__copy_xstate_to_uabi_buf() copies either from the tasks XSAVE buffer
or from init_fpstate into the ptrace buffer. Dynamic features, like
XTILEDATA, have an all zeroes init state and are not saved in
init_fpstate, which means the corresponding bit is not set in the
xfeatures bitmap of the init_fpstate header.

But __copy_xstate_to_uabi_buf() retrieves addresses for both the tasks
xstate and init_fpstate unconditionally via __raw_xsave_addr().

So if the tasks XSAVE buffer has a dynamic feature set, then the
address retrieval for init_fpstate triggers the warning in
__raw_xsave_addr() which checks the feature bit in the init_fpstate
header.

Remove the address retrieval from init_fpstate for extended features.
They have an all zeroes init state so init_fpstate has zeros for them.
Then zeroing the user buffer for the init state is the same as copying
them from init_fpstate.

Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode")
Reported-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/kvm/20230221163655.920289-2-mizhang@google.com/
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/all/20230227210504.18520-2-chang.seok.bae%40intel.com
Cc: stable@vger.kernel.org

Pull x86 fpu updates from Ingo Molnar:

 - Replace zero-length array in struct xregs_state with flexible-array
   member, to help the enabling of stricter compiler checks.

 - Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads.

* tag 'x86-fpu-2023-02-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads
  x86/fpu: Replace zero-length array in struct xregs_state with flexible-array member

We don't set it on PF_KTHREAD threads as they never return to userspace,
and PF_IO_WORKER threads are identical in that regard. As they keep
running in the kernel until they die, skip setting the FPU flag on them.

More of a cosmetic thing that was found while debugging and
issue and pondering why the FPU flag is set on these threads.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/560c844c-f128-555b-40c6-31baff27537f@kernel.dk

Fix instrumentation bugs objtool found:

  vmlinux.o: warning: objtool: intel_idle_s2idle+0xd5: call to fpu_idle_fpregs() leaves .noinstr.text section
  vmlinux.o: warning: objtool: intel_idle_xstate+0x11: call to fpu_idle_fpregs() leaves .noinstr.text section
  vmlinux.o: warning: objtool: fpu_idle_fpregs+0x9: call to xfeatures_in_use() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195540.494977795@infradead.org

Pull x86 fpu updates from Dave Hansen:
 "There are two little fixes in here, one to give better XSAVE warnings
  and another to address some undefined behavior in offsetof().

  There is also a collection of patches to fix some issues with ptrace
  and the protection keys register (PKRU). PKRU is a real oddity because
  it is exposed in the XSAVE-related ABIs, but it is generally managed
  without using XSAVE in the kernel. This fix thankfully came with a
  selftest to ward off future regressions.

  Summary:

   - Clarify XSAVE consistency warnings

   - Fix up ptrace interface to protection keys register (PKRU)

   - Avoid undefined compiler behavior with TYPE_ALIGN"

* tag 'x86_fpu_for_6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Use _Alignof to avoid undefined behavior in TYPE_ALIGN
  selftests/vm/pkeys: Add a regression test for setting PKRU through ptrace
  x86/fpu: Emulate XRSTOR's behavior if the xfeatures PKRU bit is not set
  x86/fpu: Allow PKRU to be (once again) written by ptrace.
  x86/fpu: Add a pkru argument to copy_uabi_to_xstate()
  x86/fpu: Add a pkru argument to copy_uabi_from_kernel_to_xstate().
  x86/fpu: Take task_struct* in copy_sigframe_from_user_to_xstate()
  x86/fpu/xstate: Fix XSTATE_WARN_ON() to emit relevant diagnostics

WG14 N2350 specifies that it is an undefined behavior to have type
definitions within offsetof", see

  https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm

This specification is also part of C23.

Therefore, replace the TYPE_ALIGN macro with the _Alignof builtin to
avoid undefined behavior. (_Alignof itself is C11 and the kernel is
built with -gnu11).

ISO C11 _Alignof is subtly different from the GNU C extension
__alignof__. Latter is the preferred alignment and _Alignof the
minimal alignment. For long long on x86 these are 8 and 4
respectively.

The macro TYPE_ALIGN's behavior matches _Alignof rather than
__alignof__.

  [ bp: Massage commit message. ]

Signed-off-by: YingChi Long <me@inclyc.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20220925153151.2467884-1-me@inclyc.cn

The hardware XRSTOR instruction resets the PKRU register to its hardware
init value (namely 0) if the PKRU bit is not set in the xfeatures mask.
Emulating that here restores the pre-5.14 behavior for PTRACE_SET_REGSET
with NT_X86_XSTATE, and makes sigreturn (which still uses XRSTOR) and
ptrace behave identically. KVM has never used XRSTOR and never had this
behavior, so KVM opts-out of this emulation by passing a NULL pkru pointer
to copy_uabi_to_xstate().

Fixes: e84ba47e313d ("x86/fpu: Hook up PKRU into ptrace()")
Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-6-khuey%40kylehuey.com

Move KVM's PKRU handling code in fpu_copy_uabi_to_guest_fpstate() to
copy_uabi_to_xstate() so that it is shared with other APIs that write the
XSTATE such as PTRACE_SETREGSET with NT_X86_XSTATE.

This restores the pre-5.14 behavior of ptrace. The regression can be seen
by running gdb and executing `p $pkru`, `set $pkru = 42`, and `p $pkru`.
On affected kernels (5.14+) the write to the PKRU register (which gdb
performs through ptrace) is ignored.

[ dhansen: removed stable@ tag for now.  The ABI was broken for long
	   enough that this is not urgent material.  Let's let it stew
	   in tip for a few weeks before it's submitted to stable
	   because there are so many ABIs potentially affected. ]

Fixes: e84ba47e313d ("x86/fpu: Hook up PKRU into ptrace()")
Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-5-khuey%40kylehuey.com

In preparation for moving PKRU handling code out of
fpu_copy_uabi_to_guest_fpstate() and into copy_uabi_to_xstate(), add an
argument that copy_uabi_from_kernel_to_xstate() can use to pass the
canonical location of the PKRU value. For
copy_sigframe_from_user_to_xstate() the kernel will actually restore the
PKRU value from the fpstate, but pass in the thread_struct's pkru location
anyways for consistency.

Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-4-khuey%40kylehuey.com

Both KVM (through KVM_SET_XSTATE) and ptrace (through PTRACE_SETREGSET
with NT_X86_XSTATE) ultimately call copy_uabi_from_kernel_to_xstate(),
but the canonical locations for the current PKRU value for KVM guests
and processes in a ptrace stop are different (in the kvm_vcpu_arch and
the thread_state structs respectively).

In preparation for eventually handling PKRU in
copy_uabi_to_xstate, pass in a pointer to the PKRU location.

Signed-off-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20221115230932.7126-3-khuey%40kylehuey.com