Commit-ID: 35ac2d7ba787eb4b7418a5a6f5919c25e10a780a Gitweb: http://git.kernel.org/tip/35ac2d7ba787eb4b7418a5a6f5919c25e10a780a Author: Yu-cheng Yu <[email protected]> AuthorDate: Mon, 11 Jul 2016 09:18:56 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 11 Jul 2016 16:44:00 +0200
x86/fpu/xstate: Fix fpstate_init() for XRSTORS In XSAVES mode if fpstate_init() is used to initialize a task's extended state area, xsave.header.xcomp_bv[63] must be set. Otherwise, when the task is scheduled, a warning is triggered from copy_kernel_to_xregs(). One such test case is: setting an invalid extended state through PTRACE. When xstateregs_set() rejects the syscall and re-initializes the task's extended state area. This triggers the warning mentioned above. Signed-off-by: Yu-cheng Yu <[email protected]> Signed-off-by: Fenghua Yu <[email protected]> Reviewed-by: Dave Hansen <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ravi V Shankar <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/fpu/types.h | 6 ++++++ arch/x86/kernel/fpu/core.c | 8 ++++++++ 2 files changed, 14 insertions(+) diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 12dd648..48df486 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -232,6 +232,12 @@ struct xstate_header { } __attribute__((packed)); /* + * xstate_header.xcomp_bv[63] indicates that the extended_state_area + * is in compacted format. + */ +#define XCOMP_BV_COMPACTED_FORMAT ((u64)1 << 63) + +/* * This is our most modern FPU state format, as saved by the XSAVE * and restored by the XRSTOR instructions. * diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index c759bd0..3fc03a0 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -8,6 +8,7 @@ #include <asm/fpu/internal.h> #include <asm/fpu/regset.h> #include <asm/fpu/signal.h> +#include <asm/fpu/types.h> #include <asm/traps.h> #include <linux/hardirq.h> @@ -229,6 +230,13 @@ void fpstate_init(union fpregs_state *state) memset(state, 0, fpu_kernel_xstate_size); + /* + * XRSTORS requires that this bit is set in xcomp_bv, or + * it will #GP. Make sure it is replaced after the memset(). + */ + if (static_cpu_has(X86_FEATURE_XSAVES)) + state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT; + if (static_cpu_has(X86_FEATURE_FXSR)) fpstate_init_fxstate(&state->fxsave); else
