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+/*
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+ * Copyright (C) 2012 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 (at your option) 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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+
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+FILE_LICENCE ( GPL2_OR_LATER );
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+
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+/** @file
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+ *
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+ * Largest memory block
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+ *
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+ */
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+
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+#include <stdint.h>
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+#include <ipxe/uaccess.h>
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+#include <ipxe/io.h>
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+#include <ipxe/memblock.h>
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+
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+/**
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+ * Find largest usable memory region
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+ *
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+ * @ret start Start of region
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+ * @ret len Length of region
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+ */
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+size_t largest_memblock ( userptr_t *start ) {
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+ struct memory_map memmap;
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+ struct memory_region *region;
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+ physaddr_t max = ~( ( physaddr_t ) 0 );
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+ physaddr_t region_start;
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+ physaddr_t region_end;
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+ size_t region_len;
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+ unsigned int i;
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+ size_t len = 0;
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+
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+ /* Avoid returning uninitialised data on error */
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+ *start = UNULL;
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+
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+ /* Scan through all memory regions */
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+ get_memmap ( &memmap );
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+ for ( i = 0 ; i < memmap.count ; i++ ) {
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+ region = &memmap.regions[i];
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+ DBG ( "Considering [%llx,%llx)\n", region->start, region->end );
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+
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+ /* Truncate block to maximum physical address */
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+ if ( region->start > max ) {
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+ DBG ( "...starts after maximum address %lx\n", max );
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+ continue;
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+ }
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+ region_start = region->start;
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+ if ( region->end > max ) {
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+ DBG ( "...end truncated to maximum address %lx\n", max);
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+ region_end = 0; /* =max, given the wraparound */
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+ } else {
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+ region_end = region->end;
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+ }
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+ region_len = ( region_end - region_start );
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+
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+ /* Use largest block */
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+ if ( region_len > len ) {
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+ DBG ( "...new best block found\n" );
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+ *start = phys_to_user ( region_start );
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+ len = region_len;
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+ }
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+ }
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+
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+ return len;
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+}
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