slice.c

linux 内核源代码

	while (addr > len) {
		/* Go down by chunk size */
		addr = _ALIGN_DOWN(addr - len, 1ul << pshift);

		/* Check for hit with different page size */
		mask = slice_range_to_mask(addr, len);
		if (!slice_check_fit(mask, available)) {
			if (addr < SLICE_LOW_TOP)
				addr = _ALIGN_DOWN(addr, 1ul << SLICE_LOW_SHIFT);
			else if (addr < (1ul << SLICE_HIGH_SHIFT))
				addr = SLICE_LOW_TOP;
			else
				addr = _ALIGN_DOWN(addr, 1ul << SLICE_HIGH_SHIFT);
			continue;
		}

		/*
		 * Lookup failure means no vma is above this address,
		 * else if new region fits below vma->vm_start,
		 * return with success:
		 */
		vma = find_vma(mm, addr);
		if (!vma || (addr + len) <= vma->vm_start) {
			/* remember the address as a hint for next time */
			if (use_cache)
				mm->free_area_cache = addr;
			return addr;
		}

		/* remember the largest hole we saw so far */
		if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
		        mm->cached_hole_size = vma->vm_start - addr;

		/* try just below the current vma->vm_start */
		addr = vma->vm_start;
	}

	/*
	 * A failed mmap() very likely causes application failure,
	 * so fall back to the bottom-up function here. This scenario
	 * can happen with large stack limits and large mmap()
	 * allocations.
	 */
	addr = slice_find_area_bottomup(mm, len, available, psize, 0);

	/*
	 * Restore the topdown base:
	 */
	if (use_cache) {
		mm->free_area_cache = mm->mmap_base;
		mm->cached_hole_size = ~0UL;
	}

	return addr;
}


static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
				     struct slice_mask mask, int psize,
				     int topdown, int use_cache)
{
	if (topdown)
		return slice_find_area_topdown(mm, len, mask, psize, use_cache);
	else
		return slice_find_area_bottomup(mm, len, mask, psize, use_cache);
}

unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
				      unsigned long flags, unsigned int psize,
				      int topdown, int use_cache)
{
	struct slice_mask mask;
	struct slice_mask good_mask;
	struct slice_mask potential_mask = {0,0} /* silence stupid warning */;
	int pmask_set = 0;
	int fixed = (flags & MAP_FIXED);
	int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
	struct mm_struct *mm = current->mm;

	/* Sanity checks */
	BUG_ON(mm->task_size == 0);

	slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
	slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d, use_cache=%d\n",
		  addr, len, flags, topdown, use_cache);

	if (len > mm->task_size)
		return -ENOMEM;
	if (len & ((1ul << pshift) - 1))
		return -EINVAL;
	if (fixed && (addr & ((1ul << pshift) - 1)))
		return -EINVAL;
	if (fixed && addr > (mm->task_size - len))
		return -EINVAL;

	/* If hint, make sure it matches our alignment restrictions */
	if (!fixed && addr) {
		addr = _ALIGN_UP(addr, 1ul << pshift);
		slice_dbg(" aligned addr=%lx\n", addr);
	}

	/* First makeup a "good" mask of slices that have the right size
	 * already
	 */
	good_mask = slice_mask_for_size(mm, psize);
	slice_print_mask(" good_mask", good_mask);

	/* First check hint if it's valid or if we have MAP_FIXED */
	if ((addr != 0 || fixed) && (mm->task_size - len) >= addr) {

		/* Don't bother with hint if it overlaps a VMA */
		if (!fixed && !slice_area_is_free(mm, addr, len))
			goto search;

		/* Build a mask for the requested range */
		mask = slice_range_to_mask(addr, len);
		slice_print_mask(" mask", mask);

		/* Check if we fit in the good mask. If we do, we just return,
		 * nothing else to do
		 */
		if (slice_check_fit(mask, good_mask)) {
			slice_dbg(" fits good !\n");
			return addr;
		}

		/* We don't fit in the good mask, check what other slices are
		 * empty and thus can be converted
		 */
		potential_mask = slice_mask_for_free(mm);
		potential_mask.low_slices |= good_mask.low_slices;
		potential_mask.high_slices |= good_mask.high_slices;
		pmask_set = 1;
		slice_print_mask(" potential", potential_mask);
		if (slice_check_fit(mask, potential_mask)) {
			slice_dbg(" fits potential !\n");
			goto convert;
		}
	}

	/* If we have MAP_FIXED and failed the above step, then error out */
	if (fixed)
		return -EBUSY;

 search:
	slice_dbg(" search...\n");

	/* Now let's see if we can find something in the existing slices
	 * for that size
	 */
	addr = slice_find_area(mm, len, good_mask, psize, topdown, use_cache);
	if (addr != -ENOMEM) {
		/* Found within the good mask, we don't have to setup,
		 * we thus return directly
		 */
		slice_dbg(" found area at 0x%lx\n", addr);
		return addr;
	}

	/* Won't fit, check what can be converted */
	if (!pmask_set) {
		potential_mask = slice_mask_for_free(mm);
		potential_mask.low_slices |= good_mask.low_slices;
		potential_mask.high_slices |= good_mask.high_slices;
		pmask_set = 1;
		slice_print_mask(" potential", potential_mask);
	}

	/* Now let's see if we can find something in the existing slices
	 * for that size
	 */
	addr = slice_find_area(mm, len, potential_mask, psize, topdown,
			       use_cache);
	if (addr == -ENOMEM)
		return -ENOMEM;

	mask = slice_range_to_mask(addr, len);
	slice_dbg(" found potential area at 0x%lx\n", addr);
	slice_print_mask(" mask", mask);

 convert:
	slice_convert(mm, mask, psize);
	return addr;

}
EXPORT_SYMBOL_GPL(slice_get_unmapped_area);

unsigned long arch_get_unmapped_area(struct file *filp,
				     unsigned long addr,
				     unsigned long len,
				     unsigned long pgoff,
				     unsigned long flags)
{
	return slice_get_unmapped_area(addr, len, flags,
				       current->mm->context.user_psize,
				       0, 1);
}

unsigned long arch_get_unmapped_area_topdown(struct file *filp,
					     const unsigned long addr0,
					     const unsigned long len,
					     const unsigned long pgoff,
					     const unsigned long flags)
{
	return slice_get_unmapped_area(addr0, len, flags,
				       current->mm->context.user_psize,
				       1, 1);
}

unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
{
	u64 psizes;
	int index;

	if (addr < SLICE_LOW_TOP) {
		psizes = mm->context.low_slices_psize;
		index = GET_LOW_SLICE_INDEX(addr);
	} else {
		psizes = mm->context.high_slices_psize;
		index = GET_HIGH_SLICE_INDEX(addr);
	}

	return (psizes >> (index * 4)) & 0xf;
}
EXPORT_SYMBOL_GPL(get_slice_psize);

/*
 * This is called by hash_page when it needs to do a lazy conversion of
 * an address space from real 64K pages to combo 4K pages (typically
 * when hitting a non cacheable mapping on a processor or hypervisor
 * that won't allow them for 64K pages).
 *
 * This is also called in init_new_context() to change back the user
 * psize from whatever the parent context had it set to
 * N.B. This may be called before mm->context.id has been set.
 *
 * This function will only change the content of the {low,high)_slice_psize
 * masks, it will not flush SLBs as this shall be handled lazily by the
 * caller.
 */
void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
{
	unsigned long flags, lpsizes, hpsizes;
	unsigned int old_psize;
	int i;

	slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);

	spin_lock_irqsave(&slice_convert_lock, flags);

	old_psize = mm->context.user_psize;
	slice_dbg(" old_psize=%d\n", old_psize);
	if (old_psize == psize)
		goto bail;

	mm->context.user_psize = psize;
	wmb();

	lpsizes = mm->context.low_slices_psize;
	for (i = 0; i < SLICE_NUM_LOW; i++)
		if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
			lpsizes = (lpsizes & ~(0xful << (i * 4))) |
				(((unsigned long)psize) << (i * 4));

	hpsizes = mm->context.high_slices_psize;
	for (i = 0; i < SLICE_NUM_HIGH; i++)
		if (((hpsizes >> (i * 4)) & 0xf) == old_psize)
			hpsizes = (hpsizes & ~(0xful << (i * 4))) |
				(((unsigned long)psize) << (i * 4));

	mm->context.low_slices_psize = lpsizes;
	mm->context.high_slices_psize = hpsizes;

	slice_dbg(" lsps=%lx, hsps=%lx\n",
		  mm->context.low_slices_psize,
		  mm->context.high_slices_psize);

 bail:
	spin_unlock_irqrestore(&slice_convert_lock, flags);
}

/*
 * is_hugepage_only_range() is used by generic code to verify wether
 * a normal mmap mapping (non hugetlbfs) is valid on a given area.
 *
 * until the generic code provides a more generic hook and/or starts
 * calling arch get_unmapped_area for MAP_FIXED (which our implementation
 * here knows how to deal with), we hijack it to keep standard mappings
 * away from us.
 *
 * because of that generic code limitation, MAP_FIXED mapping cannot
 * "convert" back a slice with no VMAs to the standard page size, only
 * get_unmapped_area() can. It would be possible to fix it here but I
 * prefer working on fixing the generic code instead.
 *
 * WARNING: This will not work if hugetlbfs isn't enabled since the
 * generic code will redefine that function as 0 in that. This is ok
 * for now as we only use slices with hugetlbfs enabled. This should
 * be fixed as the generic code gets fixed.
 */
int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
			   unsigned long len)
{
	struct slice_mask mask, available;

	mask = slice_range_to_mask(addr, len);
	available = slice_mask_for_size(mm, mm->context.user_psize);

#if 0 /* too verbose */
	slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",
		 mm, addr, len);
	slice_print_mask(" mask", mask);
	slice_print_mask(" available", available);
#endif
	return !slice_check_fit(mask, available);
}