[PATCH v6 2/2] riscv: kprobes: add KUnit test for LR/SC sequence rejection

[Xiaofeng Yuan]

Extend the kprobes KUnit test with a function containing an LR/SC
sequence and assert that register_kprobe() accepts a probe placed right
before or right after the sequence, and rejects a probe placed on the
LR, on an instruction inside the sequence, or on the SC.

Signed-off-by: Xiaofeng Yuan <yuanxiaofeng at eswincomputing.com>
---
 .../kernel/tests/kprobes/test-kprobes-asm.S   | 30 ++++++++++++++++++
 .../riscv/kernel/tests/kprobes/test-kprobes.c | 31 +++++++++++++++++++
 .../riscv/kernel/tests/kprobes/test-kprobes.h |  3 ++
 3 files changed, 64 insertions(+)

diff --git a/arch/riscv/kernel/tests/kprobes/test-kprobes-asm.S b/arch/riscv/kernel/tests/kprobes/test-kprobes-asm.S
index 15e50934b..76826bf7e 100644
--- a/arch/riscv/kernel/tests/kprobes/test-kprobes-asm.S
+++ b/arch/riscv/kernel/tests/kprobes/test-kprobes-asm.S
@@ -100,6 +100,27 @@ test_kprobes_branch_addr8:
 	.option pop
 SYM_FUNC_END(test_kprobes_branch)
 
+/*
+ * This function is never executed; it only provides the probe addresses
+ * in test_kprobes_lrsc_offsets[] for test_kprobe_lrsc().  The lr.w/sc.w
+ * use the invalid address 0(x0) and would fault if executed, so do not
+ * add this function to test_kprobes_functions[].
+ */
+SYM_FUNC_START(test_kprobes_lrsc)
+.Llrsc_before:
+	nop
+1:
+.Llrsc_lr:
+	lr.w t0, 0(x0)
+.Llrsc_inside:
+	addi t0, t0, 1
+.Llrsc_sc:
+	sc.w t0, t0, 0(x0)
+	bnez t0, 1b
+.Llrsc_after:
+	ret
+SYM_FUNC_END(test_kprobes_lrsc)
+
 #ifdef CONFIG_RISCV_ISA_C
 
 SYM_FUNC_START(test_kprobes_c_j)
@@ -253,3 +274,12 @@ SYM_DATA_START(test_kprobes_functions)
 #endif /* CONFIG_RISCV_ISA_C */
 	RISCV_PTR 0
 SYM_DATA_END(test_kprobes_functions)
+
+.section .rodata
+SYM_DATA_START(test_kprobes_lrsc_offsets)
+	RISCV_PTR .Llrsc_before
+	RISCV_PTR .Llrsc_lr
+	RISCV_PTR .Llrsc_inside
+	RISCV_PTR .Llrsc_sc
+	RISCV_PTR .Llrsc_after
+SYM_DATA_END(test_kprobes_lrsc_offsets)
diff --git a/arch/riscv/kernel/tests/kprobes/test-kprobes.c b/arch/riscv/kernel/tests/kprobes/test-kprobes.c
index 027424a3f..c2d9c87f2 100644
--- a/arch/riscv/kernel/tests/kprobes/test-kprobes.c
+++ b/arch/riscv/kernel/tests/kprobes/test-kprobes.c
@@ -43,8 +43,39 @@ static void test_kprobe_riscv(struct kunit *test)
 	kfree(kp);
 }
 
+static void test_kprobe_lrsc(struct kunit *test)
+{
+	/*
+	 * test_kprobes_lrsc_offsets[] points, in order, at an instruction
+	 * right before an LR/SC sequence, the LR itself, an instruction
+	 * inside the sequence, the SC, and an instruction right after it.
+	 * reject[] must have the same number of entries.
+	 */
+	bool reject[] = { false, true, true, true, false };
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(reject); i++) {
+		struct kprobe kp = {};
+		int ret;
+
+		kp.pre_handler = kprobe_dummy_handler;
+		kp.addr = (kprobe_opcode_t *)test_kprobes_lrsc_offsets[i];
+
+		ret = register_kprobe(&kp);
+
+		if (reject[i])
+			KUNIT_EXPECT_LT(test, ret, 0);
+		else
+			KUNIT_EXPECT_EQ(test, ret, 0);
+
+		if (!ret)
+			unregister_kprobe(&kp);
+	}
+}
+
 static struct kunit_case kprobes_testcases[] = {
 	KUNIT_CASE(test_kprobe_riscv),
+	KUNIT_CASE(test_kprobe_lrsc),
 	{}
 };
 
diff --git a/arch/riscv/kernel/tests/kprobes/test-kprobes.h b/arch/riscv/kernel/tests/kprobes/test-kprobes.h
index 537f44aa9..65a8e7217 100644
--- a/arch/riscv/kernel/tests/kprobes/test-kprobes.h
+++ b/arch/riscv/kernel/tests/kprobes/test-kprobes.h
@@ -19,6 +19,9 @@ extern void *test_kprobes_addresses[];
 /* array of functions that return KPROBE_TEST_MAGIC */
 extern long (*test_kprobes_functions[])(void);
 
+/* offsets of the probe points inside test_kprobes_lrsc() */
+extern void *test_kprobes_lrsc_offsets[];
+
 #endif /* __ASSEMBLER__ */
 
 #endif /* TEST_KPROBES_H */
-- 
2.34.1