Commit-ID: 383c252545edcc708128e2028a2318b05c45ede4 Gitweb: https://git.kernel.org/tip/383c252545edcc708128e2028a2318b05c45ede4 Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> AuthorDate: Wed, 3 Apr 2019 18:41:45 +0200 Committer: Borislav Petkov <bp@xxxxxxx> CommitDate: Thu, 11 Apr 2019 16:21:51 +0200 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: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Aubrey Li <aubrey.li@xxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Cc: kvm ML <kvm@xxxxxxxxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20190403164156.19645-17-bigeasy@xxxxxxxxxxxxx --- arch/x86/include/asm/fpu/internal.h | 8 ++++++++ arch/x86/include/asm/thread_info.h | 2 ++ 2 files changed, 10 insertions(+) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 6eb4a0b1ad0e..da75d7b3e37d 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -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. */ diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index e0eccbcb8447..f9453536f9bb 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)
