x86 ptrace: fix PTRACE_GETFPXREGS error

ptrace has always returned only -EIO for all failures to access
registers.  The user_regset calls are allowed to return a more
meaningful variety of errors.  The REGSET_XFP calls use -ENODEV
for !cpu_has_fxsr hardware.  Make ptrace return the traditional
-EIO instead of the error code from the user_regset call.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/i387.c

@@ -162,7 +162,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 	int ret;
 
 	if (!cpu_has_fxsr)
-		return -EIO;
+		return -ENODEV;
 
 	ret = init_fpu(target);
 	if (ret)
@@ -179,7 +179,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 	int ret;
 
 	if (!cpu_has_fxsr)
-		return -EIO;
+		return -ENODEV;
 
 	ret = init_fpu(target);
 	if (ret)

arch/x86/kernel/ptrace.c

@@ -943,13 +943,13 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 		return copy_regset_to_user(child, &user_x86_32_view,
 					   REGSET_XFP,
 					   0, sizeof(struct user_fxsr_struct),
-					   datap);
+					   datap) ? -EIO : 0;
 
 	case PTRACE_SETFPXREGS:	/* Set the child extended FPU state. */
 		return copy_regset_from_user(child, &user_x86_32_view,
 					     REGSET_XFP,
 					     0, sizeof(struct user_fxsr_struct),
-					     datap);
+					     datap) ? -EIO : 0;
 #endif
 
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION