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x86: xsave: set FP, SSE bits in the xsave header in the user sigcontext

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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 <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Suresh Siddha 2008-10-07 14:04:28 -07:00 committed by H. Peter Anvin
parent f364eadab5
commit 04944b793e
2 changed files with 39 additions and 0 deletions
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14
arch/x86/kernel/i387.c
View File

@ -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;

25
arch/x86/kernel/xsave.c
View File

@ -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;
}