[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/config/defaults/efi.h

@@ -16,6 +16,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define CONSOLE_EFI
 #define TIMER_EFI
 #define UMALLOC_EFI
+#define MEMMAP_NULL
 #define SMBIOS_EFI
 #define SANBOOT_EFI
 #define BOFM_EFI

src/config/defaults/linux.h

@@ -13,6 +13,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define TIMER_LINUX
 #define UACCESS_LINUX
 #define UMALLOC_LINUX
+#define MEMMAP_NULL
 #define NAP_LINUX
 #define SMBIOS_LINUX
 #define SANBOOT_DUMMY

src/config/defaults/pcbios.h

@@ -17,6 +17,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define CONSOLE_PCBIOS
 #define NAP_PCBIOS
 #define UMALLOC_MEMTOP
+#define MEMMAP_NULL
 #define SMBIOS_PCBIOS
 #define SANBOOT_PCBIOS
 #define ENTROPY_RTC

src/config/defaults/sbi.h

@@ -19,6 +19,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define CONSOLE_SBI
 #define REBOOT_SBI
 #define UMALLOC_SBI
+#define MEMMAP_NULL
 
 #define ACPI_NULL
 #define MPAPI_NULL

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 );

src/include/bits/memmap.h

@@ -0,0 +1,15 @@
+#ifndef _BITS_MEMMAP_H
+#define _BITS_MEMMAP_H
+
+/** @file
+ *
+ * Dummy architecture-specific system memory map
+ *
+ * This file is included only if the architecture does not provide its
+ * own version of this file.
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#endif /* _BITS_MEMMAP_H */

src/include/ipxe/memmap.h

@@ -0,0 +1,235 @@
+#ifndef _IPXE_MEMMAP_H
+#define _IPXE_MEMMAP_H
+
+/** @file
+ *
+ * System memory map
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stddef.h>
+#include <stdint.h>
+#include <ipxe/api.h>
+#include <ipxe/tables.h>
+#include <config/ioapi.h>
+
+/**
+ * Calculate static inline memory map API function name
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @ret _subsys_func	Subsystem API function
+ */
+#define MEMMAP_INLINE( _subsys, _api_func ) \
+	SINGLE_API_INLINE ( MEMMAP_PREFIX_ ## _subsys, _api_func )
+
+/**
+ * Provide a memory map API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_MEMMAP( _subsys, _api_func, _func ) \
+	PROVIDE_SINGLE_API ( MEMMAP_PREFIX_ ## _subsys, _api_func, _func )
+
+/**
+ * Provide a static inline memory map API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ */
+#define PROVIDE_MEMMAP_INLINE( _subsys, _api_func ) \
+	PROVIDE_SINGLE_API_INLINE ( MEMMAP_PREFIX_ ## _subsys, _api_func )
+
+/** A memory region descriptor */
+struct memmap_region {
+	/** The address being described */
+	uint64_t addr;
+	/** Last address with the same description
+	 *
+	 * Note that this is the last address with the same
+	 * description as the address being described, not the first
+	 * address with a different description.
+	 */
+	uint64_t last;
+	/** Region flags */
+	unsigned int flags;
+	/** Region name (for debug messages) */
+	const char *name;
+};
+
+#define MEMMAP_FL_MEMORY	0x0001	/**< Contains memory */
+#define MEMMAP_FL_RESERVED	0x0002	/**< Is reserved */
+#define MEMMAP_FL_USED		0x0004	/**< Is in use by iPXE */
+#define MEMMAP_FL_INACCESSIBLE	0x0008	/**< Outside of addressable range */
+
+/**
+ * Initialise memory region descriptor
+ *
+ * @v addr		Address within region
+ * @v region		Region descriptor to fill in
+ */
+static inline __attribute__ (( always_inline )) void
+memmap_init ( uint64_t addr, struct memmap_region *region ) {
+
+	region->addr = addr;
+	region->last = ~( ( uint64_t ) 0 );
+	region->flags = 0;
+	region->name = NULL;
+}
+
+/**
+ * Check if memory region is usable
+ *
+ * @v region		Region descriptor
+ * @ret is_usable	Memory region is usable
+ */
+static inline __attribute__ (( always_inline )) int
+memmap_is_usable ( const struct memmap_region *region ) {
+
+	return ( region->flags == MEMMAP_FL_MEMORY );
+}
+
+/**
+ * Get remaining size of memory region (from the described address upwards)
+ *
+ * @v region		Region descriptor
+ * @ret size		Size of memory region
+ */
+static inline __attribute__ (( always_inline )) uint64_t
+memmap_size ( const struct memmap_region *region ) {
+
+	/* Calculate size, assuming overflow is known to be impossible */
+	return ( ( region->last + 1 ) - region->addr );
+}
+
+/** An in-use memory region */
+struct used_region {
+	/** Region name */
+	const char *name;
+	/** Start address */
+	physaddr_t start;
+	/** Length of region */
+	size_t size;
+};
+
+/** In-use memory region table */
+#define USED_REGIONS __table ( struct used_region, "used_regions" )
+
+/** Declare an in-use memory region */
+#define __used_region __table_entry ( USED_REGIONS, 01 )
+
+/* Include all architecture-independent ACPI API headers */
+#include <ipxe/null_memmap.h>
+
+/* Include all architecture-dependent ACPI API headers */
+#include <bits/memmap.h>
+
+/**
+ * Describe memory region from system memory map
+ *
+ * @v addr		Address within region
+ * @v hide		Hide in-use regions from the memory map
+ * @v region		Region descriptor to fill in
+ */
+void memmap_describe ( uint64_t addr, int hide, struct memmap_region *region );
+
+/**
+ * Synchronise in-use regions with the externally visible system memory map
+ *
+ * In environments such as x86 BIOS, we need to patch the global
+ * system memory map to hide our in-use regions, since there is no
+ * other way to communicate this information to external code.
+ */
+void memmap_sync ( void );
+
+/**
+ * Update an in-use memory region
+ *
+ * @v used		In-use memory region
+ * @v start		Start address
+ * @v size		Length of region
+ */
+static inline __attribute__ (( always_inline )) void
+memmap_use ( struct used_region *used, physaddr_t start, size_t size ) {
+
+	/* Record region */
+	used->start = start;
+	used->size = size;
+
+	/* Synchronise externally visible memory map */
+	memmap_sync();
+}
+
+/**
+ * Iterate over memory regions from a given starting address
+ *
+ * @v region		Region descriptor
+ * @v start		Starting address
+ * @v hide		Hide in-use regions from the memory map
+ */
+#define for_each_memmap_from( region, start, hide )			\
+	for ( (region)->addr = (start), (region)->last = 0 ;		\
+	      ( ( ( (region)->last + 1 ) != 0 ) &&			\
+		( memmap_describe ( (region)->addr, (hide),		\
+				    (region) ), 1 ) ) ;			\
+	      (region)->addr = ( (region)->last + 1 ) )
+
+/**
+ * Iterate over memory regions
+ *
+ * @v region		Region descriptor
+ * @v hide		Hide in-use regions from the memory map
+ */
+#define for_each_memmap( region, hide )					\
+	for_each_memmap_from ( (region), 0, (hide) )
+
+
+/**
+ * Dump memory region descriptor (for debugging)
+ *
+ * @v region		Region descriptor
+ */
+static inline void memmap_dump ( const struct memmap_region *region ) {
+	const char *name = region->name;
+	unsigned int flags = region->flags;
+
+	/* Dump region information */
+	DBGC ( region, "MEMMAP (%s%s%s%s) [%#08llx,%#08llx]%s%s\n",
+	       ( ( flags & MEMMAP_FL_MEMORY ) ? "M" : "-" ),
+	       ( ( flags & MEMMAP_FL_RESERVED ) ? "R" : "-" ),
+	       ( ( flags & MEMMAP_FL_USED ) ? "U" : "-" ),
+	       ( ( flags & MEMMAP_FL_INACCESSIBLE ) ? "X" : "-" ),
+	       ( ( unsigned long long ) region->addr ),
+	       ( ( unsigned long long ) region->last ),
+	       ( name ? " " : "" ), ( name ? name : "" ) );
+}
+
+/**
+ * Dump system memory map (for debugging)
+ *
+ * @v hide		Hide in-use regions from the memory map
+ */
+static inline void memmap_dump_all ( int hide ) {
+	struct memmap_region region;
+
+	/* Do nothing unless debugging is enabled */
+	if ( ! DBG_LOG )
+		return;
+
+	/* Describe all memory regions */
+	DBGC ( &region, "MEMMAP with in-use regions %s:\n",
+	       ( hide ? "hidden" : "ignored" ) );
+	for_each_memmap ( &region, hide )
+		memmap_dump ( &region );
+}
+
+extern void memmap_update ( struct memmap_region *region, uint64_t start,
+			    uint64_t size, unsigned int flags,
+			    const char *name );
+extern void memmap_update_used ( struct memmap_region *region );
+
+#endif /* _IPXE_MEMMAP_H */

src/include/ipxe/null_memmap.h

@@ -0,0 +1,44 @@
+#ifndef _IPXE_NULL_MEMMAP_H
+#define _IPXE_NULL_MEMMAP_H
+
+#include <stdint.h>
+
+/** @file
+ *
+ * Null system memory map API
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#ifdef MEMMAP_NULL
+#define MEMMAP_PREFIX_null
+#else
+#define MEMMAP_PREFIX_null __null_
+#endif
+
+/**
+ * Describe memory region from system memory map
+ *
+ * @v addr		Address within region
+ * @v hide		Hide in-use regions from the memory map
+ * @v region		Region descriptor to fill in
+ */
+static inline __attribute__ (( always_inline )) void
+MEMMAP_INLINE ( null, memmap_describe ) ( uint64_t addr, int hide __unused,
+					  struct memmap_region *region ) {
+
+	/* Initialise region as empty */
+	memmap_init ( addr, region );
+}
+
+/**
+ * Synchronise in-use regions with the externally visible system memory map
+ *
+ */
+static inline __attribute__ (( always_inline )) void
+MEMMAP_INLINE ( null, memmap_sync ) ( void ) {
+	/* Nothing to do */
+}
+
+#endif /* _IPXE_NULL_MEMMAP_H */