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Re: PING: PATCH: [BZ #14562] Properly handle fencepost with MALLOC_ALIGN_MASK
On Mon, Sep 24, 2012 at 11:45 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> This is the patch I am checking in. It is also needed for 2.16.
> OK for 2.16 branch?
>
> Thanks.
>
> --
> H.J.
> ---
> 2012-09-24 H.J. Lu <hongjiu.lu@intel.com>
>
> [BZ #14562]
> * malloc/arena.c (heap_trim): Properly get fencepost and adjust
> new chunk size with MALLOC_ALIGN_MASK.
>
> diff --git a/malloc/arena.c b/malloc/arena.c
> index 97c0b90..f24e76c 100644
> --- a/malloc/arena.c
> +++ b/malloc/arena.c
> @@ -655,15 +655,19 @@ heap_trim(heap_info *heap, size_t pad)
> unsigned long pagesz = GLRO(dl_pagesize);
> mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
> heap_info *prev_heap;
> - long new_size, top_size, extra;
> + long new_size, top_size, extra, prev_size, misalign;
>
> /* Can this heap go away completely? */
> while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
> prev_heap = heap->prev;
> - p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
> + 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(p->size == (0|PREV_INUSE)); /* must be fencepost */
> p = prev_chunk(p);
> - new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
> + new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ) + misalign;
> assert(new_size>0 && new_size<(long)(2*MINSIZE));
> if(!prev_inuse(p))
> new_size += p->prev_size;
OK for 2.16.
Cheers,
Carlos.