First cut at support for booting a GPT labeled disk via the BIOS bootstrap

on i386 and amd64 machines.  The overall process is that /boot/pmbr lives
in the PMBR (similar to /boot/mbr for MBR disks) and is responsible for
locating and loading /boot/gptboot.  /boot/gptboot is similar to /boot/boot
except that it groks GPT rather than MBR + bsdlabel.  Unlike /boot/boot,
/boot/gptboot lives in its own dedicated GPT partition with a new
"FreeBSD boot" type.  This partition does not have a fixed size in that
/boot/pmbr will load the entire partition into the lower 640k.  However,
it is limited in that it can only be 545k.  That's still a lot better than
the current 7.5k limit for boot2 on MBR.  gptboot mostly acts just like
boot2 in that it reads /boot.config and loads up /boot/loader.  Some more
details:
- Include uuid_equal() and uuid_is_nil() in libstand.
- Add a new 'boot' command to gpt(8) which makes a GPT disk bootable using
  /boot/pmbr and /boot/gptboot.  Note that the disk must have some free
  space for the boot partition.
  - This required exposing the backend of the 'add' function as a
    gpt_add_part() function to the rest of gpt(8).  'boot' uses this to
    create a boot partition if needed.
- Don't cripple cgbase() in the UFS boot code for /boot/gptboot so that
  it can handle a filesystem > 1.5 TB.
- /boot/gptboot has a simple loader (gptldr) that doesn't do any I/O
  unlike boot1 since /boot/pmbr loads all of gptboot up front.  The
  C portion of gptboot (gptboot.c) has been repocopied from boot2.c.
  The primary changes are to parse the GPT to find a root filesystem
  and to use 64-bit disk addresses.  Currently gptboot assumes that the
  first UFS partition on the disk is the / filesystem, but this algorithm
  will likely be improved in the future.
- Teach the biosdisk driver in /boot/loader to understand GPT tables.
  GPT partitions are identified as 'disk0pX:' (e.g. disk0p2:) which is
  similar to the /dev names the kernel uses (e.g. /dev/ad0p2).
- Add a new "freebsd-boot" alias to g_part() for the new boot UUID.

MFC after:	1 month
Discussed with:	marcel (some things might still change, but am committing
			what I have so far)

3 files changed, 10 insertions, 0 deletions

diff --git a/sys/geom/part/g_part.c b/sys/geom/part/g_part.c
index 0a35f6a..477584f 100644
--- a/sys/geom/part/g_part.c
+++ b/sys/geom/part/g_part.c
@@ -66,6 +66,7 @@ struct g_part_alias_list {
 } g_part_alias_list[G_PART_ALIAS_COUNT] = {
 	{ "efi", G_PART_ALIAS_EFI },
 	{ "freebsd", G_PART_ALIAS_FREEBSD },
+	{ "freebsd-boot", G_PART_ALIAS_FREEBSD_BOOT },
 	{ "freebsd-swap", G_PART_ALIAS_FREEBSD_SWAP },
 	{ "freebsd-ufs", G_PART_ALIAS_FREEBSD_UFS },
 	{ "freebsd-vinum", G_PART_ALIAS_FREEBSD_VINUM },
diff --git a/sys/geom/part/g_part.h b/sys/geom/part/g_part.h
index 01bf65f..1410b7a 100644
--- a/sys/geom/part/g_part.h
+++ b/sys/geom/part/g_part.h
@@ -38,6 +38,7 @@
 enum g_part_alias {
 	G_PART_ALIAS_EFI,		/* A EFI system partition entry. */
 	G_PART_ALIAS_FREEBSD,		/* A BSD labeled partition entry. */
+	G_PART_ALIAS_FREEBSD_BOOT,	/* A FreeBSD boot partition entry. */
 	G_PART_ALIAS_FREEBSD_SWAP,	/* A swap partition entry. */
 	G_PART_ALIAS_FREEBSD_UFS,	/* A UFS/UFS2 file system entry. */
 	G_PART_ALIAS_FREEBSD_VINUM,	/* A Vinum partition entry. */
diff --git a/sys/geom/part/g_part_gpt.c b/sys/geom/part/g_part_gpt.c
index 140c91a..12d28b5 100644
--- a/sys/geom/part/g_part_gpt.c
+++ b/sys/geom/part/g_part_gpt.c
@@ -121,6 +121,7 @@ G_PART_SCHEME_DECLARE(g_part_gpt_scheme);
 
 static struct uuid gpt_uuid_efi = GPT_ENT_TYPE_EFI;
 static struct uuid gpt_uuid_freebsd = GPT_ENT_TYPE_FREEBSD;
+static struct uuid gpt_uuid_freebsd_boot = GPT_ENT_TYPE_FREEBSD_BOOT;
 static struct uuid gpt_uuid_freebsd_swap = GPT_ENT_TYPE_FREEBSD_SWAP;
 static struct uuid gpt_uuid_freebsd_ufs = GPT_ENT_TYPE_FREEBSD_UFS;
 static struct uuid gpt_uuid_freebsd_vinum = GPT_ENT_TYPE_FREEBSD_VINUM;
@@ -295,6 +296,11 @@ gpt_parse_type(const char *type, struct uuid *uuid)
 		*uuid = gpt_uuid_freebsd;
 		return (0);
 	}
+	alias = g_part_alias_name(G_PART_ALIAS_FREEBSD_BOOT);
+	if (!strcasecmp(type, alias)) {
+		*uuid = gpt_uuid_freebsd_boot;
+		return (0);
+	}
 	alias = g_part_alias_name(G_PART_ALIAS_FREEBSD_SWAP);
 	if (!strcasecmp(type, alias)) {
 		*uuid = gpt_uuid_freebsd_swap;
@@ -600,6 +606,8 @@ g_part_gpt_type(struct g_part_table *basetable, struct g_part_entry *baseentry,
 		return (g_part_alias_name(G_PART_ALIAS_EFI));
 	if (EQUUID(type, &gpt_uuid_freebsd))
 		return (g_part_alias_name(G_PART_ALIAS_FREEBSD));
+	if (EQUUID(type, &gpt_uuid_freebsd_boot))
+		return (g_part_alias_name(G_PART_ALIAS_FREEBSD_BOOT));
 	if (EQUUID(type, &gpt_uuid_freebsd_swap))
 		return (g_part_alias_name(G_PART_ALIAS_FREEBSD_SWAP));
 	if (EQUUID(type, &gpt_uuid_freebsd_ufs))