[block] Allow use of a non-default EFI SAN boot filename

Some older operating systems (e.g. RHEL6) use a non-default filename
on the root disk and rely on setting an EFI variable to point to the
bootloader.  This does not work when performing a SAN boot on a
machine where the EFI variable is not present.

Fix by allowing a non-default filename to be specified via the
"sanboot --filename" option or the "san-filename" setting.  For
example:

  sanboot --filename \efi\redhat\grub.efi \
          iscsi:192.168.0.1::::iqn.2010-04.org.ipxe.demo:rhel6

or

  option ipxe.san-filename code 188 = string;
  option ipxe.san-filename "\\efi\\redhat\\grub.efi";
  option root-path "iscsi:192.168.0.1::::iqn.2010-04.org.ipxe.demo:rhel6";

Originally-implemented-by: Vishvananda Ishaya Abrams <vish.ishaya@oracle.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

4 files changed, 11 insertions, 2 deletions

diff --git a/src/include/ipxe/dhcp.h b/src/include/ipxe/dhcp.h
index 0f662d63..b7a5f004 100644
--- a/src/include/ipxe/dhcp.h
+++ b/src/include/ipxe/dhcp.h
@@ -440,6 +440,12 @@ struct dhcp_netdev_desc {
  */
 #define DHCP_EB_SAN_RETRY DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbb )
 
+/** SAN filename
+ *
+ * This is the path of the bootloader within the SAN device.
+ */
+#define DHCP_EB_SAN_FILENAME DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbc )
+
 /** SAN drive number
  *
  * This is the drive number for a SAN-hooked drive.  For BIOS, 0x80 is
diff --git a/src/include/ipxe/sanboot.h b/src/include/ipxe/sanboot.h
index 8737bbc0..8b3e2b28 100644
--- a/src/include/ipxe/sanboot.h
+++ b/src/include/ipxe/sanboot.h
@@ -155,9 +155,10 @@ void san_unhook ( unsigned int drive );
  * Attempt to boot from a SAN device
  *
  * @v drive		Drive number
+ * @v filename		Filename (or NULL to use default)
  * @ret rc		Return status code
  */
-int san_boot ( unsigned int drive );
+int san_boot ( unsigned int drive, const char *filename );
 
 /**
  * Describe SAN devices for SAN-booted operating system
diff --git a/src/include/ipxe/settings.h b/src/include/ipxe/settings.h
index 521efa99..36b4c241 100644
--- a/src/include/ipxe/settings.h
+++ b/src/include/ipxe/settings.h
@@ -452,6 +452,8 @@ filename_setting __setting ( SETTING_BOOT, filename );
 extern const struct setting
 root_path_setting __setting ( SETTING_SANBOOT, root-path );
 extern const struct setting
+san_filename_setting __setting ( SETTING_SANBOOT, san-filename );
+extern const struct setting
 username_setting __setting ( SETTING_AUTH, username );
 extern const struct setting
 password_setting __setting ( SETTING_AUTH, password );
diff --git a/src/include/usr/autoboot.h b/src/include/usr/autoboot.h
index c62d06c6..f88b8494 100644
--- a/src/include/usr/autoboot.h
+++ b/src/include/usr/autoboot.h
@@ -32,7 +32,7 @@ extern void set_autoboot_ll_addr ( const void *ll_addr, size_t len );
 
 extern int uriboot ( struct uri *filename, struct uri **root_paths,
 		     unsigned int root_path_count, int drive,
-		     unsigned int flags );
+		     const char *san_filename, unsigned int flags );
 extern struct uri *
 fetch_next_server_and_filename ( struct settings *settings );
 extern int netboot ( struct net_device *netdev );