On Fri, Aug 12, 2016 at 09:29:10AM -0500, Josh Poimboeuf wrote:
> Convert arch_within_stack_frames() to use the new unwinder.
>
> Boot tested with CONFIG_HARDENED_USERCOPY.
>
> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
> ---
> arch/x86/lib/usercopy.c | 25 +++++++++++++++++++------
> 1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
> index 96ce151..9d0913c 100644
> --- a/arch/x86/lib/usercopy.c
> +++ b/arch/x86/lib/usercopy.c
> @@ -50,12 +50,21 @@ int arch_within_stack_frames(const void * const stack,
> const void * const stackend,
> const void *obj, unsigned long len)
> {
> - const void *frame = NULL;
> - const void *oldframe;
> + struct unwind_state state;
> + const void *frame, *oldframe;
> +
> + unwind_start(&state, current, NULL, NULL);
> +
> + if (!unwind_next_frame(&state))
> + return 0;
> +
> + oldframe = unwind_get_stack_ptr(&state);
> +
> + if (!unwind_next_frame(&state))
> + return 0;
> +
> + frame = unwind_get_stack_ptr(&state);
>
> - oldframe = __builtin_frame_address(2);
> - if (oldframe)
> - frame = __builtin_frame_address(3);
> /*
> * low ----------------------------------------------> high
> * [saved bp][saved ip][args][local vars][saved bp][saved ip]
> @@ -71,8 +80,12 @@ int arch_within_stack_frames(const void * const stack,
> */
> if (obj + len <= frame)
> return obj >= oldframe + 2 * sizeof(void *) ? 1 : -1;
> +
> + if (!unwind_next_frame(&state))
> + return 0;
I think there's another issue here. This return needs to be tweaked.
IIUC, if it reliably reaches the end of the stack without finding the
object, it should return -1, but if there's something wrong with the
frame pointers which prevents the unwinder from reaching the end of the
stack, it should return 0.
--
Josh
