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Subject[PATCH 19/19] [INCOMPLETE] ARM: make return_address available for ARM_UNWIND
Date
From: sahara <keun-o.park@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@windriver.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Martin <dave.martin@linaro.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <linux@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


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