proc: test /proc/self/wchan

This patch starts testing /proc.  Many more tests to come (I promise).

Read from /proc/self/wchan should always return "0" as current is in
TASK_RUNNING state while reading /proc/self/wchan.

Link: http://lkml.kernel.org/r/20180226212006.GA742@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 33 insertions, 0 deletions

diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore
new file mode 100644
index 000000000000..4c851db80bd5
--- /dev/null
+++ b/tools/testing/selftests/proc/.gitignore
@@ -0,0 +1 @@
+/proc-self-wchan
diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile
new file mode 100644
index 000000000000..592603a5d675
--- /dev/null
+++ b/tools/testing/selftests/proc/Makefile
@@ -0,0 +1,6 @@
+CFLAGS += -Wall -O2
+
+TEST_GEN_PROGS :=
+TEST_GEN_PROGS += proc-self-wchan
+
+include ../lib.mk
diff --git a/tools/testing/selftests/proc/config b/tools/testing/selftests/proc/config
new file mode 100644
index 000000000000..68fbd2b35884
--- /dev/null
+++ b/tools/testing/selftests/proc/config
@@ -0,0 +1 @@
+CONFIG_PROC_FS=y
diff --git a/tools/testing/selftests/proc/proc-self-wchan.c b/tools/testing/selftests/proc/proc-self-wchan.c
new file mode 100644
index 000000000000..b8d8728a6869
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-self-wchan.c
@@ -0,0 +1,25 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+
+int main(void)
+{
+	char buf[64];
+	int fd;
+
+	fd = open("/proc/self/wchan", O_RDONLY);
+	if (fd == -1) {
+		if (errno == ENOENT)
+			return 2;
+		return 1;
+	}
+
+	buf[0] = '\0';
+	if (read(fd, buf, sizeof(buf)) != 1)
+		return 1;
+	if (buf[0] != '0')
+		return 1;
+	return 0;
+}