selftests/nolibc: recreate and populate /dev and /proc if missing

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>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index eeb254749239ca11aa1c257b62038983f4de67fd..a697182c87f57770bbf49da1f552c1ab4ac3932f 100644 (file)
--- 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: