126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
/*
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* Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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/**
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* @file
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*
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* ACPI Root System Description Pointer
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*
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*/
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#include <stdint.h>
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#include <realmode.h>
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#include <bios.h>
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#include <ipxe/acpi.h>
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#include <ipxe/rsdp.h>
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/** EBDA RSDP maximum segment */
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#define RSDP_EBDA_END_SEG 0xa000
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/** Fixed BIOS area RSDP start address */
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#define RSDP_BIOS_START 0xe0000
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/** Fixed BIOS area RSDP length */
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#define RSDP_BIOS_LEN 0x20000
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/** Stride at which to search for RSDP */
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#define RSDP_STRIDE 16
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/**
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* Locate ACPI root system description table within a memory range
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*
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* @v start Start address to search
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* @v len Length to search
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* @ret rsdt ACPI root system description table, or UNULL
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*/
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static userptr_t rsdp_find_rsdt_range ( userptr_t start, size_t len ) {
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static const char signature[8] = RSDP_SIGNATURE;
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struct acpi_rsdp rsdp;
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userptr_t rsdt;
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size_t offset;
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uint8_t sum;
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unsigned int i;
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/* Search for RSDP */
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for ( offset = 0 ; ( ( offset + sizeof ( rsdp ) ) < len ) ;
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offset += RSDP_STRIDE ) {
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/* Check signature and checksum */
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copy_from_user ( &rsdp, start, offset, sizeof ( rsdp ) );
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if ( memcmp ( rsdp.signature, signature,
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sizeof ( signature ) ) != 0 )
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continue;
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for ( sum = 0, i = 0 ; i < sizeof ( rsdp ) ; i++ )
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sum += *( ( ( uint8_t * ) &rsdp ) + i );
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if ( sum != 0 )
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continue;
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/* Extract RSDT */
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rsdt = phys_to_user ( le32_to_cpu ( rsdp.rsdt ) );
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DBGC ( rsdt, "RSDT %#08lx found via RSDP %#08lx\n",
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user_to_phys ( rsdt, 0 ),
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user_to_phys ( start, offset ) );
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return rsdt;
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}
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return UNULL;
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}
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/**
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* Locate ACPI root system description table
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*
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* @ret rsdt ACPI root system description table, or UNULL
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*/
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static userptr_t rsdp_find_rsdt ( void ) {
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static userptr_t rsdt;
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uint16_t ebda_seg;
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userptr_t ebda;
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size_t ebda_len;
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/* Return existing RSDT if already found */
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if ( rsdt )
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return rsdt;
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/* Search EBDA */
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get_real ( ebda_seg, BDA_SEG, BDA_EBDA );
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if ( ebda_seg < RSDP_EBDA_END_SEG ) {
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ebda = real_to_user ( ebda_seg, 0 );
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ebda_len = ( ( RSDP_EBDA_END_SEG - ebda_seg ) * 16 );
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rsdt = rsdp_find_rsdt_range ( ebda, ebda_len );
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if ( rsdt )
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return rsdt;
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}
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/* Search fixed BIOS area */
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rsdt = rsdp_find_rsdt_range ( phys_to_user ( RSDP_BIOS_START ),
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RSDP_BIOS_LEN );
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if ( rsdt )
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return rsdt;
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return UNULL;
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}
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PROVIDE_ACPI ( rsdp, acpi_find_rsdt, rsdp_find_rsdt );
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