linux/Documentation/x86
Linus Torvalds 1423e2660c Fixes and improvements for FPU handling on x86:
- Prevent sigaltstack out of bounds writes. The kernel unconditionally
     writes the FPU state to the alternate stack without checking whether
     the stack is large enough to accomodate it.
 
     Check the alternate stack size before doing so and in case it's too
     small force a SIGSEGV instead of silently corrupting user space data.
 
   - MINSIGSTKZ and SIGSTKSZ are constants in signal.h and have never been
     updated despite the fact that the FPU state which is stored on the
     signal stack has grown over time which causes trouble in the field
     when AVX512 is available on a CPU. The kernel does not expose the
     minimum requirements for the alternate stack size depending on the
     available and enabled CPU features.
 
     ARM already added an aux vector AT_MINSIGSTKSZ for the same reason.
     Add it to x86 as well
 
   - A major cleanup of the x86 FPU code. The recent discoveries of XSTATE
     related issues unearthed quite some inconsistencies, duplicated code
     and other issues.
 
     The fine granular overhaul addresses this, makes the code more robust
     and maintainable, which allows to integrate upcoming XSTATE related
     features in sane ways.
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Merge tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fpu updates from Thomas Gleixner:
 "Fixes and improvements for FPU handling on x86:

   - Prevent sigaltstack out of bounds writes.

     The kernel unconditionally writes the FPU state to the alternate
     stack without checking whether the stack is large enough to
     accomodate it.

     Check the alternate stack size before doing so and in case it's too
     small force a SIGSEGV instead of silently corrupting user space
     data.

   - MINSIGSTKZ and SIGSTKSZ are constants in signal.h and have never
     been updated despite the fact that the FPU state which is stored on
     the signal stack has grown over time which causes trouble in the
     field when AVX512 is available on a CPU. The kernel does not expose
     the minimum requirements for the alternate stack size depending on
     the available and enabled CPU features.

     ARM already added an aux vector AT_MINSIGSTKSZ for the same reason.
     Add it to x86 as well.

   - A major cleanup of the x86 FPU code. The recent discoveries of
     XSTATE related issues unearthed quite some inconsistencies,
     duplicated code and other issues.

     The fine granular overhaul addresses this, makes the code more
     robust and maintainable, which allows to integrate upcoming XSTATE
     related features in sane ways"

* tag 'x86-fpu-2021-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits)
  x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() again
  x86/fpu/signal: Let xrstor handle the features to init
  x86/fpu/signal: Handle #PF in the direct restore path
  x86/fpu: Return proper error codes from user access functions
  x86/fpu/signal: Split out the direct restore code
  x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing()
  x86/fpu/signal: Sanitize the xstate check on sigframe
  x86/fpu/signal: Remove the legacy alignment check
  x86/fpu/signal: Move initial checks into fpu__restore_sig()
  x86/fpu: Mark init_fpstate __ro_after_init
  x86/pkru: Remove xstate fiddling from write_pkru()
  x86/fpu: Don't store PKRU in xstate in fpu_reset_fpstate()
  x86/fpu: Remove PKRU handling from switch_fpu_finish()
  x86/fpu: Mask PKRU from kernel XRSTOR[S] operations
  x86/fpu: Hook up PKRU into ptrace()
  x86/fpu: Add PKRU storage outside of task XSAVE buffer
  x86/fpu: Dont restore PKRU in fpregs_restore_userspace()
  x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi()
  x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()
  x86/fpu: Rename __fpregs_load_activate() to fpregs_restore_userregs()
  ...
2021-07-07 11:12:01 -07:00
..
i386 Documentation: x86: convert i386/IO-APIC.txt to reST 2019-05-08 14:34:11 -06:00
x86_64 doc: Remove references to IBM Calgary 2021-06-10 18:19:36 +02:00
amd-memory-encryption.rst x86/msr: Rename MSR_K8_SYSCFG to MSR_AMD64_SYSCFG 2021-05-10 07:51:38 +02:00
boot.rst docs: x86: avoid using ReST :doc:foo markup 2021-06-17 13:24:39 -06:00
booting-dt.rst dt: Remove booting-without-of.rst 2020-10-13 13:33:16 -05:00
buslock.rst Documentation/x86: Add ratelimit in buslock.rst 2021-05-18 16:39:31 +02:00
cpuinfo.rst Documentation/x86: Add documentation for /proc/cpuinfo feature flags 2020-09-01 11:07:15 +02:00
earlyprintk.rst Documentation: x86: earlyprintk: drop doubled words 2020-07-13 09:47:38 -06:00
elf_auxvec.rst x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ 2021-05-19 12:18:45 +02:00
entry_64.rst Documentation: x86: convert entry_64.txt to reST 2019-05-08 14:34:09 -06:00
exception-tables.rst Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-03-31 11:04:05 -07:00
features.rst docs: archis: add a per-architecture features list 2020-12-03 15:10:15 -07:00
index.rst Fixes and improvements for FPU handling on x86: 2021-07-07 11:12:01 -07:00
intel_txt.rst docs: x86: move two x86-specific files to x86 arch dir 2019-07-15 11:03:01 -03:00
intel-iommu.rst docs: prevent warnings due to autosectionlabel 2020-03-20 17:01:29 -06:00
kernel-stacks.rst Some late arriving documentation changes. In particular, this contains the 2019-05-10 13:24:53 -04:00
mds.rst x86/speculation/mds: Improve CPU buffer clear documentation 2019-05-16 09:05:12 +02:00
microcode.rst Documentation: x86: convert microcode.txt to reST 2019-05-08 14:34:11 -06:00
mtrr.rst docs: x86: avoid using ReST :doc:foo markup 2021-06-17 13:24:39 -06:00
orc-unwinder.rst Documentation: x86: convert orc-unwinder.txt to reST 2019-05-08 14:34:11 -06:00
pat.rst remove ioremap_nocache and devm_ioremap_nocache 2020-01-06 09:45:59 +01:00
pti.rst Documentation: x86: convert pti.txt to reST 2019-05-08 14:34:10 -06:00
resctrl.rst Documentation/x86: Rename resctrl_ui.rst and add two errata to the file 2020-10-27 16:47:00 +01:00
sgx.rst x86/sgx: Introduce virtual EPC for use by KVM guests 2021-04-06 09:43:17 +02:00
sva.rst Documentation/x86: Add documentation for SVA (Shared Virtual Addressing) 2020-09-17 19:29:42 +02:00
tlb.rst Documentation: x86: convert tlb.txt to reST 2019-05-08 14:34:10 -06:00
topology.rst x86/CPU/AMD: Save AMD NodeId as cpu_die_id 2020-11-19 11:43:13 +01:00
tsx_async_abort.rst x86/speculation/taa: Add documentation for TSX Async Abort 2019-10-28 08:37:00 +01:00
usb-legacy-support.rst Documentation: x86: convert usb-legacy-support.txt to reST 2019-05-08 14:34:11 -06:00
zero-page.rst Documentation: x86: convert zero-page.txt to reST 2019-05-08 14:34:10 -06:00