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[pcbios] Restrict external memory allocations to the low 4GB 

When running the 64-bit BIOS version of iPXE, restrict external memory
allocations to the low 4GB to ensure that allocations (such as for
initrds) fall within our identity-mapped memory region, and will be
accessible to the potentially 32-bit operating system.

Move largest_memblock() back to memtop_umalloc.c, since this change
imposes a restriction that applies only to BIOS builds.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2016-03-08 13:06:06 +00:00
parent 5a7fd2cc90
commit d3db00ecf9
2 changed files with 53 additions and 85 deletions
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53
src/arch/x86/interface/pcbios/memtop_umalloc.c
View File

@ -38,6 +38,9 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <ipxe/memblock.h>
#include <ipxe/umalloc.h>
/** Maximum usable address for external allocated memory */
#define EM_MAX_ADDRESS 0xffffffffUL
/** Alignment of external allocated memory */
#define EM_ALIGN ( 4 * 1024 )
@ -61,6 +64,56 @@ static userptr_t bottom = UNULL;
/** Remaining space on heap */
static size_t heap_size;
/**
* 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 = EM_MAX_ADDRESS;
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;
}
/**
* Initialise external heap
*

85
src/core/memblock.c
View File

@ -1,85 +0,0 @@
/*
* 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.
*
* 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 );
/** @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;
}