[PATCH bpf-next 1/3] riscv: stacktrace: Implement arch_bpf_stack_walk() for BPF

[Pu Lehui]

Hi Varun,

Thank you for implementing bpf exception for riscv64.

On 2026/6/21 22:42, Varun R Mallya wrote:
> This will be used by bpf_throw() to unwind till the program marked as
> exception boundary and run the callback with the stack of the main
> program.
> This is required for supporting BPF exceptions on RISC-V.
> This depends on the frame pointer unwinder, so it is only built under
> CONFIG_FRAME_POINTER, else falls back to the weak no-op.
> 
> Signed-off-by: Varun R Mallya <varunrmallya at gmail.com>
> ---
>   arch/riscv/kernel/stacktrace.c | 28 ++++++++++++++++++++++++++++
>   1 file changed, 28 insertions(+)
> 
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index b41b6255751c..a4c2411f4038 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -5,6 +5,7 @@
>    */
>   
>   #include <linux/export.h>
> +#include <linux/filter.h>
>   #include <linux/kallsyms.h>
>   #include <linux/sched.h>
>   #include <linux/sched/debug.h>
> @@ -102,6 +103,33 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
>   	}
>   }
>   
> +void notrace arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp),
> +				 void *cookie)
> +{
> +	unsigned long fp, sp, pc;
> +
> +	fp = (unsigned long)__builtin_frame_address(0);
> +	sp = current_stack_pointer;
> +	pc = (unsigned long)arch_bpf_stack_walk;
> +
> +	for (;;) {
> +		struct stackframe *frame;
> +
> +		if (unlikely(!__kernel_text_address(pc)))
> +			break;
> +		/* pc belongs to the function whose frame pointer is fp */
> +		if (!consume_fn(cookie, pc, sp, fp))
> +			break;
> +		if (unlikely(!fp_is_valid(fp, sp)))
> +			break;
> +
> +		frame = (struct stackframe *)fp - 1;
> +		sp = fp;
> +		fp = READ_ONCE_TASK_STACK(current, frame->fp);
> +		pc = READ_ONCE_TASK_STACK(current, frame->ra);
> +	}
> +}
> +
>   #else /* !CONFIG_FRAME_POINTER */
>   
>   void notrace walk_stackframe(struct task_struct *task,

Reviewed-by: Pu Lehui <pulehui at huawei.com>