malloc.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 1,140 行 · 第 1/2 页

#ifndef OSKIT
/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <[e-mail]> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 * ----------------------------------------------------------------------------
 *
 * $Id: malloc.c,v 1.43.2.1 1999/05/09 18:41:49 alc Exp $
 *
 */

/*
 * Defining EXTRA_SANITY will enable extra checks which are related
 * to internal conditions and consistency in malloc.c. This has a
 * noticeable runtime performance hit, and generally will not do you
 * any good unless you fiddle with the internals of malloc or want
 * to catch random pointer corruption as early as possible.
 */
#ifndef MALLOC_EXTRA_SANITY
#undef MALLOC_EXTRA_SANITY
#endif

/*
 * What to use for Junk.  This is the byte value we use to fill with
 * when the 'J' option is enabled.
 */
#define SOME_JUNK	0xd0		/* as in "Duh" :-) */

/*
 * The basic parameters you can tweak.
 *
 * malloc_pageshift	pagesize = 1 << malloc_pageshift
 *			It's probably best if this is the native
 *			page size, but it doesn't have to be.
 *
 * malloc_minsize	minimum size of an allocation in bytes.
 *			If this is too small it's too much work
 *			to manage them.  This is also the smallest
 *			unit of alignment used for the storage
 *			returned by malloc/realloc.
 *
 */

#if defined(__FreeBSD__)
#   if defined(__i386__)
#       define malloc_pageshift		12U
#       define malloc_minsize		16U
#   endif
#   if defined(__alpha__)
#       define malloc_pageshift		13U
#       define malloc_minsize		16U
#   endif
#   if !defined(__NETBSD_SYSCALLS)
#       define HAS_UTRACE
#   endif
    /*
     * Make malloc/free/realloc thread-safe in libc for use with
     * kernel threads.
     */
#   include "libc_private.h"
#   include "spinlock.h"
    static spinlock_t thread_lock	= _SPINLOCK_INITIALIZER;
#   define THREAD_LOCK()		if (__isthreaded) _SPINLOCK(&thread_lock);
#   define THREAD_UNLOCK()		if (__isthreaded) _SPINUNLOCK(&thread_lock);
#endif /* __FreeBSD__ */

#if defined(__sparc__) && defined(sun)
#   define malloc_pageshift		12U
#   define malloc_minsize		16U
#   define MAP_ANON			(0)
    static int fdzero;
#   define MMAP_FD	fdzero
#   define INIT_MMAP() \
	{ if ((fdzero=open("/dev/zero", O_RDWR, 0000)) == -1) \
	    wrterror("open of /dev/zero"); }
#   define MADV_FREE			MADV_DONTNEED
#endif /* __sparc__ */

/* Insert your combination here... */
#if defined(__FOOCPU__) && defined(__BAROS__)
#   define malloc_pageshift		12U
#   define malloc_minsize		16U
#endif /* __FOOCPU__ && __BAROS__ */


/*
 * No user serviceable parts behind this point.
 */
#include <sys/types.h>
#include <sys/mman.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * This structure describes a page worth of chunks.
 */

struct pginfo {
    struct pginfo	*next;	/* next on the free list */
    void		*page;	/* Pointer to the page */
    u_short		size;	/* size of this page's chunks */
    u_short		shift;	/* How far to shift for this size chunks */
    u_short		free;	/* How many free chunks */
    u_short		total;	/* How many chunk */
    u_int		bits[1]; /* Which chunks are free */
};

/*
 * This structure describes a number of free pages.
 */

struct pgfree {
    struct pgfree	*next;	/* next run of free pages */
    struct pgfree	*prev;	/* prev run of free pages */
    void		*page;	/* pointer to free pages */
    void		*end;	/* pointer to end of free pages */
    size_t		size;	/* number of bytes free */
};

/*
 * How many bits per u_int in the bitmap.
 * Change only if not 8 bits/byte
 */
#define	MALLOC_BITS	(8*sizeof(u_int))

/*
 * Magic values to put in the page_directory
 */
#define MALLOC_NOT_MINE	((struct pginfo*) 0)
#define MALLOC_FREE 	((struct pginfo*) 1)
#define MALLOC_FIRST	((struct pginfo*) 2)
#define MALLOC_FOLLOW	((struct pginfo*) 3)
#define MALLOC_MAGIC	((struct pginfo*) 4)

#ifndef malloc_pageshift
#define malloc_pageshift		12U
#endif

#ifndef malloc_minsize
#define malloc_minsize			16U
#endif

#if !defined(malloc_pagesize)
#define malloc_pagesize			(1UL<<malloc_pageshift)
#endif

#if ((1<<malloc_pageshift) != malloc_pagesize)
#error	"(1<<malloc_pageshift) != malloc_pagesize"
#endif

#ifndef malloc_maxsize
#define malloc_maxsize			((malloc_pagesize)>>1)
#endif

/* A mask for the offset inside a page.  */
#define malloc_pagemask	((malloc_pagesize)-1)

#define pageround(foo) (((foo) + (malloc_pagemask))&(~(malloc_pagemask)))
#define ptr2index(foo) (((u_long)(foo) >> malloc_pageshift)-malloc_origo)

#ifndef THREAD_LOCK
#define THREAD_LOCK()
#endif

#ifndef THREAD_UNLOCK
#define THREAD_UNLOCK()
#endif

#ifndef MMAP_FD
#define MMAP_FD (-1)
#endif

#ifndef INIT_MMAP
#define INIT_MMAP()
#endif

/* Set when initialization has been done */
static unsigned malloc_started;	

/* Recusion flag for public interface. */
static int malloc_active;

/* Number of free pages we cache */
static unsigned malloc_cache = 16;

/* The offset from pagenumber to index into the page directory */
static u_long malloc_origo;

/* The last index in the page directory we care about */
static u_long last_index;

/* Pointer to page directory. Allocated "as if with" malloc */
static struct	pginfo **page_dir;

/* How many slots in the page directory */
static unsigned	malloc_ninfo;

/* Free pages line up here */
static struct pgfree free_list;

/* Abort(), user doesn't handle problems.  */
static int malloc_abort;

/* Are we trying to die ?  */
static int suicide;

/* always realloc ?  */
static int malloc_realloc;

/* pass the kernel a hint on free pages ?  */
static int malloc_hint = 0;

/* xmalloc behaviour ?  */
static int malloc_xmalloc;

/* sysv behaviour for malloc(0) ?  */
static int malloc_sysv;

/* zero fill ?  */
static int malloc_zero;

/* junk fill ?  */
static int malloc_junk;

#ifdef HAS_UTRACE

/* utrace ?  */
static int malloc_utrace;

struct ut { void *p; size_t s; void *r; };

void utrace __P((struct ut *, int));

#define UTRACE(a, b, c) \
	if (malloc_utrace) \
		{struct ut u; u.p=a; u.s = b; u.r=c; utrace(&u, sizeof u);}
#else /* !HAS_UTRACE */
#define UTRACE(a,b,c)
#endif /* HAS_UTRACE */

/* my last break. */
static void *malloc_brk;

/* one location cache for free-list holders */
static struct pgfree *px;

/* compile-time options */
char *malloc_options;

/* Name of the current public function */
static char *malloc_func;

/* Macro for mmap */
#define MMAP(size) \
	mmap(0, (size), PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, \
	    MMAP_FD, 0);

/*
 * Necessary function declarations
 */
static int extend_pgdir(u_long index);
static void *imalloc(size_t size);
static void ifree(void *ptr);
static void *irealloc(void *ptr, size_t size);

extern char *__progname;

static void
wrterror(char *p)
{
    char *q = " error: ";
    write(STDERR_FILENO, __progname, strlen(__progname));
    write(STDERR_FILENO, malloc_func, strlen(malloc_func));
    write(STDERR_FILENO, q, strlen(q));
    write(STDERR_FILENO, p, strlen(p));
    suicide = 1;
    abort();
}

static void
wrtwarning(char *p)
{
    char *q = " warning: ";
    if (malloc_abort)
	wrterror(p);
    write(STDERR_FILENO, __progname, strlen(__progname));
    write(STDERR_FILENO, malloc_func, strlen(malloc_func));
    write(STDERR_FILENO, q, strlen(q));
    write(STDERR_FILENO, p, strlen(p));
}


/*
 * Allocate a number of pages from the OS
 */
static void *
map_pages(int pages)
{
    caddr_t result, tail;

    result = (caddr_t)pageround((u_long)sbrk(0));
    tail = result + (pages << malloc_pageshift);

    if (brk(tail)) {
#ifdef EXTRA_SANITY
	wrterror("(ES): map_pages fails\n");
#endif /* EXTRA_SANITY */
	return 0;
    }

    last_index = ptr2index(tail) - 1;
    malloc_brk = tail;

    if ((last_index+1) >= malloc_ninfo && !extend_pgdir(last_index))
	return 0;;

    return result;
}

/*
 * Extend page directory
 */
static int
extend_pgdir(u_long index)
{
    struct  pginfo **new, **old;
    int i, oldlen;

    /* Make it this many pages */
    i = index * sizeof *page_dir;
    i /= malloc_pagesize;
    i += 2;

    /* remember the old mapping size */
    oldlen = malloc_ninfo * sizeof *page_dir;

    /*
     * NOTE: we allocate new pages and copy the directory rather than tempt
     * fate by trying to "grow" the region.. There is nothing to prevent
     * us from accidently re-mapping space that's been allocated by our caller
     * via dlopen() or other mmap().
     *
     * The copy problem is not too bad, as there is 4K of page index per
     * 4MB of malloc arena.
     *
     * We can totally avoid the copy if we open a file descriptor to associate
     * the anon mappings with.  Then, when we remap the pages at the new
     * address, the old pages will be "magically" remapped..  But this means
     * keeping open a "secret" file descriptor.....
     */

    /* Get new pages */
    new = (struct pginfo**) MMAP(i * malloc_pagesize);
    if (new == (struct pginfo **)-1)
	return 0;

    /* Copy the old stuff */
    memcpy(new, page_dir,
	    malloc_ninfo * sizeof *page_dir);

    /* register the new size */
    malloc_ninfo = i * malloc_pagesize / sizeof *page_dir;

    /* swap the pointers */
    old = page_dir;
    page_dir = new;

    /* Now free the old stuff */
    munmap(old, oldlen);
    return 1;
}

/*
 * Initialize the world
 */
static void
malloc_init ()
{
    char *p, b[64];
    int i, j;
    int errnosave;

    INIT_MMAP();

#ifdef EXTRA_SANITY
    malloc_junk = 1;
#endif /* EXTRA_SANITY */

    for (i = 0; i < 3; i++) {
	if (i == 0) {
	    errnosave = errno;
	    j = readlink("/etc/malloc.conf", b, sizeof b - 1);
	    errno = errnosave;
	    if (j <= 0)
		continue;
	    b[j] = '\0';
	    p = b;
	} else if (i == 1) {
	    p = getenv("MALLOC_OPTIONS");
	} else {
	    p = malloc_options;
	}
	for (; p && *p; p++) {
	    switch (*p) {
		case '>': malloc_cache   <<= 1; break;
		case '<': malloc_cache   >>= 1; break;
		case 'a': malloc_abort   = 0; break;
		case 'A': malloc_abort   = 1; break;
		case 'h': malloc_hint    = 0; break;
		case 'H': malloc_hint    = 1; break;
		case 'r': malloc_realloc = 0; break;
		case 'R': malloc_realloc = 1; break;
		case 'j': malloc_junk    = 0; break;
		case 'J': malloc_junk    = 1; break;
#ifdef HAS_UTRACE
		case 'u': malloc_utrace  = 0; break;
		case 'U': malloc_utrace  = 1; break;
#endif
		case 'v': malloc_sysv    = 0; break;
		case 'V': malloc_sysv    = 1; break;
		case 'x': malloc_xmalloc = 0; break;
		case 'X': malloc_xmalloc = 1; break;
		case 'z': malloc_zero    = 0; break;
		case 'Z': malloc_zero    = 1; break;
		default:
		    j = malloc_abort;
		    malloc_abort = 0;
		    wrtwarning("unknown char in MALLOC_OPTIONS\n");
		    malloc_abort = j;
		    break;
	    }
	}
    }

    UTRACE(0, 0, 0);

    /*
     * We want junk in the entire allocation, and zero only in the part
     * the user asked for.
     */
    if (malloc_zero)
	malloc_junk=1;

    /*
     * If we run with junk (or implicitly from above: zero), we want to
     * force realloc() to get new storage, so we can DTRT with it.
     */
    if (malloc_junk)
	malloc_realloc=1;

    /* Allocate one page for the page directory */
    page_dir = (struct pginfo **) MMAP(malloc_pagesize);

    if (page_dir == (struct pginfo **) -1)
	wrterror("mmap(2) failed, check limits.\n");

    /*
     * We need a maximum of malloc_pageshift buckets, steal these from the
     * front of the page_directory;
     */
    malloc_origo = ((u_long)pageround((u_long)sbrk(0))) >> malloc_pageshift;
    malloc_origo -= malloc_pageshift;

    malloc_ninfo = malloc_pagesize / sizeof *page_dir;

    /* Recalculate the cache size in bytes, and make sure it's nonzero */

    if (!malloc_cache)
	malloc_cache++;

    malloc_cache <<= malloc_pageshift;

    /*
     * This is a nice hack from Kaleb Keithly ([e-mail]).
     * We can sbrk(2) further back when we keep this on a low address.
     */
    px = (struct pgfree *) imalloc (sizeof *px);

    /* Been here, done that */
    malloc_started++;
}

/*
 * Allocate a number of complete pages
 */
static void *
malloc_pages(size_t size)
{
    void *p, *delay_free = 0;
    int i;
    struct pgfree *pf;
    u_long index;

    size = pageround(size);

    p = 0;

    /* Look for free pages before asking for more */
    for(pf = free_list.next; pf; pf = pf->next) {

#ifdef EXTRA_SANITY
	if (pf->size & malloc_pagemask)
	    wrterror("(ES): junk length entry on free_list\n");
	if (!pf->size)
	    wrterror("(ES): zero length entry on free_list\n");
	if (pf->page == pf->end)
	    wrterror("(ES): zero entry on free_list\n");
	if (pf->page > pf->end) 
	    wrterror("(ES): sick entry on free_list\n");
	if ((void*)pf->page >= (void*)sbrk(0))
	    wrterror("(ES): entry on free_list past brk\n");
	if (page_dir[ptr2index(pf->page)] != MALLOC_FREE) 
	    wrterror("(ES): non-free first page on free-list\n");
	if (page_dir[ptr2index(pf->end)-1] != MALLOC_FREE)
	    wrterror("(ES): non-free last page on free-list\n");
#endif /* EXTRA_SANITY */

	if (pf->size < size)
	    continue;

	if (pf->size == size) {
	    p = pf->page;
	    if (pf->next)
		    pf->next->prev = pf->prev;
	    pf->prev->next = pf->next;
	    delay_free = pf;
	    break;
	} 

	p = pf->page;
	pf->page = (char *)pf->page + size;
	pf->size -= size;
	break;
    }

#ifdef EXTRA_SANITY
    if (p && page_dir[ptr2index(p)] != MALLOC_FREE)
	wrterror("(ES): allocated non-free page on free-list\n");
#endif /* EXTRA_SANITY */

    size >>= malloc_pageshift;

    /* Map new pages */
    if (!p)
	p = map_pages(size);

    if (p) {

	index = ptr2index(p);
	page_dir[index] = MALLOC_FIRST;
	for (i=1;i<size;i++)
	    page_dir[index+i] = MALLOC_FOLLOW;

	if (malloc_junk)
	    memset(p, SOME_JUNK, size << malloc_pageshift);
    }

    if (delay_free) {
	if (!px)
	    px = delay_free;
	else
	    ifree(delay_free);
    }