linux-kernel - [RFC PATCH v2 2/6] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION

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Message-Id: <169139092722.324433.16681957760325391475.stgit@devnote2>
Date:   Mon,  7 Aug 2023 15:48:47 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Florent Revest <revest@...omium.org>
Cc:     linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alan Maguire <alan.maguire@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC PATCH v2 2/6] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

In order to be able to use ftrace_regs even from features unrelated to
function tracer (e.g. kretprobe), expose ftrace_regs structures and
APIs even if the CONFIG_FUNCTION_TRACER=n.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 include/linux/ftrace.h |   45 ++++++++++++++++++++++++---------------------
 1 file changed, 24 insertions(+), 21 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index ce156c7704ee..3fb94a1a2461 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
 }
 #endif
 
-#ifdef CONFIG_FUNCTION_TRACER
-
-extern int ftrace_enabled;
-
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+/*
+ * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
+ * tracer, define the default(pt_regs compatible) ftrace_regs.
+ */
+#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
 
 struct ftrace_regs {
 	struct pt_regs		regs;
@@ -129,6 +129,22 @@ struct ftrace_regs {
  * HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports live kernel patching.
  */
 #define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
+
+#define ftrace_regs_get_instruction_pointer(fregs) \
+	instruction_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_get_argument(fregs, n) \
+	regs_get_kernel_argument(ftrace_get_regs(fregs), n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+	kernel_stack_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_return_value(fregs) \
+	regs_return_value(ftrace_get_regs(fregs))
+#define ftrace_regs_set_return_value(fregs, ret) \
+	regs_set_return_value(ftrace_get_regs(fregs), ret)
+#define ftrace_override_function_with_return(fregs) \
+	override_function_with_return(ftrace_get_regs(fregs))
+#define ftrace_regs_query_register_offset(name) \
+	regs_query_register_offset(name)
+
 #endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
 
 static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
@@ -151,22 +167,9 @@ static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
 	return ftrace_get_regs(fregs) != NULL;
 }
 
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
-#define ftrace_regs_get_instruction_pointer(fregs) \
-	instruction_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_get_argument(fregs, n) \
-	regs_get_kernel_argument(ftrace_get_regs(fregs), n)
-#define ftrace_regs_get_stack_pointer(fregs) \
-	kernel_stack_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_return_value(fregs) \
-	regs_return_value(ftrace_get_regs(fregs))
-#define ftrace_regs_set_return_value(fregs, ret) \
-	regs_set_return_value(ftrace_get_regs(fregs), ret)
-#define ftrace_override_function_with_return(fregs) \
-	override_function_with_return(ftrace_get_regs(fregs))
-#define ftrace_regs_query_register_offset(name) \
-	regs_query_register_offset(name)
-#endif
+#ifdef CONFIG_FUNCTION_TRACER
+
+extern int ftrace_enabled;
 
 typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
 			      struct ftrace_ops *op, struct ftrace_regs *fregs);