kprobes: add testcases for s390

Add a few testcases to make sure that it's not possible to place
a kprobe in the mid of an instruction on s390.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/Kconfig

@@ -946,4 +946,16 @@ config S390_UNWIND_SELFTEST
 
 	  Say N if you are unsure.
 
+config S390_KPROBES_SANITY_TEST
+	def_tristate n
+	prompt "Enable s390 specific kprobes tests"
+	depends on KPROBES
+	depends on KUNIT
+	help
+	  This option enables an s390 specific kprobes test module. This option
+	  is not useful for distributions or general kernels, but only for kernel
+	  developers working on architecture code.
+
+	  Say N if you are unsure.
+
 endmenu

arch/s390/configs/debug_defconfig

@@ -62,6 +62,7 @@ CONFIG_CMM=m
 CONFIG_APPLDATA_BASE=y
 CONFIG_KVM=m
 CONFIG_S390_UNWIND_SELFTEST=y
+CONFIG_S390_KPROBES_SANITY_TEST=y
 CONFIG_KPROBES=y
 CONFIG_JUMP_LABEL=y
 CONFIG_STATIC_KEYS_SELFTEST=y

arch/s390/lib/Makefile

@@ -7,6 +7,8 @@ lib-y += delay.o string.o uaccess.o find.o spinlock.o
 obj-y += mem.o xor.o
 lib-$(CONFIG_KPROBES) += probes.o
 lib-$(CONFIG_UPROBES) += probes.o
+obj-$(CONFIG_S390_KPROBES_SANITY_TEST) += test_kprobes_s390.o
+test_kprobes_s390-objs += test_kprobes_asm.o test_kprobes.o
 
 # Instrumenting memory accesses to __user data (in different address space)
 # produce false positives

arch/s390/lib/test_kprobes.c

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/random.h>
+#include <kunit/test.h>
+#include "test_kprobes.h"
+
+static struct kprobe kp;
+
+static void setup_kprobe(struct kunit *test, struct kprobe *kp,
+			 const char *symbol, int offset)
+{
+	kp->offset = offset;
+	kp->addr = NULL;
+	kp->symbol_name = symbol;
+}
+
+static void test_kprobe_offset(struct kunit *test, struct kprobe *kp,
+			       const char *target, int offset)
+{
+	int ret;
+
+	setup_kprobe(test, kp, target, 0);
+	ret = register_kprobe(kp);
+	if (!ret)
+		unregister_kprobe(kp);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	setup_kprobe(test, kp, target, offset);
+	ret = register_kprobe(kp);
+	KUNIT_EXPECT_EQ(test, -EINVAL, ret);
+	if (!ret)
+		unregister_kprobe(kp);
+}
+
+static void test_kprobe_odd(struct kunit *test)
+{
+	test_kprobe_offset(test, &kp, "kprobes_target_odd",
+			   kprobes_target_odd_offs);
+}
+
+static void test_kprobe_in_insn4(struct kunit *test)
+{
+	test_kprobe_offset(test, &kp, "kprobes_target_in_insn4",
+			   kprobes_target_in_insn4_offs);
+}
+
+static void test_kprobe_in_insn6_lo(struct kunit *test)
+{
+	test_kprobe_offset(test, &kp, "kprobes_target_in_insn6_lo",
+			   kprobes_target_in_insn6_lo_offs);
+}
+
+static void test_kprobe_in_insn6_hi(struct kunit *test)
+{
+	test_kprobe_offset(test, &kp, "kprobes_target_in_insn6_hi",
+			   kprobes_target_in_insn6_hi_offs);
+}
+
+static struct kunit_case kprobes_testcases[] = {
+	KUNIT_CASE(test_kprobe_odd),
+	KUNIT_CASE(test_kprobe_in_insn4),
+	KUNIT_CASE(test_kprobe_in_insn6_lo),
+	KUNIT_CASE(test_kprobe_in_insn6_hi),
+	{}
+};
+
+static struct kunit_suite kprobes_test_suite = {
+	.name = "kprobes_test_s390",
+	.test_cases = kprobes_testcases,
+};
+
+kunit_test_suites(&kprobes_test_suite);
+
+MODULE_LICENSE("GPL");

arch/s390/lib/test_kprobes.h

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+#ifndef TEST_KPROBES_H
+#define TEST_KPROBES_H
+
+extern unsigned long kprobes_target_odd_offs;
+extern unsigned long kprobes_target_in_insn4_offs;
+extern unsigned long kprobes_target_in_insn6_lo_offs;
+extern unsigned long kprobes_target_in_insn6_hi_offs;
+
+#endif

arch/s390/lib/test_kprobes_asm.S

@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#include <linux/linkage.h>
+#include <asm/ftrace.h>
+
+#define KPROBES_TARGET_START(name)	\
+	SYM_FUNC_START(name);		\
+	FTRACE_GEN_NOP_ASM(name)
+
+#define KPROBES_TARGET_END(name)	\
+	SYM_FUNC_END(name);		\
+	SYM_DATA(name##_offs, .quad 1b - name)
+
+KPROBES_TARGET_START(kprobes_target_in_insn4)
+	.word 0x4700 // bc 0,0
+1:	.word 0x0000
+	br %r14
+KPROBES_TARGET_END(kprobes_target_in_insn4)
+
+KPROBES_TARGET_START(kprobes_target_in_insn6_lo)
+	.word 0xe310 // ly 1,0
+1:	.word 0x0000
+	.word 0x0058
+	br %r14
+KPROBES_TARGET_END(kprobes_target_in_insn6_lo)
+
+KPROBES_TARGET_START(kprobes_target_in_insn6_hi)
+	.word 0xe310 // ly 1,0
+	.word 0x0000
+1:	.word 0x0058
+	br %r14
+KPROBES_TARGET_END(kprobes_target_in_insn6_hi)
+
+KPROBES_TARGET_START(kprobes_target_bp)
+	nop
+	.word 0x0000
+	nop
+1:	br %r14
+KPROBES_TARGET_END(kprobes_target_bp)
+
+KPROBES_TARGET_START(kprobes_target_odd)
+	.byte 0x07
+1:	.byte 0x07
+	br %r14
+KPROBES_TARGET_END(kprobes_target_odd)