On Mon, Jul 23, 2018 at 06:48:00PM -0700, Andy Lutomirski wrote: > On 07/23/2018 05:55 AM, Fenghua Yu wrote: > >The instructions can be implemented in intrinsic functions in future > >GCC. But the vDSO interfaces are available to user without the > I'm not convinced that any of this belongs in the vDSO at all. You could > just add AT_HWCAP (or AT_HWCAP2) flags for the new instructions. Or user
Thomas asked to use vDSO. Please see the discussion thread: https://lkml.org/lkml/2018/6/19/316 > code could use CPUID just like for any other new instruction. But, if there > really is some compelling reason to add this to the vDSO, then see below: > >+notrace bool __vdso_movdiri_supported(void) > >+{ > >+ return _vdso_funcs_data->movdiri_supported; > return static_cpu_has(X86_FEATURE_MOVDIRI); But boot_cpu_data (used in static_cpu_has) cannot be accessed by user unless mapped in VVAR. So this change cannot be compiled. > And all the VVAR stuff can be removed. The VVAR stuff needs to map the kernel data _vdso_funcs_data to user space before user can access it. Thanks. -Fenghua
