efi_connect.c

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/*
 * Copyright (C) 2025 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

/** @file
 *
 * EFI driver connection and disconnection
 *
 */

#include <errno.h>
#include <string.h>
#include <ipxe/efi/efi.h>

/* Disambiguate the various error causes */
#define EINFO_EEFI_CONNECT                                              \
        __einfo_uniqify ( EINFO_EPLATFORM, 0x01,                        \
                          "Could not connect controllers" )
#define EINFO_EEFI_CONNECT_PROHIBITED                                   \
        __einfo_platformify ( EINFO_EEFI_CONNECT,                       \
                              EFI_SECURITY_VIOLATION,                   \
                              "Connecting controllers prohibited by "   \
                              "security policy" )
#define EEFI_CONNECT_PROHIBITED                                         \
        __einfo_error ( EINFO_EEFI_CONNECT_PROHIBITED )
#define EEFI_CONNECT( efirc ) EPLATFORM ( EINFO_EEFI_CONNECT, efirc,    \
                                          EEFI_CONNECT_PROHIBITED )

/**
 * Connect UEFI driver(s)
 *
 * @v device            EFI device handle
 * @v driver            EFI driver handle, or NULL
 * @ret rc              Return status code
 */
int efi_connect ( EFI_HANDLE device, EFI_HANDLE driver ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_HANDLE driverlist[2] = { driver, NULL };
        EFI_HANDLE *drivers = ( driver ? driverlist : NULL );
        EFI_STATUS efirc;
        int rc;

        /* Attempt connection at external TPL */
        DBGC ( device, "EFI %s connecting ", efi_handle_name ( device ) );
        DBGC ( device, "%s driver at %s TPL\n",
               ( driver ? efi_handle_name ( driver ) : "any" ),
               efi_tpl_name ( efi_external_tpl ) );
        bs->RestoreTPL ( efi_external_tpl );
        efirc = bs->ConnectController ( device, drivers, NULL, TRUE );
        bs->RaiseTPL ( efi_internal_tpl );
        if ( efirc != 0 ) {
                rc = -EEFI_CONNECT ( efirc );
                DBGC ( device, "EFI %s could not connect: %s\n",
                       efi_handle_name ( device ), strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Disconnect UEFI driver(s)
 *
 * @v device            EFI device handle
 * @v driver            EFI driver handle, or NULL
 * @ret rc              Return status code
 */
int efi_disconnect ( EFI_HANDLE device, EFI_HANDLE driver ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_STATUS efirc;
        int rc;

        /* Attempt disconnection at external TPL */
        DBGC ( device, "EFI %s disconnecting ", efi_handle_name ( device ) );
        DBGC ( device, "%s driver at %s TPL\n",
               ( driver ? efi_handle_name ( driver ) : "any" ),
               efi_tpl_name ( efi_external_tpl ) );
        bs->RestoreTPL ( efi_external_tpl );
        efirc = bs->DisconnectController ( device, driver, NULL );
        bs->RaiseTPL ( efi_internal_tpl );
        if ( ( efirc != 0 ) && ( efirc != EFI_NOT_FOUND ) ) {
                rc = -EEFI ( efirc );
                DBGC ( device, "EFI %s could not disconnect: %s\n",
                       efi_handle_name ( device ), strerror ( rc ) );
                return rc;
        }

        return 0;
}