Re: [RFC PATCH v2] linux-user: Use FD_32BIT_MODE fd flag for 32-bit guests

[Laurent Vivier]

Le 23/06/2020 à 12:01, Peter Maydell a écrit :
> If the guest is 32 bit then there is a potential problem if the
> host gives us back a 64-bit sized value that we can't fit into
> the ABI the guest requires. This is a theoretical issue for many
> syscalls, but a real issue for directory reads where the host
> is using ext3 or ext4. There the 'offset' values retured via
> the getdents syscall are hashes, and on a 64-bit system they
> will always fill the full 64 bits.
> 
> Use the FD_32BIT_MODE fd flag to tell the kernel to stick
> to 32-bit sized hashes for fds used by the guest.
> 
> This is an RFC patch because the kernel patch that adds the
> new fd flag hasn't yet been accepted upstream. The kernel
> patch is:
>  https://patchew.org/QEMU/20200529072017.2906-1-linus.walleij@linaro.org/
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> This is just a minor update of the testing patch I sent out in the
> thread discussing Linus's v1 kernel patch.
> 
>  linux-user/syscall.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>