xfeatures_mask_fpstate() is no longer valid when dynamically enabled
features come into play.
Rework restore_regs_from_fpstate() so it takes a constant mask which will
then be applied against the maximum feature set so that the restore
operation brings all features which are not in the xsave buffer xfeature
bitmap into init state.
This ensures that if the previous task used a dynamically enabled feature
that the task which restores has all unused components properly initialized.
Cleanup the last user of xfeatures_mask_fpstate() as well and remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.461348278@linutronix.de
Use the new fpu_user_cfg to retrieve the information instead of
xfeatures_mask_uabi() which will be no longer correct when dynamically
enabled features become available.
Using fpu_user_cfg is appropriate when setting XCOMP_BV in the
init_fpstate since it has space allocated for "max_features". But,
normal fpstates might only have space for default xfeatures. Since
XRSTOR* derives the format of the XSAVE buffer from XCOMP_BV, this can
lead to XRSTOR reading out of bounds.
So when copying actively used fpstate, simply read the XCOMP_BV features
bits directly out of the fpstate instead.
This correction courtesy of Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.408879849@linutronix.de
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 <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.296830097@linutronix.de
Provide a struct to store information about the maximum supported and the
default feature set and buffer sizes for both user and kernel space.
This allows quick retrieval of this information for the upcoming support
for dynamically enabled features.
[ bp: Add vertical spacing between the struct members. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211014230739.126107370@linutronix.de
For dynamically enabled features it's required to get the features which
are enabled for that context when restoring from sigframe.
The same applies for all signal frame size calculations.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/87ilxz5iew.ffs@tglx
Prepare for dynamically enabled states per task. The function needs to
retrieve the features and sizes which are valid in a fpstate
context. Retrieve them from fpstate.
Move the function declarations to the core header as they are not
required anywhere else.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145323.233529986@linutronix.de
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 <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145322.921388806@linutronix.de
If fork fails early then the copied task struct would carry the fpstate
pointer of the parent task.
Not a problem right now, but later when dynamically allocated buffers
are available, keeping the pointer might result in freeing the
parent's buffer. Set it to NULL which prevents that. If fork reaches
clone_thread(), the pointer will be correctly set to the new task
context.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145322.817101108@linutronix.de
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 <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145322.234458659@linutronix.de
internal.h is a kitchen sink which needs to get out of the way to prepare
for the upcoming changes.
Move the context switch and exit to user inlines into a separate header,
which is all that code needs.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.349132461@linutronix.de
Prepare for replacing the KVM copy xstate to user function by extending
copy_xstate_to_uabi_buf() with a pkru argument which allows the caller to
hand in the pkru value, which is required for KVM because the guest PKRU is
not accessible via current. Fixup all callsites accordingly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.191902137@linutronix.de
Copying a user space buffer to the memory buffer is already available in
the FPU core. The copy mechanism in KVM lacks sanity checks and needs to
use cpuid() to lookup the offset of each component, while the FPU core has
this information cached.
Make the FPU core variant accessible for KVM and replace the home brewed
mechanism.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: kvm@vger.kernel.org
Link: https://lkml.kernel.org/r/20211015011539.134065207@linutronix.de
There is no reason why kernel and IO worker threads need a full clone of
the parent's FPU state. Both are kernel threads which are not supposed to
use FPU. So copying a large state or doing XSAVE() is pointless. Just clean
out the minimally required state for those tasks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011538.839822981@linutronix.de
Zeroing the forked task's FPU registers buffer to avoid leaking init
optimized stale data into the clone is a pointless exercise for the case
where the current task has TIF_NEED_FPU_LOAD set. In that case, the FPU
registers state is copied from current's FPU register buffer which can
contain stale init optimized data as well.
The alledged information leak is non-existant because this stale init
optimized data is used nowhere and cannot leak anywhere.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011538.722854569@linutronix.de
