x86, xsave: save/restore the extended state context in sigframe

On cpu's supporting xsave/xrstor, fpstate pointer in the sigcontext, will
include the extended state information along with fpstate information. Presence
of extended state information is indicated by the presence
of FP_XSTATE_MAGIC1 at fpstate.sw_reserved.magic1 and FP_XSTATE_MAGIC2
at fpstate + (fpstate.sw_reserved.extended_size - FP_XSTATE_MAGIC2_SIZE).

Extended feature bit mask that is saved in the memory layout is represented
by the fpstate.sw_reserved.xstate_bv

For RT signal frames, UC_FP_XSTATE in the uc_flags also indicate the
presence of extended state information in the sigcontext's fpstate
pointer.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 76 insertions, 6 deletions

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 7daf3a011dd9..cbb9dc474a21 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -26,6 +26,7 @@
 # define _fpstate_ia32          _fpstate
 # define _xstate_ia32           _xstate
 # define sig_xstate_ia32_size   sig_xstate_size
+# define fx_sw_reserved_ia32    fx_sw_reserved
 # define user_i387_ia32_struct  user_i387_struct
 # define user32_fxsr_struct     user_fxsr_struct
 #endif
@@ -447,12 +448,30 @@ static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
         if (err)
                 return -1;
 
-        if (__copy_to_user(&buf->_fxsr_env[0], fx,
-                           sizeof(struct i387_fxsave_struct)))
+        if (__copy_to_user(&buf->_fxsr_env[0], fx, xstate_size))
                 return -1;
         return 1;
 }
 
+static int save_i387_xsave(void __user *buf)
+{
+        struct _fpstate_ia32 __user *fx = buf;
+        int err = 0;
+
+        if (save_i387_fxsave(fx) < 0)
+                return -1;
+
+        err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved_ia32,
+                             sizeof(struct _fpx_sw_bytes));
+        err |= __put_user(FP_XSTATE_MAGIC2,
+                          (__u32 __user *) (buf + sig_xstate_ia32_size
+                                            - FP_XSTATE_MAGIC2_SIZE));
+        if (err)
+                return -1;
+
+        return 1;
+}
+
 int save_i387_xstate_ia32(void __user *buf)
 {
         struct _fpstate_ia32 __user *fp = (struct _fpstate_ia32 __user *) buf;
@@ -477,6 +496,8 @@ int save_i387_xstate_ia32(void __user *buf)
 
         unlazy_fpu(tsk);
 
+        if (cpu_has_xsave)
+                return save_i387_xsave(fp);
         if (cpu_has_fxsr)
                 return save_i387_fxsave(fp);
         else
@@ -491,14 +512,15 @@ static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
                                 sizeof(struct i387_fsave_struct));
 }
 
-static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
+static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf,
+                               unsigned int size)
 {
         struct task_struct *tsk = current;
         struct user_i387_ia32_struct env;
         int err;
 
         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
-                               sizeof(struct i387_fxsave_struct));
+                               size);
         /* mxcsr reserved bits must be masked to zero for security reasons */
         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
         if (err || __copy_from_user(&env, buf, sizeof(env)))
@@ -508,6 +530,51 @@ static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
         return 0;
 }
 
+static int restore_i387_xsave(void __user *buf)
+{
+        struct _fpx_sw_bytes fx_sw_user;
+        struct _fpstate_ia32 __user *fx_user =
+                        ((struct _fpstate_ia32 __user *) buf);
+        struct i387_fxsave_struct __user *fx =
+                (struct i387_fxsave_struct __user *) &fx_user->_fxsr_env[0];
+        struct xsave_hdr_struct *xsave_hdr =
+                                &current->thread.xstate->xsave.xsave_hdr;
+        unsigned int lmask, hmask;
+        int err;
+
+        if (check_for_xstate(fx, buf, &fx_sw_user))
+                goto fx_only;
+
+        lmask = fx_sw_user.xstate_bv;
+        hmask = fx_sw_user.xstate_bv >> 32;
+
+        err = restore_i387_fxsave(buf, fx_sw_user.xstate_size);
+
+        xsave_hdr->xstate_bv &=  (pcntxt_lmask | (((u64) pcntxt_hmask) << 32));
+        /*
+         * These bits must be zero.
+         */
+        xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
+
+        /*
+         * Init the state that is not present in the memory layout
+         * and enabled by the OS.
+         */
+        lmask = ~(pcntxt_lmask & ~lmask);
+        hmask = ~(pcntxt_hmask & ~hmask);
+        xsave_hdr->xstate_bv &=  (lmask | (((u64) hmask) << 32));
+
+        return err;
+fx_only:
+        /*
+         * Couldn't find the extended state information in the memory
+         * layout. Restore the FP/SSE and init the other extended state
+         * enabled by the OS.
+         */
+        xsave_hdr->xstate_bv = XSTATE_FPSSE;
+        return restore_i387_fxsave(buf, sizeof(struct i387_fxsave_struct));
+}
+
 int restore_i387_xstate_ia32(void __user *buf)
 {
         int err;
@@ -535,8 +602,11 @@ int restore_i387_xstate_ia32(void __user *buf)
         }
 
         if (HAVE_HWFP) {
-                if (cpu_has_fxsr)
-                        err = restore_i387_fxsave(fp);
+                if (cpu_has_xsave)
+                        err = restore_i387_xsave(buf);
+                else if (cpu_has_fxsr)
+                        err = restore_i387_fxsave(fp, sizeof(struct
+                                                           i387_fxsave_struct));
                 else
                         err = restore_i387_fsave(fp);
         } else {