kboot: Add hostdisk override

When hostdisk_override is set, all the /dev devices are hidden, and only
the files in that directory are used. This will allow filesystem testing
on FreeBSD without root, for example. Adjust the parse routine to not
require devices start with /dev (plus fix a leak for an error
condition). Add a match routine to allow the device name to be something
like "/home/user/testing/zfsfoo:" instead of strictly in /dev. Note:
since we need to look at all the devices in the system to probe for ZFS
zpools, you can't generally use a full path to get a 'virtual disk' at
this time.

Sponsored by:		Netflix
Reviewed by:		kevans
Differential Revision:	https://reviews.freebsd.org/D38011

stand/kboot/hostdisk.c

@@ -47,6 +47,7 @@ static int hostdisk_close(struct open_file *f);
 static int hostdisk_ioctl(struct open_file *f, u_long cmd, void *data);
 static int hostdisk_print(int verbose);
 static char *hostdisk_fmtdev(struct devdesc *vdev);
+static bool hostdisk_match(struct devsw *devsw, const char *devspec);
 static int hostdisk_parsedev(struct devdesc **idev, const char *devspec, const char **path);
 
 struct devsw hostdisk = {
@@ -60,6 +61,7 @@ struct devsw hostdisk = {
 	.dv_print = hostdisk_print,
 	.dv_cleanup = nullsys,
 	.dv_fmtdev = hostdisk_fmtdev,
+	.dv_match = hostdisk_match,
 	.dv_parsedev = hostdisk_parsedev,
 };
 
@@ -247,15 +249,59 @@ hostdisk_one_disk(struct host_dirent64 *dent, void *argp __unused)
 	return (true);
 }
 
+static bool
+hostdisk_fake_one_disk(struct host_dirent64 *dent, void *argp)
+{
+	char *override_dir = argp;
+	char *fn = NULL;
+	hdinfo_t *hd = NULL;
+	struct host_kstat sb;
+
+	/*
+	 * We only do regular files. Each one is treated as a disk image
+	 * accessible via /dev/${dent->d_name}.
+	 */
+	if (dent->d_type != HOST_DT_REG && dent->d_type != HOST_DT_LNK)
+		return (true);
+	if (asprintf(&fn, "%s/%s", override_dir, dent->d_name) == -1)
+		return (true);
+	if (host_stat(fn, &sb) != 0)
+		goto err;
+	if (!HOST_S_ISREG(sb.st_mode))
+		return (true);
+	if (sb.st_size == 0)
+		goto err;
+	if ((hd = calloc(1, sizeof(*hd))) == NULL)
+		goto err;
+	hd->hd_dev = fn;
+	hd->hd_size = sb.st_size;
+	hd->hd_sectorsize = 512;	/* XXX configurable? */
+	hd->hd_sectors = hd->hd_size / hd->hd_sectorsize;
+	if (hd->hd_size < HOSTDISK_MIN_SIZE)
+		goto err;
+	hd->hd_flags = 0;
+	STAILQ_INIT(&hd->hd_children);
+	printf("%s: %ju %ju %ju\n",
+	    hd->hd_dev, hd->hd_size, hd->hd_sectors, hd->hd_sectorsize);
+	STAILQ_INSERT_TAIL(&hdinfo, hd, hd_link);
+	/* XXX no partiions? -- is that OK? */
+	return (true);
+err:
+	free(hd);
+	free(fn);
+	return (true);
+}
+
 static void
 hostdisk_find_block_devices(void)
 {
-	/*
-	 * Start here XXX open SYSBLK, walk through all directories, keep the
-	 * ones that return a size and a 'block' device when we 'stat' it. Try
-	 * to avoid partitions and only do raw devices.
-	 */
-	foreach_file(SYSBLK, hostdisk_one_disk, NULL, 0);
+	char *override;
+
+	override=getenv("hostdisk_override");
+	if (override != NULL)
+		foreach_file(override, hostdisk_fake_one_disk, override, 0);
+	else
+		foreach_file(SYSBLK, hostdisk_one_disk, NULL, 0);
 }
 
 static int
@@ -387,6 +433,23 @@ hostdisk_fmtdev(struct devdesc *vdev)
 	return ((char *)hd_name(dev2hd(vdev)));
 }
 
+static bool
+hostdisk_match(struct devsw *devsw, const char *devspec)
+{
+	hdinfo_t *hd;
+	const char *colon;
+	char *cp;
+
+	colon = strchr(devspec, ':');
+	if (colon == NULL)
+		return false;
+	cp = strdup(devspec);
+	cp[colon - devspec] = '\0';
+	hd = hostdisk_find(cp);
+	free(cp);
+	return (hd != NULL);
+}
+
 static int
 hostdisk_parsedev(struct devdesc **idev, const char *devspec, const char **path)
 {
@@ -396,9 +459,6 @@ hostdisk_parsedev(struct devdesc **idev, const char *devspec, const char **path)
 	int len;
 	char *fn;
 
-	/* Must start with /dev */
-	if (strncmp(devspec, "/dev", 4) != 0)
-		return (EINVAL);
 	/* Must have a : in it */
 	cp = strchr(devspec, ':');
 	if (cp == NULL)
@@ -412,6 +472,7 @@ hostdisk_parsedev(struct devdesc **idev, const char *devspec, const char **path)
 	hd = hostdisk_find(fn);
 	if (hd == NULL) {
 		printf("Can't find hdinfo for %s\n", fn);
+		free(fn);
 		return (EINVAL);
 	}
 	free(fn);

stand/kboot/main.c

@@ -192,9 +192,12 @@ main(int argc, const char **argv)
 #if defined(LOADER_ZFS_SUPPORT)
 	if (strcmp(bootdev, "zfs:") == 0) {
 		/*
-		 * Pseudo device that says go find the right ZFS pool.
+		 * Pseudo device that says go find the right ZFS pool. This will be
+		 * the first pool that we find that passes the sanity checks (eg looks
+		 * like it might be vbootable) and sets currdev to the right thing based
+		 * on active BEs, etc
 		 */
-		printf("WARNING: bare 'zfs:' for boot device not yet implemented\n");
+		hostdisk_zfs_find_default();
 	}
 #endif