From 04944b793e18ece23f63c0252646b310c1845940 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Tue, 7 Oct 2008 14:04:28 -0700 Subject: x86: xsave: set FP, SSE bits in the xsave header in the user sigcontext If a processor implementation discern that a processor state component is in its initialized state, it may modify the corresponding bit in the xsave header.xstate_bv as '0'. State in the memory layout setup by 'xsave' will be consistent with the bit values in the header. During signal handling, legacy applications may change the FP/SSE bits in the sigcontext memory layout without touching the FP/SSE header bits in the xsave header. So always set FP/SSE bits in the xsave header while saving the sigcontext state to the user space. During signal return, this will enable the kernel to capture any changes to the FP/SSE bits by the legacy applications which don't touch xsave headers. xsave aware apps can change the xstate_bv in the xsave header aswell as change any contents in the memory layout. xrestor as part of sigreturn will capture all the changes. Signed-off-by: Suresh Siddha Signed-off-by: H. Peter Anvin --- arch/x86/kernel/i387.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'arch/x86/kernel/i387.c') diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 45723f1fe19..1f20608d4ca 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -468,9 +468,23 @@ static int save_i387_fxsave(struct _fpstate_ia32 __user *buf) static int save_i387_xsave(void __user *buf) { + struct task_struct *tsk = current; struct _fpstate_ia32 __user *fx = buf; int err = 0; + /* + * For legacy compatible, we always set FP/SSE bits in the bit + * vector while saving the state to the user context. + * This will enable us capturing any changes(during sigreturn) to + * the FP/SSE bits by the legacy applications which don't touch + * xstate_bv in the xsave header. + * + * xsave aware applications can change the xstate_bv in the xsave + * header as well as change any contents in the memory layout. + * xrestore as part of sigreturn will capture all the changes. + */ + tsk->thread.xstate->xsave.xsave_hdr.xstate_bv |= XSTATE_FPSSE; + if (save_i387_fxsave(fx) < 0) return -1; -- cgit v1.2.3-18-g5258