A reliable unwinder needs to validate that every frame record it reads
is fully contained in a known kernel stack, and it needs to refuse to
walk back into a stack it has already left. Add the building blocks
for that:

   * struct stack_info / struct unwind_state in a new
     asm/stacktrace/common.h, modelled on the arm64 reference
     implementation.
   * stackinfo_get_irq() / stackinfo_get_task() / stackinfo_get_overflow()
     plus the corresponding on_*_stack() predicates in asm/stacktrace.h,
     so callers can ask "is this object on stack X?" by stack kind
     rather than open-coded address arithmetic.
   * unwind_init_common(), unwind_find_stack() and
     unwind_consume_stack() helpers that enforce the
     forward-progress-only invariant required for reliability.

No existing user is wired up to these helpers in this commit; the
unwinder switch comes in a follow-up. The header changes leave
on_thread_stack() with the same semantics as before, just expressed in
terms of the new helpers.

Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Signed-off-by: Wang Han <redacted>
---
  arch/riscv/include/asm/stacktrace.h        |  65 ++++++++-
  arch/riscv/include/asm/stacktrace/common.h | 159 +++++++++++++++++++++
  2 files changed, 222 insertions(+), 2 deletions(-)
  create mode 100644 arch/riscv/include/asm/stacktrace/common.h

diff --git a/arch/riscv/include/asm/stacktrace.h b/arch/riscv/include/asm/stacktrace.h
index b1495a7e06ce..bc87c4940379 100644
--- a/arch/riscv/include/asm/stacktrace.h
+++ b/arch/riscv/include/asm/stacktrace.h

@@ -3,8 +3,13 @@
  #ifndef _ASM_RISCV_STACKTRACE_H
  #define _ASM_RISCV_STACKTRACE_H
  
+#include <linux/percpu.h>
  #include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/irq_stack.h>
  #include <asm/ptrace.h>
+#include <asm/stacktrace/common.h>
  
  struct stackframe {
  	unsigned long fp;

@@ -16,14 +21,70 @@ extern void notrace walk_stackframe(struct task_struct *task, struct pt_regs *re
  extern void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
  			   const char *loglvl);
  
-static inline bool on_thread_stack(void)
+/*
+ * IRQ stack accessors
+ */
+static inline struct stack_info stackinfo_get_irq(void)
+{
+	unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);