linux-stable.git/arch/x86/kernel/fpu/init.c, branch linux-6.3.y

x86/fpu: Use _Alignof to avoid undefined behavior in TYPE_ALIGN

2022-11-22T16:13:03+00:00

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 
Signed-off-by: Borislav Petkov 
Reviewed-by: Nick Desaulniers 
Link: https://lore.kernel.org/r/20220925153151.2467884-1-me@inclyc.cn

x86/fpu: Configure init_fpstate attributes orderly

2022-10-17T13:44:25+00:00

The init_fpstate setup code is spread out and out of order. The init image
is recorded before its scoped features and the buffer size are determined.

Determine the scope of init_fpstate components and its size before
recording the init state. Also move the relevant code together.

Signed-off-by: Chang S. Bae 
Signed-off-by: Thomas Gleixner 
Acked-by: neelnatu@google.com
Link: https://lore.kernel.org/r/20220824191223.1248-2-chang.seok.bae@intel.com

x86/fpu: Add fpu_state_config::legacy_features

2021-10-26T08:18:09+00:00

The upcoming prctl() which is required to request the permission for a
dynamically enabled feature will also provide an option to retrieve the
supported features. If the CPU does not support XSAVE, the supported
features would be 0 even when the CPU supports FP and SSE.

Provide separate storage for the legacy feature set to avoid that and fill
in the bits in the legacy init function.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Chang S. Bae 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211021225527.10184-6-chang.seok.bae@intel.com

x86/fpu: Move xstate feature masks to fpu_*_cfg

2021-10-21T18:36:58+00:00

Move the feature mask storage to the kernel and user config
structs. Default and maximum feature set are the same for now.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211014230739.352041752@linutronix.de

x86/fpu: Move xstate size to fpu_*_cfg

2021-10-21T17:38:55+00:00

Use the new kernel and user space config storage to store and retrieve the
XSTATE buffer sizes. The default and the maximum size are the same for now,
but will change when support for dynamically enabled features is added.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211014230739.296830097@linutronix.de

x86/fpu: Cleanup fpu__init_system_xstate_size_legacy()

2021-10-21T17:18:43+00:00

Clean the function up before making changes.

No functional change.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211014230739.184014242@linutronix.de

x86/fpu: Add size and mask information to fpstate

2021-10-21T11:51:42+00:00

Add state size and feature mask information to the fpstate container. This
will be used for runtime checks with the upcoming support for dynamically
enabled features and dynamically sized buffers. That avoids conditionals
all over the place as the required information is accessible for both
default and extended buffers.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211013145322.921388806@linutronix.de

x86/fpu: Remove fpu::state

2021-10-20T21:58:29+00:00

All users converted. Remove it along with the sanity checks.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211013145322.765063318@linutronix.de

x86/fpu/core: Convert to fpstate

2021-10-20T21:54:26+00:00

Convert the rest of the core code to the new register storage mechanism in
preparation for dynamically sized buffers.

No functional change.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211013145322.659456185@linutronix.de

x86/fpu: Provide struct fpstate

2021-10-20T20:26:24+00:00

New xfeatures will not longer be automatically stored in the regular XSAVE
buffer in thread_struct::fpu.

The kernel will provide the default sized buffer for storing the regular
features up to AVX512 in thread_struct::fpu and if a task requests to use
one of the new features then the register storage has to be extended.

The state will be accessed via a pointer in thread_struct::fpu which
defaults to the builtin storage and can be switched when extended storage
is required.

To avoid conditionals all over the code, create a new container for the
register storage which will gain other information, e.g. size, feature
masks etc., later. For now it just contains the register storage, which
gives it exactly the same layout as the exiting fpu::state.

Stick fpu::state and the new fpu::__fpstate into an anonymous union and
initialize the pointer. Add build time checks to validate that both are
at the same place and have the same size.

This allows step by step conversion of all users.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211013145322.234458659@linutronix.de