LoongArch: Add guess unwinder support

Name "guess unwinder" comes from x86, it scans the stack and reports
every kernel text address it finds.

Unwinders can be used by dump_stack() and other stacktrace functions.

Three stages when we do unwind,
  1) unwind_start(), the prapare of unwinding, fill unwind_state.
  2) unwind_done(), judge whether the unwind process is finished or not.
  3) unwind_next_frame(), unwind the next frame.

Add get_stack_info() to get stack info. At present we have irq stack and
task stack. The next_sp is the key info between two types of stacks.

Dividing unwinder helps to add new unwinders in the future.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 36 insertions, 0 deletions

diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
new file mode 100644
index 000000000000..206fcbe24c0a
--- /dev/null
+++ b/arch/loongarch/include/asm/unwind.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Most of this ideas comes from x86.
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_UNWIND_H
+#define _ASM_UNWIND_H
+
+#include <linux/sched.h>
+
+#include <asm/stacktrace.h>
+
+struct unwind_state {
+	struct stack_info stack_info;
+	struct task_struct *task;
+	bool first, error;
+	unsigned long sp, pc;
+};
+
+void unwind_start(struct unwind_state *state,
+		  struct task_struct *task, struct pt_regs *regs);
+bool unwind_next_frame(struct unwind_state *state);
+unsigned long unwind_get_return_address(struct unwind_state *state);
+
+static inline bool unwind_done(struct unwind_state *state)
+{
+	return state->stack_info.type == STACK_TYPE_UNKNOWN;
+}
+
+static inline bool unwind_error(struct unwind_state *state)
+{
+	return state->error;
+}
+
+#endif /* _ASM_UNWIND_H */