riscv: stacktrace: Fixup ftrace_graph_ret_addr retp argument

The 'retp' is a pointer to the return address on the stack, so we
must pass the current return address pointer as the 'retp'
argument to ftrace_push_return_trace(). Not parent function's
return address on the stack.

Fixes: b785ec1 ("riscv/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support")
Signed-off-by: Guo Ren <[email protected]>
Signed-off-by: Guo Ren <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Cc: [email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: guoren83

arch/riscv/kernel/stacktrace.c

@@ -58,7 +58,7 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 		} else {
 			fp = frame->fp;
 			pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
-						   (unsigned long *)(fp - 8));
+						   &frame->ra);
 		}
 
 	}