Re: [Xen-devel] trap bounce flags

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir@xxxxxxxxxxxxx> 25.04.07 12:56 >>>
>On 25/4/07 11:41, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:
>
>> Attached is my own proposed patch which I think cleans up all the issues.
>> Checking just flags in asm and keeping the null-bounce check in
>> init_int80_direct_trap() seems fine to me.
>
>The change of a movw $0 to a movb $TBF_EXCEPTION in that patch is wrong, by
>the way. Should be movb $0.

Which means there's not really a dependency on this being non-zero...

The patch looks otherwise okay to me, though I think there's one more
issue here: There's another suffix-less instruction (updating UREGS_rip
in int80_slow_path) - this must be a subq, and it must imply that no 32-bit
guest places an int $0x80 at 0xfffffffe.

And my patch has a not directly related adjustment removing the

        movl  $TRAP_syscall,UREGS_entry_vector+8(%rsp)

close to the end of compat_create_bounce_frame, as this is meaningless
here.


Jan


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