Re: [PATCH v2 11/13] powerpc/ftrace: directly call of function graph tracer by ftrace caller

[Naveen N. Rao]

Christophe Leroy wrote:
Modify function graph tracer to be handled directly by the standard
ftrace caller.
This is made possible as powerpc now supports
CONFIG_DYNAMIC_FTRACE_WITH_ARGS.

This change simplifies the call of function graph ftrace.

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 arch/powerpc/include/asm/ftrace.h             |  6 ++
 arch/powerpc/kernel/trace/ftrace.c            | 11 ++++
 arch/powerpc/kernel/trace/ftrace_32.S         | 53 +--------------
 .../powerpc/kernel/trace/ftrace_64_mprofile.S | 64 +------------------
 4 files changed, 20 insertions(+), 114 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h 
b/arch/powerpc/include/asm/ftrace.h
index 45c3d6f11daa..70b457097098 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -38,6 +38,12 @@ static __always_inline void 
ftrace_instruction_pointer_set(struct ftrace_regs *f
 {
        regs_set_return_ip(&fregs->regs, ip);
 }
+
+struct ftrace_ops;
+
+#define ftrace_graph_func ftrace_graph_func
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+                      struct ftrace_ops *op, struct ftrace_regs *fregs);
 #endif
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index ce673764cb69..74a176e394ef 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -917,6 +917,9 @@ static int ftrace_modify_ftrace_graph_caller(bool enable)
        unsigned long stub = (unsigned long)(&ftrace_graph_stub);
        ppc_inst_t old, new;
 
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
+               return 0;
+
        old = ftrace_call_replace(ip, enable ? stub : addr, 0);
        new = ftrace_call_replace(ip, enable ? addr : stub, 0);
 
@@ -955,6 +958,14 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
 out:
        return parent;
 }

For x86, commit 0c0593b45c9b4e ("x86/ftrace: Make function graph use 
ftrace directly") also adds recursion check before the call to 
function_graph_enter() in prepare_ftrace_return(). Do we need that on
powerpc as well?


- Naveen