[PATCH 10/17] selftests/nolibc: recreate and populate /dev and /proc if missing

Willy Tarreau
2022-07-19T21:45:28Z

Most of the time the program will be run alone in an initramfs. There
is no value in requiring the user to populate /dev and /proc for such
tests, we can do it ourselves, and it participates to the tests at the
same time.

What's done here is that when called as init (getpid()==1) we check
if /dev exists or create it, if /dev/console and /dev/null exists,
otherwise we try to mount a devtmpfs there, and if it fails we fall
back to mknod. The console is reopened if stdout was closed. Finally
/proc is created and mounted if /proc/self cannot be found. This is
sufficient for most tests.

Signed-off-by: Willy Tarreau <w@1wt.eu>
---
tools/testing/selftests/nolibc/nolibc-test.c | 56 ++++++++++++++++++++
1 file changed, 56 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 45793b6f2244..0bbfe0b3b648 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -530,6 +530,54 @@ int run_stdlib(int min, int max)
return ret;
}

+/* prepare what needs to be prepared for pid 1 (stdio, /dev, /proc, etc) */
+int prepare(void)
+{
+ struct stat stat_buf;
+
+ /* It's possible that /dev doesn't even exist or was not mounted, so
+ * we'll try to create it, mount it, or create minimal entries into it.
+ * We want at least /dev/null and /dev/console.
+ */
+ if (stat("/dev/.", &stat_buf) == 0 || mkdir("/dev", 0755) == 0) {
+ if (stat("/dev/console", &stat_buf) != 0 ||
+ stat("/dev/null", &stat_buf) != 0) {
+ /* try devtmpfs first, otherwise fall back to manual creation */
+ if (mount("/dev", "/dev", "devtmpfs", 0, 0) != 0) {
+ mknod("/dev/console", 0600 | S_IFCHR, makedev(5, 1));
+ mknod("/dev/null", 0666 | S_IFCHR, makedev(1, 3));
+ }
+ }
+ }
+
+ /* If no /dev/console was found before calling init, stdio is closed so
+ * we need to reopen it from /dev/console. If it failed above, it will
+ * still fail here and we cannot emit a message anyway.
+ */
+ if (close(dup(1)) == -1) {
+ int fd = open("/dev/console", O_RDWR);
+
+ if (fd >= 0) {
+ if (fd != 0)
+ dup2(fd, 0);
+ if (fd != 1)
+ dup2(fd, 1);
+ if (fd != 2)
+ dup2(fd, 2);
+ if (fd > 2)
+ close(fd);
+ puts("\nSuccessfully reopened /dev/console.");
+ }
+ }
+
+ /* try to mount /proc if not mounted. Silently fail otherwise */
+ if (stat("/proc/.", &stat_buf) == 0 || mkdir("/proc", 0755) == 0) {
+ if (stat("/proc/self", &stat_buf) != 0)
+ mount("/proc", "/proc", "proc", 0, 0);
+ }
+
+ return 0;
+}

/* This is the definition of known test names, with their functions */
static struct test test_names[] = {
@@ -550,6 +598,14 @@ int main(int argc, char **argv, char **envp)

environ = envp;

+ /* when called as init, it's possible that no console was opened, for
+ * example if no /dev file system was provided. We'll check that fd#1
+ * was opened, and if not we'll attempt to create and open /dev/console
+ * and /dev/null that we'll use for later tests.
+ */
+ if (getpid() == 1)
+ prepare();
+
/* the definition of a series of tests comes from either argv[1] or the
* "NOLIBC_TEST" environment variable. It's made of a comma-delimited
* series of test names and optional ranges:
--
2.17.5