linux/arch/ia64
Linus Torvalds 94a855111e - 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
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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
  ...
2022-12-14 15:03:00 -08:00
..
configs ia64: update config files 2022-10-11 18:51:10 -07:00
hp/common ACPI: make remove callback of ACPI driver void 2022-11-23 19:11:22 +01:00
include MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
kernel ia64: replace IS_ERR() with IS_ERR_VALUE() 2022-11-18 13:55:07 -08:00
lib Merge branch 'work.csum_and_copy' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-10-12 16:24:13 -07:00
mm hugetlb: simplify hugetlb handling in follow_page_mask 2022-11-08 17:37:10 -08:00
pci PCI/sysfs: Find shadow ROM before static attribute initialization 2022-01-26 10:41:21 -06:00
scripts kbuild: remove PYTHON variable 2021-02-01 10:37:19 +09:00
uv ia64: remove support for machvecs 2019-08-16 14:32:26 -07:00
install.sh kbuild: factor out the common installation code into scripts/install.sh 2022-05-11 21:45:53 +09:00
Kbuild ia64: move core-y in arch/ia64/Makefile to arch/ia64/Kbuild 2021-09-03 08:17:20 +09:00
Kconfig arch: Introduce CONFIG_FUNCTION_ALIGNMENT 2022-10-17 16:40:58 +02:00
Kconfig.debug ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG_PRINTK 2021-10-04 10:45:58 +02:00
Makefile arch: Introduce CONFIG_FUNCTION_ALIGNMENT 2022-10-17 16:40:58 +02:00