Messages in this thread | | | Date | Mon, 27 Mar 2023 19:47:46 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v16 8/8] x86/smpboot: Allow parallel bringup for SEV-ES |
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On Thu, Mar 23, 2023 at 10:23:02AM -0400, Brian Gerst wrote: > Making sure that the stack protector is either disabled or properly > set up, and disabling any instrumentation/profiling/debug crap that > isn't initialized yet.
Lemme dump brain of what Tom and I were talking about today so that it is documented somewhere.
* re: stack protector: I was thinking to mark this function
__attribute__((no_stack_protector))
but gcc added the function attribute way later:
~/src/gcc/gcc.git> git tag --contains 346b302d09c1e6db56d9fe69048acb32fbb97845 basepoints/gcc-12 basepoints/gcc-13 releases/gcc-11.1.0 releases/gcc-11.2.0 releases/gcc-11.3.0 releases/gcc-12.1.0 releases/gcc-12.2.0
which means, that function would have to live somewhere in a file which has stack protector disabled. One possible place would be arch/x86/mm/mem_encrypt_identity.c which is kinda related.
* re: stack: in order to be able to call a C function that early, we'd have to put the VA of the initial stack back into %rsp as we switch pagetables a bit earlier in there (thx Tom).
So by then, doing all that cargo-cult just in order to not have a bunch of lines in asm doesn't sound all that great anymore.
* The __head per-function attribute is easily solved by lifting the __head define into a common header.
So meh, dunno. I guess we can do the asm thing for now, until a cleaner solution without too many warts presents itself.
As to exporting cc_vendor:
https://lore.kernel.org/r/20230318115634.9392-1-bp@alien8.de
I'll redo those and the SEV-ES patch won't have to add cc_get_vendor().
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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