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/*
* Copyright (C) 2021 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 );
#include <string.h>
#include <errno.h>
#include <ipxe/acpi.h>
#include <ipxe/base16.h>
#include <ipxe/ethernet.h>
#include <ipxe/if_ether.h>
#include <ipxe/acpimac.h>
/** @file
*
* ACPI MAC address
*
*/
/** Colour for debug messages */
#define colour FADT_SIGNATURE
/** AMAC signature */
#define AMAC_SIGNATURE ACPI_SIGNATURE ( 'A', 'M', 'A', 'C' )
/** MACA signature */
#define MACA_SIGNATURE ACPI_SIGNATURE ( 'M', 'A', 'C', 'A' )
/** Maximum number of bytes to skip after AMAC/MACA signature
*
* This is entirely empirical.
*/
#define AUXMAC_MAX_SKIP 8
/**
* Extract MAC address from DSDT/SSDT
*
* @v zsdt DSDT or SSDT
* @v len Length of DSDT/SSDT
* @v offset Offset of signature within DSDT/SSDT
* @v data Data buffer
* @ret rc Return status code
*
* Some vendors provide a "system MAC address" within the DSDT/SSDT,
* to be used to override the MAC address for a USB docking station.
*
* A full implementation would require an ACPI bytecode interpreter,
* since at least one OEM allows the MAC address to be constructed by
* executable ACPI bytecode (rather than a fixed data structure).
*
* We instead attempt to extract a plausible-looking "_AUXMAC_#.....#"
* string that appears shortly after an "AMAC" or "MACA" signature.
* This should work for most implementations encountered in practice.
*/
static int acpi_extract_mac ( userptr_t zsdt, size_t len, size_t offset,
void *data ) {
static const char prefix[9] = "_AUXMAC_#";
uint8_t *hw_addr = data;
size_t skip = 0;
char auxmac[ sizeof ( prefix ) /* "_AUXMAC_#" */ +
( ETH_ALEN * 2 ) /* MAC */ + 1 /* "#" */ + 1 /* NUL */ ];
char *mac = &auxmac[ sizeof ( prefix ) ];
int decoded_len;
int rc;
/* Skip signature and at least one tag byte */
offset += ( 4 /* signature */ + 1 /* tag byte */ );
/* Scan for "_AUXMAC_#.....#" close to signature */
for ( skip = 0 ;
( ( skip < AUXMAC_MAX_SKIP ) &&
( offset + skip + sizeof ( auxmac ) ) < len ) ;
skip++ ) {
/* Read value */
copy_from_user ( auxmac, zsdt, ( offset + skip ),
sizeof ( auxmac ) );
/* Check for expected format */
if ( memcmp ( auxmac, prefix, sizeof ( prefix ) ) != 0 )
continue;
if ( auxmac[ sizeof ( auxmac ) - 2 ] != '#' )
continue;
if ( auxmac[ sizeof ( auxmac ) - 1 ] != '\0' )
continue;
DBGC ( colour, "ACPI found MAC string \"%s\"\n", auxmac );
/* Terminate MAC address string */
mac = &auxmac[ sizeof ( prefix ) ];
mac[ ETH_ALEN * 2 ] = '\0';
/* Decode MAC address */
decoded_len = base16_decode ( mac, hw_addr, ETH_ALEN );
if ( decoded_len < 0 ) {
rc = decoded_len;
DBGC ( colour, "ACPI could not decode MAC \"%s\": %s\n",
mac, strerror ( rc ) );
return rc;
}
/* Check MAC address validity */
if ( ! is_valid_ether_addr ( hw_addr ) ) {
DBGC ( colour, "ACPI has invalid MAC %s\n",
eth_ntoa ( hw_addr ) );
return -EINVAL;
}
return 0;
}
return -ENOENT;
}
/**
* Extract MAC address from DSDT/SSDT
*
* @v hw_addr MAC address to fill in
* @ret rc Return status code
*/
int acpi_mac ( uint8_t *hw_addr ) {
int rc;
/* Look for an "AMAC" address */
if ( ( rc = acpi_extract ( AMAC_SIGNATURE, hw_addr,
acpi_extract_mac ) ) == 0 )
return 0;
/* Look for a "MACA" address */
if ( ( rc = acpi_extract ( MACA_SIGNATURE, hw_addr,
acpi_extract_mac ) ) == 0 )
return 0;
return -ENOENT;
}
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