[PATCH v2] ARM: unwinder: Fix handling of 'fp' in thumb2 mode

[Nikolay Borisov]

The thread_save_fp macro has been defined so that it always reads the fp member
of the cpu_context_save struct. However, in the case of THUMB2 the fp is saved
not in the fp (r11) member but rather in r7.

This patch changes the way the macro is defined such that FP is read from the
correct place depending on whether we are a THUMB2 kernel or not. This enables
the backtrace in sitaution such as "echo t > /proc/sysrq-trigger" or the
function in which a process sleeping when "ps -Al" is invoked.

Another place where similar change is requried is when working with pt_reg.
regs->ARM_fp is defined such that r11 is always referenced as the frame pointer,
so the definition of ARM_fp needs to change depending on the type of kernel we
are running.

Changes since v1:
* Added changes for the pt_reg structure.

Signed-off-by: Nikolay Borisov <Nikolay.Borisov at arm.com>

handle the case when we've got regs present
---
 arch/arm/include/asm/thread_info.h | 6 ++++++
 arch/arm/include/uapi/asm/ptrace.h | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index f989d7c..e4e4208 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -114,8 +114,14 @@ static inline struct thread_info *current_thread_info(void)
 	((unsigned long)(task_thread_info(tsk)->cpu_context.pc))
 #define thread_saved_sp(tsk)	\
 	((unsigned long)(task_thread_info(tsk)->cpu_context.sp))
+
+#ifndef CONFIG_THUMB2_KERNEL
 #define thread_saved_fp(tsk)	\
 	((unsigned long)(task_thread_info(tsk)->cpu_context.fp))
+#else
+#define thread_saved_fp(tsk)	\
+	((unsigned long)(task_thread_info(tsk)->cpu_context.r7))
+#endif
 
 extern void crunch_task_disable(struct thread_info *);
 extern void crunch_task_copy(struct thread_info *, void *);
diff --git a/arch/arm/include/uapi/asm/ptrace.h b/arch/arm/include/uapi/asm/ptrace.h
index 5af0ed1..92e1bae 100644
--- a/arch/arm/include/uapi/asm/ptrace.h
+++ b/arch/arm/include/uapi/asm/ptrace.h
@@ -131,7 +131,11 @@ struct pt_regs {
 #define ARM_lr		uregs[14]
 #define ARM_sp		uregs[13]
 #define ARM_ip		uregs[12]
+#ifndef CONFIG_THUMB2_KERNEL
 #define ARM_fp		uregs[11]
+#else
+#define ARM_fp		uregs[7]
+#endif
 #define ARM_r10		uregs[10]
 #define ARM_r9		uregs[9]
 #define ARM_r8		uregs[8]
-- 
1.8.1.5