Re: [PATCH v2 3/8] KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array

Kees Cook
2022-05-31T18:04:12Z

On Thu, May 26, 2022 at 09:08:12PM +0000, Sean Christopherson wrote:
> Omit RIP from the emulator's _regs array, which is used only for GPRs,
> i.e. registers that can be referenced via ModRM and/or SIB bytes. The
> emulator uses the dedicated _eip field for RIP, and manually reads from
> _eip to handle RIP-relative addressing.
>
> To avoid an even bigger, slightly more dangerous change, hardcode the
> number of GPRs to 16 for the time being even though 32-bit KVM's emulator
> technically should only have 8 GPRs. Add a TODO to address that in a
> future commit.
>
> See also the comments above the read_gpr() and write_gpr() declarations,
> and obviously the handling in writeback_registers().
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook