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>

tools/testing/selftests/powerpc/Makefile

@@ -13,7 +13,7 @@ CFLAGS := -Wall -O2 -flto -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(CUR
 
 export CC CFLAGS
 
-SUB_DIRS = pmu copyloops mm tm primitives stringloops vphn
+SUB_DIRS = pmu copyloops mm tm primitives stringloops vphn switch_endian
 
 endif
 

tools/testing/selftests/powerpc/switch_endian/.gitignore

+switch_endian_test
+check-reversed.S

tools/testing/selftests/powerpc/switch_endian/Makefile

+CC := $(CROSS_COMPILE)gcc
+PROGS := switch_endian_test
+
+ASFLAGS += -O2 -Wall -g -nostdlib -m64
+
+all: $(PROGS)
+
+switch_endian_test: check-reversed.S
+
+check-reversed.o: check.o
+	$(CROSS_COMPILE)objcopy -j .text --reverse-bytes=4 -O binary $< $@
+
+check-reversed.S: check-reversed.o
+	hexdump -v -e '/1 ".byte 0x%02X\n"' $< > $@
+
+run_tests: all
+	@-for PROG in $(PROGS); do \
+		./$$PROG; \
+	done;
+
+clean:
+	rm -f $(PROGS) *.o check-reversed.S
+
+.PHONY: all run_tests clean

tools/testing/selftests/powerpc/switch_endian/check.S

+#include "common.h"
+
+/*
+ * Checks that registers contain what we expect, ie. they were not clobbered by
+ * the syscall.
+ *
+ * r15: pattern to check registers against.
+ *
+ * At the end r3 == 0 if everything's OK.
+ */
+	nop			# guaranteed to be illegal in reverse-endian
+	mr	r9,r15
+	cmpd    r9,r3		# check r3
+	bne     1f
+	addi    r9,r15,4	# check r4
+	cmpd    r9,r4
+	bne     1f
+	lis     r9,0x00FF	# check CR
+	ori     r9,r9,0xF000
+	mfcr    r10
+	and     r10,r10,r9
+	cmpw    r9,r10
+	addi    r9,r15,34
+	bne     1f
+	addi    r9,r15,32	# check LR
+	mflr    r10
+	cmpd    r9,r10
+	bne     1f
+	addi    r9,r15,5	# check r5
+	cmpd    r9,r5
+	bne     1f
+	addi    r9,r15,6	# check r6
+	cmpd    r9,r6
+	bne     1f
+	addi    r9,r15,7	# check r7
+	cmpd    r9,r7
+	bne     1f
+	addi    r9,r15,8	# check r8
+	cmpd    r9,r8
+	bne     1f
+	addi    r9,r15,13	# check r13
+	cmpd    r9,r13
+	bne     1f
+	addi    r9,r15,14	# check r14
+	cmpd    r9,r14
+	bne     1f
+	addi    r9,r15,16	# check r16
+	cmpd    r9,r16
+	bne     1f
+	addi    r9,r15,17	# check r17
+	cmpd    r9,r17
+	bne     1f
+	addi    r9,r15,18	# check r18
+	cmpd    r9,r18
+	bne     1f
+	addi    r9,r15,19	# check r19
+	cmpd    r9,r19
+	bne     1f
+	addi    r9,r15,20	# check r20
+	cmpd    r9,r20
+	bne     1f
+	addi    r9,r15,21	# check r21
+	cmpd    r9,r21
+	bne     1f
+	addi    r9,r15,22	# check r22
+	cmpd    r9,r22
+	bne     1f
+	addi    r9,r15,23	# check r23
+	cmpd    r9,r23
+	bne     1f
+	addi    r9,r15,24	# check r24
+	cmpd    r9,r24
+	bne     1f
+	addi    r9,r15,25	# check r25
+	cmpd    r9,r25
+	bne     1f
+	addi    r9,r15,26	# check r26
+	cmpd    r9,r26
+	bne     1f
+	addi    r9,r15,27	# check r27
+	cmpd    r9,r27
+	bne     1f
+	addi    r9,r15,28	# check r28
+	cmpd    r9,r28
+	bne     1f
+	addi    r9,r15,29	# check r29
+	cmpd    r9,r29
+	bne     1f
+	addi    r9,r15,30	# check r30
+	cmpd    r9,r30
+	bne     1f
+	addi    r9,r15,31	# check r31
+	cmpd    r9,r31
+	bne     1f
+	b	2f
+1:	mr	r3, r9
+	li	r0, __NR_exit
+	sc
+2:	li	r0, __NR_switch_endian
+	nop

tools/testing/selftests/powerpc/switch_endian/common.h

+#include <ppc-asm.h>
+#include <asm/unistd.h>
+
+#ifndef __NR_switch_endian
+#define __NR_switch_endian 363
+#endif

tools/testing/selftests/powerpc/switch_endian/switch_endian_test.S

+#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       .