71 lines
1.4 KiB
C
71 lines
1.4 KiB
C
// Physical memory allocator, intended to allocate
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// memory for user processes, kernel stacks, page table pages,
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// and pipe buffers. Allocates 4096-byte pages.
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#include <stdint.h>
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#include "mem.h"
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#include "console.h"
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#include "cpu/memlayout.h"
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#include "cpu/x86.h"
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struct run {
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struct run *next;
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};
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struct {
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struct run *freelist;
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} kmem;
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void
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freerange(void *vstart, void *vend)
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{
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char *p;
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p = (char*)PGROUNDUP((uintptr_t)vstart);
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for(; p + PGSIZE <= (char*)vend; p += PGSIZE)
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kfree(p);
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}
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void*
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memset(void *dst, unsigned c, uint64_t n)
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{
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if ((uintptr_t)dst%4 == 0 && n%4 == 0){
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c &= 0xFF;
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stosl(dst, (c<<24)|(c<<16)|(c<<8)|c, n/4);
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} else
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stosb(dst, c, n);
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return dst;
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}
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// Free the page of physical memory pointed at by v,
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// which normally should have been returned by a
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// call to kalloc(). (The exception is when
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// initializing the allocator; see kinit above.)
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void
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kfree(char *v)
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{
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struct run *r;
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if((uintptr_t)v % PGSIZE || V2P(v) >= PHYSTOP)
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panic("kfree");
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// Fill with junk to catch dangling refs.
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memset(v, 1, PGSIZE);
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r = (struct run*)v;
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r->next = kmem.freelist;
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kmem.freelist = r;
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}
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// Allocate one 4096-byte page of physical memory.
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// Returns a pointer that the kernel can use.
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// Returns 0 if the memory cannot be allocated.
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void* kalloc(void)
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{
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struct run *r;
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r = kmem.freelist;
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if(r)
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kmem.freelist = r->next;
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return (char*)r;
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}
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