2009-02-08 Vesa Jääskeläinen <chaac@nic.fi>
* kern/mm.c: Add more comments.
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parent
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2b40d6bb9f
2 changed files with 79 additions and 22 deletions
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@ -1,3 +1,7 @@
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2009-02-08 Vesa Jääskeläinen <chaac@nic.fi>
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* kern/mm.c: Add more comments.
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2009-02-08 Robert Millan <rmh@aybabtu.com>
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Patch from Javier Martín.
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97
kern/mm.c
97
kern/mm.c
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@ -129,7 +129,7 @@ get_header_from_pointer (void *ptr, grub_mm_header_t *p, grub_mm_region_t *r)
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if (! *r)
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grub_fatal ("out of range pointer %p", ptr);
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*p = (grub_mm_header_t) ptr - 1;
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if ((*p)->magic != GRUB_MM_ALLOC_MAGIC)
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grub_fatal ("alloc magic is broken at %p", *p);
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@ -155,7 +155,7 @@ grub_mm_init_region (void *addr, grub_size_t size)
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r = (grub_mm_region_t) (((grub_addr_t) addr + GRUB_MM_ALIGN - 1)
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& (~(GRUB_MM_ALIGN - 1)));
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size -= (char *) r - (char *) addr + sizeof (*r);
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h = (grub_mm_header_t) ((char *) r + GRUB_MM_ALIGN);
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h->next = h;
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h->magic = GRUB_MM_FREE_MAGIC;
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@ -170,22 +170,26 @@ grub_mm_init_region (void *addr, grub_size_t size)
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for (p = &base, q = *p; q; p = &(q->next), q = *p)
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if (q->size > r->size)
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break;
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*p = r;
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r->next = q;
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}
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/* Allocate the number of units N with the alignment ALIGN from the ring
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buffer starting from *FIRST. ALIGN must be a power of two. Return a
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non-NULL if successful, otherwise return NULL. */
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buffer starting from *FIRST. ALIGN must be a power of two. Both N and
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ALIGN are in units of GRUB_MM_ALIGN. Return a non-NULL if successful,
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otherwise return NULL. */
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static void *
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grub_real_malloc (grub_mm_header_t *first, grub_size_t n, grub_size_t align)
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{
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grub_mm_header_t p, q;
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/* When everything is allocated side effect is that *first will have alloc
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magic marked, meaning that there is no room in this region. */
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if ((*first)->magic == GRUB_MM_ALLOC_MAGIC)
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return 0;
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/* Try to search free slot for allocation in this memory region. */
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for (q = *first, p = q->next; ; q = p, p = p->next)
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{
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grub_off_t extra;
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@ -204,11 +208,37 @@ grub_real_malloc (grub_mm_header_t *first, grub_size_t n, grub_size_t align)
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{
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if (extra == 0 && p->size == n)
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{
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/* There is no special alignment requirement and memory block
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is complete match.
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1. Just mark memory block as allocated and remove it from
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free list.
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Result:
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+---------------+ previous block's next
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| alloc, size=n | |
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+---------------+ v
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*/
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q->next = p->next;
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p->magic = GRUB_MM_ALLOC_MAGIC;
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}
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else if (extra == 0 || p->size == n + extra)
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{
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/* There might be alignment requirement, when taking it into
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account memory block fits in.
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1. Allocate new area at end of memory block.
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2. Reduce size of available blocks from original node.
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3. Mark new area as allocated and "remove" it from free
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list.
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Result:
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+---------------+
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| free, size-=n | next --+
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+---------------+ |
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| alloc, size=n | |
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+---------------+ v
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*/
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p->size -= n;
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p += p->size;
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p->size = n;
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@ -216,13 +246,32 @@ grub_real_malloc (grub_mm_header_t *first, grub_size_t n, grub_size_t align)
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}
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else
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{
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/* There is alignment requirement and there is room in memory
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block. Split memory block to three pieces.
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1. Create new memory block right after section being
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allocated. Mark it as free.
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2. Add new memory block to free chain.
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3. Mark current memory block having only extra blocks.
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4. Advance to aligned block and mark that as allocated and
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"remove" it from free list.
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Result:
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+------------------------------+
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| free, size=extra | next --+
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+------------------------------+ |
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| alloc, size=n | |
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+------------------------------+ |
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| free, size=orig.size-extra-n | <------+, next --+
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+------------------------------+ v
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*/
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grub_mm_header_t r;
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r = p + extra + n;
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r->magic = GRUB_MM_FREE_MAGIC;
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r->size = p->size - extra - n;
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r->next = p->next;
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p->size = extra;
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p->next = r;
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p += extra;
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@ -230,11 +279,15 @@ grub_real_malloc (grub_mm_header_t *first, grub_size_t n, grub_size_t align)
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p->magic = GRUB_MM_ALLOC_MAGIC;
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}
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/* Mark find as a start marker for next allocation to fasten it.
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This will have side effect of fragmenting memory as small
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pieces before this will be un-used. */
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*first = q;
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return p + 1;
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}
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/* Search was completed without result. */
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if (p == *first)
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break;
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}
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@ -249,17 +302,17 @@ grub_memalign (grub_size_t align, grub_size_t size)
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grub_mm_region_t r;
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grub_size_t n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
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int count = 0;
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align = (align >> GRUB_MM_ALIGN_LOG2);
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if (align == 0)
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align = 1;
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again:
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for (r = base; r; r = r->next)
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{
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void *p;
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p = grub_real_malloc (&(r->first), n, align);
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if (p)
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return p;
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@ -273,7 +326,7 @@ grub_memalign (grub_size_t align, grub_size_t size)
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grub_disk_cache_invalidate_all ();
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count++;
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goto again;
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case 1:
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/* Unload unneeded modules. */
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grub_dl_unload_unneeded ();
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@ -283,7 +336,7 @@ grub_memalign (grub_size_t align, grub_size_t size)
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default:
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break;
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}
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grub_error (GRUB_ERR_OUT_OF_MEMORY, "out of memory");
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return 0;
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}
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@ -326,12 +379,12 @@ grub_free (void *ptr)
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}
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while (q != r->first);
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#endif
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for (q = r->first; q >= p || q->next <= p; q = q->next)
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{
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if (q->magic != GRUB_MM_FREE_MAGIC)
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grub_fatal ("free magic is broken at %p: 0x%x", q, q->magic);
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if (q >= q->next && (q < p || q->next > p))
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break;
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}
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@ -339,7 +392,7 @@ grub_free (void *ptr)
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p->magic = GRUB_MM_FREE_MAGIC;
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p->next = q->next;
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q->next = p;
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if (p + p->size == p->next)
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{
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if (p->next == q)
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@ -349,7 +402,7 @@ grub_free (void *ptr)
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p->size += p->next->size;
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p->next = p->next->next;
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}
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if (q + q->size == p)
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{
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p->magic = 0;
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@ -370,7 +423,7 @@ grub_realloc (void *ptr, grub_size_t size)
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grub_mm_region_t r;
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void *q;
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grub_size_t n;
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if (! ptr)
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return grub_malloc (size);
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@ -383,14 +436,14 @@ grub_realloc (void *ptr, grub_size_t size)
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/* FIXME: Not optimal. */
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n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
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get_header_from_pointer (ptr, &p, &r);
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if (p->size >= n)
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return ptr;
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q = grub_malloc (size);
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if (! q)
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return q;
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grub_memcpy (q, ptr, size);
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grub_free (ptr);
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return q;
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@ -434,7 +487,7 @@ grub_mm_dump (unsigned lineno)
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for (r = base; r; r = r->next)
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{
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grub_mm_header_t p;
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for (p = (grub_mm_header_t) ((r->addr + GRUB_MM_ALIGN - 1)
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& (~(GRUB_MM_ALIGN - 1)));
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(grub_addr_t) p < r->addr + r->size;
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@ -493,7 +546,7 @@ grub_debug_memalign (const char *file, int line, grub_size_t align,
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grub_size_t size)
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{
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void *ptr;
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if (grub_mm_debug)
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grub_printf ("%s:%d: memalign (0x%x, 0x%x) = ",
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file, line, align, size);
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