if (ioctl(fd, KCOV_ENABLE, 0))
+			perror("ioctl"), exit(1);
+		__atomic_store_n(&cover[0], 0, __ATOMIC_RELAXED);
+		execve(argv[1], argv + 1, envp);
+		perror("execve");
+		exit(1);
+	}
+	while (waitpid(-1, &status, __WALL) != pid) {
+	}
+	n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED);
+	for (i = 0; i < n; i++)
+		printf("0x%lx\n", cover[i + 1]);
+	if (munmap(cover, COVER_SIZE * sizeof(unsigned long)))
+		perror("munmap"), exit(1);
+	if (close(fd))
+		perror("close"), exit(1);
+	return 0;
+}