[block] Allow SAN boot device to be identified by an extra filename

Add an "--extra" option that can be used to specify an extra
(non-boot) filename that must exist within the booted filesystem.

Note that only files within the FAT-formatted bootable partition will
be visible to this filter.  Files within the operating system's root
disk (e.g. "/etc/redhat-release") are not generally accessible to the
firmware and so cannot be used as the existence check filter filename.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

3 files changed, 68 insertions, 28 deletions

diff --git a/src/hci/commands/sanboot_cmd.c b/src/hci/commands/sanboot_cmd.c
index b3d9ccad..add0756d 100644
--- a/src/hci/commands/sanboot_cmd.c
+++ b/src/hci/commands/sanboot_cmd.c
@@ -47,8 +47,10 @@ struct sanboot_options {
 	int no_describe;
 	/** Keep SAN device */
 	int keep;
-	/** Filename */
+	/** Boot filename */
 	char *filename;
+	/** Required extra filename */
+	char *extra;
 	/** UUID */
 	struct uuid_option uuid;
 };
@@ -56,7 +58,7 @@ struct sanboot_options {
 /** "sanboot" option list */
 static union {
 	/* "sanboot" takes all options */
-	struct option_descriptor sanboot[5];
+	struct option_descriptor sanboot[6];
 	/* "sanhook" takes only --drive and --no-describe */
 	struct option_descriptor sanhook[2];
 	/* "sanunhook" takes only --drive */
@@ -71,6 +73,8 @@ static union {
 			      struct sanboot_options, keep, parse_flag ),
 		OPTION_DESC ( "filename", 'f', required_argument,
 			      struct sanboot_options, filename, parse_string ),
+		OPTION_DESC ( "extra", 'e', required_argument,
+			      struct sanboot_options, extra, parse_string ),
 		OPTION_DESC ( "uuid", 'u', required_argument,
 			      struct sanboot_options, uuid, parse_uuid ),
 	},
@@ -130,6 +134,7 @@ static int sanboot_core_exec ( int argc, char **argv,
 
 	/* Construct configuration parameters */
 	config.filename = opts.filename;
+	config.extra = opts.extra;
 	config.uuid = opts.uuid.value;
 
 	/* Construct flags */
diff --git a/src/include/ipxe/sanboot.h b/src/include/ipxe/sanboot.h
index 9841edda..91c848b0 100644
--- a/src/include/ipxe/sanboot.h
+++ b/src/include/ipxe/sanboot.h
@@ -110,6 +110,8 @@ enum san_device_flags {
 struct san_boot_config {
 	/** Boot filename (or NULL to use default) */
 	const char *filename;
+	/** Required extra filename (or NULL to ignore) */
+	const char *extra;
 	/** UUID (or NULL to ignore UUID) */
 	union uuid *uuid;
 };
diff --git a/src/interface/efi/efi_block.c b/src/interface/efi/efi_block.c
index f5b913f1..269b9abd 100644
--- a/src/interface/efi/efi_block.c
+++ b/src/interface/efi/efi_block.c
@@ -506,55 +506,77 @@ static int efi_block_describe ( void ) {
 }
 
 /**
- * Check for existence of a file within a filesystem
+ * Open root directory within a filesystem
  *
  * @v drive		Drive number
  * @v handle		Filesystem handle
- * @v filename		Filename (or NULL to use default)
+ * @v root		Root directory file to fill in
  * @ret rc		Return status code
  */
-static int efi_block_filename ( unsigned int drive, EFI_HANDLE handle,
-				const char *filename ) {
+static int efi_block_root ( unsigned int drive, EFI_HANDLE handle,
+			    EFI_FILE_PROTOCOL **root ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_GUID *protocol = &efi_simple_file_system_protocol_guid;
-	CHAR16 tmp[ filename ? ( strlen ( filename ) + 1 /* wNUL */ ) : 0 ];
 	union {
 		EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *fs;
 		void *interface;
 	} u;
-	CHAR16 *wname;
-	EFI_FILE_PROTOCOL *root;
-	EFI_FILE_PROTOCOL *file;
 	EFI_STATUS efirc;
 	int rc;
 
-	/* Construct filename */
-	if ( filename ) {
-		efi_snprintf ( tmp, sizeof ( tmp ), "%s", filename );
-		wname = tmp;
-	} else {
-		wname = efi_block_boot_filename;
-	}
-
-	/* Open file system protocol */
+	/* Open filesystem protocol */
 	if ( ( efirc = bs->OpenProtocol ( handle, protocol, &u.interface,
 					  efi_image_handle, handle,
 					  EFI_OPEN_PROTOCOL_GET_PROTOCOL ))!=0){
 		rc = -EEFI ( efirc );
-		DBGC ( drive, "EFIBLK %#02x could not open %s device path: "
-		       "%s\n", drive, efi_handle_name ( handle ),
-		       strerror ( rc ) );
+		DBGC ( drive, "EFIBLK %#02x could not open %s filesystem: %s\n",
+		       drive, efi_handle_name ( handle ), strerror ( rc ) );
 		goto err_open;
 	}
 
 	/* Open root volume */
-	if ( ( efirc = u.fs->OpenVolume ( u.fs, &root ) ) != 0 ) {
+	if ( ( efirc = u.fs->OpenVolume ( u.fs, root ) ) != 0 ) {
 		rc = -EEFI ( efirc );
 		DBGC ( drive, "EFIBLK %#02x could not open %s root: %s\n",
 		       drive, efi_handle_name ( handle ), strerror ( rc ) );
 		goto err_volume;
 	}
 
+	/* Success */
+	rc = 0;
+
+ err_volume:
+	bs->CloseProtocol ( handle, protocol, efi_image_handle, handle );
+ err_open:
+	return rc;
+}
+
+/**
+ * Check for existence of a file within a filesystem
+ *
+ * @v drive		Drive number
+ * @v handle		Filesystem handle
+ * @v root		Root directory
+ * @v filename		Filename (or NULL to use default)
+ * @ret rc		Return status code
+ */
+static int efi_block_filename ( unsigned int drive, EFI_HANDLE handle,
+				EFI_FILE_PROTOCOL *root,
+				const char *filename ) {
+	CHAR16 tmp[ filename ? ( strlen ( filename ) + 1 /* wNUL */ ) : 0 ];
+	CHAR16 *wname;
+	EFI_FILE_PROTOCOL *file;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Construct filename */
+	if ( filename ) {
+		efi_snprintf ( tmp, sizeof ( tmp ), "%s", filename );
+		wname = tmp;
+	} else {
+		wname = efi_block_boot_filename;
+	}
+
 	/* Try opening file */
 	if ( ( efirc = root->Open ( root, &file, wname,
 				    EFI_FILE_MODE_READ, 0 ) ) != 0 ) {
@@ -570,10 +592,6 @@ static int efi_block_filename ( unsigned int drive, EFI_HANDLE handle,
 
 	file->Close ( file );
  err_file:
-	root->Close ( root );
- err_volume:
-	bs->CloseProtocol ( handle, protocol, efi_image_handle, handle );
- err_open:
 	return rc;
 }
 
@@ -597,6 +615,7 @@ static int efi_block_match ( unsigned int drive, EFI_HANDLE handle,
 		EFI_DEVICE_PATH_PROTOCOL *path;
 		void *interface;
 	} u;
+	EFI_FILE *root;
 	union uuid guid;
 	EFI_STATUS efirc;
 	int rc;
@@ -639,16 +658,30 @@ static int efi_block_match ( unsigned int drive, EFI_HANDLE handle,
 		}
 	}
 
+	/* Open root directory */
+	if ( ( rc = efi_block_root ( drive, handle, &root ) ) != 0 )
+		goto err_root;
+
 	/* Check if filesystem contains boot filename */
-	if ( ( rc = efi_block_filename ( drive, handle,
+	if ( ( rc = efi_block_filename ( drive, handle, root,
 					 config->filename ) ) != 0 ) {
 		goto err_filename;
 	}
 
+	/* Check if filesystem contains additional filename, if applicable */
+	if ( config->extra &&
+	     ( ( rc = efi_block_filename ( drive, handle, root,
+					   config->extra ) ) != 0 ) ) {
+		goto err_extra;
+	}
+
 	/* Success */
 	rc = 0;
 
+ err_extra:
  err_filename:
+	root->Close ( root );
+ err_root:
  err_wrong_guid:
  err_no_guid:
  err_not_child: