[PATCH] arch/powerpc/mm/slice: Cleanup leftover use of task_size
Aneesh Kumar K.V
aneesh.kumar at linux.vnet.ibm.com
Thu Apr 13 20:58:46 AEST 2017
ricklind at linux.vnet.ibm.com writes:
> From: Rick Lindsley <ricklind at linux.vnet.ibm.com>
>
> With the 512TB virtual addressing capability, a new field was added to
> the paca and mm_context (addr_limit) to track the process's desire to
> use the larger addressing space. Functions in the radix-enabled path
> (mmap.c) were modified to inspect this value when deciding whether to
> grant or deny requests in that range.
>
> However, the non-radix path falls through to the old, hashed slice code
> (slice_get_unmapped_area, etc.) and these code paths still inspect
> task_size. The same attention to addr_limit made in (for example)
> radix__arch_get_unmapped_area() should also be applied to (correspondingly)
> slice_get_unmapped_area().
I would suggest we don't do this change now. But rather we audit the
usage of TASK_SIZE(), mm->task_size and move them correctly to
mm->task_size and mm->context.addr_limit. The context.addr_limit is
added as an optimization for slice_mask copy and we need to closely
audit to make sure we can use that as a boundary condition for error
checking in case of mmap.
IMHO we should do this while consoliding
TASK_SIZE/mm->task_size/mm->context.addr_limit.
A previous attempt can be found at
https://lkml.kernel.org/r/20161230155634.8692-1-dsafonov@virtuozzo.com
We should start working in that direction. Some arch even have thread_info.addr_limit
>
> Signed-off-by: Rick Lindsley <ricklind at linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/slice.c | 12 ++++++------
> 1 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
> index 251b6ba..c023bff 100644
> --- a/arch/powerpc/mm/slice.c
> +++ b/arch/powerpc/mm/slice.c
> @@ -96,7 +96,7 @@ static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
> {
> struct vm_area_struct *vma;
>
> - if ((mm->task_size - len) < addr)
> + if ((mm->addr_limit - len) < addr)
> return 0;
> vma = find_vma(mm, addr);
> return (!vma || (addr + len) <= vma->vm_start);
> @@ -133,7 +133,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret)
> if (!slice_low_has_vma(mm, i))
> ret->low_slices |= 1u << i;
>
> - if (mm->task_size <= SLICE_LOW_TOP)
> + if (mm->addr_limit <= SLICE_LOW_TOP)
> return;
>
> for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.addr_limit); i++)
> @@ -444,20 +444,20 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> bitmap_zero(compat_mask.high_slices, SLICE_NUM_HIGH);
>
> /* Sanity checks */
> - BUG_ON(mm->task_size == 0);
> + BUG_ON(mm->addr_limit == 0);
> VM_BUG_ON(radix_enabled());
>
> slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
> slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
> addr, len, flags, topdown);
>
> - if (len > mm->task_size)
> + if (len > mm->addr_limit)
> return -ENOMEM;
> if (len & ((1ul << pshift) - 1))
> return -EINVAL;
> if (fixed && (addr & ((1ul << pshift) - 1)))
> return -EINVAL;
> - if (fixed && addr > (mm->task_size - len))
> + if (fixed && addr > (mm->addr_limit - len))
> return -ENOMEM;
>
> /* If hint, make sure it matches our alignment restrictions */
> @@ -465,7 +465,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
> addr = _ALIGN_UP(addr, 1ul << pshift);
> slice_dbg(" aligned addr=%lx\n", addr);
> /* Ignore hint if it's too large or overlaps a VMA */
> - if (addr > mm->task_size - len ||
> + if (addr > mm->addr_limit - len ||
> !slice_area_is_free(mm, addr, len))
> addr = 0;
> }
> --
> 1.7.1
-aneesh
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