| Date | Fri, 28 Aug 2020 20:13:46 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v6 31/76] x86/head/64: Setup MSR_GS_BASE before calling into C code |
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On Mon, Aug 24, 2020 at 10:54:26AM +0200, Joerg Roedel wrote: > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 2b2e91627221..800053219054 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -78,6 +78,14 @@ SYM_CODE_START_NOALIGN(startup_64) > call startup_64_setup_env > popq %rsi > > + /* > + * Setup %gs here already to make stack-protector work - it needs to be > + * setup again after the switch to kernel addresses. The address read > + * from initial_gs is a kernel address, so it needs to be adjusted first > + * for the identity mapping. > + */ > + movl $MSR_GS_BASE,%ecx
I'm confused: is this missing those three lines:
movl initial_gs(%rip),%eax movl initial_gs+4(%rip),%edx wrmsr
as it is done in secondary_startup_64 ?
Or why would you otherwise put 0xc0000101 in %ecx and not do anything with it...
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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