ftrace: abstract DYNAMIC_FTRACE_WITH_ARGS accesses

In subsequent patches we'll arrange for architectures to have an
ftrace_regs which is entirely distinct from pt_regs. In preparation for
this, we need to minimize the use of pt_regs to where strictly necessary
in the core ftrace code.

This patch adds new ftrace_regs_{get,set}_*() helpers which can be used
to manipulate ftrace_regs. When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y,
these can always be used on any ftrace_regs, and when
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=n these can be used when regs are
available. A new ftrace_regs_has_args(fregs) helper is added which code
can use to check when these are usable.
Co-developed-by: Florent Revest <revest@chromium.org>
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20221103170520.931305-4-mark.rutland@arm.comSigned-off-by: Will Deacon <will@kernel.org>

arch/powerpc/include/asm/ftrace.h

@@ -44,6 +44,25 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
 	regs_set_return_ip(&fregs->regs, ip);
 }
 
+static __always_inline unsigned long
+ftrace_regs_get_instruction_pointer(struct ftrace_regs *fregs)
+{
+	return instruction_pointer(&fregs->regs);
+}
+
+#define ftrace_regs_get_argument(fregs, n) \
+	regs_get_kernel_argument(&(fregs)->regs, n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+	kernel_stack_pointer(&(fregs)->regs)
+#define ftrace_regs_return_value(fregs) \
+	regs_return_value(&(fregs)->regs)
+#define ftrace_regs_set_return_value(fregs, ret) \
+	regs_set_return_value(&(fregs)->regs, ret)
+#define ftrace_override_function_with_return(fregs) \
+	override_function_with_return(&(fregs)->regs)
+#define ftrace_regs_query_register_offset(name) \
+	regs_query_register_offset(name)
+
 struct ftrace_ops;
 
 #define ftrace_graph_func ftrace_graph_func

arch/s390/include/asm/ftrace.h

@@ -54,6 +54,12 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *
 	return NULL;
 }
 
+static __always_inline unsigned long
+ftrace_regs_get_instruction_pointer(const struct ftrace_regs *fregs)
+{
+	return fregs->regs.psw.addr;
+}
+
 static __always_inline void
 ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
 				    unsigned long ip)
@@ -61,6 +67,19 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
 	fregs->regs.psw.addr = ip;
 }
 
+#define ftrace_regs_get_argument(fregs, n) \
+	regs_get_kernel_argument(&(fregs)->regs, n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+	kernel_stack_pointer(&(fregs)->regs)
+#define ftrace_regs_return_value(fregs) \
+	regs_return_value(&(fregs)->regs)
+#define ftrace_regs_set_return_value(fregs, ret) \
+	regs_set_return_value(&(fregs)->regs, ret)
+#define ftrace_override_function_with_return(fregs) \
+	override_function_with_return(&(fregs)->regs)
+#define ftrace_regs_query_register_offset(name) \
+	regs_query_register_offset(name)
+
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 /*
  * When an ftrace registered caller is tracing a function that is

arch/x86/include/asm/ftrace.h

@@ -51,6 +51,22 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
 #define ftrace_regs_set_instruction_pointer(fregs, _ip)	\
 	do { (fregs)->regs.ip = (_ip); } while (0)
 
+#define ftrace_regs_get_instruction_pointer(fregs) \
+	((fregs)->regs.ip)
+
+#define ftrace_regs_get_argument(fregs, n) \
+	regs_get_kernel_argument(&(fregs)->regs, n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+	kernel_stack_pointer(&(fregs)->regs)
+#define ftrace_regs_return_value(fregs) \
+	regs_return_value(&(fregs)->regs)
+#define ftrace_regs_set_return_value(fregs, ret) \
+	regs_set_return_value(&(fregs)->regs, ret)
+#define ftrace_override_function_with_return(fregs) \
+	override_function_with_return(&(fregs)->regs)
+#define ftrace_regs_query_register_offset(name) \
+	regs_query_register_offset(name)
+
 struct ftrace_ops;
 #define ftrace_graph_func ftrace_graph_func
 void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,

include/linux/ftrace.h

@@ -126,6 +126,35 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
 	return arch_ftrace_get_regs(fregs);
 }
 
+/*
+ * When true, the ftrace_regs_{get,set}_*() functions may be used on fregs.
+ * Note: this can be true even when ftrace_get_regs() cannot provide a pt_regs.
+ */
+static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
+{
+	if (IS_ENABLED(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS))
+		return true;
+
+	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
+
 typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
 			      struct ftrace_ops *op, struct ftrace_regs *fregs);
 

kernel/trace/Kconfig

@@ -46,10 +46,10 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
 	bool
 	help
 	 If this is set, then arguments and stack can be found from
-	 the pt_regs passed into the function callback regs parameter
+	 the ftrace_regs passed into the function callback regs parameter
 	 by default, even without setting the REGS flag in the ftrace_ops.
-	 This allows for use of regs_get_kernel_argument() and
-	 kernel_stack_pointer().
+	 This allows for use of ftrace_regs_get_argument() and
+	 ftrace_regs_get_stack_pointer().
 
 config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
 	bool