Varun! Thanks for spending time on getting RV eBPF more feature complete! Sorry for the slow replies.
Varun R Mallya <[email protected]> writes: > 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 <[email protected]> > Reviewed-by: Pu Lehui <[email protected]> > --- > arch/riscv/kernel/stacktrace.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c > index c7555447149b..64929381bb30 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 +103,36 @@ 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; > + int graph_idx = 0; > + > + 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); > + pc = ftrace_graph_ret_addr(current, &graph_idx, pc, > + &frame->ra); > + } > +} We don't need more stack unwinders. Can you see if you can extend walk_stackframe() with "cookie" to match BPF's needs? Have a look at what arm64 does. Sashiko had a good point about ftrace_graph_ret_addr() -- now what about kretprobe? Do we need to take that in consideration as well? Thanks, Björn
