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authorSuresh Siddha <suresh.b.siddha@intel.com>2008-10-07 14:04:28 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-10-07 14:36:08 -0700
commit04944b793e18ece23f63c0252646b310c1845940 (patch)
treec8a99e14a910aedcd7147d5ccf2e63be5b26ca0a /arch/x86/kernel
parentf364eadab59b316ea0bd9f9bc01af0ad89065569 (diff)
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 <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/i387.c14
-rw-r--r--arch/x86/kernel/xsave.c25
2 files changed, 39 insertions, 0 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 45723f1fe198..1f20608d4ca8 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;
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 448fde96963c..2f98323716d9 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -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;
}