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From:   Qing Zhang <zhangqing@loongson.cn>
To:     Huacai Chen <chenhuacai@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>
Cc:     WANG Xuerui <kernel@xen0n.name>, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org,
        Jiaxun Yang <jiaxun.yang@flygoat.com>, hejinyang@loongson.cn
Subject: [PATCH v2 6/9] LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support
Date:   Fri, 26 Aug 2022 15:31:11 +0800
Message-Id: <20220826073114.1515-7-zhangqing@loongson.cn>
In-Reply-To: <20220826073114.1515-1-zhangqing@loongson.cn>
References: <20220826073114.1515-1-zhangqing@loongson.cn>
MIME-Version: 1.0
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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>
---
 arch/loongarch/Kconfig              |  1 +
 arch/loongarch/include/asm/ftrace.h | 17 +++++++++++++++++
 arch/loongarch/kernel/ftrace_dyn.c  | 12 ++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 22eb3d6f8537..96902647b692 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -84,6 +84,7 @@ 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_EXIT_THREAD
 	select HAVE_FAST_GUP
diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index a3f974a7a5ce..4a9db84f8264 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -28,6 +28,23 @@ struct dyn_ftrace;
 int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
 #define ftrace_init_nop ftrace_init_nop
 
+#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;
+}
+
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs);
+#define ftrace_graph_func ftrace_graph_func
+#endif
+
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 #define ARCH_SUPPORTS_FTRACE_OPS 1
 #endif
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
index ec3d951be50c..f538829312d7 100644
--- a/arch/loongarch/kernel/ftrace_dyn.c
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -144,6 +144,17 @@ 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)
 {
 	unsigned long pc, func;
@@ -170,4 +181,5 @@ 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 */
-- 
2.20.1