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Remove empty files which were supposed to get removed with the
respective commits removing the functionality in them:
$ find arch/x86/ -empty
arch/x86/lib/mmx_32.c
arch/x86/include/asm/fpu/internal.h
arch/x86/include/asm/mmx.h
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220520101723.12006-1-bp@alien8.de
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Now that the file is empty, fixup all references with the proper includes
and delete the former kitchen sink.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011540.001197214@linutronix.de
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Move the global interfaces to api.h and the rest into the core.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.948837194@linutronix.de
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In order to remove internal.h make signal.h independent of it.
Include asm/fpu/xstate.h to fix a missing update_regset_xstate_info()
prototype, which is
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.844565975@linutronix.de
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Move function declarations which need to be globally available to api.h
where they belong.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.792363754@linutronix.de
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Only used internally in the FPU core code.
While at it, convert to the percpu accessors which verify preemption is
disabled.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.686806639@linutronix.de
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No point in being in global headers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.628516182@linutronix.de
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Nothing outside the core code requires them.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.572439164@linutronix.de
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Nothing outside the core code needs these.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.513368075@linutronix.de
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It's only required in the xstate init code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.455836597@linutronix.de
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Further disintegration of internal.h:
Move the CPU feature tests to a core header and remove the unused one.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.401510559@linutronix.de
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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
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Swapping the host/guest FPU is directly fiddling with FPU internals which
requires 5 exports. The upcoming support of dynamically enabled states
would even need more.
Implement a swap function in the FPU core code and export that instead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Link: https://lkml.kernel.org/r/20211015011539.076072399@linutronix.de
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No point in having this duplicated all over the place with needlessly
different defines.
Provide a proper initialization function which initializes user buffers
properly and make KVM use it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011538.897664678@linutronix.de
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Unused since the FPU switching rework.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011538.433135710@linutronix.de
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None of the call sites cares about the error code. All they need to know is
whether the function succeeded or not.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.909065931@linutronix.de
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None of the call sites cares about the actual return code. Change the
return type to boolean and return 'true' on success.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.736773588@linutronix.de
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There is no reason to have the header zeroing in the pagefault disabled
region. Do it upfront once.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.621674721@linutronix.de
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FPU restore from a signal frame can trigger various exceptions. The
exceptions are caught with an exception table entry. The handler of this
entry stores the trap number in EAX. The FPU specific fixup negates that
trap number to convert it into an negative error code.
Any other exception than #PF is fatal and recovery is not possible. This
relies on the fact that the #PF exception number is the same as EFAULT, but
that's not really obvious.
Remove the negation from the exception fixup as it really has no value and
check for X86_TRAP_PF at the call site.
There is still confusion due to the return code conversion for the error
case which will be cleaned up separately.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.506192488@linutronix.de
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The macros used for restoring FPU state from a user space buffer can handle
all exceptions including #MC. They need to return the trap number in the
error case as the code which invokes them needs to distinguish the cause of
the failure. It aborts the operation for anything except #PF.
Use the new EX_TYPE_FAULT_MCE_SAFE exception table fixup type to document
the nature of the fixup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210908132525.387464538@linutronix.de
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The exception table entries contain the instruction address, the fixup
address and the handler address. All addresses are relative. Storing the
handler address has a few downsides:
1) Most handlers need to be exported
2) Handlers can be defined everywhere and there is no overview about the
handler types
3) MCE needs to check the handler type to decide whether an in kernel #MC
can be recovered. The functionality of the handler itself is not in any
way special, but for these checks there need to be separate functions
which in the worst case have to be exported.
Some of these 'recoverable' exception fixups are pretty obscure and
just reuse some other handler to spare code. That obfuscates e.g. the
#MC safe copy functions. Cleaning that up would require more handlers
and exports
Rework the exception fixup mechanics by storing a fixup type number instead
of the handler address and invoke the proper handler for each fixup
type. Also teach the extable sort to leave the type field alone.
This makes most handlers static except for special cases like the MCE
MSR fixup and the BPF fixup. This allows to add more types for cleaning up
the obscure places without adding more handler code and exports.
There is a marginal code size reduction for a production config and it
removes _eight_ exported symbols.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lkml.kernel.org/r/20210908132525.211958725@linutronix.de
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When *RSTOR from user memory raises an exception, there is no way to
differentiate them. That's bad because it forces the slow path even when
the failure was not a fault. If the operation raised eg. #GP then going
through the slow path is pointless.
Use _ASM_EXTABLE_FAULT() which stores the trap number and let the exception
fixup return the negated trap number as error.
This allows to separate the fast path and let it handle faults directly and
avoid the slow path for all other exceptions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121457.601480369@linutronix.de
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PKRU is already updated and the xstate is not longer the proper source
of information.
[ bp: Use cpu_feature_enabled() ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.708180184@linutronix.de
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As the PKRU state is managed separately restoring it from the xstate
buffer would be counterproductive as it might either restore a stale
value or reinit the PKRU state to 0.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.606745195@linutronix.de
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switch_to() and flush_thread() write the task's PKRU value eagerly so
the PKRU value of current is always valid in the hardware.
That means there is no point in restoring PKRU on exit to user or when
reactivating the task's FPU registers in the signal frame setup path.
This allows to remove all the xstate buffer updates with PKRU values once
the PKRU state is stored in thread struct while a task is scheduled out.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.303919033@linutronix.de
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Rename it so it's clear that this is about user ABI features which can
differ from the feature set which the kernel saves and restores because the
kernel handles e.g. PKRU differently. But the user ABI (ptrace, signal
frame) expects it to be there.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.211585137@linutronix.de
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copy_kernel_to_fpregs() restores all xfeatures but it is also the place
where the AMD FXSAVE_LEAK bug is handled.
That prevents fpregs_restore_userregs() to limit the restored features,
which is required to untangle PKRU and XSTATE handling and also for the
upcoming supervisor state management.
Move the FXSAVE_LEAK quirk into __copy_kernel_to_fpregs() and deinline that
function which has become rather fat.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.114271278@linutronix.de
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Rename it so that it becomes entirely clear what this function is
about. It's purpose is to restore the FPU registers to the state which was
saved in the task's FPU memory state either at context switch or by an in
kernel FPU user.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.018867925@linutronix.de
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Make it clear what the function is about.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.827979263@linutronix.de
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Both function names are a misnomer.
fpu__save() is actually about synchronizing the hardware register state
into the task's memory state so that either coredump or a math exception
handler can inspect the state at the time where the problem happens.
The function guarantees to preserve the register state, while "save" is a
common terminology for saving the current state so it can be modified and
restored later. This is clearly not the case here.
Rename it to fpu_sync_fpstate().
fpu__copy() is used to clone the current task's FPU state when duplicating
task_struct. While the register state is a copy the rest of the FPU state
is not.
Name it accordingly and remove the really pointless @src argument along
with the warning which comes along with it.
Nothing can ever copy the FPU state of a non-current task. It's clearly
just a consequence of arch_dup_task_struct(), but it makes no sense to
proliferate that further.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.196727450@linutronix.de
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This is not a copy functionality. It restores the register state from the
supplied kernel buffer.
No functional changes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121454.716058365@linutronix.de
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The FNSAVE support requires conditionals in quite some call paths because
FNSAVE reinitializes the FPU hardware. If the save has to preserve the FPU
register state then the caller has to conditionally restore it from memory
when FNSAVE is in use.
This also requires a conditional in context switch because the restore
avoidance optimization cannot work with FNSAVE. As this only affects 20+
years old CPUs there is really no reason to keep this optimization
effective for FNSAVE. It's about time to not optimize for antiques anymore.
Just unconditionally FRSTOR the save content to the registers and clean up
the conditionals all over the place.
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121454.617369268@linutronix.de
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A copy is guaranteed to leave the source intact, which is not the case when
FNSAVE is used as that reinitilizes the registers.
Save does not make such guarantees and it matches what this is about,
i.e. to save the state for a later restore.
Rename it to save_fpregs_to_fpstate().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121454.508853062@linutronix.de
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The function names for fnsave/fnrstor operations are horribly named and
a permanent source of confusion.
Rename:
copy_kernel_to_fregs() to frstor()
copy_fregs_to_user() to fnsave_to_user_sigframe()
copy_user_to_fregs() to frstor_from_user_sigframe()
so it's clear what these are doing. All these functions are really low
level wrappers around the equally named instructions, so mapping to the
documentation is just natural.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121454.223594101@linutronix.de
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The function names for fxsave/fxrstor operations are horribly named and
a permanent source of confusion.
Rename:
copy_fxregs_to_kernel() to fxsave()
copy_kernel_to_fxregs() to fxrstor()
copy_fxregs_to_user() to fxsave_to_user_sigframe()
copy_user_to_fxregs() to fxrstor_from_user_sigframe()
so it's clear what these are doing. All these functions are really low
level wrappers around the equally named instructions, so mapping to the
documentation is just natural.
While at it, replace the static_cpu_has(X86_FEATURE_FXSR) with
use_fxsr() to be consistent with the rest of the code.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121454.017863494@linutronix.de
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The function names for xsave[s]/xrstor[s] operations are horribly named and
a permanent source of confusion.
Rename:
copy_xregs_to_user() to xsave_to_user_sigframe()
copy_user_to_xregs() to xrstor_from_user_sigframe()
so it's entirely clear what this is about. This is also a clear indicator
of the potentially different storage format because this is user ABI and
cannot use compacted format.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.924266705@linutronix.de
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The function names for xsave[s]/xrstor[s] operations are horribly named and
a permanent source of confusion.
Rename:
copy_xregs_to_kernel() to os_xsave()
copy_kernel_to_xregs() to os_xrstor()
These are truly low level wrappers around the actual instructions
XSAVE[OPT]/XRSTOR and XSAVES/XRSTORS with the twist that the selection
based on the available CPU features happens with an alternative to avoid
conditionals all over the place and to provide the best performance for hot
paths.
The os_ prefix tells that this is the OS selected mechanism.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.830239347@linutronix.de
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The only usecase for fpu__write_begin is the set() callback of regset, so
the function is pointlessly global.
Move it to the regset code and rename it to fpu_force_restore() which is
exactly decribing what the function does.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.328652975@linutronix.de
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The function can only be used from the regset get() callbacks safely. So
there is no reason to have it globally exposed.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.234942936@linutronix.de
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No more users.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121453.124819167@linutronix.de
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They are only used in fpstate_init() and there is no point to have them in
a header just to make reading the code harder.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.023118522@linutronix.de
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This function is really not doing what the comment advertises:
"Find supported xfeatures based on cpu features and command-line input.
This must be called after fpu__init_parse_early_param() is called and
xfeatures_mask is enumerated."
fpu__init_parse_early_param() does not exist anymore and the function just
returns a constant.
Remove it and fix the caller and get rid of further references to
fpu__init_parse_early_param().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121451.816404717@linutronix.de
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The XSAVE init code initializes all enabled and supported components with
XRSTOR(S) to init state. Then it XSAVEs the state of the components back
into init_fpstate which is used in several places to fill in the init state
of components.
This works correctly with XSAVE, but not with XSAVEOPT and XSAVES because
those use the init optimization and skip writing state of components which
are in init state. So init_fpstate.xsave still contains all zeroes after
this operation.
There are two ways to solve that:
1) Use XSAVE unconditionally, but that requires to reshuffle the buffer when
XSAVES is enabled because XSAVES uses compacted format.
2) Save the components which are known to have a non-zero init state by other
means.
Looking deeper, #2 is the right thing to do because all components the
kernel supports have all-zeroes init state except the legacy features (FP,
SSE). Those cannot be hard coded because the states are not identical on all
CPUs, but they can be saved with FXSAVE which avoids all conditionals.
Use FXSAVE to save the legacy FP/SSE components in init_fpstate along with
a BUILD_BUG_ON() which reminds developers to validate that a newly added
component has all zeroes init state. As a bonus remove the now unused
copy_xregs_to_kernel_booting() crutch.
The XSAVE and reshuffle method can still be implemented in the unlikely
case that components are added which have a non-zero init state and no
other means to save them. For now, FXSAVE is just simple and good enough.
[ bp: Fix a typo or two in the text. ]
Fixes: 6bad06b76892 ("x86, xsave: Use xsaveopt in context-switch path when supported")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210618143444.587311343@linutronix.de
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When user space brings PKRU into init state, then the kernel handling is
broken:
T1 user space
xsave(state)
state.header.xfeatures &= ~XFEATURE_MASK_PKRU;
xrstor(state)
T1 -> kernel
schedule()
XSAVE(S) -> T1->xsave.header.xfeatures[PKRU] == 0
T1->flags |= TIF_NEED_FPU_LOAD;
wrpkru();
schedule()
...
pk = get_xsave_addr(&T1->fpu->state.xsave, XFEATURE_PKRU);
if (pk)
wrpkru(pk->pkru);
else
wrpkru(DEFAULT_PKRU);
Because the xfeatures bit is 0 and therefore the value in the xsave
storage is not valid, get_xsave_addr() returns NULL and switch_to()
writes the default PKRU. -> FAIL #1!
So that wrecks any copy_to/from_user() on the way back to user space
which hits memory which is protected by the default PKRU value.
Assumed that this does not fail (pure luck) then T1 goes back to user
space and because TIF_NEED_FPU_LOAD is set it ends up in
switch_fpu_return()
__fpregs_load_activate()
if (!fpregs_state_valid()) {
load_XSTATE_from_task();
}
But if nothing touched the FPU between T1 scheduling out and back in,
then the fpregs_state is still valid which means switch_fpu_return()
does nothing and just clears TIF_NEED_FPU_LOAD. Back to user space with
DEFAULT_PKRU loaded. -> FAIL #2!
The fix is simple: if get_xsave_addr() returns NULL then set the
PKRU value to 0 instead of the restrictive default PKRU value in
init_pkru_value.
[ bp: Massage in minor nitpicks from folks. ]
Fixes: 0cecca9d03c9 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144346.045616965@linutronix.de
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switch_fpu_finish() checks current->mm as indicator for kernel threads.
That's wrong because kernel threads can temporarily use a mm of a user
process via kthread_use_mm().
Check the task flags for PF_KTHREAD instead.
Fixes: 0cecca9d03c9 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210608144345.912645927@linutronix.de
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While digesting the XSAVE-related horrors which got introduced with
the supervisor/user split, the recent addition of ENQCMD-related
functionality got on the radar and turned out to be similarly broken.
update_pasid(), which is only required when X86_FEATURE_ENQCMD is
available, is invoked from two places:
1) From switch_to() for the incoming task
2) Via a SMP function call from the IOMMU/SMV code
#1 is half-ways correct as it hacks around the brokenness of get_xsave_addr()
by enforcing the state to be 'present', but all the conditionals in that
code are completely pointless for that.
Also the invocation is just useless overhead because at that point
it's guaranteed that TIF_NEED_FPU_LOAD is set on the incoming task
and all of this can be handled at return to user space.
#2 is broken beyond repair. The comment in the code claims that it is safe
to invoke this in an IPI, but that's just wishful thinking.
FPU state of a running task is protected by fregs_lock() which is
nothing else than a local_bh_disable(). As BH-disabled regions run
usually with interrupts enabled the IPI can hit a code section which
modifies FPU state and there is absolutely no guarantee that any of the
assumptions which are made for the IPI case is true.
Also the IPI is sent to all CPUs in mm_cpumask(mm), but the IPI is
invoked with a NULL pointer argument, so it can hit a completely
unrelated task and unconditionally force an update for nothing.
Worse, it can hit a kernel thread which operates on a user space
address space and set a random PASID for it.
The offending commit does not cleanly revert, but it's sufficient to
force disable X86_FEATURE_ENQCMD and to remove the broken update_pasid()
code to make this dysfunctional all over the place. Anything more
complex would require more surgery and none of the related functions
outside of the x86 core code are blatantly wrong, so removing those
would be overkill.
As nothing enables the PASID bit in the IA32_XSS MSR yet, which is
required to make this actually work, this cannot result in a regression
except for related out of tree train-wrecks, but they are broken already
today.
Fixes: 20f0afd1fb3d ("x86/mmu: Allocate/free a PASID")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtsd6gr9.ffs@nanos.tec.linutronix.de
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Pull x86 SEV-ES support from Borislav Petkov:
"SEV-ES enhances the current guest memory encryption support called SEV
by also encrypting the guest register state, making the registers
inaccessible to the hypervisor by en-/decrypting them on world
switches. Thus, it adds additional protection to Linux guests against
exfiltration, control flow and rollback attacks.
With SEV-ES, the guest is in full control of what registers the
hypervisor can access. This is provided by a guest-host exchange
mechanism based on a new exception vector called VMM Communication
Exception (#VC), a new instruction called VMGEXIT and a shared
Guest-Host Communication Block which is a decrypted page shared
between the guest and the hypervisor.
Intercepts to the hypervisor become #VC exceptions in an SEV-ES guest
so in order for that exception mechanism to work, the early x86 init
code needed to be made able to handle exceptions, which, in itself,
brings a bunch of very nice cleanups and improvements to the early
boot code like an early page fault handler, allowing for on-demand
building of the identity mapping. With that, !KASLR configurations do
not use the EFI page table anymore but switch to a kernel-controlled
one.
The main part of this series adds the support for that new exchange
mechanism. The goal has been to keep this as much as possibly separate
from the core x86 code by concentrating the machinery in two
SEV-ES-specific files:
arch/x86/kernel/sev-es-shared.c
arch/x86/kernel/sev-es.c
Other interaction with core x86 code has been kept at minimum and
behind static keys to minimize the performance impact on !SEV-ES
setups.
Work by Joerg Roedel and Thomas Lendacky and others"
* tag 'x86_seves_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (73 commits)
x86/sev-es: Use GHCB accessor for setting the MMIO scratch buffer
x86/sev-es: Check required CPU features for SEV-ES
x86/efi: Add GHCB mappings when SEV-ES is active
x86/sev-es: Handle NMI State
x86/sev-es: Support CPU offline/online
x86/head/64: Don't call verify_cpu() on starting APs
x86/smpboot: Load TSS and getcpu GDT entry before loading IDT
x86/realmode: Setup AP jump table
x86/realmode: Add SEV-ES specific trampoline entry point
x86/vmware: Add VMware-specific handling for VMMCALL under SEV-ES
x86/kvm: Add KVM-specific VMMCALL handling under SEV-ES
x86/paravirt: Allow hypervisor-specific VMMCALL handling under SEV-ES
x86/sev-es: Handle #DB Events
x86/sev-es: Handle #AC Events
x86/sev-es: Handle VMMCALL Events
x86/sev-es: Handle MWAIT/MWAITX Events
x86/sev-es: Handle MONITOR/MONITORX Events
x86/sev-es: Handle INVD Events
x86/sev-es: Handle RDPMC Events
x86/sev-es: Handle RDTSC(P) Events
...
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Pull x86 PASID updates from Borislav Petkov:
"Initial support for sharing virtual addresses between the CPU and
devices which doesn't need pinning of pages for DMA anymore.
Add support for the command submission to devices using new x86
instructions like ENQCMD{,S} and MOVDIR64B. In addition, add support
for process address space identifiers (PASIDs) which are referenced by
those command submission instructions along with the handling of the
PASID state on context switch as another extended state.
Work by Fenghua Yu, Ashok Raj, Yu-cheng Yu and Dave Jiang"
* tag 'x86_pasid_for_5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/asm: Add an enqcmds() wrapper for the ENQCMDS instruction
x86/asm: Carve out a generic movdir64b() helper for general usage
x86/mmu: Allocate/free a PASID
x86/cpufeatures: Mark ENQCMD as disabled when configured out
mm: Add a pasid member to struct mm_struct
x86/msr-index: Define an IA32_PASID MSR
x86/fpu/xstate: Add supervisor PASID state for ENQCMD
x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions
Documentation/x86: Add documentation for SVA (Shared Virtual Addressing)
iommu/vt-d: Change flags type to unsigned int in binding mm
drm, iommu: Change type of pasid to u32
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A PASID is allocated for an "mm" the first time any thread binds to an
SVA-capable device and is freed from the "mm" when the SVA is unbound
by the last thread. It's possible for the "mm" to have different PASID
values in different binding/unbinding SVA cycles.
The mm's PASID (non-zero for valid PASID or 0 for invalid PASID) is
propagated to a per-thread PASID MSR for all threads within the mm
through IPI, context switch, or inherited. This is done to ensure that a
running thread has the right PASID in the MSR matching the mm's PASID.
[ bp: s/SVM/SVA/g; massage. ]
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/1600187413-163670-10-git-send-email-fenghua.yu@intel.com
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The xgetbv() function is needed in the pre-decompression boot code,
but asm/fpu/internal.h can't be included there directly. Doing so
opens the door to include-hell due to various include-magic in
boot/compressed/misc.h.
Avoid that by moving xgetbv()/xsetbv() to a separate header file and
include it instead.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-27-joro@8bytes.org
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Borislav Petkov
Thomas Gleixner
Linus Torvalds
Fenghua Yu
Joerg Roedel