Signed-off-by: Wang Han <redacted>
---
  arch/riscv/include/asm/ptrace.h           |  9 ++++
  arch/riscv/include/asm/stacktrace/frame.h | 53 +++++++++++++++++++++++
  arch/riscv/kernel/asm-offsets.c           |  6 +++
  arch/riscv/kernel/entry.S                 | 39 ++++++++++++++++-
  arch/riscv/kernel/head.S                  | 23 ++++++++++
  arch/riscv/kernel/process.c               | 33 +++++++++++++-
  6 files changed, 159 insertions(+), 4 deletions(-)
  create mode 100644 arch/riscv/include/asm/stacktrace/frame.h

diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
index addc8188152f..4b9b0f279214 100644
--- a/arch/riscv/include/asm/ptrace.h
+++ b/arch/riscv/include/asm/ptrace.h

@@ -8,6 +8,7 @@
  
  #include <uapi/asm/ptrace.h>
  #include <asm/csr.h>
+#include <asm/stacktrace/frame.h>
  #include <linux/compiler.h>
  
  #ifndef __ASSEMBLER__

@@ -53,6 +54,14 @@ struct pt_regs {
  	unsigned long cause;
  	/* a0 value before the syscall */
  	unsigned long orig_a0;
+
+	/*
+	 * This frame record is entirely zeroed on exception entry, allowing the
+	 * unwinder to identify exception boundaries. The type field encodes
+	 * whether the exception was taken from user (FINAL) or kernel (PT_REGS)
+	 * mode.
+	 */
+	struct frame_record_meta stackframe;
  };
  
  #define PTRACE_SYSEMU			0x1f

diff --git a/arch/riscv/include/asm/stacktrace/frame.h b/arch/riscv/include/asm/stacktrace/frame.h
new file mode 100644
index 000000000000..5720a6c65fe8
--- /dev/null
+++ b/arch/riscv/include/asm/stacktrace/frame.h

@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_RISCV_STACKTRACE_FRAME_H
+#define __ASM_RISCV_STACKTRACE_FRAME_H
+
+/*
+ * See: arch/arm64/include/asm/stacktrace/frame.h for the reference
+ * implementation.
+ */
+
+/*
+ * - FRAME_META_TYPE_NONE
+ *
+ *   This value is reserved.
+ *
+ * - FRAME_META_TYPE_FINAL
+ *
+ *   The record is the last entry on the stack.
+ *   Unwinding should terminate successfully.
+ *
+ * - FRAME_META_TYPE_PT_REGS
+ *
+ *   The record is embedded within a struct pt_regs, recording the registers at
+ *   an arbitrary point in time.
+ *   Unwinding should consume pt_regs::epc, followed by pt_regs::ra.
+ *
+ * Note: all other values are reserved and should result in unwinding
+ * terminating with an error.
+ */
+#define FRAME_META_TYPE_NONE		0
+#define FRAME_META_TYPE_FINAL		1
+#define FRAME_META_TYPE_PT_REGS		2
+
+#ifndef __ASSEMBLER__
+/*
+ * A standard RISC-V frame record.
+ */
+struct frame_record {
+	unsigned long fp;
+	unsigned long ra;
+};
+
+/*
+ * A metadata frame record indicating a special unwind.
+ * The record::{fp,ra} fields must be zero to indicate the presence of
+ * metadata.
+ */
+struct frame_record_meta {
+	struct frame_record record;
+	unsigned long type;
+};
+#endif /* __ASSEMBLER__ */
+
+#endif /* __ASM_RISCV_STACKTRACE_FRAME_H */

diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index a75f0cfea1e9..bc8e8cd7130a 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c

@@ -131,6 +131,9 @@ void asm_offsets(void)
  	OFFSET(PT_BADADDR, pt_regs, badaddr);
  	OFFSET(PT_CAUSE, pt_regs, cause);
  
+	DEFINE(S_STACKFRAME,		offsetof(struct pt_regs, stackframe));
+	DEFINE(S_STACKFRAME_TYPE,	offsetof(struct pt_regs, stackframe.type));
+
  	OFFSET(SUSPEND_CONTEXT_REGS, suspend_context, regs);
  
  	OFFSET(HIBERN_PBE_ADDR, pbe, address);

@@ -503,6 +506,9 @@ void asm_offsets(void)
  	DEFINE(STACKFRAME_SIZE_ON_STACK, ALIGN(sizeof(struct stackframe), STACK_ALIGN));
  	DEFINE(STACKFRAME_FP, offsetof(struct stackframe, fp) - sizeof(struct stackframe));
  	DEFINE(STACKFRAME_RA, offsetof(struct stackframe, ra) - sizeof(struct stackframe));
+	DEFINE(STACKFRAME_RECORD_SIZE, sizeof(struct stackframe));