userboot: support environment and symlinks in test application

Pass the environment on to the loader.
Also define USERBOOT=1 in the environment varables.

Add support for symlinks in the test application open callback.

stat the root directory when opening file
Without this, running "ls" command on the root directory encounters
issues getting the directory listing.

Reviewed by:	jhb
Obtained from:	Juniper Networks, Inc.
Differential Revision:	https://reviews.freebsd.org/D44625

stand/userboot/test/test.c

@@ -1,5 +1,6 @@
 /*-
  * Copyright (c) 2011 Google, Inc.
+ * Copyright (c) 2023-2024 Juniper Networks, Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -35,7 +36,9 @@
 #include <fcntl.h>
 #include <getopt.h>
 #include <inttypes.h>
+#include <libgen.h>
 #include <limits.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -44,6 +47,8 @@
 
 #include <userboot.h>
 
+char **vars;
+
 char *host_base = NULL;
 struct termios term, oldterm;
 char *image;
@@ -102,47 +107,164 @@ struct test_file {
 	} tf_u;
 };
 
-int
-test_open(void *arg, const char *filename, void **h_return)
+static int
+test_open_internal(void *arg, const char *filename, void **h_return,
+    struct test_file *tf, int depth)
 {
-	struct stat st;
-	struct test_file *tf;
 	char path[PATH_MAX];
+	char linkpath[PATH_MAX];
+	char *component, *cp, *linkptr;
+	ssize_t slen;
+	int comp_fd, dir_fd, error;
+	char c;
+	bool openbase;
+
+	if (depth++ >= MAXSYMLINKS)
+		return (ELOOP);
+
+	openbase = false;
+	error = EINVAL;
+	if (tf == NULL) {
+		tf = calloc(1, sizeof(struct test_file));
+		if (tf == NULL)
+			return (error);
+		openbase = true;
+	} else if (tf->tf_isdir) {
+		if (filename[0] == '/') {
+			closedir(tf->tf_u.dir);
+			openbase = true;
+		}
+	} else
+		return (error);
 
-	if (!host_base)
-		return (ENOENT);
-
-	strlcpy(path, host_base, PATH_MAX);
-	if (path[strlen(path) - 1] == '/')
-		path[strlen(path) - 1] = 0;
-	strlcat(path, filename, PATH_MAX);
-	tf = malloc(sizeof(struct test_file));
-	if (stat(path, &tf->tf_stat) < 0) {
-		free(tf);
-		return (errno);
-	}
+	if (openbase) {
+		dir_fd = open(host_base, O_RDONLY);
+		if (dir_fd < 0)
+			goto out;
 
-	tf->tf_size = st.st_size;
-	if (S_ISDIR(tf->tf_stat.st_mode)) {
 		tf->tf_isdir = 1;
-		tf->tf_u.dir = opendir(path);
-		if (!tf->tf_u.dir)
+		tf->tf_u.dir = fdopendir(dir_fd);
+
+		if (fstat(dir_fd, &tf->tf_stat) < 0) {
+			error = errno;
 			goto out;
-                *h_return = tf;
-		return (0);
+		}
+		tf->tf_size = tf->tf_stat.st_size;
 	}
-	if (S_ISREG(tf->tf_stat.st_mode)) {
-		tf->tf_isdir = 0;
-		tf->tf_u.fd = open(path, O_RDONLY);
-		if (tf->tf_u.fd < 0)
+
+	strlcpy(path, filename, sizeof(path));
+	cp = path;
+	while (*cp) {
+		/*
+		 * The test file should be a directory at this point.
+		 * If it is not, then the caller provided an invalid filename.
+		 */
+		if (!tf->tf_isdir)
+			goto out;
+
+		/* Trim leading slashes */
+		while (*cp == '/')
+			cp++;
+
+		/* If we reached the end, we are done */
+		if (*cp == '\0')
+			break;
+
+		/* Get the file descriptor for the directory */
+		dir_fd = dirfd(tf->tf_u.dir);
+
+		/* Get the next component path */
+		component = cp;
+		while ((c = *cp) != '\0' && c != '/')
+			cp++;
+		if (c == '/')
+			*cp++ = '\0';
+
+		/* Get status of the component */
+		if (fstatat(dir_fd, component, &tf->tf_stat,
+		    AT_SYMLINK_NOFOLLOW) < 0) {
+			error = errno;
 			goto out;
-                *h_return = tf;
-		return (0);
+		}
+		tf->tf_size = tf->tf_stat.st_size;
+
+		/*
+		 * Check that the path component is a directory, regular file,
+		 * or a symlink.
+		 */
+		if (!S_ISDIR(tf->tf_stat.st_mode) &&
+		    !S_ISREG(tf->tf_stat.st_mode) &&
+		    !S_ISLNK(tf->tf_stat.st_mode))
+			goto out;
+
+		/* For anything that is not a symlink, open it */
+		if (!S_ISLNK(tf->tf_stat.st_mode)) {
+			comp_fd = openat(dir_fd, component, O_RDONLY);
+			if (comp_fd < 0)
+				goto out;
+		}
+
+		if (S_ISDIR(tf->tf_stat.st_mode)) {
+			/* Directory */
+
+			/* close the parent directory */
+			closedir(tf->tf_u.dir);
+
+			/* Open the directory from the component descriptor */
+			tf->tf_isdir = 1;
+			tf->tf_u.dir = fdopendir(comp_fd);
+			if (!tf->tf_u.dir)
+				goto out;
+		} else if (S_ISREG(tf->tf_stat.st_mode)) {
+			/* Regular file */
+
+			/* close the parent directory */
+			closedir(tf->tf_u.dir);
+
+			/* Stash the component descriptor */
+			tf->tf_isdir = 0;
+			tf->tf_u.fd = comp_fd;
+		} else if (S_ISLNK(tf->tf_stat.st_mode)) {
+			/* Symlink */
+
+			/* Read what the symlink points to */
+			slen = readlinkat(dir_fd, component, linkpath,
+			    sizeof(linkpath));
+			if (slen < 0)
+				goto out;
+			/* NUL-terminate the string */
+			linkpath[(size_t)slen] = '\0';
+
+			/* Open the thing that the symlink points to */
+			error = test_open_internal(arg, linkpath, NULL,
+			    tf, depth);
+			if (error != 0)
+				goto out;
+		}
 	}
 
+	/* Completed the entire path and have a good file/directory */
+	if (h_return != NULL)
+		*h_return = tf;
+	return (0);
+
 out:
+	/* Failure of some sort, clean up */
+	if (tf->tf_isdir)
+		closedir(tf->tf_u.dir);
+	else
+		close(tf->tf_u.fd);
 	free(tf);
-	return (EINVAL);
+	return (error);
+}
+
+int
+test_open(void *arg, const char *filename, void **h_return)
+{
+	if (host_base == NULL)
+		return (ENOENT);
+
+	return (test_open_internal(arg, filename, h_return, NULL, 0));
 }
 
 int
@@ -394,13 +516,15 @@ test_getmem(void *arg, uint64_t *lowmem, uint64_t *highmem)
 char *
 test_getenv(void *arg, int idx)
 {
-	static char *vars[] = {
-		"foo=bar",
-		"bar=barbar",
-		NULL
+	static char *myvars[] = {
+		"USERBOOT=1"
 	};
+	static const int num_myvars = nitems(myvars);
 
-	return (vars[idx]);
+	if (idx < num_myvars)
+		return (myvars[idx]);
+	else
+		return (vars[idx - num_myvars]);
 }
 
 struct loader_callbacks cb = {
@@ -444,14 +568,16 @@ usage()
 }
 
 int
-main(int argc, char** argv)
+main(int argc, char** argv, char ** environment)
 {
 	void *h;
 	void (*func)(struct loader_callbacks *, void *, int, int) __dead2;
 	int opt;
 	const char *userboot_obj = "/boot/userboot.so";
 	int oflag = O_RDONLY;
 
+	vars = environment;
+
 	while ((opt = getopt(argc, argv, "wb:d:h:")) != -1) {
 		switch (opt) {
 		case 'b':