[memmap] Define an API for managing the system memory map

Define a generic system memory map API, based on the abstraction
created for parsing the FDT memory map and adding a concept of hidden
in-use memory regions as required to support patching the BIOS INT 15
memory map.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/memmap.c

@@ -0,0 +1,114 @@
+/*
+ * 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/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 last;
+
+	/* Sanity check */
+	assert ( region->last >= region->addr );
+
+	/* Ignore empty regions */
+	if ( ! size )
+		return;
+
+	/* Calculate last addresses (and truncate if necessary) */
+	last = ( start + size - 1 );
+	if ( last < start ) {
+		last = ~( ( uint64_t ) 0 );
+		DBGC ( region, "MEMMAP [%#08llx,%#08llx] %s truncated "
+		       "(invalid size %#08llx)\n",
+		       ( ( unsigned long long ) start ),
+		       ( ( unsigned long long ) last ), name,
+		       ( ( unsigned long long ) size ) );
+	}
+
+	/* Ignore regions entirely below the region of interest */
+	if ( last < region->addr )
+		return;
+
+	/* Ignore regions entirely above the region of interest */
+	if ( start > region->last )
+		return;
+
+	/* Update region of interest as applicable */
+	if ( start <= region->addr ) {
+
+		/* Record this region as covering the region of interest */
+		region->flags |= flags;
+		if ( name )
+			region->name = name;
+
+		/* Update last address if no closer boundary exists */
+		if ( last < region->last )
+			region->last = last;
+
+	} else if ( start < region->last ) {
+
+		/* Update last address if no closer boundary exists */
+		region->last = ( start - 1 );
+	}
+
+	/* Sanity check */
+	assert ( region->last >= region->addr );
+}
+
+/**
+ * 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 );
+	}
+}
+
+PROVIDE_MEMMAP_INLINE ( null, memmap_describe );
+PROVIDE_MEMMAP_INLINE ( null, memmap_sync );