Subversion Repositories Code-Repo

Rev

Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
141 Kevin 1 
/*
2 
 * memlib.c - a module that simulates the memory system.  Needed because it
3 
 *            allows us to interleave calls from the student's malloc package
4 
 *            with the system's malloc package in libc.
5 
 */
6 
#include <stdio.h>
7 
#include <stdlib.h>
8 
#include <assert.h>
9 
#include <unistd.h>
10 
#include <sys/mman.h>
11 
#include <string.h>
12 
#include <errno.h>
13 
 
14 
#include "memlib.h"
15 
#include "config.h"
16 
 
17 
/* private variables */
18 
static char *mem_start_brk;  /* points to first byte of heap */
19 
static char *mem_brk;        /* points to last byte of heap */
20 
static char *mem_max_addr;   /* largest legal heap address */
21 
static int use_mmap;         /* Use mmap instead of malloc */
22 
static void * mmap_addr = (void *)0x58000000;
23 
 
24 
/*
25 
 * mem_init - initialize the memory system model
26 
 */
27 
void mem_init(int _use_mmap)
28 
{
29 
    use_mmap = _use_mmap;
30 
 
31 
    /* allocate the storage we will use to model the available VM */
32 
    if (use_mmap) {
33 
        mem_start_brk = (char *)mmap(mmap_addr, MAX_HEAP, PROT_READ|PROT_WRITE,
34 
                                 MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
35 
        if (mem_start_brk == MAP_FAILED) {
36 
            perror("mem_init_vm: mmap error:");
37 
            exit(1);
38 
        }
39 
        if (mem_start_brk != mmap_addr) {
40 
            perror("mmap");
41 
            fprintf(stderr,
42 
                "mem_init_vm: could not obtain memory at address %p\n",
43 
                mmap_addr);
44 
            exit(1);
45 
        }
46 
    } else {
47 
        if ((mem_start_brk = (char *)malloc(MAX_HEAP)) == NULL) {
48 
            fprintf(stderr, "mem_init_vm: malloc error\n");
49 
            exit(1);
50 
        }
51 
    }
52 
 
53 
    mem_max_addr = mem_start_brk + MAX_HEAP;  /* max legal heap address */
54 
    mem_brk = mem_start_brk;                  /* heap is empty initially */
55 
}
56 
 
57 
/*
58 
 * mem_deinit - free the storage used by the memory system model
59 
 */
60 
void mem_deinit(void)
61 
{
62 
    if (use_mmap) {
63 
        if (munmap(mem_start_brk, MAX_HEAP))
64 
            perror("munmap");
65 
    } else {
66 
        free(mem_start_brk);
67 
    }
68 
}
69 
 
70 
/*
71 
 * mem_reset_brk - reset the simulated brk pointer to make an empty heap
72 
 */
73 
void mem_reset_brk()
74 
{
75 
    mem_brk = mem_start_brk;
76 
}
77 
 
78 
/*
79 
 * mem_sbrk - simple model of the sbrk function. Extends the heap
80 
 *    by incr bytes and returns the start address of the new area. In
81 
 *    this model, the heap cannot be shrunk.
82 
 */
83 
void *mem_sbrk(int incr)
84 
{
85 
    char *old_brk = mem_brk;
86 
 
87 
    if ( (incr < 0) || ((mem_brk + incr) > mem_max_addr)) {
88 
	errno = ENOMEM;
89 
	fprintf(stderr, "ERROR: mem_sbrk failed. Ran out of memory...\n");
90 
	return NULL;
91 
    }
92 
    mem_brk += incr;
93 
    return (void *)old_brk;
94 
}
95 
 
96 
/*
97 
 * mem_heap_lo - return address of the first heap byte
98 
 */
99 
void *mem_heap_lo()
100 
{
101 
    return (void *)mem_start_brk;
102 
}
103 
 
104 
/*
105 
 * mem_heap_hi - return address of last heap byte
106 
 */
107 
void *mem_heap_hi()
108 
{
109 
    return (void *)(mem_brk - 1);
110 
}
111 
 
112 
/*
113 
 * mem_heapsize() - returns the heap size in bytes
114 
 */
115 
size_t mem_heapsize()
116 
{
117 
    return (size_t)(mem_brk - mem_start_brk);
118 
}
119 
 
120 
/*
121 
 * mem_pagesize() - returns the page size of the system
122 
 */
123 
size_t mem_pagesize()
124 
{
125 
    return (size_t)getpagesize();
126 
}