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/*
* Copyright (C) 2017 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
*
* ACPI Root System Description Pointer
*
*/
#include <stdint.h>
#include <realmode.h>
#include <bios.h>
#include <ipxe/acpi.h>
#include <ipxe/rsdp.h>
/** EBDA RSDP maximum segment */
#define RSDP_EBDA_END_SEG 0xa000
/** Fixed BIOS area RSDP start address */
#define RSDP_BIOS_START 0xe0000
/** Fixed BIOS area RSDP length */
#define RSDP_BIOS_LEN 0x20000
/** Stride at which to search for RSDP */
#define RSDP_STRIDE 16
/**
* Locate ACPI root system description table within a memory range
*
* @v start Start address to search
* @v len Length to search
* @ret rsdt ACPI root system description table, or UNULL
*/
static userptr_t rsdp_find_rsdt_range ( userptr_t start, size_t len ) {
static const char signature[8] = RSDP_SIGNATURE;
struct acpi_rsdp rsdp;
userptr_t rsdt;
size_t offset;
uint8_t sum;
unsigned int i;
/* Search for RSDP */
for ( offset = 0 ; ( ( offset + sizeof ( rsdp ) ) < len ) ;
offset += RSDP_STRIDE ) {
/* Check signature and checksum */
copy_from_user ( &rsdp, start, offset, sizeof ( rsdp ) );
if ( memcmp ( rsdp.signature, signature,
sizeof ( signature ) ) != 0 )
continue;
for ( sum = 0, i = 0 ; i < sizeof ( rsdp ) ; i++ )
sum += *( ( ( uint8_t * ) &rsdp ) + i );
if ( sum != 0 )
continue;
/* Extract RSDT */
rsdt = phys_to_user ( le32_to_cpu ( rsdp.rsdt ) );
DBGC ( rsdt, "RSDT %#08lx found via RSDP %#08lx\n",
user_to_phys ( rsdt, 0 ),
user_to_phys ( start, offset ) );
return rsdt;
}
return UNULL;
}
/**
* Locate ACPI root system description table
*
* @ret rsdt ACPI root system description table, or UNULL
*/
static userptr_t rsdp_find_rsdt ( void ) {
static userptr_t rsdt;
uint16_t ebda_seg;
userptr_t ebda;
size_t ebda_len;
/* Return existing RSDT if already found */
if ( rsdt )
return rsdt;
/* Search EBDA */
get_real ( ebda_seg, BDA_SEG, BDA_EBDA );
if ( ebda_seg < RSDP_EBDA_END_SEG ) {
ebda = real_to_user ( ebda_seg, 0 );
ebda_len = ( ( RSDP_EBDA_END_SEG - ebda_seg ) * 16 );
rsdt = rsdp_find_rsdt_range ( ebda, ebda_len );
if ( rsdt )
return rsdt;
}
/* Search fixed BIOS area */
rsdt = rsdp_find_rsdt_range ( phys_to_user ( RSDP_BIOS_START ),
RSDP_BIOS_LEN );
if ( rsdt )
return rsdt;
return UNULL;
}
PROVIDE_ACPI ( rsdp, acpi_find_rsdt, rsdp_find_rsdt );
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