minix/lib/libc/ansi/malloc-debug.c

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/* pointless without assertions */
#ifdef NDEBUG
#undef NDEBUG
#endif
#include <assert.h>
#include <machine/vm.h>
#include <minix/minlib.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include "malloc-debug.h"
#if 0
#include <stdio.h>
static int reenter;
#define LOG(args) if (!reenter) { reenter++; printf args; reenter--; }
#else
#define LOG(args)
#endif
#define PAGE_SIZE I386_PAGE_SIZE
struct block {
size_t size;
unsigned magic;
};
static u8_t *ptr_min, *ptr_max;
#define MIN(x, y) ((x) < (y) ? (x) : (y))
static unsigned long page_round_down(unsigned long x)
{
return x - x % PAGE_SIZE;
}
static unsigned long page_round_up(unsigned long x)
{
unsigned long rem;
rem = x % PAGE_SIZE;
if (rem)
x += PAGE_SIZE - rem;
return x;
}
#define page_round_down_ptr(x) ((u8_t *) page_round_down((unsigned long) (x)))
#define page_round_up_ptr(x) ((u8_t *) page_round_up((unsigned long) (x)))
static unsigned long block_compute_magic(struct block *block)
{
return (unsigned long) block + block->size + 0xDEADBEEFUL;
}
static size_t block_get_totalsize(size_t size)
{
return page_round_up(sizeof(struct block) + size);
}
static u8_t *block_get_endptr(struct block *block)
{
return (u8_t *) block + block_get_totalsize(block->size);
}
static u8_t *block_get_dataptr(struct block *block)
{
return block_get_endptr(block) - block->size;
}
static void block_check(struct block *block)
{
u8_t *dataptr, *p;
/* check location */
assert(block);
assert(!((unsigned long) block % PAGE_SIZE));
assert((u8_t *) block >= ptr_min);
assert((u8_t *) block <= ptr_max);
/* check size */
assert(block->size > 0);
/* check fillers */
assert(block->magic == block_compute_magic(block));
dataptr = block_get_dataptr(block);
for (p = (u8_t *) (block + 1); p < dataptr; p++)
assert(*p == ((unsigned long) p & 0xff));
}
static struct block *block_alloc(size_t size)
{
struct block *block;
u8_t *dataptr, *p, *ptr;
unsigned page_index, page_index_max;
size_t sizerem, totalsize;
u64_t tsc;
LOG(("block_alloc; size=0x%x\n", size));
assert(size > 0);
/* round size up to machine word size */
sizerem = size % sizeof(long);
if (sizerem)
size += sizeof(long) - sizerem;
/* initialize address range */
if (!ptr_min && !ptr_max) {
/* keep a safe distance from areas that are in use:
* - 4MB from the break (should not change if traditional
* malloc is not used so a small margin is sufficient
* - 256MB from the stack (big margin because memory beyond
* this may be allocated by mmap when the address space
* starts to fill up)
*/
ptr_min = page_round_up_ptr((u8_t *) sbrk(0) + 0x400000);
ptr_max = page_round_down_ptr((u8_t *) &size - 0x10000000);
}
assert(ptr_min);
assert(ptr_max);
assert(ptr_min < ptr_max);
/* select address at random */
read_tsc_64(&tsc);
totalsize = block_get_totalsize(size);
page_index_max = (ptr_max - ptr_min - totalsize) / PAGE_SIZE;
page_index = (page_index_max > 0) ? (ex64lo(tsc) % page_index_max) : 0;
ptr = ptr_min + page_index * PAGE_SIZE;
/* allocate block */
block = (struct block *) mmap(
ptr, /* addr */
totalsize, /* len */
PROT_READ|PROT_WRITE, /* prot */
MAP_PREALLOC, /* flags */
-1, /* fd */
0); /* offset */
if (block == MAP_FAILED) {
/* mmap call failed */
abort();
}
/* block may not be at the requested location if that is in use */
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if (ptr_min > (u8_t *) block)
ptr_min = (u8_t *) block;
if (ptr_max < (u8_t *) block)
ptr_max = (u8_t *) block;
/* initialize block, including fillers */
block->size = size;
block->magic = block_compute_magic(block);
dataptr = block_get_dataptr(block);
for (p = (u8_t *) (block + 1); p < dataptr; p++)
*p = ((unsigned long) p & 0xff);
LOG(("block_alloc; block=0x%x\n", block));
return block;
}
static struct block *block_find(const void *ptr)
{
struct block *block;
LOG(("block_find; ptr=0x%x\n", ptr));
assert(ptr);
/* locate block based on pointer, then check whether it is valid */
block = (struct block *) page_round_down(
(unsigned long) ((struct block *) ptr - 1));
block_check(block);
LOG(("block_find; block=0x%x\n", block));
return block;
}
static void block_free(struct block *block)
{
LOG(("block_free; block=0x%x\n", block));
assert(block);
/* simply unmap the block */
if (munmap(block, block_get_totalsize(block->size)) < 0) {
/* munmap call failed */
abort();
}
}
void *_dbg_malloc(size_t size)
{
struct block *newblock;
u8_t *ptr;
LOG(("_dbg_malloc; size=0x%x\n", size));
assert(size > 0); /* enforced by regular malloc */
newblock = block_alloc(size);
if (!newblock)
return NULL;
ptr = block_get_dataptr(newblock);
LOG(("_dbg_malloc; ptr=0x%x\n", ptr));
return ptr;
}
void *_dbg_realloc(void *oldp, size_t size)
{
u8_t *newp;
struct block *oldblock, *newblock;
LOG(("_dbg_realloc; oldp=0x%x; size=0x%x\n", oldp, size));
assert(oldp); /* enforced by regular realloc */
assert(size > 0); /* enforced by regular realloc */
/* always allocate new block */
newblock = block_alloc(size);
if (!newblock)
return NULL;
/* copy the data */
oldblock = block_find(oldp);
memcpy(block_get_dataptr(newblock),
block_get_dataptr(oldblock),
MIN(newblock->size, oldblock->size));
/* deallocate old block */
block_free(oldblock);
newp = block_get_dataptr(newblock);
LOG(("_dbg_realloc; newp=0x%x\n", newp));
return newp;
}
void _dbg_free(void *ptr)
{
LOG(("_dbg_free; ptr=0x%x\n", ptr));
assert(ptr); /* enforced by regular free */
/* find the block and free it */
block_free(block_find(ptr));
LOG(("_dbg_free done\n"));
}