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/*
* linux/mm/initmem.c
*
* Copyright (C) 1999 Ingo Molnar
*
* simple boot-time physical memory area allocator and
* free memory collector. It's used to deal with reserved
* system memory and memory holes as well.
*/
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/swapctl.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <asm/dma.h>
/*
* Pointer to a bitmap - the bits represent all physical memory pages
* from physical address 0 to physical address end_mem.
*
* Access to this subsystem has to be serialized externally. (this is
* true for the boot process anyway)
*/
unsigned long max_low_pfn;
static void * bootmem_map = NULL;
/*
* Called once to set up the allocator itself.
*/
unsigned long __init init_bootmem (unsigned long start, unsigned long pages)
{
unsigned long mapsize = (pages+7)/8;
bootmem_map = phys_to_virt(start << PAGE_SHIFT);
max_low_pfn = pages;
/*
* Initially all pages are reserved - setup_arch() has to
* register free RAM areas explicitly.
*/
memset(bootmem_map, 0xff, mapsize);
return mapsize;
}
/*
* Marks a particular physical memory range as usable. Usable RAM
* might be used for boot-time allocations - or it might get added
* to the free page pool later on.
*/
void __init reserve_bootmem (unsigned long addr, unsigned long size)
{
unsigned long i;
/*
* round up, partially reserved pages are considered
* fully reserved.
*/
unsigned long end = (addr + size + PAGE_SIZE-1)/PAGE_SIZE;
if (!size) BUG();
if (end > max_low_pfn)
BUG();
for (i = addr/PAGE_SIZE; i < end; i++)
if (test_and_set_bit(i, bootmem_map))
BUG();
}
void __init free_bootmem (unsigned long addr, unsigned long size)
{
unsigned long i;
unsigned long start;
/*
* round down end of usable mem, partially free pages are
* considered reserved.
*/
unsigned long end = (addr + size)/PAGE_SIZE;
if (!size) BUG();
if (end > max_low_pfn)
BUG();
/*
* Round up the beginning of the address.
*/
start = (addr + PAGE_SIZE-1) / PAGE_SIZE;
for (i = start; i < end; i++) {
if (!test_and_clear_bit(i, bootmem_map))
BUG();
}
}
/*
* We 'merge' subsequent allocations to save space. We might 'lose'
* some fraction of a page if allocations cannot be satisfied due to
* size constraints on boxes where there is physical RAM space
* fragmentation - in these cases * (mostly large memory boxes) this
* is not a problem.
*
* On low memory boxes we get it right in 100% of the cases.
*/
static unsigned long last_pos = 0;
static unsigned long last_offset = 0;
/*
* alignment has to be a power of 2 value.
*/
void * __init __alloc_bootmem (unsigned long size, unsigned long align, unsigned long goal)
{
int area = 0;
unsigned long i, start = 0, reserved;
void *ret;
unsigned long offset, remaining_size;
unsigned long areasize, preferred;
if (!size) BUG();
/*
* We try to allocate bootmem pages above 'goal'
* first, then we try to allocate lower pages.
*/
if (goal) {
preferred = goal >> PAGE_SHIFT;
if (preferred >= max_low_pfn)
preferred = 0;
} else
preferred = 0;
areasize = (size+PAGE_SIZE-1)/PAGE_SIZE;
restart_scan:
for (i = preferred; i < max_low_pfn; i++) {
reserved = test_bit(i, bootmem_map);
if (!reserved) {
if (!area) {
area = 1;
start = i;
}
if (i - start + 1 == areasize)
goto found;
} else {
area = 0;
start = -1;
}
}
if (preferred) {
preferred = 0;
goto restart_scan;
}
/*
* Whoops, we cannot satisfy the allocation request.
*/
BUG();
found:
if (start >= max_low_pfn)
BUG();
/*
* Is the next page of the previous allocation-end the start
* of this allocation's buffer? If yes then we can 'merge'
* the previous partial page with this allocation.
*/
if (last_offset && (last_pos+1 == start)) {
offset = (last_offset+align-1) & ~(align-1);
if (offset > PAGE_SIZE)
BUG();
remaining_size = PAGE_SIZE-offset;
if (remaining_size > PAGE_SIZE)
BUG();
if (size < remaining_size) {
areasize = 0;
// last_pos unchanged
last_offset = offset+size;
ret = phys_to_virt(last_pos*PAGE_SIZE + offset);
} else {
size -= remaining_size;
areasize = (size+PAGE_SIZE-1)/PAGE_SIZE;
ret = phys_to_virt(last_pos*PAGE_SIZE + offset);
last_pos = start+areasize-1;
last_offset = size;
}
last_offset &= ~PAGE_MASK;
} else {
last_pos = start + areasize - 1;
last_offset = size & ~PAGE_MASK;
ret = phys_to_virt(start * PAGE_SIZE);
}
/*
* Reserve the area now:
*/
for (i = start; i < start+areasize; i++)
if (test_and_set_bit(i, bootmem_map))
BUG();
return ret;
}
unsigned long __init free_all_bootmem (void)
{
struct page * page;
unsigned long i, count, total = 0;
if (!bootmem_map) BUG();
page = mem_map;
count = 0;
for (i = 0; i < max_low_pfn; i++, page++) {
if (!test_bit(i, bootmem_map)) {
count++;
ClearPageReserved(page);
set_page_count(page, 1);
if (i >= (virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT))
clear_bit(PG_DMA, &page->flags);
__free_page(page);
}
}
total += count;
/*
* Now free the allocator bitmap itself, it's not
* needed anymore:
*/
page = mem_map + MAP_NR(bootmem_map);
count = 0;
for (i = 0; i < (max_low_pfn/8 + PAGE_SIZE-1)/PAGE_SIZE; i++,page++) {
count++;
ClearPageReserved(page);
set_page_count(page, 1);
__free_page(page);
}
total += count;
bootmem_map = NULL;
return total;
}
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