1 files changed, 347 insertions, 0 deletions
diff --git a/arch/s390/lib/test_unwind.c b/arch/s390/lib/test_unwind.c
new file mode 100644
index 000000000000..bda7ac0ddd29
--- /dev/null
+++ b/arch/s390/lib/test_unwind.c
@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test module for unwind_for_each_frame
+ */
+
+#define pr_fmt(fmt) "test_unwind: " fmt
+#include <asm/unwind.h>
+#include <linux/completion.h>
+#include <linux/kallsyms.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/kprobes.h>
+#include <linux/wait.h>
+#include <asm/irq.h>
+#include <asm/delay.h>
+
+#define BT_BUF_SIZE (PAGE_SIZE * 4)
+
+/*
+ * To avoid printk line limit split backtrace by lines
+ */
+static void print_backtrace(char *bt)
+{
+	char *p;
+
+	while (true) {
+		p = strsep(&bt, "\n");
+		if (!p)
+			break;
+		pr_err("%s\n", p);
+	}
+}
+
+/*
+ * Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
+ * contains unwindme_func2 followed by unwindme_func1.
+ */
+static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
+				unsigned long sp)
+{
+	int frame_count, prev_is_func2, seen_func2_func1;
+	const int max_frames = 128;
+	struct unwind_state state;
+	size_t bt_pos = 0;
+	int ret = 0;
+	char *bt;
+
+	bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
+	if (!bt) {
+		pr_err("failed to allocate backtrace buffer\n");
+		return -ENOMEM;
+	}
+	/* Unwind. */
+	frame_count = 0;
+	prev_is_func2 = 0;
+	seen_func2_func1 = 0;
+	unwind_for_each_frame(&state, task, regs, sp) {
+		unsigned long addr = unwind_get_return_address(&state);
+		char sym[KSYM_SYMBOL_LEN];
+
+		if (frame_count++ == max_frames)
+			break;
+		if (state.reliable && !addr) {
+			pr_err("unwind state reliable but addr is 0\n");
+			return -EINVAL;
+		}
+		sprint_symbol(sym, addr);
+		if (bt_pos < BT_BUF_SIZE) {
+			bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos,
+					   state.reliable ? " [%-7s%px] %pSR\n" :
+							    "([%-7s%px] %pSR)\n",
+					   stack_type_name(state.stack_info.type),
+					   (void *)state.sp, (void *)state.ip);
+			if (bt_pos >= BT_BUF_SIZE)
+				pr_err("backtrace buffer is too small\n");
+		}
+		frame_count += 1;
+		if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
+			seen_func2_func1 = 1;
+		prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
+	}
+
+	/* Check the results. */
+	if (unwind_error(&state)) {
+		pr_err("unwind error\n");
+		ret = -EINVAL;
+	}
+	if (!seen_func2_func1) {
+		pr_err("unwindme_func2 and unwindme_func1 not found\n");
+		ret = -EINVAL;
+	}
+	if (frame_count == max_frames) {
+		pr_err("Maximum number of frames exceeded\n");
+		ret = -EINVAL;
+	}
+	if (ret)
+		print_backtrace(bt);
+	kfree(bt);
+	return ret;
+}
+
+/* State of the task being unwound. */
+struct unwindme {
+	int flags;
+	int ret;
+	struct task_struct *task;
+	struct completion task_ready;
+	wait_queue_head_t task_wq;
+	unsigned long sp;
+};
+
+static struct unwindme *unwindme;
+
+/* Values of unwindme.flags. */
+#define UWM_DEFAULT		0x0
+#define UWM_THREAD		0x1	/* Unwind a separate task. */
+#define UWM_REGS		0x2	/* Pass regs to test_unwind(). */
+#define UWM_SP			0x4	/* Pass sp to test_unwind(). */
+#define UWM_CALLER		0x8	/* Unwind starting from caller. */
+#define UWM_SWITCH_STACK	0x10	/* Use CALL_ON_STACK. */
+#define UWM_IRQ			0x20	/* Unwind from irq context. */
+#define UWM_PGM			0x40	/* Unwind from program check handler. */
+
+static __always_inline unsigned long get_psw_addr(void)
+{
+	unsigned long psw_addr;
+
+	asm volatile(
+		"basr	%[psw_addr],0\n"
+		: [psw_addr] "=d" (psw_addr));
+	return psw_addr;
+}
+
+#ifdef CONFIG_KPROBES
+static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct unwindme *u = unwindme;
+
+	u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL,
+			     (u->flags & UWM_SP) ? u->sp : 0);
+	return 0;
+}
+#endif
+
+/* This function may or may not appear in the backtrace. */
+static noinline int unwindme_func4(struct unwindme *u)
+{
+	if (!(u->flags & UWM_CALLER))
+		u->sp = current_frame_address();
+	if (u->flags & UWM_THREAD) {
+		complete(&u->task_ready);
+		wait_event(u->task_wq, kthread_should_park());
+		kthread_parkme();
+		return 0;
+#ifdef CONFIG_KPROBES
+	} else if (u->flags & UWM_PGM) {
+		struct kprobe kp;
+		int ret;
+
+		unwindme = u;
+		memset(&kp, 0, sizeof(kp));
+		kp.symbol_name = "do_report_trap";
+		kp.pre_handler = pgm_pre_handler;
+		ret = register_kprobe(&kp);
+		if (ret < 0) {
+			pr_err("register_kprobe failed %d\n", ret);
+			return -EINVAL;
+		}
+
+		/*
+		 * trigger specification exception
+		 */
+		asm volatile(
+			"	mvcl	%%r1,%%r1\n"
+			"0:	nopr	%%r7\n"
+			EX_TABLE(0b, 0b)
+			:);
+
+		unregister_kprobe(&kp);
+		unwindme = NULL;
+		return u->ret;
+#endif
+	} else {
+		struct pt_regs regs;
+
+		memset(&regs, 0, sizeof(regs));
+		regs.psw.addr = get_psw_addr();
+		regs.gprs[15] = current_stack_pointer();
+		return test_unwind(NULL,
+				   (u->flags & UWM_REGS) ? &regs : NULL,
+				   (u->flags & UWM_SP) ? u->sp : 0);
+	}
+}
+
+/* This function may or may not appear in the backtrace. */
+static noinline int unwindme_func3(struct unwindme *u)
+{
+	u->sp = current_frame_address();
+	return unwindme_func4(u);
+}
+
+/* This function must appear in the backtrace. */
+static noinline int unwindme_func2(struct unwindme *u)
+{
+	int rc;
+
+	if (u->flags & UWM_SWITCH_STACK) {
+		preempt_disable();
+		rc = CALL_ON_STACK(unwindme_func3, S390_lowcore.nodat_stack, 1, u);
+		preempt_enable();
+		return rc;
+	} else {
+		return unwindme_func3(u);
+	}
+}
+
+/* This function must follow unwindme_func2 in the backtrace. */
+static noinline int unwindme_func1(void *u)
+{
+	return unwindme_func2((struct unwindme *)u);
+}
+
+static void unwindme_irq_handler(struct ext_code ext_code,
+				       unsigned int param32,
+				       unsigned long param64)
+{
+	struct unwindme *u = READ_ONCE(unwindme);
+
+	if (u && u->task == current) {
+		unwindme = NULL;
+		u->task = NULL;
+		u->ret = unwindme_func1(u);
+	}
+}
+
+static int test_unwind_irq(struct unwindme *u)
+{
+	preempt_disable();
+	if (register_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler)) {
+		pr_info("Couldn't reqister external interrupt handler");
+		return -1;
+	}
+	u->task = current;
+	unwindme = u;
+	udelay(1);
+	unregister_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler);
+	preempt_enable();
+	return u->ret;
+}
+
+/* Spawns a task and passes it to test_unwind(). */
+static int test_unwind_task(struct unwindme *u)
+{
+	struct task_struct *task;
+	int ret;
+
+	/* Initialize thread-related fields. */
+	init_completion(&u->task_ready);
+	init_waitqueue_head(&u->task_wq);
+
+	/*
+	 * Start the task and wait until it reaches unwindme_func4() and sleeps
+	 * in (task_ready, unwind_done] range.
+	 */
+	task = kthread_run(unwindme_func1, u, "%s", __func__);
+	if (IS_ERR(task)) {
+		pr_err("kthread_run() failed\n");
+		return PTR_ERR(task);
+	}
+	/*
+	 * Make sure task reaches unwindme_func4 before parking it,
+	 * we might park it before kthread function has been executed otherwise
+	 */
+	wait_for_completion(&u->task_ready);
+	kthread_park(task);
+	/* Unwind. */
+	ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
+	kthread_stop(task);
+	return ret;
+}
+
+static int test_unwind_flags(int flags)
+{
+	struct unwindme u;
+
+	u.flags = flags;
+	if (u.flags & UWM_THREAD)
+		return test_unwind_task(&u);
+	else if (u.flags & UWM_IRQ)
+		return test_unwind_irq(&u);
+	else
+		return unwindme_func1(&u);
+}
+
+static int test_unwind_init(void)
+{
+	int ret = 0;
+
+#define TEST(flags)							\
+do {									\
+	pr_info("[ RUN      ] " #flags "\n");				\
+	if (!test_unwind_flags((flags))) {				\
+		pr_info("[       OK ] " #flags "\n");			\
+	} else {							\
+		pr_err("[  FAILED  ] " #flags "\n");			\
+		ret = -EINVAL;						\
+	}								\
+} while (0)
+
+	TEST(UWM_DEFAULT);
+	TEST(UWM_SP);
+	TEST(UWM_REGS);
+	TEST(UWM_SWITCH_STACK);
+	TEST(UWM_SP | UWM_REGS);
+	TEST(UWM_CALLER | UWM_SP);
+	TEST(UWM_CALLER | UWM_SP | UWM_REGS);
+	TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
+	TEST(UWM_THREAD);
+	TEST(UWM_THREAD | UWM_SP);
+	TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
+	TEST(UWM_IRQ);
+	TEST(UWM_IRQ | UWM_SWITCH_STACK);
+	TEST(UWM_IRQ | UWM_SP);
+	TEST(UWM_IRQ | UWM_REGS);
+	TEST(UWM_IRQ | UWM_SP | UWM_REGS);
+	TEST(UWM_IRQ | UWM_CALLER | UWM_SP);
+	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS);
+	TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
+#ifdef CONFIG_KPROBES
+	TEST(UWM_PGM);
+	TEST(UWM_PGM | UWM_SP);
+	TEST(UWM_PGM | UWM_REGS);
+	TEST(UWM_PGM | UWM_SP | UWM_REGS);
+#endif
+#undef TEST
+
+	return ret;
+}
+
+static void test_unwind_exit(void)
+{
+}
+
+module_init(test_unwind_init);
+module_exit(test_unwind_exit);
+MODULE_LICENSE("GPL");