Re: [PATCH v3 08/16] x86/extable: Add support for immediate form MSR instructions

[Jürgen Groß]

On 18.02.26 16:48, Andrew Cooper wrote:
> Ideally please CC xen-devel on all patches if you've CC'd some, or at
> least CC me on all patches that you partially send to xen-devel.  Having
> only 4 patches of the series is very awkward to reply to.
>
> > + /* + * To maintain consistency with existing RDMSR and WRMSR(NS)
> > instructions, + * the register operand for immediate form MSR
> > instructions is ALWAYS + * encoded as RAX in <asm/msr.h> for reading
> > or writing the MSR value. + */ + u64 msr_val = regs->ax;
>
> This is unsafe.  It assumes that the only source of MSR $IMM
> instructions anywhere are the wrappers.
>
> While this might be the wish of the developers, that doesn't make it true.
>
>
> You've already decoded the instruction and got the ModRM byte, so either
> check that it really is encoding %rax, or select the proper GPR based on
> ModRM.

I'll use the proper GPR.

Thanks,


Juergen

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