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From: Kees Cook <keescook@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Robert Dinse <nanook@eskimo.com>
Subject: Re: [PATCH v2 3/8] KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array
Date: Tue, 31 May 2022 11:04:05 -0700	[thread overview]
Message-ID: <202205311104.5D8D79E3F2@keescook> (raw)
In-Reply-To: <20220526210817.3428868-4-seanjc@google.com>

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

  reply	other threads:[~2022-05-31 18:04 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-26 21:08 [PATCH v2 0/8] KVM: x86: Emulator _regs fixes and cleanups Sean Christopherson
2022-05-26 21:08 ` [PATCH v2 1/8] KVM: x86: Grab regs_dirty in local 'unsigned long' Sean Christopherson
2022-05-26 21:08 ` [PATCH v2 2/8] KVM: x86: Harden _regs accesses to guard against buggy input Sean Christopherson
2022-05-26 21:08 ` [PATCH v2 3/8] KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array Sean Christopherson
2022-05-31 18:04   ` Kees Cook [this message]
2022-05-26 21:08 ` [PATCH v2 4/8] KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs Sean Christopherson
2022-05-26 21:08 ` [PATCH v2 5/8] KVM: x86: Reduce the number of emulator GPRs to '8' for 32-bit KVM Sean Christopherson
2022-05-31 18:04   ` Kees Cook
2022-05-26 21:08 ` [PATCH v2 6/8] KVM: x86: Bug the VM if the emulator accesses a non-existent GPR Sean Christopherson
2022-05-31 18:06   ` Kees Cook
2022-06-01  8:29   ` Vitaly Kuznetsov
2022-06-02 16:01     ` Sean Christopherson
2022-05-26 21:08 ` [PATCH v2 7/8] KVM: x86: Bug the VM if the emulator generates a bogus exception vector Sean Christopherson
2022-05-31 18:06   ` Kees Cook
2022-06-01  8:31   ` Vitaly Kuznetsov
2022-05-26 21:08 ` [PATCH v2 8/8] KVM: x86: Bug the VM on an out-of-bounds data read Sean Christopherson
2022-05-31 18:06   ` Kees Cook
2022-06-01  8:39   ` Vitaly Kuznetsov
2022-05-26 23:14 ` [PATCH v2 0/8] KVM: x86: Emulator _regs fixes and cleanups Robert Dinse
2022-06-08 12:23 ` Paolo Bonzini

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