71 lines
1.4 KiB
C
71 lines
1.4 KiB
C
// Physical memory allocator, intended to allocate
|
|
// memory for user processes, kernel stacks, page table pages,
|
|
// and pipe buffers. Allocates 4096-byte pages.
|
|
|
|
#include "types.h"
|
|
#include "defs.h"
|
|
#include "param.h"
|
|
#include "mmu.h"
|
|
#include "spinlock.h"
|
|
|
|
struct run {
|
|
struct run *next;
|
|
};
|
|
|
|
struct {
|
|
struct spinlock lock;
|
|
struct run *freelist;
|
|
} kmem;
|
|
|
|
// Initialize free list of physical pages.
|
|
void
|
|
kinit(void)
|
|
{
|
|
extern char end[];
|
|
|
|
initlock(&kmem.lock, "kmem");
|
|
char *p = (char*)PGROUNDUP((uint)end);
|
|
for( ; p + PGSIZE - 1 < (char*) PHYSTOP; p += PGSIZE)
|
|
kfree(p);
|
|
}
|
|
|
|
//PAGEBREAK: 21
|
|
// Free the page of physical memory pointed at by v,
|
|
// which normally should have been returned by a
|
|
// call to kalloc(). (The exception is when
|
|
// initializing the allocator; see kinit above.)
|
|
void
|
|
kfree(char *v)
|
|
{
|
|
struct run *r;
|
|
|
|
if(((uint) v) % PGSIZE || (uint)v < 1024*1024 || (uint)v >= PHYSTOP)
|
|
panic("kfree");
|
|
|
|
// Fill with junk to catch dangling refs.
|
|
memset(v, 1, PGSIZE);
|
|
|
|
acquire(&kmem.lock);
|
|
r = (struct run *) v;
|
|
r->next = kmem.freelist;
|
|
kmem.freelist = r;
|
|
release(&kmem.lock);
|
|
}
|
|
|
|
// Allocate one 4096-byte page of physical memory.
|
|
// Returns a pointer that the kernel can use.
|
|
// Returns 0 if the memory cannot be allocated.
|
|
char*
|
|
kalloc()
|
|
{
|
|
struct run *r;
|
|
|
|
acquire(&kmem.lock);
|
|
r = kmem.freelist;
|
|
if(r)
|
|
kmem.freelist = r->next;
|
|
release(&kmem.lock);
|
|
return (char*) r;
|
|
}
|
|
|