Move common on_accessible_stack checks to stacktrace/common.h. This is
used in the implementation of the nVHE hypervisor unwinder later in
this series.
Signed-off-by: Kalesh Singh <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Reviewed-by: Mark Brown <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
---
Changes in v6:
- Add Fuad's Tested-by tag
Changes in v5:
- Add Reviewed-by tags from Mark Brown and Fuad
- Remove random whitespace change, per Mark Brown
arch/arm64/include/asm/stacktrace.h | 6 ++----
arch/arm64/include/asm/stacktrace/common.h | 18 ++++++++++++++++++
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 79f455b37c84..43f4b4a6d383 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -65,8 +65,8 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
unsigned long sp, unsigned long size,
struct stack_info *info)
{
- if (info)
- info->type = STACK_TYPE_UNKNOWN;
+ if (on_accessible_stack_common(tsk, sp, size, info))
+ return true;
if (on_task_stack(tsk, sp, size, info))
return true;
@@ -74,8 +74,6 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
return false;
if (on_irq_stack(sp, size, info))
return true;
- if (on_overflow_stack(sp, size, info))
- return true;
if (on_sdei_stack(sp, size, info))
return true;
diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
index 64ae4f6b06fe..f58b786460d3 100644
--- a/arch/arm64/include/asm/stacktrace/common.h
+++ b/arch/arm64/include/asm/stacktrace/common.h
@@ -62,6 +62,9 @@ struct unwind_state {
struct task_struct *task;
};
+static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
+ struct stack_info *info);
+
static inline bool on_stack(unsigned long sp, unsigned long size,
unsigned long low, unsigned long high,
enum stack_type type, struct stack_info *info)
@@ -80,6 +83,21 @@ static inline bool on_stack(unsigned long sp, unsigned long size,
return true;
}
+static inline bool on_accessible_stack_common(const struct task_struct *tsk,
+ unsigned long sp,
+ unsigned long size,
+ struct stack_info *info)
+{
+ if (info)
+ info->type = STACK_TYPE_UNKNOWN;
+
+ /*
+ * Both the kernel and nvhe hypervisor make use of
+ * an overflow_stack
+ */
+ return on_overflow_stack(sp, size, info);
+}
+
static inline void unwind_init_common(struct unwind_state *state,
struct task_struct *task)
{
--
2.37.1.359.gd136c6c3e2-goog
On Tue, 26 Jul 2022 08:37:35 +0100,
Kalesh Singh <[email protected]> wrote:
>
> Move common on_accessible_stack checks to stacktrace/common.h. This is
> used in the implementation of the nVHE hypervisor unwinder later in
> this series.
>
> Signed-off-by: Kalesh Singh <[email protected]>
> Reviewed-by: Fuad Tabba <[email protected]>
> Reviewed-by: Mark Brown <[email protected]>
> Tested-by: Fuad Tabba <[email protected]>
> ---
>
> Changes in v6:
> - Add Fuad's Tested-by tag
>
> Changes in v5:
> - Add Reviewed-by tags from Mark Brown and Fuad
> - Remove random whitespace change, per Mark Brown
>
> arch/arm64/include/asm/stacktrace.h | 6 ++----
> arch/arm64/include/asm/stacktrace/common.h | 18 ++++++++++++++++++
> 2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
> index 79f455b37c84..43f4b4a6d383 100644
> --- a/arch/arm64/include/asm/stacktrace.h
> +++ b/arch/arm64/include/asm/stacktrace.h
> @@ -65,8 +65,8 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
> unsigned long sp, unsigned long size,
> struct stack_info *info)
> {
> - if (info)
> - info->type = STACK_TYPE_UNKNOWN;
> + if (on_accessible_stack_common(tsk, sp, size, info))
> + return true;
>
> if (on_task_stack(tsk, sp, size, info))
> return true;
> @@ -74,8 +74,6 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
> return false;
> if (on_irq_stack(sp, size, info))
> return true;
> - if (on_overflow_stack(sp, size, info))
> - return true;
> if (on_sdei_stack(sp, size, info))
> return true;
>
> diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> index 64ae4f6b06fe..f58b786460d3 100644
> --- a/arch/arm64/include/asm/stacktrace/common.h
> +++ b/arch/arm64/include/asm/stacktrace/common.h
> @@ -62,6 +62,9 @@ struct unwind_state {
> struct task_struct *task;
> };
>
> +static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
> + struct stack_info *info);
> +
> static inline bool on_stack(unsigned long sp, unsigned long size,
> unsigned long low, unsigned long high,
> enum stack_type type, struct stack_info *info)
> @@ -80,6 +83,21 @@ static inline bool on_stack(unsigned long sp, unsigned long size,
> return true;
> }
>
> +static inline bool on_accessible_stack_common(const struct task_struct *tsk,
> + unsigned long sp,
> + unsigned long size,
> + struct stack_info *info)
> +{
> + if (info)
> + info->type = STACK_TYPE_UNKNOWN;
> +
> + /*
> + * Both the kernel and nvhe hypervisor make use of
> + * an overflow_stack
> + */
> + return on_overflow_stack(sp, size, info);
> +}
on_accessible_stack has the following comment:
/*
* We can only safely access per-cpu stacks from current in a non-preemptible
* context.
*/
With this change, I don't think we satisfy this requirement anymore,
as we're checking the overflow stack *before* the preemptible check,
which is a big change in behaviour.
The hypervisor doesn't have this requirement: the unwinding is either
done out of context (nVHE, where EL1 unwinds EL2) or in a
non-preemptible section (pKVM, where the whole thing is
non-preemptible). But the kernel is usually preemptible, so this patch
needs fixing.
I'll see if I can address it locally (I'm currently moving things
around, stay tuned).
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
On Tue, Jul 26, 2022 at 9:01 AM Marc Zyngier <[email protected]> wrote:
>
> On Tue, 26 Jul 2022 08:37:35 +0100,
> Kalesh Singh <[email protected]> wrote:
> >
> > Move common on_accessible_stack checks to stacktrace/common.h. This is
> > used in the implementation of the nVHE hypervisor unwinder later in
> > this series.
> >
> > Signed-off-by: Kalesh Singh <[email protected]>
> > Reviewed-by: Fuad Tabba <[email protected]>
> > Reviewed-by: Mark Brown <[email protected]>
> > Tested-by: Fuad Tabba <[email protected]>
> > ---
> >
> > Changes in v6:
> > - Add Fuad's Tested-by tag
> >
> > Changes in v5:
> > - Add Reviewed-by tags from Mark Brown and Fuad
> > - Remove random whitespace change, per Mark Brown
> >
> > arch/arm64/include/asm/stacktrace.h | 6 ++----
> > arch/arm64/include/asm/stacktrace/common.h | 18 ++++++++++++++++++
> > 2 files changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
> > index 79f455b37c84..43f4b4a6d383 100644
> > --- a/arch/arm64/include/asm/stacktrace.h
> > +++ b/arch/arm64/include/asm/stacktrace.h
> > @@ -65,8 +65,8 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
> > unsigned long sp, unsigned long size,
> > struct stack_info *info)
> > {
> > - if (info)
> > - info->type = STACK_TYPE_UNKNOWN;
> > + if (on_accessible_stack_common(tsk, sp, size, info))
> > + return true;
> >
> > if (on_task_stack(tsk, sp, size, info))
> > return true;
> > @@ -74,8 +74,6 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
> > return false;
> > if (on_irq_stack(sp, size, info))
> > return true;
> > - if (on_overflow_stack(sp, size, info))
> > - return true;
> > if (on_sdei_stack(sp, size, info))
> > return true;
> >
> > diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> > index 64ae4f6b06fe..f58b786460d3 100644
> > --- a/arch/arm64/include/asm/stacktrace/common.h
> > +++ b/arch/arm64/include/asm/stacktrace/common.h
> > @@ -62,6 +62,9 @@ struct unwind_state {
> > struct task_struct *task;
> > };
> >
> > +static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
> > + struct stack_info *info);
> > +
> > static inline bool on_stack(unsigned long sp, unsigned long size,
> > unsigned long low, unsigned long high,
> > enum stack_type type, struct stack_info *info)
> > @@ -80,6 +83,21 @@ static inline bool on_stack(unsigned long sp, unsigned long size,
> > return true;
> > }
> >
> > +static inline bool on_accessible_stack_common(const struct task_struct *tsk,
> > + unsigned long sp,
> > + unsigned long size,
> > + struct stack_info *info)
> > +{
> > + if (info)
> > + info->type = STACK_TYPE_UNKNOWN;
> > +
> > + /*
> > + * Both the kernel and nvhe hypervisor make use of
> > + * an overflow_stack
> > + */
> > + return on_overflow_stack(sp, size, info);
> > +}
>
> on_accessible_stack has the following comment:
>
> /*
> * We can only safely access per-cpu stacks from current in a non-preemptible
> * context.
> */
>
> With this change, I don't think we satisfy this requirement anymore,
> as we're checking the overflow stack *before* the preemptible check,
> which is a big change in behaviour.
>
> The hypervisor doesn't have this requirement: the unwinding is either
> done out of context (nVHE, where EL1 unwinds EL2) or in a
> non-preemptible section (pKVM, where the whole thing is
> non-preemptible). But the kernel is usually preemptible, so this patch
> needs fixing.
>
> I'll see if I can address it locally (I'm currently moving things
> around, stay tuned).
Hi Marc,
You are right it changes the order of the checks. I think the simplest
way then is to drop this patch, and replace uses of on_accessible
_stack_common().
Thanks,
Kalesh
>
> Thanks,
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.