Sebastian Andrzej Siewior 926b21f37b x86/fpu: Restore from kernel memory on the 64-bit path too ... The 64-bit case (both 64-bit and 32-bit frames) loads the new state from user memory. However, doing this is not desired if the FPU state is going to be restored on return to userland: it would be required to disable preemption in order to avoid a context switch which would set TIF_NEED_FPU_LOAD. If this happens before the restore operation then the loaded registers would become volatile. Furthermore, disabling preemption while accessing user memory requires to disable the pagefault handler. An error during FXRSTOR would then mean that either a page fault occurred (and it would have to be retried with enabled page fault handler) or a #GP occurred because the xstate is bogus (after all, the signal handler can modify it). In order to avoid that mess, copy the FPU state from userland, validate it and then load it. The copy_kernel_…() helpers are basically just like the old helpers except that they operate on kernel memory and the fault handler just sets the error value and the caller handles it. copy_user_to_fpregs_zeroing() and its helpers remain and will be used later for a fastpath optimisation. [ bp: Clarify commit message. ] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Dave Hansen <dave.hansen@intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Aubrey Li <aubrey.li@intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: kvm ML <kvm@vger.kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Rik van Riel <riel@surriel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190403164156.19645-22-bigeasy@linutronix.de		2019-04-12 15:02:41 +02:00
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api.h	x86/fpu: Add an __fpregs_load_activate() internal helper	2019-04-10 16:23:14 +02:00
internal.h	x86/fpu: Restore from kernel memory on the 64-bit path too	2019-04-12 15:02:41 +02:00
regset.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
signal.h	x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()	2019-04-09 19:27:29 +02:00
types.h	x86/fpu: Remove fpu->initialized	2019-04-10 15:42:40 +02:00
xstate.h	x86/fpu: Eager switch PKRU state	2019-04-11 15:57:10 +02:00