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Re: [Qemu-devel] [PATCH 04/10] linux-user: init_guest_space: Correctly h
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PATCH 04/10] linux-user: init_guest_space: Correctly handle guest_start in commpage initialization |
Date: |
Fri, 9 Mar 2018 21:26:56 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
Le 28/12/2017 à 19:08, Luke Shumaker a écrit :
> From: Luke Shumaker <address@hidden>
>
> init_guest_commpage needs to check if the mapped space, which ends at
> real_start+real_size overlaps with where it needs to put the commpage,
> which is (assuming sane qemu_host_page_size) guest_base + 0xffff000, where
> guest_base is real_start - guest_start.
>
> [guest_base][ 0xffff0000 ][commpage]
> [guest_base][guest_start][real_size] [commpage]
> [ real_start ][real_size] [commpage]
> ^
> fail if this gap < 0
>
> Since init_guest_commpage wants to do everything relative to guest_base
> (rather than real_start), it obviously needs to be comparing 0xffff0000
> against guest_start+real_size, not just real_size.
>
> This bug has been present since 806d102141b99d4f1e55a97d68b7ea8c8ba3129f in
> 2012, but guest_start is usually 0, and prior to v2.11 real_size was
> usually much smaller than 0xffff0000, so it was uncommon for it to have
> made a difference.
>
> Signed-off-by: Luke Shumaker <address@hidden>
> ---
> linux-user/elfload.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Applied to my 'linux-user-for-2.12' branch.
Thanks,
Laurent