LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support

Allow for arguments to be passed in to ftrace_regs by default. If this
is set, then arguments and stack can be found from the pt_regs.

1. HAVE_DYNAMIC_FTRACE_WITH_ARGS don't need special hook for graph
tracer entry point, but instead we can use graph_ops::func function to
install the return_hooker.

2. Livepatch requires this option in the future.
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/Kconfig

@@ -89,6 +89,7 @@ config LOONGARCH
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
+	select HAVE_DYNAMIC_FTRACE_WITH_ARGS
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_EBPF_JIT
 	select HAVE_EXIT_THREAD

arch/loongarch/include/asm/ftrace.h

@@ -37,6 +37,23 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent);
 
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
+#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+struct ftrace_ops;
+
+struct ftrace_regs {
+	struct pt_regs regs;
+};
+
+static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *fregs)
+{
+	return &fregs->regs;
+}
+
+#define ftrace_graph_func ftrace_graph_func
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs);
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* CONFIG_FUNCTION_TRACER */

arch/loongarch/kernel/ftrace_dyn.c

@@ -139,6 +139,16 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
 		*parent = return_hooker;
 }
 
+#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	struct pt_regs *regs = &fregs->regs;
+	unsigned long *parent = (unsigned long *)&regs->regs[1];
+
+	prepare_ftrace_return(ip, (unsigned long *)parent);
+}
+#else
 static int ftrace_modify_graph_caller(bool enable)
 {
 	u32 branch, nop;
@@ -166,4 +176,5 @@ int ftrace_disable_ftrace_graph_caller(void)
 {
 	return ftrace_modify_graph_caller(false);
 }
+#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */