[umalloc] Split largest_memblock() function out from init_eheap()

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

src/arch/i386/interface/pcbios/memtop_umalloc.c

@@ -31,6 +31,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/uaccess.h>
 #include <ipxe/hidemem.h>
 #include <ipxe/io.h>
+#include <ipxe/memblock.h>
 #include <ipxe/umalloc.h>
 
 /** Alignment of external allocated memory */
@@ -59,53 +60,14 @@ static size_t heap_size;
 /**
  * Initialise external heap
  *
- * @ret rc		Return status code
  */
-static int init_eheap ( void ) {
-	struct memory_map memmap;
-	unsigned int i;
-
-	DBG ( "Allocating external heap\n" );
-
-	get_memmap ( &memmap );
-	heap_size = 0;
-	for ( i = 0 ; i < memmap.count ; i++ ) {
-		struct memory_region *region = &memmap.regions[i];
-		unsigned long r_start, r_end;
-		unsigned long r_size;
-
-		DBG ( "Considering [%llx,%llx)\n", region->start, region->end);
-
-		/* Truncate block to 4GB */
-		if ( region->start > UINT_MAX ) {
-			DBG ( "...starts after 4GB\n" );
-			continue;
-		}
-		r_start = region->start;
-		if ( region->end > UINT_MAX ) {
-			DBG ( "...end truncated to 4GB\n" );
-			r_end = 0; /* =4GB, given the wraparound */
-		} else {
-			r_end = region->end;
-		}
-
-		/* Use largest block */
-		r_size = ( r_end - r_start );
-		if ( r_size > heap_size ) {
-			DBG ( "...new best block found\n" );
-			top = bottom = phys_to_user ( r_end );
-			heap_size = r_size;
-		}
-	}
-
-	if ( ! heap_size ) {
-		DBG ( "No external heap available\n" );
-		return -ENOMEM;
-	}
+static void init_eheap ( void ) {
+	userptr_t base;
 
+	heap_size = largest_memblock ( &base );
+	bottom = top = userptr_add ( base, heap_size );
 	DBG ( "External heap grows downwards from %lx (size %zx)\n",
 	      user_to_phys ( top, 0 ), heap_size );
-	return 0;
 }
 
 /**
@@ -144,13 +106,10 @@ static userptr_t memtop_urealloc ( userptr_t ptr, size_t new_size ) {
 	struct external_memory extmem;
 	userptr_t new = ptr;
 	size_t align;
-	int rc;
 
-	/* Initialise external memory allocator if necessary */
-	if ( bottom == top ) {
-		if ( ( rc = init_eheap() ) != 0 )
-			return UNULL;
-	}
+	/* (Re)initialise external memory allocator if necessary */
+	if ( bottom == top )
+		init_eheap();
 
 	/* Get block properties into extmem */
 	if ( ptr && ( ptr != UNOWHERE ) ) {

src/core/memblock.c

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * Largest memory block
+ *
+ */
+
+#include <stdint.h>
+#include <ipxe/uaccess.h>
+#include <ipxe/io.h>
+#include <ipxe/memblock.h>
+
+/**
+ * Find largest usable memory region
+ *
+ * @ret start		Start of region
+ * @ret len		Length of region
+ */
+size_t largest_memblock ( userptr_t *start ) {
+	struct memory_map memmap;
+	struct memory_region *region;
+	physaddr_t max = ~( ( physaddr_t ) 0 );
+	physaddr_t region_start;
+	physaddr_t region_end;
+	size_t region_len;
+	unsigned int i;
+	size_t len = 0;
+
+	/* Avoid returning uninitialised data on error */
+	*start = UNULL;
+
+	/* Scan through all memory regions */
+	get_memmap ( &memmap );
+	for ( i = 0 ; i < memmap.count ; i++ ) {
+		region = &memmap.regions[i];
+		DBG ( "Considering [%llx,%llx)\n", region->start, region->end );
+
+		/* Truncate block to maximum physical address */
+		if ( region->start > max ) {
+			DBG ( "...starts after maximum address %lx\n", max );
+			continue;
+		}
+		region_start = region->start;
+		if ( region->end > max ) {
+			DBG ( "...end truncated to maximum address %lx\n", max);
+			region_end = 0; /* =max, given the wraparound */
+		} else {
+			region_end = region->end;
+		}
+		region_len = ( region_end - region_start );
+
+		/* Use largest block */
+		if ( region_len > len ) {
+			DBG ( "...new best block found\n" );
+			*start = phys_to_user ( region_start );
+			len = region_len;
+		}
+	}
+
+	return len;
+}

src/include/ipxe/memblock.h

@@ -0,0 +1,17 @@
+#ifndef _IPXE_MEMBLOCK_H
+#define _IPXE_MEMBLOCK_H
+
+/** @file
+ *
+ * Largest memory block
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/uaccess.h>
+
+extern size_t largest_memblock ( userptr_t *start );
+
+#endif /* _IPXE_MEMBLOCK_H */