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[PATCH RFC] x86: SYSENTER/SYSEXIT are unavailable in 64-bit mode on AMD

H.J. Lu hjl.tools@gmail.com
Mon Nov 11 17:13:00 GMT 2019 
On Mon, Nov 11, 2019 at 4:01 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> opcodes/
> 2019-11-XX  Jan Beulich  <jbeulich@suse.com>
>
>         * i386-opc.tbl (sysenter, sysexit): Split into AMD64 and Intel64
>         forms.
>         * i386-tbl.h: Re-generate.
> ---
> RFC because this is liable to cause problems for existing code, but I
> think we should still correct this. We may want to have a directive
> (besides the command line option) such that the accepted ISA can be
> overridden in a more fine granular manner.

I think it is an overkill.

> --- a/opcodes/i386-opc.tbl
> +++ b/opcodes/i386-opc.tbl
> @@ -891,8 +891,10 @@ rdmsr, 0, 0xf32, None, 2, Cpu586, No_bSu
>  cmpxchg8b, 1, 0xfc7, 0x1, 2, Cpu586, Modrm|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_ldSuf|IsLockable|NoRex64|HLEPrefixOk, { Qword|Unspecified|BaseIndex }
>
>  // Pentium II/Pentium Pro extensions.
> -sysenter, 0, 0xf34, None, 2, Cpu686, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
> -sysexit, 0, 0xf35, None, 2, Cpu686, No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
> +sysenter, 0, 0xf34, None, 2, Cpu686, Intel64|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
> +sysenter, 0, 0xf34, None, 2, Cpu686|CpuNo64, AMD64|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
> +sysexit, 0, 0xf35, None, 2, Cpu686, Intel64|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
> +sysexit, 0, 0xf35, None, 2, Cpu686|CpuNo64, AMD64|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { 0 }
>  fxsave, 1, 0xfae, 0x0, 2, CpuFXSR, Modrm|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_ldSuf, { Unspecified|BaseIndex }
>  fxsave64, 1, 0xfae, 0x0, 2, CpuFXSR|Cpu64, Modrm|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf|Rex64, { Unspecified|BaseIndex }
>  fxrstor, 1, 0xfae, 0x1, 2, CpuFXSR, Modrm|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_ldSuf, { Unspecified|BaseIndex }

Are there any usages in 64-bit mode?  If not, just disallow them in 64-bit mode.

-- 
H.J.
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