Commit 383c2525 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Borislav Petkov
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x86/entry: Add TIF_NEED_FPU_LOAD 



Add TIF_NEED_FPU_LOAD. This flag is used for loading the FPU registers
before returning to userland. It must not be set on systems without a
FPU.

If this flag is cleared, the CPU's FPU registers hold the latest,
up-to-date content of the current task's (current()) FPU registers.
The in-memory copy (union fpregs_state) is not valid.

If this flag is set, then all of CPU's FPU registers may hold a random
value (except for PKRU) and it is required to load the content of the
FPU registers on return to userland.

Introduce it now as a preparatory change before adding the main feature.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Reviewed-by: default avatarThomas 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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.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: Tim Chen <tim.c.chen@linux.intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-17-bigeasy@linutronix.de
parent 0cecca9d

arch/x86/include/asm/fpu/internal.h

+8 −0
Original line number Diff line number Diff line
@@ -508,6 +508,14 @@ static inline void __fpregs_load_activate(struct fpu *fpu, int cpu) 
 *  - switch_fpu_finish() restores the new state as

 *    necessary.

 *

 * If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers

 * are saved in the current thread's FPU register state.

 *

 * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not

 * hold current()'s FPU registers. It is required to load the

 * registers before returning to userland or using the content

 * otherwise.

 *

 * The FPU context is only stored/restored for a user task and

 * ->mm is used to distinguish between kernel and user threads.

 */

arch/x86/include/asm/thread_info.h

+2 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct thread_info { 
#define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */

#define TIF_UPROBE		12	/* breakpointed or singlestepping */

#define TIF_PATCH_PENDING	13	/* pending live patching update */

#define TIF_NEED_FPU_LOAD	14	/* load FPU on return to userspace */

#define TIF_NOCPUID		15	/* CPUID is not accessible in userland */

#define TIF_NOTSC		16	/* TSC is not accessible in userland */

#define TIF_IA32		17	/* IA32 compatibility process */
@@ -117,6 +118,7 @@ struct thread_info { 
#define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)

#define _TIF_UPROBE		(1 << TIF_UPROBE)

#define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)

#define _TIF_NEED_FPU_LOAD	(1 << TIF_NEED_FPU_LOAD)

#define _TIF_NOCPUID		(1 << TIF_NOCPUID)

#define _TIF_NOTSC		(1 << TIF_NOTSC)

#define _TIF_IA32		(1 << TIF_IA32)

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