Re: [PATCH v2 5/8] riscv: stacktrace: introduce stack-bound tracking helpers

On 5/28/26 4:23 PM, Wang Han wrote:
> 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.
> 
> Signed-off-by: Wang Han <[email protected]>
> ---
>   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);
> +	unsigned long high = low + IRQ_STACK_SIZE;
> +
> +	return (struct stack_info) {
> +		.low = low,
> +		.high = high,
> +	};
> +}
> +
> +static inline bool on_irq_stack(unsigned long sp, unsigned long size)
> +{
> +	struct stack_info info = stackinfo_get_irq();
> +
> +	return stackinfo_on_stack(&info, sp, size);
> +}
> +
> +/*
> + * Task stack accessors
> + */
> +static inline struct stack_info stackinfo_get_task(const struct task_struct *tsk)
>   {
> -	return !(((unsigned long)(current->stack) ^ current_stack_pointer) & ~(THREAD_SIZE - 1));
> +	unsigned long low = (unsigned long)task_stack_page(tsk);
> +	unsigned long high = low + THREAD_SIZE;
> +
> +	return (struct stack_info) {
> +		.low = low,
> +		.high = high,
> +	};
> +}
> +
> +static inline bool on_task_stack(const struct task_struct *tsk,
> +				 unsigned long sp, unsigned long size)
> +{
> +	struct stack_info info = stackinfo_get_task(tsk);
> +
> +	return stackinfo_on_stack(&info, sp, size);
>   }
>   
> +/*
> + * Cast is necessary since current->stack is an opaque ptr.
> + */
> +#define on_thread_stack()	(on_task_stack(current, current_stack_pointer, 1))
>   
> +/*
> + * Overflow stack accessors
> + */
>   #ifdef CONFIG_VMAP_STACK
>   DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
> +
> +static inline struct stack_info stackinfo_get_overflow(void)
> +{
> +	unsigned long low = (unsigned long)raw_cpu_ptr(overflow_stack);
> +	unsigned long high = low + OVERFLOW_STACK_SIZE;
> +
> +	return (struct stack_info) {
> +		.low = low,
> +		.high = high,
> +	};
> +}
>   #endif /* CONFIG_VMAP_STACK */
>   
>   #endif /* _ASM_RISCV_STACKTRACE_H */
> diff --git a/arch/riscv/include/asm/stacktrace/common.h b/arch/riscv/include/asm/stacktrace/common.h
> new file mode 100644
> index 000000000000..87d6d40672f3
> --- /dev/null
> +++ b/arch/riscv/include/asm/stacktrace/common.h
> @@ -0,0 +1,159 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * RISC-V common stack unwinder types and helpers.
> + *
> + * See: arch/arm64/include/asm/stacktrace/common.h for the reference
> + * implementation.
> + *
> + * Copyright (C) 2024

Nit: The new common.h carries "Copyright (C) 2024", but this is a 2026
submission.

Reviewed-by: Shuai Xue <[email protected]>

Thanks.
Shuai