[PATCH 15/22] x86/entry: Add TIF_NEED_FPU_LOAD

Sebastian Andrzej Siewior
2019-01-09T11:47:37Z

Add TIF_NEED_FPU_LOAD. This is reserved for loading the FPU registers
before returning to userland. This flag must not be set for systems
without a FPU.
If this flag is cleared, the CPU's FPU register hold the current content
of current()'s FPU register. The in-memory copy (union fpregs_state) is
not valid.
If this flag is set, then all of CPU's FPU register may hold a random
value (except for PKRU) and it is required to load the content of the
FPU register on return to userland.

It is introduced now, so we can add code handling it now before adding
the main feature.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/include/asm/thread_info.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index e0eccbcb8447d..f9453536f9bbc 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -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)
--
2.20.1