memmap.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 (at your option) 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 <assert.h>
#include <ipxe/io.h>
#include <ipxe/memmap.h>

/** @file
 *
 * System memory map
 *
 */

/**
 * Update memory region descriptor
 *
 * @v region            Memory region of interest to be updated
 * @v start             Start address of known region
 * @v size              Size of known region
 * @v flags             Flags for known region
 * @v name              Name of known region (for debugging)
 *
 * Update a memory region descriptor based on a known existent region.
 */
void memmap_update ( struct memmap_region *region, uint64_t start,
                     uint64_t size, unsigned int flags, const char *name ) {
        uint64_t max;

        /* Sanity check */
        assert ( region->max >= region->min );

        /* Ignore empty regions */
        if ( ! size )
                return;

        /* Calculate max addresses (and truncate if necessary) */
        max = ( start + size - 1 );
        if ( max < start ) {
                max = ~( ( uint64_t ) 0 );
                DBGC ( region, "MEMMAP [%#08llx,%#08llx] %s truncated "
                       "(invalid size %#08llx)\n",
                       ( ( unsigned long long ) start ),
                       ( ( unsigned long long ) max ), name,
                       ( ( unsigned long long ) size ) );
        }

        /* Ignore regions entirely below the region of interest */
        if ( max < region->min )
                return;

        /* Ignore regions entirely above the region of interest */
        if ( start > region->max )
                return;

        /* Update region of interest as applicable */
        if ( start <= region->min ) {

                /* Record this region as covering the region of interest */
                region->flags |= flags;
                if ( name )
                        region->name = name;

                /* Update max address if no closer boundary exists */
                if ( max < region->max )
                        region->max = max;

        } else if ( start < region->max ) {

                /* Update max address if no closer boundary exists */
                region->max = ( start - 1 );
        }

        /* Sanity check */
        assert ( region->max >= region->min );
}

/**
 * Update memory region descriptor based on all in-use memory regions
 *
 * @v region            Memory region of interest to be updated
 */
void memmap_update_used ( struct memmap_region *region ) {
        struct used_region *used;

        /* Update descriptor to hide all in-use regions */
        for_each_table_entry ( used, USED_REGIONS ) {
                memmap_update ( region, used->start, used->size,
                                MEMMAP_FL_USED, used->name );
        }
}

/**
 * Find largest usable memory region
 *
 * @v start             Start address to fill in
 * @ret len             Length of region
 */
size_t memmap_largest ( physaddr_t *start ) {
        struct memmap_region region;
        size_t largest;
        size_t size;

        /* Find largest usable region */
        DBGC ( &region, "MEMMAP finding largest usable region\n" );
        *start = 0;
        largest = 0;
        for_each_memmap ( &region, 1 ) {
                DBGC_MEMMAP ( &region, &region );
                if ( ! memmap_is_usable ( &region ) )
                        continue;
                size = memmap_size ( &region );
                if ( size > largest ) {
                        DBGC ( &region, "...new largest region found\n" );
                        largest = size;
                        *start = region.min;
                }
        }
        return largest;
}

PROVIDE_MEMMAP_INLINE ( null, memmap_describe );
PROVIDE_MEMMAP_INLINE ( null, memmap_sync );