linux/tools
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
..
accounting tools/accounting/procacct: remove some unused variables 2022-11-18 13:55:09 -08:00
arch platform-drivers-x86 for v6.2-1 2022-12-12 10:47:10 -08:00
bootconfig
bpf bpftool: Fix memory leak in do_build_table_cb 2022-12-06 21:20:42 +01:00
build perf bpf: Fix build with libbpf 0.7.0 by checking if bpf_program__set_insns() is available 2022-10-25 17:40:48 -03:00
certs
cgroup
counter
debugging
edid
firewire
firmware
gpio
hv
iio tools: iio: iio_generic_buffer: Fix read size 2022-11-01 08:48:13 +00:00
include - Add the call depth tracking mitigation for Retbleed which has 2022-12-14 15:03:00 -08:00
io_uring
kvm/kvm_stat tools/kvm_stat: update exit reasons for vmx/svm/aarch64/userspace 2022-11-09 12:26:52 -05:00
laptop
leds
lib libbpf: Parse usdt args without offset on x86 (e.g. 8@(%rsp)) 2022-12-06 16:16:50 -08:00
memory-model tools/memory-model: Weaken ctrl dependency definition in explanation.txt 2022-10-18 15:14:52 -07:00
objtool - Add the call depth tracking mitigation for Retbleed which has 2022-12-14 15:03:00 -08:00
pci
pcmcia
perf Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-11-17 18:30:39 -08:00
power ACPI updates for 6.2-rc1 2022-12-12 13:38:17 -08:00
rcu
scripts
spi
testing memblock: extend test coverage 2022-12-14 12:17:57 -08:00
thermal
time
tracing rtla: Fix exit status when returning from calls to usage() 2022-12-09 18:06:24 -05:00
usb
verification Documentation/rv: Add verification/rv man pages 2022-12-09 18:06:24 -05:00
virtio
vm MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
wmi
Makefile