From b8b9b6ba9dec3f155c7555cb208ba4078e97aedb Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 12 Feb 2016 13:02:35 -0800 Subject: x86/fpu: Allow setting of XSAVE state We want to modify the Protection Key rights inside the kernel, so we need to change PKRU's contents. But, if we do a plain 'wrpkru', when we return to userspace we might do an XRSTOR and wipe out the kernel's 'wrpkru'. So, we need to go after PKRU in the xsave buffer. We do this by: 1. Ensuring that we have the XSAVE registers (fpregs) in the kernel FPU buffer (fpstate) 2. Looking up the location of a given state in the buffer 3. Filling in the stat 4. Ensuring that the hardware knows that state is present there (basically that the 'init optimization' is not in place). 5. Copying the newly-modified state back to the registers if necessary. Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Quentin Casasnovas Cc: Rik van Riel Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20160212210235.5A3139BF@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/fpu/internal.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/include/asm/fpu/internal.h') diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index a2124343edf5..31ac8e6d9f36 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -25,6 +25,8 @@ extern void fpu__activate_curr(struct fpu *fpu); extern void fpu__activate_fpstate_read(struct fpu *fpu); extern void fpu__activate_fpstate_write(struct fpu *fpu); +extern void fpu__current_fpstate_write_begin(void); +extern void fpu__current_fpstate_write_end(void); extern void fpu__save(struct fpu *fpu); extern void fpu__restore(struct fpu *fpu); extern int fpu__restore_sig(void __user *buf, int ia32_frame); -- cgit v1.2.3