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comparison source/kalloc.c @ 0:c450faca55f4

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Init
author Tatsuki IHA <innparusu@cr.ie.u-ryukyu.ac.jp>
date Sun, 22 Oct 2017 18:25:39 +0900
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-1:000000000000 0:c450faca55f4
1 #include "types.h"
2 #include "defs.h"
3 #include "param.h"
4 #include "memlayout.h"
5 #include "mmu.h"
6 #include "spinlock.h"
7
8 void freerange(void *vstart, void *vend);
9 extern char end[]; // first address after kernel loaded from ELF file
10
11 struct run {
12 struct run *next;
13 };
14
15 struct {
16 struct spinlock lock;
17 int use_lock;
18 struct run *freelist;
19 } kmem;
20
21 // Initialization happens in two phases.
22 // 1. main() calls kinit1() while still using entrypgdir to place just
23 // the pages mapped by entrypgdir on free list.
24 // 2. main() calls kinit2() with the rest of the physical pages
25 // after installing a full page table that maps them on all cores.
26 void
27 kinit1(void *vstart, void *vend)
28 {
29 initlock(&kmem.lock, "kmem");
30 kmem.use_lock = 0;
31 kmem.freelist = 0;
32 freerange(vstart, vend);
33 }
34
35 void
36 kinit2(void *vstart, void *vend)
37 {
38 freerange(vstart, vend);
39 kmem.use_lock = 1;
40 }
41
42 void
43 freerange(void *vstart, void *vend)
44 {
45 char *p;
46 p = (char*)PGROUNDUP((uint)vstart);
47 for(; p + PGSIZE <= (char*)vend; p += PGSIZE)
48 kfree(p);
49 }
50
51 //PAGEBREAK: 21
52 // Free the page of physical memory pointed at by v,
53 // which normally should have been returned by a
54 // call to kalloc(). (The exception is when
55 // initializing the allocator; see kinit above.)
56 void
57 kfree(char *v)
58 {
59 struct run *r;
60
61 if((uint)v % PGSIZE || v < end || v2p(v) >= PHYSTOP)
62 panic("kfree");
63
64 // Fill with junk to catch dangling refs.
65 memset(v, 1, PGSIZE);
66
67 if(kmem.use_lock)
68 acquire(&kmem.lock);
69 r = (struct run*)v;
70 r->next = kmem.freelist;
71 kmem.freelist = r;
72 if(kmem.use_lock)
73 release(&kmem.lock);
74 }
75
76 // Allocate one 4096-byte page of physical memory.
77 // Returns a pointer that the kernel can use.
78 // Returns 0 if the memory cannot be allocated.
79 char*
80 kalloc(void)
81 {
82 struct run *r;
83
84 if(kmem.use_lock)
85 acquire(&kmem.lock);
86 r = kmem.freelist;
87 if(r)
88 kmem.freelist = r->next;
89 if(kmem.use_lock)
90 release(&kmem.lock);
91 return (char*)r;
92 }
93
94