（CSAPP第三版系列）导航篇传送门
9.12 对于下面的地址，重复习题9.11：
虚拟地址： 0x03a9A. 虚拟地址格式
B. 地址翻译
| 参数 |
值 |
| VPN |
0xE |
| TLB索引 |
0x2 |
| TLB标记 |
0x3 |
| TLB命中？（是/否） |
否 |
| 缺页？（是/否） |
否 |
| PPN |
0x11 |
D. 物理地址引用
| 参数 |
值 |
| 字节偏移 |
0x1 |
| 缓存索引 |
0xA |
| 缓存标记 |
0x11 |
| 缓存命中？（是/否） |
否 |
| 返回的缓存字节 |
—— |
9.14 编写一个C程序，使用mmap将hello.txt的内容改变为“Jello,world!\n”。
程序如下（已经过运行测试）：
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
int main()
{
int fd = open("hello.txt",O_RDWR,0);
char *start = mmap(NULL,1,PROT_WRITE,MAP_SHARED,fd,0);
close(fd);
if(start == MAP_FAILED)
printf("error!\n");
else
{
*start = 'J';
munmap(start,1);
return 0;
}
}
| 对齐要求 |
已分配块 |
空闲块 |
最小块大小（字节） |
| 单字 |
头部和脚部 |
头部和脚部 |
16 |
| 单字 |
头部，但是没有脚部 |
头部和脚部 |
12 |
| 双字 |
头部和脚部 |
头部和脚部 |
16 |
| 双字 |
头部，但是没有脚部 |
头部和脚部 |
16 |
9.18修改分配器，使得空闲块需要头部和脚部，而已分配块只需要头部。
mm.c文件：
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "mm.h"
#include "memlib.h"
/* $begin mallocmacros */
/* Basic constants and macros */
#define WSIZE 4 /* Word and header/footer size (bytes) */ //line:vm:mm:beginconst
#define DSIZE 8 /* Double word size (bytes) */
#define CHUNKSIZE (1<<12) /* Extend heap by this amount (bytes) */ //line:vm:mm:endconst
#define MAX(x, y) ((x) > (y)? (x) : (y))
/* Pack a size and allocated bit into a word */
#define PACK(size, alloc) ((size) | (alloc)) //line:vm:mm:pack
/* Read and write a word at address p */
#define GET(p) (*(unsigned int *)(p)) //line:vm:mm:get
#define PUT(p, val) (*(unsigned int *)(p) = (val)) //line:vm:mm:put
/* Read the size and allocated fields from address p */
#define GET_SIZE(p) (GET(p) & ~0x7) //line:vm:mm:getsize
#define GET_ALLOC(p) (GET(p) & 0x1) //line:vm:mm:getalloc
#define GET_PREVIOUS_ALLOC(p) (GET(p) & 0x2) /* ! CHANGED ! */
/* Given block ptr bp, compute address of its header and footer */
#define HDRP(bp) ((char *)(bp) - WSIZE) //line:vm:mm:hdrp
#define FTRP(bp) ((char *)(bp) + GET_SIZE(HDRP(bp)) - DSIZE) //line:vm:mm:ftrp
/* Given block ptr bp, compute address of next and previous blocks */
#define NEXT_BLKP(bp) ((char *)(bp) + GET_SIZE(((char *)(bp) - WSIZE))) //line:vm:mm:nextblkp
#define PREV_BLKP(bp) ((char *)(bp) - GET_SIZE(((char *)(bp) - DSIZE))) //line:vm:mm:prevblkp
/* $end mallocmacros */
/* Global variables */
static char *heap_listp = 0; /* Pointer to first block */
static char *rover; /* Next fit rover */
/* Function prototypes for internal helper routines */
static void *extend_heap(size_t words);
static void place(void *bp, size_t asize);
static void *find_fit(size_t asize);
static void *coalesce(void *bp);
/*
* mm_init - Initialize the memory manager
*/
/* $begin mminit */
int mm_init(void)
{
/* Create the initial empty heap */
if ((heap_listp = mem_sbrk(4*WSIZE)) == (void *)-1) //line:vm:mm:begininit
return -1;
PUT(heap_listp, 0); /* Alignment padding */
PUT(heap_listp + (1*WSIZE), PACK(DSIZE, 0x1 | 0x2)); /* Prologue header */
PUT(heap_listp + (2*WSIZE), PACK(DSIZE, 0x1 | 0x2)); /* Prologue footer */
PUT(heap_listp + (3*WSIZE), PACK(0, 0x1 | 0x2)); /* Epilogue header */
heap_listp += (2*WSIZE); //line:vm:mm:endinit
/* $end mminit */
rover = heap_listp;
/* $begin mminit */
/* Extend the empty heap with a free block of CHUNKSIZE bytes */
if (extend_heap(CHUNKSIZE/WSIZE) == NULL)
return -1;
return 0;
}
/* $end mminit */
/*
* mm_malloc - Allocate a block with at least size bytes of payload
*/
/* $begin mmmalloc */
void *mm_malloc(size_t size)
{
size_t Wsize; /* round up to an WSIZE */ /* ! CHANGED ! */
size_t Dsize; /* DSIZE after align WSIZE */ /* ! CHANGED ! */
size_t asize; /* Adjusted block size */
size_t extendsize; /* Amount to extend heap if no fit */
char *bp;
/* $end mmmalloc */
if (heap_listp == 0){
mm_init();
}
/* $begin mmmalloc */
/* Ignore spurious requests */
if (size == 0)
return NULL;
Wsize = (size + (WSIZE-1)) / WSIZE; /* ! CHANGED ! */
Dsize = Wsize/2 + 1; /* ! CHANGED ! */
asize = DSIZE * Dsize; /* ! CHANGED ! */
/* Search the free list for a fit */
if ((bp = find_fit(asize)) != NULL) { //line:vm:mm:findfitcall
place(bp, asize); //line:vm:mm:findfitplace
return bp;
}
/* No fit found. Get more memory and place the block */
extendsize = MAX(asize,CHUNKSIZE); //line:vm:mm:growheap1
if ((bp = extend_heap(extendsize/WSIZE)) == NULL)
return NULL; //line:vm:mm:growheap2
place(bp, asize); //line:vm:mm:growheap3
return bp;
}
/* $end mmmalloc */
/*
* mm_free - Free a block
*/
/* $begin mmfree */
void mm_free(void *bp)
{
/* $end mmfree */
if (bp == 0)
return;
/* $begin mmfree */
size_t size = GET_SIZE(HDRP(bp));
/* $end mmfree */
if (heap_listp == 0){
mm_init();
}
/* $begin mmfree */
if (GET_PREVIOUS_ALLOC(HDRP(bp))) /* ! CHANGED ! */
{
PUT(HDRP(bp), PACK(size, 0x2));
}
else
{
PUT(HDRP(bp), PACK(size, 0));
}
PUT(FTRP(bp), PACK(size, 0)); /* ! CHANGED ! */
/* pack next block */
*HDRP(NEXT_BLKP(bp)) &= ~0x2; /* ! CHANGED ! */
coalesce(bp);
}
/* $end mmfree */
/*
* coalesce - Boundary tag coalescing. Return ptr to coalesced block
*/
/* $begin mmfree */
static void *coalesce(void *bp)
{
size_t prev_alloc = GET_PREVIOUS_ALLOC(HDRP(bp)); /* ! CHANGED ! */
size_t next_alloc = GET_ALLOC(HDRP(NEXT_BLKP(bp)));
size_t size = GET_SIZE(HDRP(bp));
if (prev_alloc && next_alloc) { /* Case 1 */
return bp;
}
else if (prev_alloc && !next_alloc) { /* Case 2 */
size += GET_SIZE(HDRP(NEXT_BLKP(bp)));
PUT(HDRP(bp), PACK(size, 0x2)); /* ! CHANGED ! */
PUT(FTRP(bp), PACK(size,0)); /* ! CHANGED ! */
}
else if (!prev_alloc && next_alloc) { /* Case 3 */
size += GET_SIZE(HDRP(PREV_BLKP(bp)));
PUT(FTRP(bp), PACK(size, 0));
if (GET_PREVIOUS_ALLOC(HDRP(PREV_BLKP(bp)))) /* ! CHANGED ! */
{
PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0x2));
}
else
{
PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
}
bp = PREV_BLKP(bp); /* ! CHANGED ! */
}
else { /* Case 4 */
size += GET_SIZE(HDRP(PREV_BLKP(bp))) +
GET_SIZE(FTRP(NEXT_BLKP(bp)));
if (GET_PREVIOUS_ALLOC(HDRP(PREV_BLKP(bp)))) /* ! CHANGED ! */
{
PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0x2));
}
else
{
PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
}
PUT(FTRP(NEXT_BLKP(bp)), PACK(size, 0));
bp = PREV_BLKP(bp);
}
/* $end mmfree */
/* Make sure the rover isn't pointing into the free block */
/* that we just coalesced */
if ((rover > (char *)bp) && (rover < NEXT_BLKP(bp)))
rover = bp;
/* $begin mmfree */
return bp;
}
/* $end mmfree */
/*
* mm_realloc - Naive implementation of realloc
*/
void *mm_realloc(void *ptr, size_t size)
{
size_t oldsize;
void *newptr;
/* If size == 0 then this is just free, and we return NULL. */
if(size == 0) {
mm_free(ptr);
return 0;
}
/* If oldptr is NULL, then this is just malloc. */
if(ptr == NULL) {
return mm_malloc(size);
}
newptr = mm_malloc(size);
/* If realloc() fails the original block is left untouched */
if(!newptr) {
return 0;
}
/* Copy the old data. */
oldsize = GET_SIZE(HDRP(ptr));
if(size < oldsize) oldsize = size;
memcpy(newptr, ptr, oldsize);
/* Free the old block. */
mm_free(ptr);
return newptr;
}
/*
* The remaining routines are internal helper routines
*/
/*
* extend_heap - Extend heap with free block and return its block pointer
*/
/* $begin mmextendheap */
static void *extend_heap(size_t words)
{
char *bp;
size_t size;
/* Allocate an even number of words to maintain alignment */
size = (words % 2) ? (words+1) * WSIZE : words * WSIZE; //line:vm:mm:beginextend
if ((long)(bp = mem_sbrk(size)) == -1)
return NULL; //line:vm:mm:endextend
/* Initialize free block header/footer and the epilogue header */
if (GET_PREVIOUS_ALLOC(HDRP(bp))) /* ! CHANGED ! */
{
PUT(HDRP(bp), PACK(size, 0x2));
}
else
{
PUT(HDRP(bp), PACK(size, 0));
}
PUT(FTRP(bp), PACK(size, 0)); /* Free block footer */ //line:vm:mm:freeblockftr
PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 1)); /* New epilogue header */ //line:vm:mm:newepihdr
/* Coalesce if the previous block was free */
return coalesce(bp); //line:vm:mm:returnblock
}
/* $end mmextendheap */
/*
* place - Place block of asize bytes at start of free block bp
* and split if remainder would be at least minimum block size
*/
/* $begin mmplace */
/* $begin mmplace-proto */
static void place(void *bp, size_t asize)
/* $end mmplace-proto */
{
size_t csize = GET_SIZE(HDRP(bp));
if ((csize - asize) >= DSIZE) { /* ! CHANGED ! */
if (GET_PREVIOUS_ALLOC(HDRP(bp))) /* ! CHANGED ! */
{
PUT(HDRP(bp), PACK(asize, 0x2|0x1));
}
else
{
PUT(HDRP(bp), PACK(asize, 0x1));
}
PUT(FTRP(bp), PACK(asize, 1));
bp = NEXT_BLKP(bp);
PUT(HDRP(bp), PACK(csize-asize, 0x2)); /* ! CHANGED ! */
PUT(FTRP(bp), PACK(csize-asize, 0));
}
else {
if (GET_PREVIOUS_ALLOC(HDRP(bp))) /* ! CHANGED ! */
{
PUT(HDRP(bp), PACK(csize, 0x2|0x1));
}
else
{
PUT(HDRP(bp), PACK(csize, 0x1));
}
PUT(FTRP(bp), PACK(csize, 1)); /* ! CHANGED ! */
*HDRP(NEXT_BLKP(bp)) |= 0x2; /* ! CHANGED ! */
}
}
/* $end mmplace */
/*
* find_fit - Find a fit for a block with asize bytes
*/
static void *find_fit(size_t asize)
{
/* Next fit search */
char *oldrover = rover;
/* Search from the rover to the end of list */
for ( ; GET_SIZE(HDRP(rover)) > 0; rover = NEXT_BLKP(rover))
if (!GET_ALLOC(HDRP(rover)) && (asize <= GET_SIZE(HDRP(rover))))
return rover;
/* search from start of list to old rover */
for (rover = heap_listp; rover < oldrover; rover = NEXT_BLKP(rover))
if (!GET_ALLOC(HDRP(rover)) && (asize <= GET_SIZE(HDRP(rover))))
return rover;
return NULL; /* no fit found */
}
/* $end mmfirstfit */