[PATCH bpf-next v3 3/6] riscv, stacktrace: Implement arch_bpf_stack_walk() for BPF

[Varun R Mallya]

This will be used by bpf_throw() to unwind till the program marked as
exception boundary and run the exception callback with the stack of the
main program.
This is a wrapper around walk_stackframe(), which now passes (pc, sp and
fp) to it's consume callback.

Signed-off-by: Varun R Mallya <varunrmallya at gmail.com>
---
 arch/riscv/kernel/stacktrace.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 30b369dd2815..c0f2393e5163 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>
@@ -104,6 +105,30 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 	}
 }
 
+struct bpf_unwind_consume_entry_data {
+	bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp);
+	void *cookie;
+};
+
+static bool bpf_unwind_consume_entry(void *arg, unsigned long pc,
+				     unsigned long sp, unsigned long fp)
+{
+	struct bpf_unwind_consume_entry_data *data = arg;
+
+	return data->consume_entry(data->cookie, pc, sp, fp);
+}
+
+void notrace arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp),
+				 void *cookie)
+{
+	struct bpf_unwind_consume_entry_data data = {
+		.consume_entry = consume_fn,
+		.cookie = cookie,
+	};
+
+	walk_stackframe(current, NULL, bpf_unwind_consume_entry, &data);
+}
+
 #else /* !CONFIG_FRAME_POINTER */
 
 void notrace walk_stackframe(struct task_struct *task,
-- 
2.55.0