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Date: Thu, 20 Oct 2022 16:51:00 +0000 From: Andrew Cooper <Andrew.Cooper3@...rix.com> To: Evgeniy Baskov <baskov@...ras.ru> CC: Ard Biesheuvel <ardb@...nel.org>, Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Alexey Khoroshilov <khoroshilov@...ras.ru>, "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>, "x86@...nel.org" <x86@...nel.org>, "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>, Andrew Cooper <Andrew.Cooper3@...rix.com> Subject: Re: [PATCH 06/16] x86/boot: Setup memory protection for bzImage code On 20/10/2022 14:30, Evgeniy Baskov wrote: > On 2022-10-19 10:57, Andrew Cooper wrote: >> On 06/09/2022 11:41, Evgeniy Baskov wrote: >>> diff --git a/arch/x86/boot/compressed/head_64.S >>> b/arch/x86/boot/compressed/head_64.S >>> index 5273367283b7..889ca7176aa7 100644 >>> --- a/arch/x86/boot/compressed/head_64.S >>> +++ b/arch/x86/boot/compressed/head_64.S >>> @@ -602,6 +603,28 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) >>> jmp *%rax >>> SYM_FUNC_END(.Lrelocated) >>> >>> +SYM_FUNC_START_LOCAL_NOALIGN(startup32_enable_nx_if_supported) >>> + pushq %rbx >>> + >>> + leaq has_nx(%rip), %rcx >>> + >>> + mov $0x80000001, %eax >>> + cpuid >>> + btl $20, %edx >> >> btl $(X86_FEATURE_NX & 31), %edx >> >> But also need to check for the availability of the extended leaf in the >> first place. > > Yes, thank you for suggestion, that looks more readable. I will > also add the leaf node check. Is there any processor though that > supports long mode and does not support 0x80000001 leaf node? No, good point. The Long Mode feature bit is in this leaf too. ~Andrew
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