Re: [patch] make exception handler in copy_user more robust

[david mosberger <dmosberger@gmail.com>]

Since we no longer support GCC 2.x, could that code perhaps be
simplified by taking advantage of tags?

  --david

On 9/6/05, Chen, Kenneth W <kenneth.w.chen@intel.com> wrote:
> The exception handler in copy user always expects fault occurs only on
> user space address and the fall back recovery code is written with that
> very assumption in mind.  Recent source code inspection revealed that
> while it worked splendid and to the expectation under normal circumstances,
> It broke down under unexpected condition where some address calculation
> might go outside the legal address range the original copy_user was
> called for.  This patch is to make copy_user exception handler more robust
> and to prevent potential memory corruption.
> 
> 
> Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
> 
> 
> --- linux-2.6.13/arch/ia64/lib/memcpy_mck.S.orig        2005-09-06 15:15:29.560795174 -0700
> +++ linux-2.6.13/arch/ia64/lib/memcpy_mck.S     2005-09-06 15:21:46.798095240 -0700
> @@ -625,8 +625,11 @@ EK(.ex_handler,  (p17)     st8     [dst1]=r39,8)
>         clrrrb
>         ;;
>         alloc   saved_pfs_stack=ar.pfs,3,3,3,0
> +       cmp.lt  p8,p0=A,r0
>         sub     B = dst0, saved_in0     // how many byte copied so far
>         ;;
> +(p8)   mov     A = 0;                  // A shouldn't be negative, cap it
> +       ;;
>         sub     C = A, B
>         sub     D = saved_in2, A
>         ;;
> 
> -
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