Provide {get,set}_fbms() in basemem.h.

set_fbms() will also update the E820 hidden region.

src/arch/i386/firmware/pcbios/basemem.c

@@ -1,185 +1,44 @@
-#include "stdint.h"
-#include "stddef.h"
-#include "memsizes.h"
-#include "etherboot.h"
-#include "basemem.h"
-
-/* Routines to allocate base memory in a BIOS-compatible way, by
- * updating the Free Base Memory Size counter at 40:13h.
- *
- * Michael Brown <mbrown@fensystems.co.uk> (mcb30)
- *
- * We no longer have anything to do with the real-mode stack.  The
- * only code that can end up creating a huge bubble of wasted base
- * memory is the UNDI driver, so we make it the responsibility of the
- * UNDI driver to reallocate the real-mode stack if required.
- */
-
-/* "fbms" is an alias to the BIOS FBMS counter at 40:13, and acts just
- * like any other uint16_t.  We can't be used under -DKEEP_IT_REAL
- * anyway, so we may as well be efficient.
- */
-#define fbms ( * ( ( uint16_t * ) phys_to_virt ( 0x413 ) ) )
-#define FBMS_MAX ( 640 )
-
-/* Local prototypes */
-static void free_unused_base_memory ( void );
-
 /*
- * Return amount of free base memory in bytes
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
  *
- */
-unsigned int get_free_base_memory ( void ) {
-	return fbms << 10;
-}
-
-/* Allocate N bytes of base memory.  Amount allocated will be rounded
- * up to the nearest kB, since that's the granularity of the BIOS FBMS
- * counter.  Returns NULL if memory cannot be allocated.
+ * 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-void * alloc_base_memory ( size_t size ) {
-	unsigned int size_kb = ( size + 1023 ) >> 10;
-	void *ptr;
-
-	DBG ( "Trying to allocate %d bytes of base memory from %d kB free\n",
-	      size, fbms );
-
-	/* Free up any unused memory before we start */
-	free_unused_base_memory();
 
-	/* Check available base memory */
-	if ( size_kb > fbms ) {
-		DBG ( "Could not allocate %d kB of base memory: "
-		      "only %d kB free\n", size_kb, fbms );
-		return NULL;
-	}
+#include <stdint.h>
+#include <realmode.h>
+#include <bios.h>
+#include <basemem.h>
+#include <gpxe/hidemem.h>
 
-	/* Reduce available base memory */
-	fbms -= size_kb;
-
-	/* Calculate address of memory allocated */
-	ptr = phys_to_virt ( fbms << 10 );
-
-	/* Zero out memory.  We do this so that allocation of
-	 * already-used space will show up in the form of a crash as
-	 * soon as possible.
-	 *
-	 * Update: there's another reason for doing this.  If we don't
-	 * zero the contents, then they could still retain our "free
-	 * block" markers and be liable to being freed whenever a
-	 * base-memory allocation routine is next called.
-	 */
-	memset ( ptr, 0, size_kb << 10 );
-
-	DBG ( "Allocated %d kB of base memory at [%4.4lx:0000,%4.4lx:0000), "
-	      "%d kB now free\n", size_kb,
-	      ( virt_to_phys ( ptr ) >> 4 ),
-	      ( ( virt_to_phys ( ptr ) + ( size_kb << 10 ) ) >> 4 ), fbms );
-
-	/* Update our memory map */
-	get_memsizes();
-
-	return ptr;
-}
-
-/* Free base memory allocated by alloc_base_memory.  The BIOS provides
- * nothing better than a LIFO mechanism for freeing memory (i.e. it
- * just has the single "total free memory" counter), but we improve
- * upon this slightly; as long as you free all the allocated blocks, it
- * doesn't matter what order you free them in.  (This will only work
- * for blocks that are freed via free_base_memory()).
+/** @file
  *
- * Yes, it's annoying that you have to remember the size of the blocks
- * you've allocated.  However, since our granularity of allocation is
- * 1K, the alternative is to risk wasting the occasional kB of base
- * memory, which is a Bad Thing.  Really, you should be using as
- * little base memory as possible, so consider the awkwardness of the
- * API to be a feature! :-)
+ * Base memory allocation
  *
  */
-void free_base_memory ( void *ptr, size_t size ) {
-	unsigned int remainder = virt_to_phys ( ptr ) & 1023;
-	unsigned int size_kb = ( size + remainder + 1023 ) >> 10;
-	union free_base_memory_block *free_block = 
-		( ( void * ) ( ptr - remainder ) );
-	
-	if ( ( ptr == NULL ) || ( size == 0 ) ) { 
-		return; 
-	}
 
-	DBG ( "Trying to free %d bytes base memory at %4.4lx:%4.4lx "
-	      "from %d kB free\n", size,
-	      ( virt_to_phys ( ptr - remainder ) >> 4 ),
-	      ( virt_to_phys ( ptr - remainder ) & 0xf ) + remainder,
-	      fbms );
-
-	/* Mark every kilobyte within this block as free.  This is
-	 * overkill for normal purposes, but helps when something has
-	 * allocated base memory with a granularity finer than the
-	 * BIOS granularity of 1kB.  PXE ROMs tend to do this when
-	 * they allocate their own memory.  This method allows us to
-	 * free their blocks (admittedly in a rather dangerous,
-	 * tread-on-anything-either-side sort of way, but there's no
-	 * other way to do it).
-	 *
-	 * Since we're marking every kB as free, there's actually no
-	 * need for recording the size of the blocks.  However, we
-	 * keep this in so that debug messages are friendlier.  It
-	 * probably adds around 8 bytes to the overall code size.
-	 */
-	for ( ; size_kb > 0 ; free_block++, size_kb-- ) {
-		/* Mark this block as unused */
-		free_block->header.magic = FREE_BLOCK_MAGIC;
-		free_block->header.size_kb = size_kb;
-	}
-
-	/* Free up unused base memory */
-	free_unused_base_memory();
-
-	/* Update our memory map */
-	get_memsizes();
-}
-
-/* Do the actual freeing of memory.  This is split out from
- * free_base_memory() so that it may be called separately.  It
- * should be called whenever base memory is deallocated by an external
- * entity (if we can detect that it has done so) so that we get the
- * chance to free up our own blocks.
+/**
+ * Set the BIOS free base memory counter
+ *
+ * @v new_fbms		New free base memory counter (in kB)
  */
-static void free_unused_base_memory ( void ) {
-	union free_base_memory_block *free_block;
-
-	/* Try to release memory back to the BIOS.  Free all
-	 * consecutive blocks marked as free.
-	 */
-	while ( 1 ) {
-		/* Calculate address of next potential free block */
-		free_block = phys_to_virt ( fbms << 10 );
-		
-		/* Stop processing if we're all the way up to 640K or
-		 * if this is not a free block
-		 */
-		if ( ( fbms == FBMS_MAX ) ||
-		     ( free_block->header.magic != FREE_BLOCK_MAGIC ) ) {
-			break;
-		}
+void set_fbms ( unsigned int new_fbms ) {
+	uint16_t fbms = new_fbms;
 
-		/* Return memory to BIOS */
-		fbms += free_block->header.size_kb;
+	/* Update the BIOS memory counter */
+	put_real ( fbms, BDA_SEG, BDA_FBMS );
 
-		DBG ( "Freed %ld kB of base memory at [%4.4lx:0000,%4.4lx:0000), "
-		      "%d kB now free\n",
-		      free_block->header.size_kb,
-		      ( virt_to_phys ( free_block ) >> 4 ),
-		      ( ( virt_to_phys ( free_block ) + 
-			  ( free_block->header.size_kb << 10 ) ) >> 4 ),
-		      fbms );
-		
-		/* Do not zero out the freed block, because it might
-		 * be the one containing librm, in which case we're
-		 * going to have severe problems the next time we use
-		 * DBG() or, failing that, call get_memsizes().
-		 */
-	}
+	/* Update our hidden memory region map */
+	hide_basemem();
 }

src/arch/i386/firmware/pcbios/hidemem.c

@@ -16,8 +16,8 @@
  */
 
 #include <realmode.h>
-#include <bios.h>
 #include <biosint.h>
+#include <basemem.h>
 #include <gpxe/hidemem.h>
 
 /** Alignment for hidden memory regions */
@@ -71,10 +71,12 @@ void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
 	/* Some operating systems get a nasty shock if a region of the
 	 * E820 map seems to start on a non-page boundary.  Make life
 	 * safer by rounding out our edited region.
-	 */	
+	 */
 	region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
 	region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
-	DBG ( "Hiding [%lx,%lx)\n", region->start, region->end );
+
+	DBG ( "Hiding region %d [%lx,%lx)\n",
+	      region_id, region->start, region->end );
 }
 
 /**
@@ -94,15 +96,12 @@ static void hide_text ( void ) {
  * Hide used base memory
  *
  */
-static void hide_basemem ( void ) {
-	uint16_t fbms;
-
+void hide_basemem ( void ) {
 	/* Hide from the top of free base memory to 640kB.  Don't use
 	 * hide_region(), because we don't want this rounded to the
 	 * nearest page boundary.
 	 */
-	get_real ( fbms, BDA_SEG, BDA_FBMS );
-	hidden_regions[BASEMEM].start = ( fbms * 1024 );
+	hidden_regions[BASEMEM].start = ( get_fbms() * 1024 );
 }
 
 /**

src/arch/i386/include/basemem.h

@@ -1,33 +1,33 @@
-#ifndef BASEMEM_H
-#define BASEMEM_H
-
-#ifdef ASSEMBLY
-
-/* Must match sizeof(struct free_base_memory_header) */
-#define FREE_BASEMEM_HEADER_SIZE 8
-
-#else /* ASSEMBLY */
-
-#include "stdint.h"
-
-/* Structures that we use to represent a free block of base memory */
-
-#define FREE_BLOCK_MAGIC ( ('!'<<0) + ('F'<<8) + ('R'<<16) + ('E'<<24) )
-struct free_base_memory_header {
-	uint32_t	magic;
-	uint32_t	size_kb;
-};
-
-union free_base_memory_block {
-	struct free_base_memory_header header;
-	char bytes[1024];
-};
-
-/* Function prototypes */
-extern unsigned int get_free_base_memory ( void );
-extern void * alloc_base_memory ( size_t size );
-extern void free_base_memory ( void *ptr, size_t size );
-
-#endif /* ASSEMBLY */
-
-#endif /* BASEMEM_H */
+#ifndef _BASEMEM_H
+#define _BASEMEM_H
+
+/** @file
+ *
+ * Base memory allocation
+ *
+ */
+
+#include <stdint.h>
+#include <realmode.h>
+#include <bios.h>
+
+/**
+ * Read the BIOS free base memory counter
+ *
+ * @ret fbms		Free base memory counter (in kB)
+ */
+static inline unsigned int get_fbms ( void ) {
+	uint16_t fbms;
+
+	get_real ( fbms, BDA_SEG, BDA_FBMS );
+	return fbms;
+}
+
+extern void set_fbms ( unsigned int new_fbms );
+
+/* Actually in hidemem.c, but putting it here avoids polluting the
+ * architecture-independent include/hidemem.h.
+ */
+extern void hide_basemem ( void );
+
+#endif /* _BASEMEM_H */