Messages in this thread | | | Subject | Re: [PATCH v5 04/27] x86/fpu/xstate: Add XSAVES system states for shadow stack | From | Dave Hansen <> | Date | Thu, 8 Nov 2018 13:48:54 -0800 |
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On 11/8/18 1:22 PM, Andy Lutomirski wrote: >> +struct cet_kernel_state { >> + u64 kernel_ssp; /* kernel shadow stack */ >> + u64 pl1_ssp; /* ring-1 shadow stack */ >> + u64 pl2_ssp; /* ring-2 shadow stack */ >> +} __packed; >> + > Why are these __packed? It seems like it'll generate bad code for no > obvious purpose.
It's a hardware-defined in-memory structure. Granted, we'd need a really wonky compiler to make that anything *other* than a nicely-packed 24-byte structure, but the __packed makes it explicit.
It is probably a really useful long-term thing to stop using __packed and start using "__hw_defined" or something that #defines down to __packed.
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