Re: [PATCH v2 5/5] powerpc64/ftrace: Implement support for ftrace_regs_caller()

Steven Rostedt wrote:

On Wed, 21 Mar 2018 16:13:22 +0530
"Naveen N. Rao" [off-list ref] wrote:
=20

quoted

 int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
 {
 	mod->arch.toc =3D my_r2(sechdrs, mod);
-	mod->arch.tramp =3D create_ftrace_stub(sechdrs, mod);
+	mod->arch.tramp =3D create_ftrace_stub(sechdrs, mod,
+					(unsigned long)ftrace_caller);
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+	mod->arch.tramp_regs =3D create_ftrace_stub(sechdrs, mod,
+					(unsigned long)ftrace_regs_caller);

=20
So you only reference ftrace_regs_caller if you have
DYNAMIC_FTRACE_WITH_REGS defined?

Yes.

=20

quoted

+	if (!mod->arch.tramp_regs)
+		return -ENOENT;
+#endif
=20
 	if (!mod->arch.tramp)
 		return -ENOENT;

=20
=20

quoted

diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/power=

pc/kernel/trace/ftrace_64_mprofile.S

quoted

index 8f2380304ef1..7b81db85f76e 100644

--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S

@@ -20,8 +20,8 @@
 #ifdef CONFIG_DYNAMIC_FTRACE
 /*
  *
- * ftrace_caller() is the function that replaces _mcount() when ftrace =

is

quoted

- * active.
+ * ftrace_caller()/ftrace_regs_caller() is the function that replaces _=

mcount()

quoted

+ * when ftrace is active.
  *
  * We arrive here after a function A calls function B, and we are the t=

race

quoted

  * function for B. When we enter r1 points to A's stack frame, B has no=

t yet

quoted

@@ -37,7 +37,7 @@
  * Our job is to save the register state into a struct pt_regs (on the =

stack)

quoted

  * and then arrange for the ftrace function to be called.
  */

=20
Perhaps you want to add:
=20
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
=20
here.

I think that will always be set here. ftrace_64_mprofile.S is only built=20
for -mprofile-kernel and we select HAVE_DYNAMIC_FTRACE_WITH_REGS if=20
MPROFILE_KERNEL is enabled. It looks like there is no way to unset just=20
CONFIG_DYNAMIC_FTRACE_WITH_REGS and so, for -mprofile-kernel, we can=20
assume it is always set?

- Naveen

=