From 35ac2d7ba787eb4b7418a5a6f5919c25e10a780a Mon Sep 17 00:00:00 2001 From: Yu-cheng Yu Date: Mon, 11 Jul 2016 09:18:56 -0700 Subject: 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 Signed-off-by: Fenghua Yu Reviewed-by: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Ravi V Shankar Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1468253937-40008-4-git-send-email-fenghua.yu@intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/core.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/x86/kernel/fpu') diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index c759bd01ec99..3fc03a09a93b 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include @@ -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 -- cgit v1.2.3