Messages in this thread | | | Date | Thu, 10 Aug 2017 09:42:32 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v4 1/2] x86/unwind: add ORC unwinder |
| |
On Thu, Aug 10, 2017 at 09:09:03AM -0500, Josh Poimboeuf wrote: > static inline notrace unsigned long arch_local_save_flags(void) > { > return PVOP_CALLEE0(unsigned long, pv_irq_ops.save_fl, > "pushfq; popq %rax", CPU_FEATURE_NATIVE, > "call __raw_callee_save_xen_save_fl", CPU_FEATURE_XEN, > "call __raw_callee_save_vsmp_save_fl", CPU_FEATURE_VSMP, > "call __raw_callee_save_lguest_save_fl", CPU_FEATURE_LGUEST); > }
Just a few clarifications on this idea:
It would probably be better to have the PVOP macros do the function name translation, so maybe it would be something like this instead:
return PVOP_CALLEE0(unsigned long, pv_irq_ops.save_fl, "pushfq; popq %rax", CPU_FEATURE_NATIVE, xen_save_fl, CPU_FEATURE_XEN, vsmp_save_fl, CPU_FEATURE_VSMP, lguest_save_fl, CPU_FEATURE_LGUEST);
One issue is that it would fail to link if CONFIG_XEN or CONFIG_LGUEST_GUEST isn't set. However I've seen some crazy macro magic which lets you detect the number of variable arguments. So if we got that to work, it could be:
return PVOP_CALLEE0(unsigned long, pv_irq_ops.save_fl, "pushfq; popq %rax", CPU_FEATURE_NATIVE, #ifdef CONFIG_XEN xen_save_fl, CPU_FEATURE_XEN, #endif vsmp_save_fl, CPU_FEATURE_VSMP, #ifdef CONFIG_LGUEST_GUEST lguest_save_fl, CPU_FEATURE_LGUEST, #endif );
And then maybe the PVOP_CALL macros could detect the number of arguments and call the corresponding version of ALTERNATIVE_X. Macro fun :-)
> Which would eventually translate to something like: > > asm volatile(ALTERNATIVE_4("call *pv_irq_ops.save_fl", > "pushfq; popq %rax", CPU_FEATURE_NATIVE, > "call __raw_callee_save_xen_save_fl", CPU_FEATURE_XEN, > "call __raw_callee_save_vsmp_save_fl", CPU_FEATURE_VSMP, > "call __raw_callee_save_lguest_save_fl", CPU_FEATURE_LGUEST > : ... pvop clobber stuff ... ); > > where ALTERNATIVE_4 is a logical extension of ALTERNATIVE_2 and > CPU_FEATURE_NATIVE would always be set. > > It might need some more macro magic, but if it worked I think it would > be a lot clearer than the current voodoo. > > Thoughts?
-- Josh
| |