ftrace: pass fregs to arch_ftrace_set_direct_caller()

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 changes the prototype of arch_ftrace_set_direct_caller() to
take ftrace_regs rather than pt_regs, and moves the extraction of the
pt_regs into arch_ftrace_set_direct_caller().

On x86, arch_ftrace_set_direct_caller() can be used even when
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=n, and <linux/ftrace.h> defines
struct ftrace_regs. Due to this, it's necessary to define
arch_ftrace_set_direct_caller() as a macro to avoid using an incomplete
type. I've also moved the body of arch_ftrace_set_direct_caller() after
the CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y defineidion of struct
ftrace_regs.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Florent Revest <revest@chromium.org>
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/20221103170520.931305-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/s390/include/asm/ftrace.h

@@ -60,17 +60,20 @@ static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *f
 	fregs->regs.psw.addr = ip;
 }
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 /*
  * When an ftrace registered caller is tracing a function that is
  * also set by a register_ftrace_direct() call, it needs to be
  * differentiated in the ftrace_caller trampoline. To do this,
  * place the direct caller in the ORIG_GPR2 part of pt_regs. This
  * tells the ftrace_caller that there's a direct caller.
  */
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr)
 {
+	struct pt_regs *regs = &fregs->regs;
 	regs->orig_gpr2 = addr;
 }
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 /*
  * Even though the system call numbers are identical for s390/s390x a

arch/x86/include/asm/ftrace.h

@@ -34,19 +34,6 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
 	return addr;
 }
 
-/*
- * When a ftrace registered caller is tracing a function that is
- * also set by a register_ftrace_direct() call, it needs to be
- * differentiated in the ftrace_caller trampoline. To do this, we
- * place the direct caller in the ORIG_AX part of pt_regs. This
- * tells the ftrace_caller that there's a direct caller.
- */
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
-{
-	/* Emulate a call */
-	regs->orig_ax = addr;
-}
-
 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 struct ftrace_regs {
 	struct pt_regs		regs;
@@ -72,6 +59,24 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
 #define FTRACE_GRAPH_TRAMP_ADDR FTRACE_GRAPH_ADDR
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+/*
+ * When a ftrace registered caller is tracing a function that is
+ * also set by a register_ftrace_direct() call, it needs to be
+ * differentiated in the ftrace_caller trampoline. To do this, we
+ * place the direct caller in the ORIG_AX part of pt_regs. This
+ * tells the ftrace_caller that there's a direct caller.
+ */
+static inline void
+__arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
+{
+	/* Emulate a call */
+	regs->orig_ax = addr;
+}
+#define arch_ftrace_set_direct_caller(fregs, addr) \
+	__arch_ftrace_set_direct_caller(&(fregs)->regs, addr)
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 struct dyn_arch_ftrace {

include/linux/ftrace.h

@@ -37,9 +37,10 @@ extern void ftrace_boot_snapshot(void);
 static inline void ftrace_boot_snapshot(void) { }
 #endif
 
-#ifdef CONFIG_FUNCTION_TRACER
 struct ftrace_ops;
 struct ftrace_regs;
+
+#ifdef CONFIG_FUNCTION_TRACER
 /*
  * If the arch's mcount caller does not support all of ftrace's
  * features, then it must call an indirect function that
@@ -427,9 +428,7 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
 {
 	return -ENODEV;
 }
-#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 /*
  * This must be implemented by the architecture.
  * It is the way the ftrace direct_ops helper, when called
@@ -443,9 +442,9 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
  * the return from the trampoline jump to the direct caller
  * instead of going back to the function it just traced.
  */
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs,
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
 						 unsigned long addr) { }
-#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 #ifdef CONFIG_STACK_TRACER
 

kernel/trace/ftrace.c

@@ -2487,14 +2487,13 @@ ftrace_add_rec_direct(unsigned long ip, unsigned long addr,
 static void call_direct_funcs(unsigned long ip, unsigned long pip,
 			      struct ftrace_ops *ops, struct ftrace_regs *fregs)
 {
-	struct pt_regs *regs = ftrace_get_regs(fregs);
 	unsigned long addr;
 
 	addr = ftrace_find_rec_direct(ip);
 	if (!addr)
 		return;
 
-	arch_ftrace_set_direct_caller(regs, addr);
+	arch_ftrace_set_direct_caller(fregs, addr);
 }
 
 struct ftrace_ops direct_ops = {