/*-
* 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: releng/12.1/libexec/rtld-elf/rtld_malloc.c 348161 2019-05-23 12:52:19Z kib $";
#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);
static int findbucket(union overhead *freep, int srchlen);
#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;
}
/*
* When a program attempts "storage compaction" as mentioned in the
* old malloc man page, it realloc's an already freed block. Usually
* this is the last block it freed; occasionally it might be farther
* back. We have to search all the free lists for the block in order
* to determine its bucket: 1st we make one pass through the lists
* checking only the first block in each; if that fails we search
* ``realloc_srchlen'' blocks in each list for a match (the variable
* is extern so the caller can modify it). If that fails we just copy
* however many bytes was given to realloc() and hope it's not huge.
*/
static int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
void *
__crt_realloc(void *cp, size_t nbytes)
{
u_int onb;
int i;
union overhead *op;
char *res;
int was_alloced = 0;
if (cp == NULL)
return (__crt_malloc(nbytes));
op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
if (op->ov_magic == MAGIC) {
was_alloced++;
i = op->ov_index;
} else {
/*
* Already free, doing "compaction".
*
* Search for the old block of memory on the
* free list. First, check the most common
* case (last element free'd), then (this failing)
* the last ``realloc_srchlen'' items free'd.
* If all lookups fail, then assume the size of
* the memory block being realloc'd is the
* largest possible (so that all "nbytes" of new
* memory are copied into). Note that this could cause
* a memory fault if the old area was tiny, and the moon
* is gibbous. However, that is very unlikely.
*/
if ((i = findbucket(op, 1)) < 0 &&
(i = findbucket(op, realloc_srchlen)) < 0)
i = NBUCKETS;
}
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 (was_alloced) {
if (i) {
i = 1 << (i + 2);
if (i < pagesz)
i -= sizeof(*op);
else
i += pagesz - sizeof(*op);
}
if (nbytes <= onb && nbytes > (size_t)i)
return (cp);
__crt_free(cp);
}
if ((res = __crt_malloc(nbytes)) == NULL)
return (NULL);
if (cp != res) /* common optimization if "compacting" */
bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
return (res);
}
/*
* Search ``srchlen'' elements of each free list for a block whose
* header starts at ``freep''. If srchlen is -1 search the whole list.
* Return bucket number, or -1 if not found.
*/
static int
findbucket(union overhead *freep, int srchlen)
{
union overhead *p;
int i, j;
for (i = 0; i < NBUCKETS; i++) {
j = 0;
for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
if (p == freep)
return (i);
j++;
}
}
return (-1);
}
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);
}