[PATCH v4 3/9] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER

["Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>]

From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Florent Revest <revest@xxxxxxxxxxxx>
---
 Changes in v3:
  - arch/s390/include/asm/ftrace.h: hide ftrace_regs parts if
    CONFIG_FUNCTION_TRACER=n to avoid conflict.
  - Fixed typo.
  - Define accessor macros only if HAVE_REGS_AND_STACK_ACCESS_API=y
---
 arch/s390/include/asm/ftrace.h |    4 +++
 include/linux/ftrace.h         |   51 +++++++++++++++++++++++-----------------
 2 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index e5c5cb1207e2..74cd2e8bf660 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -41,6 +41,8 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
 	return addr;
 }
 
+#ifdef CONFIG_FUNCTION_TRACER
+
 struct ftrace_regs {
 	struct pt_regs regs;
 };
@@ -80,6 +82,8 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
 #define ftrace_regs_query_register_offset(name) \
 	regs_query_register_offset(name)
 
+#endif /* CONFIG_FUNCTION_TRACER */
+
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 /*
  * When an ftrace registered caller is tracing a function that is
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index aad9cf8876b5..fe335d861f08 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -112,24 +112,44 @@ 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 disables 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;
 };
 #define arch_ftrace_get_regs(fregs) (&(fregs)->regs)
 
+#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
+
 /*
  * ftrace_regs_set_instruction_pointer() is to be defined by the architecture
  * if to allow setting of the instruction pointer from the ftrace_regs when
  * HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports live kernel patching.
  */
 #define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
-#endif /* 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 /* CONFIG_HAVE_REGS_AND_STACK_ACCESS_API */
+
+#endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || !CONFIG_FUNCTION_TRACER */
 
 static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
 {
@@ -151,22 +171,9 @@ 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);