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[efi] Support the initrd autodetection mechanism in newer Linux kernels 

Linux 5.7 added the ability to autodetect an initrd by searching for a
handle via a fixed vendor-specific "Linux initrd device path" and then
locating and using the EFI_LOAD_FILE2_PROTOCOL instance on that
handle.

This maps quite naturally onto our existing concept of a "magic
initrd" as introduced for EFI in commit e5f0255 ("[efi] Provide an
"initrd.magic" file for use by UEFI kernels").

Add an EFI_LOAD_FILE2_PROTOCOL instance to our EFI virtual files
(backed by simply calling the existing EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
method to read from the file), and install the protocol instance for
the "initrd.magic" virtual file onto a new device handle that also
provides the Linux initrd device path.

The design choice in Linux of using a single fixed device path makes
this unfortunately messy to support, since device paths must be unique
within a system.  When multiple bootloaders are used (e.g. GRUB
loading iPXE loading Linux) then only one bootloader can ever install
the device path onto a handle.  Subsequent bootloaders must locate the
existing handle and replace the load file protocol instance with their
own.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/895/head
Michael Brown 2023-02-15 15:48:31 +00:00
parent cf9ad00afc
commit 6a004be0cc
1 changed files with 190 additions and 0 deletions
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190
src/interface/efi/efi_file.c
View File

@ -43,14 +43,21 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <ipxe/efi/Protocol/SimpleFileSystem.h>
#include <ipxe/efi/Protocol/BlockIo.h>
#include <ipxe/efi/Protocol/DiskIo.h>
#include <ipxe/efi/Protocol/LoadFile2.h>
#include <ipxe/efi/Guid/FileInfo.h>
#include <ipxe/efi/Guid/FileSystemInfo.h>
#include <ipxe/efi/efi_strings.h>
#include <ipxe/efi/efi_path.h>
#include <ipxe/efi/efi_file.h>
/** EFI media ID */
#define EFI_MEDIA_ID_MAGIC 0x69505845
/** Linux initrd fixed device path vendor GUID */
#define LINUX_INITRD_VENDOR_GUID \
{ 0x5568e427, 0x68fc, 0x4f3d, \
{ 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68 } }
/** An EFI virtual file reader */
struct efi_file_reader {
/** EFI file */
@ -69,6 +76,8 @@ struct efi_file {
struct refcnt refcnt;
/** EFI file protocol */
EFI_FILE_PROTOCOL file;
/** EFI load file protocol */
EFI_LOAD_FILE2_PROTOCOL load;
/** Image (if any) */
struct image *image;
/** Filename */
@ -370,6 +379,8 @@ efi_file_open ( EFI_FILE_PROTOCOL *this, EFI_FILE_PROTOCOL **new,
ref_init ( &file->refcnt, efi_file_free );
memcpy ( &new_file->file, &efi_file_root.file,
sizeof ( new_file->file ) );
memcpy ( &new_file->load, &efi_file_root.load,
sizeof ( new_file->load ) );
efi_file_image ( new_file, image_get ( image ) );
*new = &new_file->file;
DBGC ( new_file, "EFIFILE %s opened\n", efi_file_name ( new_file ) );
@ -684,6 +695,44 @@ static EFI_STATUS EFIAPI efi_file_flush ( EFI_FILE_PROTOCOL *this ) {
return 0;
}
/**
* Load file
*
* @v this EFI file loader
* @v path File path
* @v boot Boot policy
* @v len Buffer size
* @v data Buffer, or NULL
* @ret efirc EFI status code
*/
static EFI_STATUS EFIAPI efi_file_load ( EFI_LOAD_FILE2_PROTOCOL *this,
EFI_DEVICE_PATH_PROTOCOL *path __unused,
BOOLEAN boot __unused, UINTN *len,
VOID *data ) {
struct efi_file *file = container_of ( this, struct efi_file, load );
size_t max_len;
size_t file_len;
EFI_STATUS efirc;
/* Calculate maximum length */
max_len = ( data ? *len : 0 );
DBGC ( file, "EFIFILE %s load at %p+%#zx\n",
efi_file_name ( file ), data, max_len );
/* Check buffer size */
file_len = efi_file_len ( file );
if ( file_len > max_len ) {
*len = file_len;
return EFI_BUFFER_TOO_SMALL;
}
/* Read from file */
if ( ( efirc = efi_file_read ( &file->file, len, data ) ) != 0 )
return efirc;
return 0;
}
/** Root directory */
static struct efi_file efi_file_root = {
.refcnt = REF_INIT ( ref_no_free ),
@ -700,6 +749,9 @@ static struct efi_file efi_file_root = {
.SetInfo = efi_file_set_info,
.Flush = efi_file_flush,
},
.load = {
.LoadFile = efi_file_load,
},
.image = NULL,
.name = "",
};
@ -720,11 +772,34 @@ static struct efi_file efi_file_initrd = {
.SetInfo = efi_file_set_info,
.Flush = efi_file_flush,
},
.load = {
.LoadFile = efi_file_load,
},
.image = NULL,
.name = "initrd.magic",
.read = efi_file_read_initrd,
};
/** Linux initrd fixed device path */
static struct {
VENDOR_DEVICE_PATH vendor;
EFI_DEVICE_PATH_PROTOCOL end;
} __attribute__ (( packed )) efi_file_initrd_path = {
.vendor = {
.Header = {
.Type = MEDIA_DEVICE_PATH,
.SubType = MEDIA_VENDOR_DP,
.Length[0] = sizeof ( efi_file_initrd_path.vendor ),
},
.Guid = LINUX_INITRD_VENDOR_GUID,
},
.end = {
.Type = END_DEVICE_PATH_TYPE,
.SubType = END_ENTIRE_DEVICE_PATH_SUBTYPE,
.Length[0] = sizeof ( efi_file_initrd_path.end ),
},
};
/**
* Open root directory
*
@ -833,6 +908,110 @@ static EFI_DISK_IO_PROTOCOL efi_disk_io_protocol = {
.WriteDisk = efi_disk_io_write_disk,
};
/**
* (Re)install fixed device path file
*
* @v path Device path
* @v load Load file protocol, or NULL to uninstall protocol
* @ret rc Return status code
*
* Linux 5.7 added the ability to autodetect an initrd by searching
* for a handle via a fixed vendor-specific "Linux initrd device path"
* and then locating and using the EFI_LOAD_FILE2_PROTOCOL instance on
* that handle.
*
* The design choice in Linux of using a single fixed device path
* makes this unfortunately messy to support, since device paths must
* be unique within a system. When multiple bootloaders are used
* (e.g. GRUB loading iPXE loading Linux) then only one bootloader can
* ever install the device path onto a handle. Subsequent bootloaders
* must locate the existing handle and replace the load file protocol
* instance with their own.
*/
static int efi_file_path_install ( EFI_DEVICE_PATH_PROTOCOL *path,
EFI_LOAD_FILE2_PROTOCOL *load ) {
EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
EFI_DEVICE_PATH_PROTOCOL *end;
EFI_HANDLE handle;
VOID *path_copy;
VOID *old;
size_t path_len;
EFI_STATUS efirc;
int rc;
/* Locate or install the handle with this device path */
end = path;
if ( ( ( efirc = bs->LocateDevicePath ( &efi_device_path_protocol_guid,
&end, &handle ) ) == 0 ) &&
( end->Type == END_DEVICE_PATH_TYPE ) ) {
/* Exact match: reuse (or uninstall from) this handle */
if ( load ) {
DBGC ( path, "EFIFILE %s reusing existing handle\n",
efi_devpath_text ( path ) );
}
} else {
/* Allocate a permanent copy of the device path, since
* this handle will survive after this binary is
* unloaded.
*/
path_len = ( efi_path_len ( path ) + sizeof ( *end ) );
if ( ( efirc = bs->AllocatePool ( EfiBootServicesData, path_len,
&path_copy ) ) != 0 ) {
rc = -EEFI ( efirc );
DBGC ( path, "EFIFILE %s could not allocate device path: "
"%s\n", efi_devpath_text ( path ), strerror ( rc ) );
return rc;
}
memcpy ( path_copy, path, path_len );
/* Create a new handle with this device path */
handle = NULL;
if ( ( efirc = bs->InstallMultipleProtocolInterfaces (
&handle,
&efi_device_path_protocol_guid, path_copy,
NULL ) ) != 0 ) {
rc = -EEFI ( efirc );
DBGC ( path, "EFIFILE %s could not create handle: %s\n",
efi_devpath_text ( path ), strerror ( rc ) );
return rc;
}
}
/* Uninstall existing load file protocol instance, if any */
if ( ( ( efirc = bs->HandleProtocol ( handle, &efi_load_file2_protocol_guid,
&old ) ) == 0 ) &&
( ( efirc = bs->UninstallMultipleProtocolInterfaces (
handle,
&efi_load_file2_protocol_guid, old,
NULL ) ) != 0 ) ) {
rc = -EEFI ( efirc );
DBGC ( path, "EFIFILE %s could not uninstall %s: %s\n",
efi_devpath_text ( path ),
efi_guid_ntoa ( &efi_load_file2_protocol_guid ),
strerror ( rc ) );
return rc;
}
/* Install new load file protocol instance, if applicable */
if ( ( load != NULL ) &&
( ( efirc = bs->InstallMultipleProtocolInterfaces (
&handle,
&efi_load_file2_protocol_guid, load,
NULL ) ) != 0 ) ) {
rc = -EEFI ( efirc );
DBGC ( path, "EFIFILE %s could not install %s: %s\n",
efi_devpath_text ( path ),
efi_guid_ntoa ( &efi_load_file2_protocol_guid ),
strerror ( rc ) );
return rc;
}
return 0;
}
/**
* Install EFI simple file system protocol
*
@ -903,8 +1082,16 @@ int efi_file_install ( EFI_HANDLE handle ) {
}
assert ( diskio.diskio == &efi_disk_io_protocol );
/* Install Linux initrd fixed device path file */
if ( ( rc = efi_file_path_install ( &efi_file_initrd_path.vendor.Header,
&efi_file_initrd.load ) ) != 0 ) {
goto err_initrd;
}
return 0;
efi_file_path_install ( &efi_file_initrd_path.vendor.Header, NULL );
err_initrd:
bs->CloseProtocol ( handle, &efi_disk_io_protocol_guid,
efi_image_handle, handle );
err_open:
@ -930,6 +1117,9 @@ void efi_file_uninstall ( EFI_HANDLE handle ) {
EFI_STATUS efirc;
int rc;
/* Uninstall Linux initrd fixed device path file */
efi_file_path_install ( &efi_file_initrd_path.vendor.Header, NULL );
/* Close our own disk I/O protocol */
bs->CloseProtocol ( handle, &efi_disk_io_protocol_guid,
efi_image_handle, handle );