* [PATCH] arm64: make irq_stack_ptr more robust
@ 2016-02-11 21:53 Yang Shi
2016-02-12 13:47 ` James Morse
0 siblings, 1 reply; 6+ messages in thread
From: Yang Shi @ 2016-02-11 21:53 UTC (permalink / raw)
To: linux-arm-kernel
Switching between stacks is only valid if we are tracing ourselves while on the
irq_stack, so it is only valid when in current and non-preemptible context,
otherwise is is just zeroed off.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
arch/arm64/kernel/stacktrace.c | 13 ++++++-------
arch/arm64/kernel/traps.c | 11 ++++++++++-
2 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 12a18cb..d9751a4 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
unsigned long irq_stack_ptr;
/*
- * Use raw_smp_processor_id() to avoid false-positives from
- * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping
- * task stacks, we can be pre-empted in this case, so
- * {raw_,}smp_processor_id() may give us the wrong value. Sleeping
- * tasks can't ever be on an interrupt stack, so regardless of cpu,
- * the checks will always fail.
+ * Switching between stacks is valid when tracing current and in
+ * non-preemptible context.
*/
- irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
+ if (tsk == current && !preemptible())
+ irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
+ else
+ irq_stack_ptr = 0;
low = frame->sp;
/* irq stacks are not THREAD_SIZE aligned */
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index cbedd72..7d8db3a 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
struct stackframe frame;
- unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
+ unsigned long irq_stack_ptr;
int skip;
+ /*
+ * Switching between stacks is valid when tracing current and in
+ * non-preemptible context.
+ */
+ if (tsk == current && !preemptible())
+ irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
+ else
+ irq_stack_ptr = 0;
+
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
--
2.0.2
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] arm64: make irq_stack_ptr more robust
2016-02-11 21:53 [PATCH] arm64: make irq_stack_ptr more robust Yang Shi
@ 2016-02-12 13:47 ` James Morse
2016-02-12 17:38 ` Shi, Yang
0 siblings, 1 reply; 6+ messages in thread
From: James Morse @ 2016-02-12 13:47 UTC (permalink / raw)
To: linux-arm-kernel
Hi!
On 11/02/16 21:53, Yang Shi wrote:
> Switching between stacks is only valid if we are tracing ourselves while on the
> irq_stack, so it is only valid when in current and non-preemptible context,
> otherwise is is just zeroed off.
Given it was picked up with CONFIG_DEBUG_PREEMPT:
Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
> Signed-off-by: Yang Shi <yang.shi@linaro.org>
> ---
> arch/arm64/kernel/stacktrace.c | 13 ++++++-------
> arch/arm64/kernel/traps.c | 11 ++++++++++-
> 2 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
> index 12a18cb..d9751a4 100644
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
> unsigned long irq_stack_ptr;
>
> /*
> - * Use raw_smp_processor_id() to avoid false-positives from
> - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping
> - * task stacks, we can be pre-empted in this case, so
> - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping
> - * tasks can't ever be on an interrupt stack, so regardless of cpu,
> - * the checks will always fail.
> + * Switching between stacks is valid when tracing current and in
> + * non-preemptible context.
> */
> - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
> + if (tsk == current && !preemptible())
> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
> + else
> + irq_stack_ptr = 0;
>
> low = frame->sp;
> /* irq stacks are not THREAD_SIZE aligned */
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index cbedd72..7d8db3a 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
> static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
> {
> struct stackframe frame;
> - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
> + unsigned long irq_stack_ptr;
> int skip;
>
> + /*
> + * Switching between stacks is valid when tracing current and in
Nit: Two spaces: "between[ ][ ]stacks"
> + * non-preemptible context.
> + */
> + if (tsk == current && !preemptible())
> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
> + else
> + irq_stack_ptr = 0;
> +
> pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>
> if (!tsk)
>
Neither file includes 'linux/preempt.h' for the definition of preemptible().
(I can't talk: I should have included smp.h for smp_processor_id())
Acked-by: James Morse <james.morse@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Thanks!
James
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] arm64: make irq_stack_ptr more robust
2016-02-12 13:47 ` James Morse
@ 2016-02-12 17:38 ` Shi, Yang
2016-02-12 17:41 ` Will Deacon
2016-02-12 17:54 ` Shi, Yang
0 siblings, 2 replies; 6+ messages in thread
From: Shi, Yang @ 2016-02-12 17:38 UTC (permalink / raw)
To: linux-arm-kernel
On 2/12/2016 5:47 AM, James Morse wrote:
> Hi!
>
> On 11/02/16 21:53, Yang Shi wrote:
>> Switching between stacks is only valid if we are tracing ourselves while on the
>> irq_stack, so it is only valid when in current and non-preemptible context,
>> otherwise is is just zeroed off.
>
> Given it was picked up with CONFIG_DEBUG_PREEMPT:
>
> Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
Wii add in v2.
>
>
>> Signed-off-by: Yang Shi <yang.shi@linaro.org>
>> ---
>> arch/arm64/kernel/stacktrace.c | 13 ++++++-------
>> arch/arm64/kernel/traps.c | 11 ++++++++++-
>> 2 files changed, 16 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
>> index 12a18cb..d9751a4 100644
>> --- a/arch/arm64/kernel/stacktrace.c
>> +++ b/arch/arm64/kernel/stacktrace.c
>> @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>> unsigned long irq_stack_ptr;
>>
>> /*
>> - * Use raw_smp_processor_id() to avoid false-positives from
>> - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping
>> - * task stacks, we can be pre-empted in this case, so
>> - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping
>> - * tasks can't ever be on an interrupt stack, so regardless of cpu,
>> - * the checks will always fail.
>> + * Switching between stacks is valid when tracing current and in
>> + * non-preemptible context.
>> */
>> - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
>> + if (tsk == current && !preemptible())
>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>> + else
>> + irq_stack_ptr = 0;
>>
>> low = frame->sp;
>> /* irq stacks are not THREAD_SIZE aligned */
>> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
>> index cbedd72..7d8db3a 100644
>> --- a/arch/arm64/kernel/traps.c
>> +++ b/arch/arm64/kernel/traps.c
>> @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>> static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>> {
>> struct stackframe frame;
>> - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>> + unsigned long irq_stack_ptr;
>> int skip;
>>
>> + /*
>> + * Switching between stacks is valid when tracing current and in
>
> Nit: Two spaces: "between[ ][ ]stacks"
Will fix in v2.
>
>
>> + * non-preemptible context.
>> + */
>> + if (tsk == current && !preemptible())
>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>> + else
>> + irq_stack_ptr = 0;
>> +
>> pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>>
>> if (!tsk)
>>
>
> Neither file includes 'linux/preempt.h' for the definition of preemptible().
> (I can't talk: I should have included smp.h for smp_processor_id())
I tried to build the kernel with preempt and without preempt, both
works. And, I saw arch/arm64/include/asm/Kbuild has:
generic-y += preempt.h
So, it sounds preempt.h has been included by default.
Thanks,
Yang
>
>
> Acked-by: James Morse <james.morse@arm.com>
> Tested-by: James Morse <james.morse@arm.com>
>
>
> Thanks!
>
> James
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] arm64: make irq_stack_ptr more robust
2016-02-12 17:38 ` Shi, Yang
@ 2016-02-12 17:41 ` Will Deacon
2016-02-12 17:43 ` Shi, Yang
2016-02-12 17:54 ` Shi, Yang
1 sibling, 1 reply; 6+ messages in thread
From: Will Deacon @ 2016-02-12 17:41 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote:
> On 2/12/2016 5:47 AM, James Morse wrote:
> >On 11/02/16 21:53, Yang Shi wrote:
> >>Switching between stacks is only valid if we are tracing ourselves while on the
> >>irq_stack, so it is only valid when in current and non-preemptible context,
> >>otherwise is is just zeroed off.
> >
> >Given it was picked up with CONFIG_DEBUG_PREEMPT:
> >
> >Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
>
> Wii add in v2.
I already queued the patch with this and the whitespace fix, so no need
for a v2.
Will
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] arm64: make irq_stack_ptr more robust
2016-02-12 17:41 ` Will Deacon
@ 2016-02-12 17:43 ` Shi, Yang
0 siblings, 0 replies; 6+ messages in thread
From: Shi, Yang @ 2016-02-12 17:43 UTC (permalink / raw)
To: linux-arm-kernel
On 2/12/2016 9:41 AM, Will Deacon wrote:
> On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote:
>> On 2/12/2016 5:47 AM, James Morse wrote:
>>> On 11/02/16 21:53, Yang Shi wrote:
>>>> Switching between stacks is only valid if we are tracing ourselves while on the
>>>> irq_stack, so it is only valid when in current and non-preemptible context,
>>>> otherwise is is just zeroed off.
>>>
>>> Given it was picked up with CONFIG_DEBUG_PREEMPT:
>>>
>>> Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack")
>>
>> Wii add in v2.
>
> I already queued the patch with this and the whitespace fix, so no need
> for a v2.
Thanks so much.
Yang
>
> Will
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] arm64: make irq_stack_ptr more robust
2016-02-12 17:38 ` Shi, Yang
2016-02-12 17:41 ` Will Deacon
@ 2016-02-12 17:54 ` Shi, Yang
1 sibling, 0 replies; 6+ messages in thread
From: Shi, Yang @ 2016-02-12 17:54 UTC (permalink / raw)
To: linux-arm-kernel
On 2/12/2016 9:38 AM, Shi, Yang wrote:
> On 2/12/2016 5:47 AM, James Morse wrote:
>> Hi!
>>
>> On 11/02/16 21:53, Yang Shi wrote:
>>> Switching between stacks is only valid if we are tracing ourselves
>>> while on the
>>> irq_stack, so it is only valid when in current and non-preemptible
>>> context,
>>> otherwise is is just zeroed off.
>>
>> Given it was picked up with CONFIG_DEBUG_PREEMPT:
>>
>> Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with
>> irq_stack")
>
> Wii add in v2.
>
>>
>>
>>> Signed-off-by: Yang Shi <yang.shi@linaro.org>
>>> ---
>>> arch/arm64/kernel/stacktrace.c | 13 ++++++-------
>>> arch/arm64/kernel/traps.c | 11 ++++++++++-
>>> 2 files changed, 16 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/arch/arm64/kernel/stacktrace.c
>>> b/arch/arm64/kernel/stacktrace.c
>>> index 12a18cb..d9751a4 100644
>>> --- a/arch/arm64/kernel/stacktrace.c
>>> +++ b/arch/arm64/kernel/stacktrace.c
>>> @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk,
>>> struct stackframe *frame)
>>> unsigned long irq_stack_ptr;
>>>
>>> /*
>>> - * Use raw_smp_processor_id() to avoid false-positives from
>>> - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on
>>> sleeping
>>> - * task stacks, we can be pre-empted in this case, so
>>> - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping
>>> - * tasks can't ever be on an interrupt stack, so regardless of cpu,
>>> - * the checks will always fail.
>>> + * Switching between stacks is valid when tracing current and in
>>> + * non-preemptible context.
>>> */
>>> - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id());
>>> + if (tsk == current && !preemptible())
>>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>>> + else
>>> + irq_stack_ptr = 0;
>>>
>>> low = frame->sp;
>>> /* irq stacks are not THREAD_SIZE aligned */
>>> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
>>> index cbedd72..7d8db3a 100644
>>> --- a/arch/arm64/kernel/traps.c
>>> +++ b/arch/arm64/kernel/traps.c
>>> @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct
>>> pt_regs *regs)
>>> static void dump_backtrace(struct pt_regs *regs, struct task_struct
>>> *tsk)
>>> {
>>> struct stackframe frame;
>>> - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>>> + unsigned long irq_stack_ptr;
>>> int skip;
>>>
>>> + /*
>>> + * Switching between stacks is valid when tracing current and in
>>
>> Nit: Two spaces: "between[ ][ ]stacks"
>
> Will fix in v2.
>
>>
>>
>>> + * non-preemptible context.
>>> + */
>>> + if (tsk == current && !preemptible())
>>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
>>> + else
>>> + irq_stack_ptr = 0;
>>> +
>>> pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>>>
>>> if (!tsk)
>>>
>>
>> Neither file includes 'linux/preempt.h' for the definition of
>> preemptible().
>> (I can't talk: I should have included smp.h for smp_processor_id())
>
> I tried to build the kernel with preempt and without preempt, both
> works. And, I saw arch/arm64/include/asm/Kbuild has:
>
> generic-y += preempt.h
>
> So, it sounds preempt.h has been included by default.
In addition, linux/sched.h, which is included by both traps.c and
stacktrace.c, includes preempt.h already.
Yang
>
> Thanks,
> Yang
>
>>
>>
>> Acked-by: James Morse <james.morse@arm.com>
>> Tested-by: James Morse <james.morse@arm.com>
>>
>>
>> Thanks!
>>
>> James
>>
>>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
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2016-02-11 21:53 [PATCH] arm64: make irq_stack_ptr more robust Yang Shi
2016-02-12 13:47 ` James Morse
2016-02-12 17:38 ` Shi, Yang
2016-02-12 17:41 ` Will Deacon
2016-02-12 17:43 ` Shi, Yang
2016-02-12 17:54 ` Shi, Yang
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