Commit 04944b79 authored by Suresh Siddha's avatar Suresh Siddha Committed by H. Peter Anvin
Browse files

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: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent f364eada

arch/x86/kernel/i387.c

+14 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/kernel/xsave.c

+25 −0
Original line number Diff line number Diff line
@@ -114,6 +114,8 @@ int save_i387_xstate(void __user *buf) 


	if (task_thread_info(tsk)->status & TS_XSAVE) {

		struct _fpstate __user *fx = buf;

		struct _xstate __user *x = buf;

		u64 xstate_bv;



		err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,

				     sizeof(struct _fpx_sw_bytes));
@@ -121,6 +123,29 @@ int save_i387_xstate(void __user *buf) 
		err |= __put_user(FP_XSTATE_MAGIC2,

				  (__u32 __user *) (buf + sig_xstate_size

						    - FP_XSTATE_MAGIC2_SIZE));



		/*

		 * Read the xstate_bv which we copied (directly from the cpu or

		 * from the state in task struct) to the user buffers and

		 * set the FP/SSE bits.

		 */

		err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);



		/*

		 * 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 apps 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.

		 */

		xstate_bv |= XSTATE_FPSSE;



		err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);



		if (err)

			return err;

	}

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