Re: [Qemu-devel] [PATCH for-2.0? 1/2] page_check_range: don't bail out early after unprotecting page

[Richard Henderson <rth@twiddle.net>]

On 04/03/2014 09:45 AM, Peter Maydell wrote:
> From: Andrei Warkentin <andrey.warkentin@gmail.com>
> 
> When checking a page range, if we found that a page was
> made read-only by QEMU because it contained translated code,
> we were incorrectly returning immediately after unprotecting
> that page, rather than continuing to check the entire range,
> so we might fail to unprotect pages later in the range, or
> might incorrectly return a "success" result even if later
> pages were not writable.
> 
> In particular, this could cause segfaults in a case where
> signals are delivered back to back on a target architecture
> which uses trampoline code in the stack frame (as AArch64
> currently does). The second signal causes a segfault because
> the frame cannot be written to (it was protected because
> we translated and executed the restorer trampoline, and the
> unprotect logic did not unprotect the whole range).
> 
> Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com
> [PMM: expanded commit message a bit]
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  translate-all.c | 1 -
>  1 file changed, 1 deletion(-)

Reviewed-by: Richard Henderson <rth@twiddle.net>


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