selftests/powerpc/64: Test exception cases in copy_tofrom_user

This adds a set of test cases to test the behaviour of
copy_tofrom_user when exceptions are encountered accessing the
source or destination.  Currently, copy_tofrom_user does not always
copy as many bytes as possible when an exception occurs on a store
to the destination, and that is reflected in failures in these tests.

Based on a test program from Anton Blanchard.

[paulus@ozlabs.org - test all three paths, wrote commit description,
 made EX_TABLE create an exception table.]

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/copyloops/asm/ppc_asm.h

@@ -1,4 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SELFTESTS_POWERPC_PPC_ASM_H
+#define __SELFTESTS_POWERPC_PPC_ASM_H
 #include <ppc-asm.h>
 
 #define CONFIG_ALTIVEC
@@ -26,25 +28,10 @@
 
 #define PPC_MTOCRF(A, B)	mtocrf A, B
 
-#define EX_TABLE(x, y)
-
-FUNC_START(enter_vmx_usercopy)
-	li	r3,1
-	blr
-
-FUNC_START(exit_vmx_usercopy)
-	li	r3,0
-	blr
-
-FUNC_START(enter_vmx_ops)
-	li	r3,1
-	blr
-
-FUNC_START(exit_vmx_ops)
-	blr
-
-FUNC_START(__copy_tofrom_user_base)
-	blr
+#define EX_TABLE(x, y)			\
+	.section __ex_table,"a";	\
+	.8byte	x, y;			\
+	.previous
 
 #define BEGIN_FTR_SECTION		.if test_feature
 #define FTR_SECTION_ELSE		.else
@@ -56,3 +43,5 @@ FUNC_START(__copy_tofrom_user_base)
 
 /* Default to taking the first of any alternative feature sections */
 test_feature = 1
+
+#endif /* __SELFTESTS_POWERPC_PPC_ASM_H */