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94a855111e
been long in the making. It is a lighterweight software-only fix for Skylake-based cores where enabling IBRS is a big hammer and causes a significant performance impact. What it basically does is, it aligns all kernel functions to 16 bytes boundary and adds a 16-byte padding before the function, objtool collects all functions' locations and when the mitigation gets applied, it patches a call accounting thunk which is used to track the call depth of the stack at any time. When that call depth reaches a magical, microarchitecture-specific value for the Return Stack Buffer, the code stuffs that RSB and avoids its underflow which could otherwise lead to the Intel variant of Retbleed. This software-only solution brings a lot of the lost performance back, as benchmarks suggest: https://lore.kernel.org/all/20220915111039.092790446@infradead.org/ That page above also contains a lot more detailed explanation of the whole mechanism - Implement a new control flow integrity scheme called FineIBT which is based on the software kCFI implementation and uses hardware IBT support where present to annotate and track indirect branches using a hash to validate them - Other misc fixes and cleanups -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEzv7L6UO9uDPlPSfHEsHwGGHeVUoFAmOZp5EACgkQEsHwGGHe VUrZFxAAvi/+8L0IYSK4mKJvixGbTFjxN/Swo2JVOfs34LqGUT6JaBc+VUMwZxdb VMTFIZ3ttkKEodjhxGI7oGev6V8UfhI37SmO2lYKXpQVjXXnMlv/M+Vw3teE38CN gopi+xtGnT1IeWQ3tc/Tv18pleJ0mh5HKWiW+9KoqgXj0wgF9x4eRYDz1TDCDA/A iaBzs56j8m/FSykZHnrWZ/MvjKNPdGlfJASUCPeTM2dcrXQGJ93+X2hJctzDte0y Nuiw6Y0htfFBE7xoJn+sqm5Okr+McoUM18/CCprbgSKYk18iMYm3ZtAi6FUQZS1A ua4wQCf49loGp15PO61AS5d3OBf5D3q/WihQRbCaJvTVgPp9sWYnWwtcVUuhMllh ZQtBU9REcVJ/22bH09Q9CjBW0VpKpXHveqQdqRDViLJ6v/iI6EFGmD24SW/VxyRd 73k9MBGrL/dOf1SbEzdsnvcSB3LGzp0Om8o/KzJWOomrVKjBCJy16bwTEsCZEJmP i406m92GPXeaN1GhTko7vmF0GnkEdJs1GVCZPluCAxxbhHukyxHnrjlQjI4vC80n Ylc0B3Kvitw7LGJsPqu+/jfNHADC/zhx1qz/30wb5cFmFbN1aRdp3pm8JYUkn+l/ zri2Y6+O89gvE/9/xUhMohzHsWUO7xITiBavewKeTP9GSWybWUs= =cRy1 -----END PGP SIGNATURE----- Merge tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 core updates from Borislav Petkov: - Add the call depth tracking mitigation for Retbleed which has been long in the making. It is a lighterweight software-only fix for Skylake-based cores where enabling IBRS is a big hammer and causes a significant performance impact. What it basically does is, it aligns all kernel functions to 16 bytes boundary and adds a 16-byte padding before the function, objtool collects all functions' locations and when the mitigation gets applied, it patches a call accounting thunk which is used to track the call depth of the stack at any time. When that call depth reaches a magical, microarchitecture-specific value for the Return Stack Buffer, the code stuffs that RSB and avoids its underflow which could otherwise lead to the Intel variant of Retbleed. This software-only solution brings a lot of the lost performance back, as benchmarks suggest: https://lore.kernel.org/all/20220915111039.092790446@infradead.org/ That page above also contains a lot more detailed explanation of the whole mechanism - Implement a new control flow integrity scheme called FineIBT which is based on the software kCFI implementation and uses hardware IBT support where present to annotate and track indirect branches using a hash to validate them - Other misc fixes and cleanups * tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits) x86/paravirt: Use common macro for creating simple asm paravirt functions x86/paravirt: Remove clobber bitmask from .parainstructions x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit x86/Kconfig: Enable kernel IBT by default x86,pm: Force out-of-line memcpy() objtool: Fix weak hole vs prefix symbol objtool: Optimize elf_dirty_reloc_sym() x86/cfi: Add boot time hash randomization x86/cfi: Boot time selection of CFI scheme x86/ibt: Implement FineIBT objtool: Add --cfi to generate the .cfi_sites section x86: Add prefix symbols for function padding objtool: Add option to generate prefix symbols objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf objtool: Slice up elf_create_section_symbol() kallsyms: Revert "Take callthunks into account" x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces x86/retpoline: Fix crash printing warning x86/paravirt: Fix a !PARAVIRT build warning ...
130 lines
3.4 KiB
C
130 lines
3.4 KiB
C
#ifndef _ASM_X86_DISABLED_FEATURES_H
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#define _ASM_X86_DISABLED_FEATURES_H
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/* These features, although they might be available in a CPU
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* will not be used because the compile options to support
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* them are not present.
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*
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* This code allows them to be checked and disabled at
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* compile time without an explicit #ifdef. Use
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* cpu_feature_enabled().
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*/
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#ifdef CONFIG_X86_UMIP
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# define DISABLE_UMIP 0
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#else
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# define DISABLE_UMIP (1<<(X86_FEATURE_UMIP & 31))
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#endif
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#ifdef CONFIG_X86_64
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# define DISABLE_VME (1<<(X86_FEATURE_VME & 31))
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# define DISABLE_K6_MTRR (1<<(X86_FEATURE_K6_MTRR & 31))
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# define DISABLE_CYRIX_ARR (1<<(X86_FEATURE_CYRIX_ARR & 31))
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# define DISABLE_CENTAUR_MCR (1<<(X86_FEATURE_CENTAUR_MCR & 31))
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# define DISABLE_PCID 0
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#else
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# define DISABLE_VME 0
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# define DISABLE_K6_MTRR 0
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# define DISABLE_CYRIX_ARR 0
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# define DISABLE_CENTAUR_MCR 0
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# define DISABLE_PCID (1<<(X86_FEATURE_PCID & 31))
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#endif /* CONFIG_X86_64 */
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#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
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# define DISABLE_PKU 0
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# define DISABLE_OSPKE 0
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#else
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# define DISABLE_PKU (1<<(X86_FEATURE_PKU & 31))
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# define DISABLE_OSPKE (1<<(X86_FEATURE_OSPKE & 31))
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#endif /* CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS */
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#ifdef CONFIG_X86_5LEVEL
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# define DISABLE_LA57 0
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#else
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# define DISABLE_LA57 (1<<(X86_FEATURE_LA57 & 31))
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#endif
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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# define DISABLE_PTI 0
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#else
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# define DISABLE_PTI (1 << (X86_FEATURE_PTI & 31))
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#endif
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#ifdef CONFIG_RETPOLINE
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# define DISABLE_RETPOLINE 0
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#else
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# define DISABLE_RETPOLINE ((1 << (X86_FEATURE_RETPOLINE & 31)) | \
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(1 << (X86_FEATURE_RETPOLINE_LFENCE & 31)))
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#endif
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#ifdef CONFIG_RETHUNK
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# define DISABLE_RETHUNK 0
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#else
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# define DISABLE_RETHUNK (1 << (X86_FEATURE_RETHUNK & 31))
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#endif
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#ifdef CONFIG_CPU_UNRET_ENTRY
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# define DISABLE_UNRET 0
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#else
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# define DISABLE_UNRET (1 << (X86_FEATURE_UNRET & 31))
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#endif
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#ifdef CONFIG_CALL_DEPTH_TRACKING
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# define DISABLE_CALL_DEPTH_TRACKING 0
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#else
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# define DISABLE_CALL_DEPTH_TRACKING (1 << (X86_FEATURE_CALL_DEPTH & 31))
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#endif
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#ifdef CONFIG_INTEL_IOMMU_SVM
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# define DISABLE_ENQCMD 0
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#else
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# define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))
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#endif
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#ifdef CONFIG_X86_SGX
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# define DISABLE_SGX 0
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#else
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# define DISABLE_SGX (1 << (X86_FEATURE_SGX & 31))
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#endif
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#ifdef CONFIG_XEN_PV
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# define DISABLE_XENPV 0
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#else
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# define DISABLE_XENPV (1 << (X86_FEATURE_XENPV & 31))
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#endif
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#ifdef CONFIG_INTEL_TDX_GUEST
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# define DISABLE_TDX_GUEST 0
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#else
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# define DISABLE_TDX_GUEST (1 << (X86_FEATURE_TDX_GUEST & 31))
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#endif
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/*
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* Make sure to add features to the correct mask
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*/
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#define DISABLED_MASK0 (DISABLE_VME)
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#define DISABLED_MASK1 0
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#define DISABLED_MASK2 0
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#define DISABLED_MASK3 (DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
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#define DISABLED_MASK4 (DISABLE_PCID)
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#define DISABLED_MASK5 0
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#define DISABLED_MASK6 0
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#define DISABLED_MASK7 (DISABLE_PTI)
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#define DISABLED_MASK8 (DISABLE_XENPV|DISABLE_TDX_GUEST)
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#define DISABLED_MASK9 (DISABLE_SGX)
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#define DISABLED_MASK10 0
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#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \
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DISABLE_CALL_DEPTH_TRACKING)
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#define DISABLED_MASK12 0
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#define DISABLED_MASK13 0
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#define DISABLED_MASK14 0
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#define DISABLED_MASK15 0
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#define DISABLED_MASK16 (DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
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DISABLE_ENQCMD)
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#define DISABLED_MASK17 0
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#define DISABLED_MASK18 0
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#define DISABLED_MASK19 0
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#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 20)
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#endif /* _ASM_X86_DISABLED_FEATURES_H */
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