loader: zstd based filesystem, zstdfs like gzipfs

Off by default.

Sponsored by:		Netflix

stand/efi/loader/conf.c

@@ -57,6 +57,7 @@ struct devsw *devsw[] = {
 struct fs_ops *file_system[] = {
 #ifdef EFI_ZFS_BOOT
 	&zfs_fsops,
+	&zstdfs_fsops,
 #endif
 	&dosfs_fsops,
 	&ufs_fsops,

stand/i386/loader/conf.c

@@ -62,6 +62,7 @@ struct devsw *devsw[] = {
 struct fs_ops *file_system[] = {
 #if defined(LOADER_ZFS_SUPPORT)
     &zfs_fsops,
+    &zstdfs_fsops,
 #endif
 #if defined(LOADER_UFS_SUPPORT)
     &ufs_fsops,

stand/kboot/kboot/conf.c

@@ -85,11 +85,15 @@ struct fs_ops *file_system[] = {
 #if defined(LOADER_BZIP2_SUPPORT)
     &bzipfs_fsops,
 #endif
+#if defined(LOADER_XZ_SUPPORT)
+    &xzfs_fsops,
+#endif
 #if defined(LOADER_MSDOS_SUPPORT)
     &dosfs_fsops,
 #endif
 #if defined(LOADER_ZFS_SUPPORT)
 	&zfs_fsops,
+	&zstdfs_fsops,
 #endif
     &hostfs_fsops,
     NULL

stand/libsa/Makefile

@@ -192,6 +192,12 @@ SRCS+=	g_eli_hmac.c pkcs5v2.c
 # Maybe ZFS
 .if ${MK_LOADER_ZFS} == "yes"
 .include "${SASRC}/zfs/Makefile.inc"
+
+# zstdfs.c is a stacked filesystem for .zst files, like gzipfs.c/bzipfs.c
+# above; it's only buildable here because zfs/Makefile.inc already pulled
+# the zstd decompressor in for ZFS's on-disk compression.
+SRCS+=	zstdfs.c
+CFLAGS.zstdfs.c+= ${ZSTD_CFLAGS}
 .endif
 
 # Crypto hashing functions

stand/libsa/libsa.3

@@ -781,6 +781,20 @@ The same as
 but for
 .Xr bzip2 1 Ns -compressed
 files.
+.It Va xzfs_fsops
+The same as
+.Va gzipfs_fsops ,
+but for
+.Xr xz 1 Ns -compressed
+files.
+.It Va zstdfs_fsops
+The same as
+.Va gzipfs_fsops ,
+but for
+.Xr zstd 1 Ns -compressed
+files.
+Only available when built with ZFS support, since that is the only
+source of the zstd decompressor in the boot loader environment.
 .It Va pkgfs_fsops
 File access from a tar file typically streamed via TFTP.
 The order of files in the tar file must match the order they are

stand/libsa/stand.h

@@ -131,6 +131,7 @@ extern struct fs_ops cd9660_fsops;
 extern struct fs_ops gzipfs_fsops;
 extern struct fs_ops bzipfs_fsops;
 extern struct fs_ops xzfs_fsops;
+extern struct fs_ops zstdfs_fsops;
 extern struct fs_ops dosfs_fsops;
 extern struct fs_ops ext2fs_fsops;
 extern struct fs_ops splitfs_fsops;

stand/userboot/userboot/conf.c

@@ -67,6 +67,7 @@ struct fs_ops *file_system[] = {
 	&cd9660_fsops,
 #if defined(USERBOOT_ZFS_SUPPORT)
 	&zfs_fsops,
+	&zstdfs_fsops,
 #endif
 	&gzipfs_fsops,
 	&bzipfs_fsops,