Re: [RFC PATCH 1/6] trace/stack: Move code to save the stack trace into a separate function

In preparation to add support for stack tracer to powerpc, move code to
save stack trace and to calculate the frame sizes into a separate weak
function. Also provide access to some of the data structures used by the
stack trace code so that architectures can update those.

Signed-off-by: Naveen N. Rao <redacted>
---
 include/linux/ftrace.h     |  8 ++++
 kernel/trace/trace_stack.c | 98 ++++++++++++++++++++------------------
 2 files changed, 60 insertions(+), 46 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index a69f363b61bf73..8263427379f05c 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h

@@ -368,10 +368,18 @@ static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs,
 
 #ifdef CONFIG_STACK_TRACER
 
+#define STACK_TRACE_ENTRIES 500
+
+extern unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
+extern unsigned stack_trace_index[STACK_TRACE_ENTRIES];
+extern unsigned int stack_trace_nr_entries;
+extern unsigned long stack_trace_max_size;
 extern int stack_tracer_enabled;
 
 int stack_trace_sysctl(struct ctl_table *table, int write, void *buffer,
 		       size_t *lenp, loff_t *ppos);
+void stack_get_trace(unsigned long traced_ip, unsigned long *stack_ref,
+					unsigned long stack_size, int *tracer_frame);
 
 /* DO NOT MODIFY THIS VARIABLE DIRECTLY! */
 DECLARE_PER_CPU(int, disable_stack_tracer);

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 63c28504205162..5b63dbd37c8c25 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c

@@ -19,13 +19,11 @@
 
 #include "trace.h"
 
-#define STACK_TRACE_ENTRIES 500
+unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
+unsigned stack_trace_index[STACK_TRACE_ENTRIES];
 
-static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
-static unsigned stack_trace_index[STACK_TRACE_ENTRIES];
-
-static unsigned int stack_trace_nr_entries;
-static unsigned long stack_trace_max_size;
+unsigned int stack_trace_nr_entries;
+unsigned long stack_trace_max_size;
 static arch_spinlock_t stack_trace_max_lock =
 	(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 

@@ -152,49 +150,19 @@ static void print_max_stack(void)
  * Although the entry function is not displayed, the first function (sys_foo)
  * will still include the stack size of it.
  */
-static void check_stack(unsigned long ip, unsigned long *stack)