[PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND

[Arnd Bergmann]

From: sahara <keun-o.park at windriver.com>

This is a reminder that we still need to fix the return_address
function to work correctly with the unwinder. Keun-O Park has
made this attempt in the past, which is still under discussion[1],
and Dave Martin has also mentioned that he would provide a
solution for this problem.

Right now, this patch makes the warning go away and provides
an implementation of return_address for the arm unwinder, but
causes other problems, so we should *not* apply it. I will
keep sending this patch until we have a better solution.

[1] http://lkml.org/lkml/2013/1/11/493

Original changelog:

This fixes a warning saying:

    warning: #warning "TODO: return_address should use unwind tables"

And, this enables return_address using unwind information. If ARM_UNWIND is
selected, unwind_frame in unwind.c will be called in walk_stackframe.

Signed-off-by: sahara <keun-o.park at windriver.com>
Signed-off-by: Arnd Bergmann <arnd at arndb.de>
Cc: Dave Martin <dave.martin at linaro.org>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Russell King <linux at arm.linux.org.uk>
---
 arch/arm/include/asm/ftrace.h    |  6 ++----
 arch/arm/kernel/Makefile         | 12 +++++-------
 arch/arm/kernel/return_address.c | 10 +++-------
 arch/arm/kernel/stacktrace.c     |  3 +++
 kernel/trace/trace_irqsoff.c     | 26 ++++++++++++--------------
 5 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index f89515a..3552ad9 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -32,13 +32,11 @@ extern void ftrace_call_old(void);
 
 #ifndef __ASSEMBLY__
 
-#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
+#if defined(CONFIG_FRAME_POINTER) || defined(CONFIG_ARM_UNWIND)
 /*
  * return_address uses walk_stackframe to do it's work.  If both
  * CONFIG_FRAME_POINTER=y and CONFIG_ARM_UNWIND=y walk_stackframe uses unwind
- * information.  For this to work in the function tracer many functions would
- * have to be marked with __notrace.  So for now just depend on
- * !CONFIG_ARM_UNWIND.
+ * information.
  */
 
 void *return_address(unsigned int);
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 5bbec7b..09a0d64 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -5,13 +5,11 @@
 CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
 AFLAGS_head.o        := -DTEXT_OFFSET=$(TEXT_OFFSET)
 
-ifdef CONFIG_FUNCTION_TRACER
-CFLAGS_REMOVE_ftrace.o = -pg
-CFLAGS_REMOVE_insn.o = -pg
-CFLAGS_REMOVE_patch.o = -pg
-endif
-
-CFLAGS_REMOVE_return_address.o = -pg
+CFLAGS_REMOVE_ftrace.o		= -pg
+CFLAGS_REMOVE_insn.o		= -pg
+CFLAGS_REMOVE_patch.o		= -pg
+CFLAGS_REMOVE_unwind.o		= -pg
+CFLAGS_REMOVE_return_address.o	= -pg
 
 # Object file lists.
 
diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
index 8085417..ccb5e37 100644
--- a/arch/arm/kernel/return_address.c
+++ b/arch/arm/kernel/return_address.c
@@ -11,7 +11,7 @@
 #include <linux/export.h>
 #include <linux/ftrace.h>
 
-#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
+#if defined(CONFIG_FRAME_POINTER) || defined(CONFIG_ARM_UNWIND)
 #include <linux/sched.h>
 
 #include <asm/stacktrace.h>
@@ -56,17 +56,13 @@ void *return_address(unsigned int level)
 		return NULL;
 }
 
-#else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
-
-#if defined(CONFIG_ARM_UNWIND)
-#warning "TODO: return_address should use unwind tables"
-#endif
+#else /* CONFIG_FRAME_POINTER || CONFIG_ARM_UNWIND */
 
 void *return_address(unsigned int level)
 {
 	return NULL;
 }
 
-#endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */
+#endif /* CONFIG_FRAME_POINTER || CONFIG_ARM_UNWIND */
 
 EXPORT_SYMBOL_GPL(return_address);
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 00f79e5..aab144b 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -6,6 +6,9 @@
 
 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
 /*
+ * If both CONFIG_FRAME_POINTER=y and CONFIG_ARM_UNWIND=y walk_stackframe uses
+ * unwind information. So for now just depend on !CONFIG_ARM_UNWIND.
+ *
  * Unwind the current stack frame and store the new register values in the
  * structure passed as argument. Unwinding is equivalent to a function return,
  * hence the new PC value rather than LR should be used for backtrace.
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 713a2ca..6f207ed 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -483,20 +483,6 @@ inline void print_irqtrace_events(struct task_struct *curr)
 /*
  * We are only interested in hardirq on/off events:
  */
-void trace_hardirqs_on(void)
-{
-	if (!preempt_trace() && irq_trace())
-		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-EXPORT_SYMBOL(trace_hardirqs_on);
-
-void trace_hardirqs_off(void)
-{
-	if (!preempt_trace() && irq_trace())
-		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-}
-EXPORT_SYMBOL(trace_hardirqs_off);
-
 void trace_hardirqs_on_caller(unsigned long caller_addr)
 {
 	if (!preempt_trace() && irq_trace())
@@ -504,6 +490,12 @@ void trace_hardirqs_on_caller(unsigned long caller_addr)
 }
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
+void trace_hardirqs_on(void)
+{
+	trace_hardirqs_on_caller(CALLER_ADDR0);
+}
+EXPORT_SYMBOL(trace_hardirqs_on);
+
 void trace_hardirqs_off_caller(unsigned long caller_addr)
 {
 	if (!preempt_trace() && irq_trace())
@@ -511,6 +503,12 @@ void trace_hardirqs_off_caller(unsigned long caller_addr)
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
+void trace_hardirqs_off(void)
+{
+	trace_hardirqs_off_caller(CALLER_ADDR0);
+}
+EXPORT_SYMBOL(trace_hardirqs_off);
+
 #endif /* CONFIG_PROVE_LOCKING */
 #endif /*  CONFIG_IRQSOFF_TRACER */
 
-- 
1.8.0