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2021-10-20x86/fpu: Move os_xsave() and os_xrstor() to coreThomas Gleixner
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
2021-10-20x86/fpu: Make os_xrstor_booting() privateThomas Gleixner
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
2021-10-20x86/fpu: Clean up CPU feature testsThomas Gleixner
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
2021-10-20x86/fpu: Move context switch and exit to user inlines into sched.hThomas Gleixner
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
2021-10-20x86/fpu: Mark fpu__init_prepare_fx_sw_frame() as __initThomas Gleixner
No need to keep it around. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011539.296435736@linutronix.de
2021-10-20x86/fpu: Rework copy_xstate_to_uabi_buf()Thomas Gleixner
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
2021-10-20x86/fpu: Replace KVMs home brewed FPU copy from userThomas Gleixner
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
2021-10-20x86/fpu: Move KVMs FPU swapping to FPU coreThomas Gleixner
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
2021-10-20x86/fpu/xstate: Mark all init only functions __initThomas Gleixner
No point to keep them around after boot. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011539.017919252@linutronix.de
2021-10-20x86/fpu/xstate: Provide and use for_each_xfeature()Thomas Gleixner
These loops evaluating xfeature bits are really hard to read. Create an iterator and use for_each_set_bit_from() inside which already does the right thing. No functional changes. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011538.958107505@linutronix.de
2021-10-20x86/fpu: Cleanup xstate xcomp_bv initializationThomas Gleixner
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
2021-10-20x86/fpu: Do not inherit FPU context for kernel and IO worker threadsThomas Gleixner
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
2021-10-20x86/fpu: Remove pointless memset in fpu_clone()Thomas Gleixner
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
2021-10-20x86/fpu: Cleanup the on_boot_cpu clutterThomas Gleixner
Defensive programming is useful, but this on_boot_cpu debug is really silly. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011538.665080855@linutronix.de
2021-10-20x86/fpu: Restrict xsaves()/xrstors() to independent statesThomas Gleixner
These interfaces are really only valid for features which are independently managed and not part of the task context state for various reasons. Tighten the checks and adjust the misleading comments. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011538.608492174@linutronix.de
2021-10-20x86/fpu: Update stale commentsThomas Gleixner
copy_fpstate_to_sigframe() does not have a slow path anymore. Neither does the !ia32 restore in __fpu_restore_sig(). Update the comments accordingly. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211015011538.493570236@linutronix.de
2021-10-18gup: Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}Andreas Gruenbacher
Turn fault_in_pages_{readable,writeable} into versions that return the number of bytes not faulted in, similar to copy_to_user, instead of returning a non-zero value when any of the requested pages couldn't be faulted in. This supports the existing users that require all pages to be faulted in as well as new users that are happy if any pages can be faulted in. Rename the functions to fault_in_{readable,writeable} to make sure this change doesn't silently break things. Neither of these functions is entirely trivial and it doesn't seem useful to inline them, so move them to mm/gup.c. Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
2021-10-16Merge branch 'x86/urgent' into x86/fpu, to resolve a conflictIngo Molnar
Resolve the conflict between these commits: x86/fpu: 1193f408cd51 ("x86/fpu/signal: Change return type of __fpu_restore_sig() to boolean") x86/urgent: d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits") b2381acd3fd9 ("x86/fpu: Mask out the invalid MXCSR bits properly") Conflicts: arch/x86/kernel/fpu/signal.c Signed-off-by: Ingo Molnar <mingo@kernel.org>
2021-10-16x86/fpu: Mask out the invalid MXCSR bits properlyBorislav Petkov
This is a fix for the fix (yeah, /facepalm). The correct mask to use is not the negation of the MXCSR_MASK but the actual mask which contains the supported bits in the MXCSR register. Reported and debugged by Ville Syrjälä <ville.syrjala@linux.intel.com> Fixes: d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits") Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Tested-by: Ser Olmy <ser.olmy@protonmail.com> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/YWgYIYXLriayyezv@intel.com
2021-10-08x86/fpu: Restore the masking out of reserved MXCSR bitsBorislav Petkov
Ser Olmy reported a boot failure: init[1] bad frame in sigreturn frame:(ptrval) ip:b7c9fbe6 sp:bf933310 orax:ffffffff \ in libc-2.33.so[b7bed000+156000] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b CPU: 0 PID: 1 Comm: init Tainted: G W 5.14.9 #1 Hardware name: Hewlett-Packard HP PC/HP Board, BIOS JD.00.06 12/06/2001 Call Trace: dump_stack_lvl dump_stack panic do_exit.cold do_group_exit get_signal arch_do_signal_or_restart ? force_sig_info_to_task ? force_sig exit_to_user_mode_prepare syscall_exit_to_user_mode do_int80_syscall_32 entry_INT80_32 on an old 32-bit Intel CPU: vendor_id : GenuineIntel cpu family : 6 model : 6 model name : Celeron (Mendocino) stepping : 5 microcode : 0x3 Ser bisected the problem to the commit in Fixes. tglx suggested reverting the rejection of invalid MXCSR values which this commit introduced and replacing it with what the old code did - simply masking them out to zero. Further debugging confirmed his suggestion: fpu->state.fxsave.mxcsr: 0xb7be13b4, mxcsr_feature_mask: 0xffbf WARNING: CPU: 0 PID: 1 at arch/x86/kernel/fpu/signal.c:384 __fpu_restore_sig+0x51f/0x540 so restore the original behavior only for 32-bit kernels where you have ancient machines with buggy hardware. For 32-bit programs on 64-bit kernels, user space which supplies wrong MXCSR values is considered malicious so fail the sigframe restoration there. Fixes: 6f9866a166cd ("x86/fpu/signal: Let xrstor handle the features to init") Reported-by: Ser Olmy <ser.olmy@protonmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Ser Olmy <ser.olmy@protonmail.com> Cc: <stable@vger.kernel.org> Link: https://lkml.kernel.org/r/YVtA67jImg3KlBTw@zn.tnic
2021-09-23x86/fpu/signal: Fix missed conversion to correct boolean retval in ↵Anders Roxell
save_xstate_epilog() Fix the missing return code polarity in save_xstate_epilog(). [ bp: Massage, use the right commit in the Fixes: tag ] Fixes: 2af07f3a6e9f ("x86/fpu/signal: Change return type of copy_fpregs_to_sigframe() helpers to boolean") Reported-by: Remi Duraffort <remi.duraffort@linaro.org> Signed-off-by: Anders Roxell <anders.roxell@linaro.org> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://github.com/ClangBuiltLinux/linux/issues/1461 Link: https://lkml.kernel.org/r/20210922200901.1823741-1-anders.roxell@linaro.org
2021-09-14x86/fpu/signal: Change return code of restore_fpregs_from_user() to booleanThomas Gleixner
__fpu_sig_restore() only needs information about success or fail and no real error code. This cleans up the confusing conversion of the trap number, which is returned by the *RSTOR() exception fixups, to an error code. 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/20210908132526.084109938@linutronix.de
2021-09-14x86/fpu/signal: Change return code of check_xstate_in_sigframe() to booleanThomas Gleixner
__fpu_sig_restore() only needs success/fail information and no detailed error code. 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/20210908132526.024024598@linutronix.de
2021-09-14x86/fpu/signal: Change return type of __fpu_restore_sig() to booleanThomas Gleixner
Now that fpu__restore_sig() returns a boolean get rid of the individual error codes in __fpu_restore_sig() as well. 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/20210908132525.966197097@linutronix.de
2021-09-14x86/fpu/signal: Change return type of fpu__restore_sig() to booleanThomas Gleixner
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
2021-09-14x86/fpu/signal: Change return type of copy_fpregs_to_sigframe() helpers to ↵Thomas Gleixner
boolean Now that copy_fpregs_to_sigframe() returns boolean the individual return codes in the related helper functions do not make sense anymore. Change them to return boolean success/fail. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210908132525.794334915@linutronix.de
2021-09-14x86/fpu/signal: Change return type of copy_fpstate_to_sigframe() to booleanThomas Gleixner
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
2021-09-14x86/fpu/signal: Move xstate clearing out of copy_fpregs_to_sigframe()Thomas Gleixner
When the direct saving of the FPU registers to the user space sigframe fails, copy_fpregs_to_sigframe() attempts to clear the user buffer. The most likely reason for such a fail is a page fault. As copy_fpregs_to_sigframe() is invoked with pagefaults disabled the chance that __clear_user() succeeds is minuscule. Move the clearing out into the caller which replaces the fault_in_pages_writeable() in that error handling path. The return value confusion 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/20210908132525.679356300@linutronix.de
2021-09-14x86/fpu/signal: Move header zeroing out of xsave_to_user_sigframe()Thomas Gleixner
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
2021-09-13x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user()Thomas Gleixner
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
2021-06-24x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() againThomas Gleixner
The change which made copy_xstate_to_uabi_buf() usable for [x]fpregs_get() removed the zeroing of the header which means the header, which is copied to user space later, contains except for the xfeatures member, random stack content. Add the memset() back to zero it before usage. Fixes: eb6f51723f03 ("x86/fpu: Make copy_xstate_to_kernel() usable for [x]fpregs_get()") Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/875yy3wb8h.ffs@nanos.tec.linutronix.de
2021-06-23x86/fpu/signal: Let xrstor handle the features to initThomas Gleixner
There is no reason to do an extra XRSTOR from init_fpstate for feature bits which have been cleared by user space in the FX magic xfeatures storage. Just clear them in the task's XSTATE header and do a full restore which will put these cleared features into init state. There is no real difference in performance because the current code already does a full restore when the xfeatures bits are preserved as the signal frame setup has stored them, which is the full UABI feature set. [ bp: Use the negated mxcsr_feature_mask in the MXCSR check. ] 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/20210623121457.804115017@linutronix.de
2021-06-23x86/fpu/signal: Handle #PF in the direct restore pathThomas Gleixner
If *RSTOR raises an exception, then the slow path is taken. That's wrong because if the reason was not #PF then going through the slow path is waste of time because that will end up with the same conclusion that the data is invalid. Now that the wrapper around *RSTOR return an negative error code, which is the negated trap number, it's possible to differentiate. If the *RSTOR raised #PF then handle it directly in the fast path and if it was some other exception, e.g. #GP, then give up and do not try the fast path. This removes the legacy frame FRSTOR code from the slow path because FRSTOR is not a ia32_fxstate frame and is therefore handled in the fast path. 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/20210623121457.696022863@linutronix.de
2021-06-23x86/fpu/signal: Split out the direct restore codeThomas Gleixner
Prepare for smarter failure handling of the direct restore. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121457.493455414@linutronix.de
2021-06-23x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing()Thomas Gleixner
Now that user_xfeatures is correctly set when xsave is enabled, remove the duplicated initialization of components. Rename the function while at it. 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/20210623121457.377341297@linutronix.de
2021-06-23x86/fpu/signal: Sanitize the xstate check on sigframeThomas Gleixner
Utilize the check for the extended state magic in the FX software reserved bytes and set the parameters for restoring fx_only in the relevant members of fw_sw_user. This allows further cleanups on top because the data is consistent. 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/20210623121457.277738268@linutronix.de
2021-06-23x86/fpu/signal: Remove the legacy alignment checkThomas Gleixner
Checking for the XSTATE buffer being 64-byte aligned, and if not, deciding just to restore the FXSR state is daft. If user space provides an unaligned math frame and has the extended state magic set in the FX software reserved bytes, then it really can keep the pieces. If the frame is unaligned and the FX software magic is not set, then fx_only is already set and the restore will use fxrstor. Remove it. 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/20210623121457.184149902@linutronix.de
2021-06-23x86/fpu/signal: Move initial checks into fpu__restore_sig()Thomas Gleixner
__fpu__restore_sig() is convoluted and some of the basic checks can trivially be done in the calling function as well as the final error handling of clearing user state. [ bp: Fixup typos. ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121457.086336154@linutronix.de
2021-06-23x86/fpu: Mark init_fpstate __ro_after_initThomas Gleixner
Nothing has to write into that state after init. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121456.992342060@linutronix.de
2021-06-23x86/fpu: Don't store PKRU in xstate in fpu_reset_fpstate()Thomas Gleixner
PKRU for a task is stored in task->thread.pkru when the task is scheduled out. For 'current' the authoritative source of PKRU is the hardware. fpu_reset_fpstate() has two callers: 1) fpu__clear_user_states() for !FPU systems. For those PKRU is irrelevant 2) fpu_flush_thread() which is invoked from flush_thread(). flush_thread() resets the hardware to the kernel restrictive default value. 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/20210623121456.802850233@linutronix.de
2021-06-23x86/fpu: Mask PKRU from kernel XRSTOR[S] operationsThomas Gleixner
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
2021-06-23x86/fpu: Hook up PKRU into ptrace()Dave Hansen
One nice thing about having PKRU be XSAVE-managed is that it gets naturally exposed into the XSAVE-using ABIs. Now that XSAVE will not be used to manage PKRU, these ABIs need to be manually enabled to deal with PKRU. ptrace() uses copy_uabi_xstate_to_kernel() to collect the tracee's XSTATE. As PKRU is not in the task's XSTATE buffer, use task->thread.pkru for filling in up the ptrace buffer. Signed-off-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/20210623121456.508770763@linutronix.de
2021-06-23x86/fpu: Dont restore PKRU in fpregs_restore_userspace()Thomas Gleixner
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
2021-06-23x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi()Thomas Gleixner
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
2021-06-23x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()Thomas Gleixner
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
2021-06-23x86/fpu: Rename __fpregs_load_activate() to fpregs_restore_userregs()Thomas Gleixner
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
2021-06-23x86/fpu: Clean up the fpu__clear() variantsAndy Lutomirski
fpu__clear() currently resets both register state and kernel XSAVE buffer state. It has two modes: one for all state (supervisor and user) and another for user state only. fpu__clear_all() uses the "all state" (user_only=0) mode, while a number of signal paths use the user_only=1 mode. Make fpu__clear() work only for user state (user_only=1) and remove the "all state" (user_only=0) code. Rename it to match so it can be used by the signal paths. Replace the "all state" (user_only=0) fpu__clear() functionality. Use the TIF_NEED_FPU_LOAD functionality instead of making any actual hardware registers changes in this path. Instead of invoking fpu__initialize() just memcpy() init_fpstate into the task's FPU state because that has already the correct format and in case of PKRU also contains the default PKRU value. Move the actual PKRU write out into flush_thread() where it belongs and where it will end up anyway when PKRU and XSTATE have been untangled. For bisectability a workaround is required which stores the PKRU value in the xstate memory until PKRU is untangled from XSTATE for context switching and return to user. [ Dave Hansen: Polished changelog ] [ tglx: Fixed the PKRU fallout ] Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121455.922729522@linutronix.de
2021-06-23x86/fpu: Rename fpu__clear_all() to fpu_flush_thread()Thomas Gleixner
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
2021-06-23x86/fpu: Use pkru_write_default() in copy_init_fpstate_to_fpregs()Thomas Gleixner
There is no point in using copy_init_pkru_to_fpregs() which in turn calls write_pkru(). write_pkru() tries to fiddle with the task's xstate buffer for nothing because the XRSTOR[S](init_fpstate) just cleared the xfeature flag in the xstate header which makes get_xsave_addr() fail. It's a useless exercise anyway because the reinitialization activates the FPU so before the task's xstate buffer can be used again a XRSTOR[S] must happen which in turn dumps the PKRU value. Get rid of the now unused copy_init_pkru_to_fpregs(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210623121455.732508792@linutronix.de
2021-06-23x86/cpu: Sanitize X86_FEATURE_OSPKEThomas Gleixner
X86_FEATURE_OSPKE is enabled first on the boot CPU and the feature flag is set. Secondary CPUs have to enable CR4.PKE as well and set their per CPU feature flag. That's ineffective because all call sites have checks for boot_cpu_data. Make it smarter and force the feature flag when PKU is enabled on the boot cpu which allows then to use cpu_feature_enabled(X86_FEATURE_OSPKE) all over the place. That either compiles the code out when PKEY support is disabled in Kconfig or uses a static_cpu_has() for the feature check which makes a significant difference in hotpaths, e.g. context switch. 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/20210623121455.305113644@linutronix.de
generated by cgit (git 2.34.1) at 2025-07-18 17:23:19 +0000