98ab79066d
In Seventh Edition UNIX, the last pointer passed to free() was guaranteed to not actually have been freed allowing memory to be "compacted" via the following pattern: free(foo); foo = realloc(foo, newsize); Further, Andrew Koenig reports in "C Traps and Pitfalls" that the original realloc() implementation required this pattern. The C standard is clear that this is Undefined Behavior. Modern allocators don't support it and no portable code could rely on it so remove this support. Note: the removed implementation contains an off-by-one error and if an item isn't found on the freelist, then twice as much memory as the largest possible allocation will be copied. Reviewed by: kib, imp Obtained from: CheriBSD Sponsored by: DARPA, AFRL Differential Revision: https://reviews.freebsd.org/D21296
321 lines
8.5 KiB
C
321 lines
8.5 KiB
C
/*-
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
*
|
|
* Copyright (c) 1983 Regents of the University of California.
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. Neither the name of the University nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#if defined(LIBC_SCCS) && !defined(lint)
|
|
/*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/
|
|
static char *rcsid = "$FreeBSD$";
|
|
#endif /* LIBC_SCCS and not lint */
|
|
|
|
/*
|
|
* malloc.c (Caltech) 2/21/82
|
|
* Chris Kingsley, kingsley@cit-20.
|
|
*
|
|
* This is a very fast storage allocator. It allocates blocks of a small
|
|
* number of different sizes, and keeps free lists of each size. Blocks that
|
|
* don't exactly fit are passed up to the next larger size. In this
|
|
* implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
|
|
* This is designed for use in a virtual memory environment.
|
|
*/
|
|
|
|
#include <sys/param.h>
|
|
#include <sys/sysctl.h>
|
|
#include <sys/mman.h>
|
|
#include <errno.h>
|
|
#include <stdarg.h>
|
|
#include <stddef.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include "rtld.h"
|
|
#include "rtld_printf.h"
|
|
#include "paths.h"
|
|
|
|
/*
|
|
* Pre-allocate mmap'ed pages
|
|
*/
|
|
#define NPOOLPAGES (128*1024/pagesz)
|
|
static caddr_t pagepool_start, pagepool_end;
|
|
|
|
/*
|
|
* The overhead on a block is at least 4 bytes. When free, this space
|
|
* contains a pointer to the next free block, and the bottom two bits must
|
|
* be zero. When in use, the first byte is set to MAGIC, and the second
|
|
* byte is the size index. The remaining bytes are for alignment.
|
|
* If range checking is enabled then a second word holds the size of the
|
|
* requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
|
|
* The order of elements is critical: ov_magic must overlay the low order
|
|
* bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
|
|
*/
|
|
union overhead {
|
|
union overhead *ov_next; /* when free */
|
|
struct {
|
|
u_char ovu_magic; /* magic number */
|
|
u_char ovu_index; /* bucket # */
|
|
} ovu;
|
|
#define ov_magic ovu.ovu_magic
|
|
#define ov_index ovu.ovu_index
|
|
};
|
|
|
|
static void morecore(int bucket);
|
|
static int morepages(int n);
|
|
|
|
#define MAGIC 0xef /* magic # on accounting info */
|
|
|
|
/*
|
|
* nextf[i] is the pointer to the next free block of size 2^(i+3). The
|
|
* smallest allocatable block is 8 bytes. The overhead information
|
|
* precedes the data area returned to the user.
|
|
*/
|
|
#define NBUCKETS 30
|
|
static union overhead *nextf[NBUCKETS];
|
|
|
|
static int pagesz; /* page size */
|
|
static int pagebucket; /* page size bucket */
|
|
|
|
/*
|
|
* The array of supported page sizes is provided by the user, i.e., the
|
|
* program that calls this storage allocator. That program must initialize
|
|
* the array before making its first call to allocate storage. The array
|
|
* must contain at least one page size. The page sizes must be stored in
|
|
* increasing order.
|
|
*/
|
|
|
|
void *
|
|
__crt_malloc(size_t nbytes)
|
|
{
|
|
union overhead *op;
|
|
int bucket;
|
|
ssize_t n;
|
|
size_t amt;
|
|
|
|
/*
|
|
* First time malloc is called, setup page size and
|
|
* align break pointer so all data will be page aligned.
|
|
*/
|
|
if (pagesz == 0) {
|
|
pagesz = n = pagesizes[0];
|
|
if (morepages(NPOOLPAGES) == 0)
|
|
return NULL;
|
|
op = (union overhead *)(pagepool_start);
|
|
n = n - sizeof (*op) - ((long)op & (n - 1));
|
|
if (n < 0)
|
|
n += pagesz;
|
|
if (n) {
|
|
pagepool_start += n;
|
|
}
|
|
bucket = 0;
|
|
amt = 8;
|
|
while ((unsigned)pagesz > amt) {
|
|
amt <<= 1;
|
|
bucket++;
|
|
}
|
|
pagebucket = bucket;
|
|
}
|
|
/*
|
|
* Convert amount of memory requested into closest block size
|
|
* stored in hash buckets which satisfies request.
|
|
* Account for space used per block for accounting.
|
|
*/
|
|
if (nbytes <= (unsigned long)(n = pagesz - sizeof(*op))) {
|
|
amt = 8; /* size of first bucket */
|
|
bucket = 0;
|
|
n = -sizeof(*op);
|
|
} else {
|
|
amt = pagesz;
|
|
bucket = pagebucket;
|
|
}
|
|
while (nbytes > amt + n) {
|
|
amt <<= 1;
|
|
if (amt == 0)
|
|
return (NULL);
|
|
bucket++;
|
|
}
|
|
/*
|
|
* If nothing in hash bucket right now,
|
|
* request more memory from the system.
|
|
*/
|
|
if ((op = nextf[bucket]) == NULL) {
|
|
morecore(bucket);
|
|
if ((op = nextf[bucket]) == NULL)
|
|
return (NULL);
|
|
}
|
|
/* remove from linked list */
|
|
nextf[bucket] = op->ov_next;
|
|
op->ov_magic = MAGIC;
|
|
op->ov_index = bucket;
|
|
return ((char *)(op + 1));
|
|
}
|
|
|
|
void *
|
|
__crt_calloc(size_t num, size_t size)
|
|
{
|
|
void *ret;
|
|
|
|
if (size != 0 && (num * size) / size != num) {
|
|
/* size_t overflow. */
|
|
return (NULL);
|
|
}
|
|
|
|
if ((ret = __crt_malloc(num * size)) != NULL)
|
|
memset(ret, 0, num * size);
|
|
|
|
return (ret);
|
|
}
|
|
|
|
/*
|
|
* Allocate more memory to the indicated bucket.
|
|
*/
|
|
static void
|
|
morecore(int bucket)
|
|
{
|
|
union overhead *op;
|
|
int sz; /* size of desired block */
|
|
int amt; /* amount to allocate */
|
|
int nblks; /* how many blocks we get */
|
|
|
|
/*
|
|
* sbrk_size <= 0 only for big, FLUFFY, requests (about
|
|
* 2^30 bytes on a VAX, I think) or for a negative arg.
|
|
*/
|
|
if ((unsigned)bucket >= NBBY * sizeof(int) - 4)
|
|
return;
|
|
sz = 1 << (bucket + 3);
|
|
if (sz < pagesz) {
|
|
amt = pagesz;
|
|
nblks = amt / sz;
|
|
} else {
|
|
amt = sz + pagesz;
|
|
nblks = 1;
|
|
}
|
|
if (amt > pagepool_end - pagepool_start)
|
|
if (morepages(amt/pagesz + NPOOLPAGES) == 0)
|
|
return;
|
|
op = (union overhead *)pagepool_start;
|
|
pagepool_start += amt;
|
|
|
|
/*
|
|
* Add new memory allocated to that on
|
|
* free list for this hash bucket.
|
|
*/
|
|
nextf[bucket] = op;
|
|
while (--nblks > 0) {
|
|
op->ov_next = (union overhead *)((caddr_t)op + sz);
|
|
op = (union overhead *)((caddr_t)op + sz);
|
|
}
|
|
}
|
|
|
|
void
|
|
__crt_free(void *cp)
|
|
{
|
|
int size;
|
|
union overhead *op;
|
|
|
|
if (cp == NULL)
|
|
return;
|
|
op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
|
|
if (op->ov_magic != MAGIC)
|
|
return; /* sanity */
|
|
size = op->ov_index;
|
|
op->ov_next = nextf[size]; /* also clobbers ov_magic */
|
|
nextf[size] = op;
|
|
}
|
|
|
|
void *
|
|
__crt_realloc(void *cp, size_t nbytes)
|
|
{
|
|
u_int onb;
|
|
int i;
|
|
union overhead *op;
|
|
char *res;
|
|
|
|
if (cp == NULL)
|
|
return (__crt_malloc(nbytes));
|
|
op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
|
|
if (op->ov_magic != MAGIC)
|
|
return (NULL); /* Double-free or bad argument */
|
|
i = op->ov_index;
|
|
onb = 1 << (i + 3);
|
|
if (onb < (u_int)pagesz)
|
|
onb -= sizeof(*op);
|
|
else
|
|
onb += pagesz - sizeof(*op);
|
|
/* avoid the copy if same size block */
|
|
if (i != 0) {
|
|
i = 1 << (i + 2);
|
|
if (i < pagesz)
|
|
i -= sizeof(*op);
|
|
else
|
|
i += pagesz - sizeof(*op);
|
|
}
|
|
if (nbytes <= onb && nbytes > (size_t)i)
|
|
return (cp);
|
|
if ((res = __crt_malloc(nbytes)) == NULL)
|
|
return (NULL);
|
|
bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
|
|
__crt_free(cp);
|
|
return (res);
|
|
}
|
|
|
|
static int
|
|
morepages(int n)
|
|
{
|
|
caddr_t addr;
|
|
int offset;
|
|
|
|
if (pagepool_end - pagepool_start > pagesz) {
|
|
addr = (caddr_t)roundup2((long)pagepool_start, pagesz);
|
|
if (munmap(addr, pagepool_end - addr) != 0) {
|
|
#ifdef IN_RTLD
|
|
rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": "
|
|
"morepages: cannot munmap %p: %s\n",
|
|
addr, rtld_strerror(errno));
|
|
#endif
|
|
}
|
|
}
|
|
|
|
offset = (long)pagepool_start - rounddown2((long)pagepool_start,
|
|
pagesz);
|
|
|
|
pagepool_start = mmap(0, n * pagesz, PROT_READ | PROT_WRITE,
|
|
MAP_ANON | MAP_PRIVATE, -1, 0);
|
|
if (pagepool_start == MAP_FAILED) {
|
|
#ifdef IN_RTLD
|
|
rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": morepages: "
|
|
"cannot mmap anonymous memory: %s\n",
|
|
rtld_strerror(errno));
|
|
#endif
|
|
return (0);
|
|
}
|
|
pagepool_end = pagepool_start + n * pagesz;
|
|
pagepool_start += offset;
|
|
|
|
return (n);
|
|
}
|