selftests/powerpc: Add a test of the switch_endian() syscall

This adds a test of the switch_endian() syscall we added in the previous
commit.

We test it by calling the endian switch syscall, and then executing some
code in the other endian to check everything went as expected. That code
checks registers we expect to be maintained are. If the endian switch
failed to happen that code sequence will be illegal and cause the test
to abort.

We then switch back to the original endian, do the same checks and
finally write a success message and exit(0).

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 81 insertions, 0 deletions

diff --git a/tools/testing/selftests/powerpc/switch_endian/switch_endian_test.S b/tools/testing/selftests/powerpc/switch_endian/switch_endian_test.S
new file mode 100644
index 000000000000..ef7c971abb67
--- /dev/null
+++ b/tools/testing/selftests/powerpc/switch_endian/switch_endian_test.S
@@ -0,0 +1,81 @@
+#include "common.h"
+
+	.data
+	.balign 8
+message:
+	.ascii "success: switch_endian_test\n\0"
+
+	.section ".toc"
+	.balign 8
+pattern:
+	.llong 0x5555AAAA5555AAAA
+
+	.text
+FUNC_START(_start)
+	/* Load the pattern */
+	ld	r15, pattern@TOC(%r2)
+
+	/* Setup CR, only CR2-CR4 are maintained */
+	lis	r3, 0x00FF
+	ori	r3, r3, 0xF000
+	mtcr	r3
+
+	/* Load the pattern slightly modified into the registers */
+	mr	r3, r15
+	addi	r4, r15, 4
+
+	addi	r5, r15, 32
+	mtlr	r5
+
+	addi	r5, r15, 5
+	addi	r6, r15, 6
+	addi	r7, r15, 7
+	addi	r8, r15, 8
+
+	/* r9 - r12 are clobbered */
+
+	addi	r13, r15, 13
+	addi	r14, r15, 14
+
+	/* Skip r15 we're using it */
+
+	addi	r16, r15, 16
+	addi	r17, r15, 17
+	addi	r18, r15, 18
+	addi	r19, r15, 19
+	addi	r20, r15, 20
+	addi	r21, r15, 21
+	addi	r22, r15, 22
+	addi	r23, r15, 23
+	addi	r24, r15, 24
+	addi	r25, r15, 25
+	addi	r26, r15, 26
+	addi	r27, r15, 27
+	addi	r28, r15, 28
+	addi	r29, r15, 29
+	addi	r30, r15, 30
+	addi	r31, r15, 31
+
+	/*
+	 * Call the syscall to switch endian.
+	 * It clobbers r9-r12, XER, CTR and CR0-1,5-7.
+	 */
+	li r0, __NR_switch_endian
+	sc
+
+#include "check-reversed.S"
+
+	/* Flip back, r0 already has the switch syscall number */
+	.long	0x02000044	/* sc */
+
+#include "check.S"
+
+	li	r0, __NR_write
+	li	r3, 1	/* stdout */
+	ld	r4, message@got(%r2)
+	li	r5, 28	/* strlen(message3) */
+	sc
+	li      r0, __NR_exit
+	li	r3, 0
+	sc
+	b       .