static mchunkptr
internal_function
mem2chunk_check (void *mem, unsigned char **magic_p)
{
mchunkptr p;
INTERNAL_SIZE_T sz, c;
unsigned char magic;
if (!aligned_OK (mem))
return NULL;
p = mem2chunk (mem);
if (!chunk_is_mmapped (p))
{
/* Must be a chunk in conventional heap memory. */
int contig = contiguous (&main_arena);
sz = chunksize (p);
if ((contig &&
((char *) p < mp_.sbrk_base ||
((char *) p + sz) >= (mp_.sbrk_base + main_arena.system_mem))) ||
sz < MINSIZE || sz & MALLOC_ALIGN_MASK || !inuse (p) ||
(!prev_inuse (p) && (p->prev_size & MALLOC_ALIGN_MASK ||
(contig && (char *) prev_chunk (p) < mp_.sbrk_base) ||
next_chunk (prev_chunk (p)) != p)))
return NULL;
magic = MAGICBYTE (p);
for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c)
{
if (c <= 0 || sz < (c + 2 * SIZE_SZ))
return NULL;
}
}
else
{
unsigned long offset, page_mask = GLRO (dl_pagesize) - 1;
/* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two
alignment relative to the beginning of a page. Check this
first. */
offset = (unsigned long) mem & page_mask;
if ((offset != MALLOC_ALIGNMENT && offset != 0 && offset != 0x10 &&
offset != 0x20 && offset != 0x40 && offset != 0x80 && offset != 0x100 &&
offset != 0x200 && offset != 0x400 && offset != 0x800 && offset != 0x1000 &&
offset < 0x2000) ||
!chunk_is_mmapped (p) || (p->size & PREV_INUSE) ||
((((unsigned long) p - p->prev_size) & page_mask) != 0) ||
((sz = chunksize (p)), ((p->prev_size + sz) & page_mask) != 0))
return NULL;
magic = MAGICBYTE (p);
for (sz -= 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c)
{
if (c <= 0 || sz < (c + 2 * SIZE_SZ))
return NULL;
}
}
((unsigned char *) p)[sz] ^= 0xFF;
if (magic_p)
*magic_p = (unsigned char *) p + sz;
return p;
}
static int
internal_function
heap_trim (heap_info *heap, size_t pad)
{
mstate ar_ptr = heap->ar_ptr;
unsigned long pagesz = GLRO (dl_pagesize);
mchunkptr top_chunk = top (ar_ptr), p, bck, fwd;
heap_info *prev_heap;
long new_size, top_size, top_area, extra, prev_size, misalign;
/* Can this heap go away completely? */
while (top_chunk == chunk_at_offset (heap, sizeof (*heap)))
{
prev_heap = heap->prev;
prev_size = prev_heap->size - (MINSIZE - 2 * SIZE_SZ);
p = chunk_at_offset (prev_heap, prev_size);
/* fencepost must be properly aligned. */
misalign = ((long) p) & MALLOC_ALIGN_MASK;
p = chunk_at_offset (prev_heap, prev_size - misalign);
assert (chunksize_nomask (p) == (0 | PREV_INUSE)); /* must be fencepost */
p = prev_chunk (p);
new_size = chunksize (p) + (MINSIZE - 2 * SIZE_SZ) + misalign;
assert (new_size > 0 && new_size < (long) (2 * MINSIZE));
if (!prev_inuse (p))
new_size += prev_size (p);
assert (new_size > 0 && new_size < HEAP_MAX_SIZE);
if (new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
break;
ar_ptr->system_mem -= heap->size;
LIBC_PROBE (memory_heap_free, 2, heap, heap->size);
delete_heap (heap);
heap = prev_heap;
if (!prev_inuse (p)) /* consolidate backward */
{
p = prev_chunk (p);
unlink (ar_ptr, p, bck, fwd);
}
assert (((unsigned long) ((char *) p + new_size) & (pagesz - 1)) == 0);
assert (((char *) p + new_size) == ((char *) heap + heap->size));
top (ar_ptr) = top_chunk = p;
set_head (top_chunk, new_size | PREV_INUSE);
/*check_chunk(ar_ptr, top_chunk);*/
}
/* Uses similar logic for per-thread arenas as the main arena with systrim
and _int_free by preserving the top pad and rounding down to the nearest
page. */
top_size = chunksize (top_chunk);
if ((unsigned long)(top_size) <
(unsigned long)(mp_.trim_threshold))
return 0;
top_area = top_size - MINSIZE - 1;
if (top_area < 0 || (size_t) top_area <= pad)
return 0;
/* Release in pagesize units and round down to the nearest page. */
extra = ALIGN_DOWN(top_area - pad, pagesz);
if (extra == 0)
return 0;
/* Try to shrink. */
if (shrink_heap (heap, extra) != 0)
return 0;
ar_ptr->system_mem -= extra;
/* Success. Adjust top accordingly. */
set_head (top_chunk, (top_size - extra) | PREV_INUSE);
/*check_chunk(ar_ptr, top_chunk);*/
return 1;
}
