* [PATCH v2 1/7] ARM: Make thread_save_fp macro aware of THUMB2 mode
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame() Nikolay Borisov
` (7 subsequent siblings)
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
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.
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
Reviewed-by: Anurag Aggarwal <anurag19aggarwal@gmail.com>
---
arch/arm/include/asm/thread_info.h | 6 ++++++
1 file changed, 6 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 *);
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame()
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 1/7] ARM: Make thread_save_fp macro aware of " Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 17:20 ` Will Deacon
2014-06-02 8:05 ` Robert Richter
2014-05-30 16:59 ` [PATCH v3 3/7] ARM: perf: Make perf use arm_get_current_stackframe Nikolay Borisov
` (6 subsequent siblings)
8 siblings, 2 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Currently there are numerous places where "struct pt_regs" are used to
populate "struct stackframe", however all of those location do not
consider the situation where the kernel might be compiled in THUMB2
mode, in which case the framepointer member of pt_regs become ARM_r7
instead of ARM_fp (r11). Document this idiosyncracy in the
definition of "struct stackframe"
The easiest solution is to introduce a new function (in the spirit of
https://groups.google.com/forum/#!topic/linux.kernel/dA2YuUcSpZ4)
which would hide the complexity of initializing the stackframe struct
from pt_regs.
Also implement a macro frame_pointer(regs) that would return the correct
register so that we can use it in cases where we just require the frame
pointer and not a whole struct stackframe
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/include/asm/ptrace.h | 6 ++++++
arch/arm/include/asm/stacktrace.h | 12 ++++++++++++
2 files changed, 18 insertions(+)
diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index c877654..601264d 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -84,6 +84,12 @@ static inline long regs_return_value(struct pt_regs *regs)
#define instruction_pointer(regs) (regs)->ARM_pc
+#ifdef CONFIG_THUMB2_KERNEL
+#define frame_pointer(regs) (regs)->ARM_r7
+#else
+#define frame_pointer(regs) (regs)->ARM_fp
+#endif
+
static inline void instruction_pointer_set(struct pt_regs *regs,
unsigned long val)
{
diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
index 4d0a164..6a5b13e 100644
--- a/arch/arm/include/asm/stacktrace.h
+++ b/arch/arm/include/asm/stacktrace.h
@@ -2,12 +2,24 @@
#define __ASM_STACKTRACE_H
struct stackframe {
+ /* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled.
+ * and R11 otherwise
+ */
unsigned long fp;
unsigned long sp;
unsigned long lr;
unsigned long pc;
};
+static __always_inline
+void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
+{
+ frame->fp = frame_pointer(regs);
+ frame->sp = regs->ARM_sp;
+ frame->lr = regs->ARM_lr;
+ frame->pc = regs->ARM_pc;
+}
+
extern int unwind_frame(struct stackframe *frame);
extern void walk_stackframe(struct stackframe *frame,
int (*fn)(struct stackframe *, void *), void *data);
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame()
2014-05-30 16:59 ` [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame() Nikolay Borisov
@ 2014-05-30 17:20 ` Will Deacon
2014-06-02 8:05 ` Robert Richter
1 sibling, 0 replies; 13+ messages in thread
From: Will Deacon @ 2014-05-30 17:20 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, May 30, 2014 at 05:59:46PM +0100, Nikolay Borisov wrote:
> From: Nikolay Borisov <Nikolay.Borisov@arm.com>
>
> Currently there are numerous places where "struct pt_regs" are used to
> populate "struct stackframe", however all of those location do not
> consider the situation where the kernel might be compiled in THUMB2
> mode, in which case the framepointer member of pt_regs become ARM_r7
> instead of ARM_fp (r11). Document this idiosyncracy in the
> definition of "struct stackframe"
>
> The easiest solution is to introduce a new function (in the spirit of
> https://groups.google.com/forum/#!topic/linux.kernel/dA2YuUcSpZ4)
> which would hide the complexity of initializing the stackframe struct
> from pt_regs.
>
> Also implement a macro frame_pointer(regs) that would return the correct
> register so that we can use it in cases where we just require the frame
> pointer and not a whole struct stackframe
>
> Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
> ---
> arch/arm/include/asm/ptrace.h | 6 ++++++
> arch/arm/include/asm/stacktrace.h | 12 ++++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
> index c877654..601264d 100644
> --- a/arch/arm/include/asm/ptrace.h
> +++ b/arch/arm/include/asm/ptrace.h
> @@ -84,6 +84,12 @@ static inline long regs_return_value(struct pt_regs *regs)
>
> #define instruction_pointer(regs) (regs)->ARM_pc
>
> +#ifdef CONFIG_THUMB2_KERNEL
> +#define frame_pointer(regs) (regs)->ARM_r7
> +#else
> +#define frame_pointer(regs) (regs)->ARM_fp
> +#endif
> +
> static inline void instruction_pointer_set(struct pt_regs *regs,
> unsigned long val)
> {
> diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
> index 4d0a164..6a5b13e 100644
> --- a/arch/arm/include/asm/stacktrace.h
> +++ b/arch/arm/include/asm/stacktrace.h
> @@ -2,12 +2,24 @@
> #define __ASM_STACKTRACE_H
>
> struct stackframe {
> + /* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled.
> + * and R11 otherwise
> + */
Very minor nit: please reformat the comment like:
/*
* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled
* and R11 otherwise.
*/
for consistency with the rest of the kernel (I also moved the full-stop to
the end of the sentence).
With that:
Acked-by: Will Deacon <will.deacon@arm.com>
Will
^ permalink raw reply [flat|nested] 13+ messages in thread* [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame()
2014-05-30 16:59 ` [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame() Nikolay Borisov
2014-05-30 17:20 ` Will Deacon
@ 2014-06-02 8:05 ` Robert Richter
1 sibling, 0 replies; 13+ messages in thread
From: Robert Richter @ 2014-06-02 8:05 UTC (permalink / raw)
To: linux-arm-kernel
On 30.05.14 17:59:46, Nikolay Borisov wrote:
> diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
> index c877654..601264d 100644
> --- a/arch/arm/include/asm/ptrace.h
> +++ b/arch/arm/include/asm/ptrace.h
> @@ -84,6 +84,12 @@ static inline long regs_return_value(struct pt_regs *regs)
>
> #define instruction_pointer(regs) (regs)->ARM_pc
>
> +#ifdef CONFIG_THUMB2_KERNEL
> +#define frame_pointer(regs) (regs)->ARM_r7
> +#else
> +#define frame_pointer(regs) (regs)->ARM_fp
> +#endif
> +
> static inline void instruction_pointer_set(struct pt_regs *regs,
> unsigned long val)
> {
> diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
> index 4d0a164..6a5b13e 100644
> --- a/arch/arm/include/asm/stacktrace.h
> +++ b/arch/arm/include/asm/stacktrace.h
> @@ -2,12 +2,24 @@
> #define __ASM_STACKTRACE_H
>
> struct stackframe {
> + /* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled.
> + * and R11 otherwise
> + */
> unsigned long fp;
> unsigned long sp;
> unsigned long lr;
> unsigned long pc;
> };
>
> +static __always_inline
> +void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
> +{
> + frame->fp = frame_pointer(regs);
stacktrace.h should now include asm/ptrace.h.
Otherwise
Acked-by: Robert Richter <rric@kernel.org>
for patch 2 and 7 of this series.
-Robert
> + frame->sp = regs->ARM_sp;
> + frame->lr = regs->ARM_lr;
> + frame->pc = regs->ARM_pc;
> +}
^ permalink raw reply [flat|nested] 13+ messages in thread
* [PATCH v3 3/7] ARM: perf: Make perf use arm_get_current_stackframe
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 1/7] ARM: Make thread_save_fp macro aware of " Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame() Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 4/7] ARM: time: Make use of arm_get_current_stackframe Nikolay Borisov
` (5 subsequent siblings)
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Make the perf backend use the API so that it correctly references the FP
when in THUMB2 mode
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/kernel/perf_event.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index a6bc431..55353fd 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -621,10 +621,7 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
return;
}
- fr.fp = regs->ARM_fp;
- fr.sp = regs->ARM_sp;
- fr.lr = regs->ARM_lr;
- fr.pc = regs->ARM_pc;
+ arm_get_current_stackframe(regs, &fr);
walk_stackframe(&fr, callchain_trace, entry);
}
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 4/7] ARM: time: Make use of arm_get_current_stackframe
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (2 preceding siblings ...)
2014-05-30 16:59 ` [PATCH v3 3/7] ARM: perf: Make perf use arm_get_current_stackframe Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 5/7] ARM: unwind: Use arm_get_current_stackframe Nikolay Borisov
` (4 subsequent siblings)
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Make use of the arm_get_current_stackframe api so that
the frame pointer is correctly referenced in THUMB2 mode
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/kernel/time.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/arm/kernel/time.c b/arch/arm/kernel/time.c
index 829a96d..0cc7e58 100644
--- a/arch/arm/kernel/time.c
+++ b/arch/arm/kernel/time.c
@@ -50,10 +50,7 @@ unsigned long profile_pc(struct pt_regs *regs)
if (!in_lock_functions(regs->ARM_pc))
return regs->ARM_pc;
- frame.fp = regs->ARM_fp;
- frame.sp = regs->ARM_sp;
- frame.lr = regs->ARM_lr;
- frame.pc = regs->ARM_pc;
+ arm_get_current_stackframe(regs, &frame);
do {
int ret = unwind_frame(&frame);
if (ret < 0)
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 5/7] ARM: unwind: Use arm_get_current_stackframe
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (3 preceding siblings ...)
2014-05-30 16:59 ` [PATCH v2 4/7] ARM: time: Make use of arm_get_current_stackframe Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 6/7] ARM: traps: Make use of the frame_pointer macro Nikolay Borisov
` (3 subsequent siblings)
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Make the unwind code use the correct API so that the frame pointer
is extracted from the correct register.
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/kernel/unwind.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 3c21769..7aaec44 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -479,12 +479,10 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
tsk = current;
if (regs) {
- frame.fp = regs->ARM_fp;
- frame.sp = regs->ARM_sp;
- frame.lr = regs->ARM_lr;
+ arm_get_current_stackframe(regs, &frame);
/* PC might be corrupted, use LR in that case. */
- frame.pc = kernel_text_address(regs->ARM_pc)
- ? regs->ARM_pc : regs->ARM_lr;
+ if (!kernel_text_address(regs->ARM_pc))
+ frame.pc = regs->ARM_lr;
} else if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_sp;
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 6/7] ARM: traps: Make use of the frame_pointer macro
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (4 preceding siblings ...)
2014-05-30 16:59 ` [PATCH v2 5/7] ARM: unwind: Use arm_get_current_stackframe Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 16:59 ` [PATCH v2 7/7] ARM: oprofile: Use of arm_get_current_stackframe Nikolay Borisov
` (2 subsequent siblings)
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Use the newly-introduced frame_pointer macro to extract
the correct FP based on whether we are in THUMB2 mode or not.
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/kernel/traps.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index abd2fc0..c8e4bb7 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -31,11 +31,13 @@
#include <asm/exception.h>
#include <asm/unistd.h>
#include <asm/traps.h>
+#include <asm/ptrace.h>
#include <asm/unwind.h>
#include <asm/tls.h>
#include <asm/system_misc.h>
#include <asm/opcodes.h>
+
static const char *handler[]= {
"prefetch abort",
"data abort",
@@ -184,7 +186,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
tsk = current;
if (regs) {
- fp = regs->ARM_fp;
+ fp = frame_pointer(regs);
mode = processor_mode(regs);
} else if (tsk != current) {
fp = thread_saved_fp(tsk);
@@ -719,7 +721,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
dump_instr("", regs);
if (user_mode(regs)) {
__show_regs(regs);
- c_backtrace(regs->ARM_fp, processor_mode(regs));
+ c_backtrace(frame_pointer(regs), processor_mode(regs));
}
}
#endif
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 7/7] ARM: oprofile: Use of arm_get_current_stackframe
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (5 preceding siblings ...)
2014-05-30 16:59 ` [PATCH v2 6/7] ARM: traps: Make use of the frame_pointer macro Nikolay Borisov
@ 2014-05-30 16:59 ` Nikolay Borisov
2014-05-30 17:19 ` [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Will Deacon
2014-05-31 18:31 ` Arnd Bergmann
8 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-05-30 16:59 UTC (permalink / raw)
To: linux-arm-kernel
From: Nikolay Borisov <Nikolay.Borisov@arm.com>
Use the newly introduced API so that FP is correctly referenced from
either R7/R11 based on whether we are running in THUMB2 mode or not.
Signed-off-by: Nikolay Borisov <Nikolay.Borisov@arm.com>
---
arch/arm/oprofile/common.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index 99c63d4b..e6a3c4c 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c
@@ -107,10 +107,7 @@ static void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
if (!user_mode(regs)) {
struct stackframe frame;
- frame.fp = regs->ARM_fp;
- frame.sp = regs->ARM_sp;
- frame.lr = regs->ARM_lr;
- frame.pc = regs->ARM_pc;
+ arm_get_current_stackframe(regs, &frame);
walk_stackframe(&frame, report_trace, &depth);
return;
}
--
1.8.1.5
^ permalink raw reply related [flat|nested] 13+ messages in thread* [PATCH v2 0/7] Fix backtrace support in THUMB2 mode
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (6 preceding siblings ...)
2014-05-30 16:59 ` [PATCH v2 7/7] ARM: oprofile: Use of arm_get_current_stackframe Nikolay Borisov
@ 2014-05-30 17:19 ` Will Deacon
2014-05-31 18:31 ` Arnd Bergmann
8 siblings, 0 replies; 13+ messages in thread
From: Will Deacon @ 2014-05-30 17:19 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, May 30, 2014 at 05:59:44PM +0100, Nikolay Borisov wrote:
> From: Nikolay Borisov <Nikolay.Borisov@arm.com>
>
> Currently all the code which deals with backtrace support assumes that R11
> is the frame-pointer. While this is the case for ARM mode and is explicitly
> documented in the AAPCS, this is not the case for THUMB2 mode.
>
> There is no official document requiring that R11 has to be the frame pointer
> and GCC uses R7 as FP and given that R7's usage is so intertwined within GCC's
> mechanics it is unlikely to change, so fixing backtrace in THUMB2 mode seems
> in order.
>
> This patch series rectifies the problem by first fixing the
> thread_save_fp macro to reference the correct register. Furthermore, there
> a lot of repetetive sequences of code such as :
>
> stackframe.fp = pt_regs->ARM_fp
> stackframe.lr = pt_regs->ARM_lr
>
> so introducing a function arm_get_current_stack_frame which both
> hides this repetition and also utilizes teh frame_pointer(regs) macro
> to reference the correct register depending on the mode.
>
> Finally, change all the call sites so that they utilize the new routine.
>
> Changes since v1:
> * Nothing major, just made arg_get_current_stack frame an inline routine.
I already acked most of these, please can you add my tag?
http://www.spinics.net/lists/arm-kernel/msg334457.html
Will
^ permalink raw reply [flat|nested] 13+ messages in thread* [PATCH v2 0/7] Fix backtrace support in THUMB2 mode
2014-05-30 16:59 [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Nikolay Borisov
` (7 preceding siblings ...)
2014-05-30 17:19 ` [PATCH v2 0/7] Fix backtrace support in THUMB2 mode Will Deacon
@ 2014-05-31 18:31 ` Arnd Bergmann
2014-06-02 8:34 ` Nikolay Borisov
8 siblings, 1 reply; 13+ messages in thread
From: Arnd Bergmann @ 2014-05-31 18:31 UTC (permalink / raw)
To: linux-arm-kernel
On Friday 30 May 2014 17:59:44 Nikolay Borisov wrote:
> From: Nikolay Borisov <Nikolay.Borisov@arm.com>
>
> Currently all the code which deals with backtrace support assumes that R11
> is the frame-pointer. While this is the case for ARM mode and is explicitly
> documented in the AAPCS, this is not the case for THUMB2 mode.
>
> There is no official document requiring that R11 has to be the frame pointer
> and GCC uses R7 as FP and given that R7's usage is so intertwined within GCC's
> mechanics it is unlikely to change, so fixing backtrace in THUMB2 mode seems
> in order.
>
> This patch series rectifies the problem by first fixing the
> thread_save_fp macro to reference the correct register. Furthermore, there
> a lot of repetetive sequences of code such as :
>
> stackframe.fp = pt_regs->ARM_fp
> stackframe.lr = pt_regs->ARM_lr
>
> so introducing a function arm_get_current_stack_frame which both
> hides this repetition and also utilizes teh frame_pointer(regs) macro
> to reference the correct register depending on the mode.
>
> Finally, change all the call sites so that they utilize the new routine.
Sorry for the stupid question, but does your series relate to the
#warning "TODO: return_address should use unwind tables" that we see
all the time in arch/arm/kernel/return_address.c?
If I remember the story correctly, the problem is that so far we could
never use the frame pointer in thumb2 mode, and nobody has implemented
a version of that function using the arm unwinder.
Are we now able to use the frame pointer after all?
Arnd
^ permalink raw reply [flat|nested] 13+ messages in thread* [PATCH v2 0/7] Fix backtrace support in THUMB2 mode
2014-05-31 18:31 ` Arnd Bergmann
@ 2014-06-02 8:34 ` Nikolay Borisov
0 siblings, 0 replies; 13+ messages in thread
From: Nikolay Borisov @ 2014-06-02 8:34 UTC (permalink / raw)
To: linux-arm-kernel
[Adding Dave Martin as CC]
> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd at arndb.de]
> Sent: 31 May 2014 19:32
> To: linux-arm-kernel at lists.infradead.org
> Cc: Nikolay Borisov; rric at kernel.org; Will Deacon; u.kleine-
> koenig at pengutronix.de
> Subject: Re: [PATCH v2 0/7] Fix backtrace support in THUMB2 mode
>
> On Friday 30 May 2014 17:59:44 Nikolay Borisov wrote:
> > From: Nikolay Borisov <Nikolay.Borisov@arm.com>
> >
> > Currently all the code which deals with backtrace support assumes
> that R11
> > is the frame-pointer. While this is the case for ARM mode and is
> explicitly
> > documented in the AAPCS, this is not the case for THUMB2 mode.
> >
> > There is no official document requiring that R11 has to be the frame
> pointer
> > and GCC uses R7 as FP and given that R7's usage is so intertwined
> within GCC's
> > mechanics it is unlikely to change, so fixing backtrace in THUMB2
> mode seems
> > in order.
> >
> > This patch series rectifies the problem by first fixing the
> > thread_save_fp macro to reference the correct register. Furthermore,
> there
> > a lot of repetetive sequences of code such as :
> >
> > stackframe.fp = pt_regs->ARM_fp
> > stackframe.lr = pt_regs->ARM_lr
> >
> > so introducing a function arm_get_current_stack_frame which both
> > hides this repetition and also utilizes teh frame_pointer(regs) macro
> > to reference the correct register depending on the mode.
> >
> > Finally, change all the call sites so that they utilize the new
> routine.
>
> Sorry for the stupid question, but does your series relate to the
> #warning "TODO: return_address should use unwind tables" that we see
> all the time in arch/arm/kernel/return_address.c?
>
My changes have nothing to do with the use of unwind table whatsoever,
I guess this warning is a result of a completely different issue. Probably
Dave Martin could shed more light on this.
> If I remember the story correctly, the problem is that so far we could
> never use the frame pointer in thumb2 mode, and nobody has implemented
> a version of that function using the arm unwinder.
>
> Are we now able to use the frame pointer after all?
What my changes implement, boils down to referring the correct register
Which acts as a frame pointer depending on whether we are running a THUMB2
Kernel or not.
>
> Arnd
>
Regards,
Nikolay
-- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered in England & Wales, Company No: 2557590
ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered in England & Wales, Company No: 2548782
^ permalink raw reply [flat|nested] 13+ messages in thread