x86, ptrace: Simplify xstateregs_get()

48 bytes (bytes 464..511) of the xstateregs payload come from the
kernel defined structure (xstate_fx_sw_bytes). Rest comes from the
xstate regs structure in the thread struct. Instead of having multiple
user_regset_copyout()'s, simplify the xstateregs_get() by first
copying the SW bytes into the xstate regs structure in the thread structure
and then using one user_regset_copyout() to copyout the xstateregs.

Requested-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20100222225240.494688491@sbs-t61.sc.intel.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Oleg Nesterov <oleg@redhat.com>

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 7a8a193b514437f2fa6c293b6c482685df84a995..81e23bf12c12ffa4f2b6336ac651480e443c06fc 100644 (file)
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -243,34 +243,18 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
                return ret;
 
        /*
-        * First copy the fxsave bytes 0..463.
+        * Copy the 48bytes defined by the software first into the xstate
+        * memory layout in the thread struct, so that we can copy the entire
+        * xstateregs to the user using one user_regset_copyout().
         */
-       ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-                                 &target->thread.xstate->xsave, 0,
-                                 offsetof(struct user_xstateregs,
-                                          i387.xstate_fx_sw));
-       if (ret)
-               return ret;
-
-       /*
-        * Copy the 48bytes defined by software.
-        */
-       ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-                                 xstate_fx_sw_bytes,
-                                 offsetof(struct user_xstateregs,
-                                          i387.xstate_fx_sw),
-                                 offsetof(struct user_xstateregs,
-                                          xsave_hdr));
-       if (ret)
-               return ret;
+       memcpy(&target->thread.xstate->fxsave.sw_reserved,
+              xstate_fx_sw_bytes, sizeof(xstate_fx_sw_bytes));
 
        /*
-        * Copy the rest of xstate memory layout.
+        * Copy the xstate memory layout.
         */
        ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
-                                 &target->thread.xstate->xsave.xsave_hdr,
-                                 offsetof(struct user_xstateregs,
-                                          xsave_hdr), -1);
+                                 &target->thread.xstate->xsave, 0, -1);
        return ret;
 }