[efi] Provide access to files stored on EFI filesystems

Provide access to local files via the "file://" URI scheme.  There are
three syntaxes:

  - An opaque URI with a relative path (e.g. "file:script.ipxe").
    This will be interpreted as a path relative to the iPXE binary.

  - A hierarchical URI with a non-network absolute path
    (e.g. "file:/boot/script.ipxe").  This will be interpreted as a
    path relative to the root of the filesystem from which the iPXE
    binary was loaded.

  - A hierarchical URI with a network path in which the authority is a
    volume label (e.g. "file://bootdisk/script.ipxe").  This will be
    interpreted as a path relative to the root of the filesystem with
    the specified volume label.

Note that the potentially desirable shell mappings (e.g. "fs0:" and
"blk0:") are concepts internal to the UEFI shell binary, and do not
seem to be exposed in any way to external executables.  The old
EFI_SHELL_PROTOCOL (which did provide access to these mappings) is no
longer installed by current versions of the UEFI shell.

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

Author: mcb30

src/config/config_efi.c

@@ -21,6 +21,7 @@
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
+#include <config/general.h>
 #include <config/console.h>
 
 /** @file
@@ -45,3 +46,6 @@ REQUIRE_OBJECT ( efi_fbcon );
 #ifdef CONSOLE_FRAMEBUFFER
 REQUIRE_OBJECT ( efi_fbcon );
 #endif
+#ifdef DOWNLOAD_PROTO_FILE
+REQUIRE_OBJECT ( efi_local );
+#endif

src/config/defaults/efi.h

@@ -24,6 +24,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define TIME_EFI
 #define REBOOT_EFI
 
+#define DOWNLOAD_PROTO_FILE	/* Local filesystem access */
+
 #define	IMAGE_EFI		/* EFI image support */
 #define	IMAGE_SCRIPT		/* iPXE script image support */
 

src/config/general.h

@@ -57,6 +57,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #undef	DOWNLOAD_PROTO_FTP	/* File Transfer Protocol */
 #undef	DOWNLOAD_PROTO_SLAM	/* Scalable Local Area Multicast */
 #undef	DOWNLOAD_PROTO_NFS	/* Network File System Protocol */
+//#undef DOWNLOAD_PROTO_FILE	/* Local filesystem access */
 
 /*
  * SAN boot protocols

src/include/ipxe/errfile.h

@@ -347,6 +347,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_efi_pxe		      ( ERRFILE_OTHER | 0x004a0000 )
 #define ERRFILE_efi_usb		      ( ERRFILE_OTHER | 0x004b0000 )
 #define ERRFILE_efi_fbcon	      ( ERRFILE_OTHER | 0x004c0000 )
+#define ERRFILE_efi_local	      ( ERRFILE_OTHER | 0x004d0000 )
 
 /** @} */