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Message-ID: <CAJZ5v0ihB5AJwSRpjaOnXAmciregzxARL5xfudu1h+=_LXaE_w@mail.gmail.com>
Date: Thu, 9 Jul 2020 14:18:13 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Neal Liu <neal.liu@...iatek.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
Jacob Pan <jacob.jun.pan@...ux.intel.com>,
Matthias Brugger <matthias.bgg@...il.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>,
linux-tegra <linux-tegra@...r.kernel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
"moderated list:ARM/Mediatek SoC..."
<linux-mediatek@...ts.infradead.org>,
lkml <linux-kernel@...r.kernel.org>, wsd_upstream@...iatek.com
Subject: Re: [PATCH v2] cpuidle: change enter_s2idle() prototype
On Mon, Jul 6, 2020 at 5:13 AM Neal Liu <neal.liu@...iatek.com> wrote:
>
> Control Flow Integrity(CFI) is a security mechanism that disallows
> changes to the original control flow graph of a compiled binary,
> making it significantly harder to perform such attacks.
>
> init_state_node() assign same function callback to different
> function pointer declarations.
>
> static int init_state_node(struct cpuidle_state *idle_state,
> const struct of_device_id *matches,
> struct device_node *state_node) { ...
> idle_state->enter = match_id->data; ...
> idle_state->enter_s2idle = match_id->data; }
>
> Function declarations:
>
> struct cpuidle_state { ...
> int (*enter) (struct cpuidle_device *dev,
> struct cpuidle_driver *drv,
> int index);
>
> void (*enter_s2idle) (struct cpuidle_device *dev,
> struct cpuidle_driver *drv,
> int index); };
>
> In this case, either enter() or enter_s2idle() would cause CFI check
> failed since they use same callee.
Can you please explain this in a bit more detail?
As it stands, I don't understand the problem statement enough to apply
the patch.
> Align function prototype of enter() since it needs return value for
> some use cases. The return value of enter_s2idle() is no
> need currently.
So last time I requested you to document why ->enter_s2idle needs to
return an int in the code, which has not been done. Please do that.
> Signed-off-by: Neal Liu <neal.liu@...iatek.com>
> ---
> drivers/acpi/processor_idle.c | 6 ++++--
> drivers/cpuidle/cpuidle-tegra.c | 8 +++++---
> drivers/idle/intel_idle.c | 6 ++++--
> include/linux/cpuidle.h | 6 +++---
> 4 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 75534c5..6ffb6c9 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -655,8 +655,8 @@ static int acpi_idle_enter(struct cpuidle_device *dev,
> return index;
> }
>
> -static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv, int index)
> +static int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> {
> struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
>
> @@ -674,6 +674,8 @@ static void acpi_idle_enter_s2idle(struct cpuidle_device *dev,
> }
> }
> acpi_idle_do_entry(cx);
> +
> + return 0;
> }
>
> static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
> diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c
> index 1500458..a12fb14 100644
> --- a/drivers/cpuidle/cpuidle-tegra.c
> +++ b/drivers/cpuidle/cpuidle-tegra.c
> @@ -253,11 +253,13 @@ static int tegra_cpuidle_enter(struct cpuidle_device *dev,
> return err ? -1 : index;
> }
>
> -static void tegra114_enter_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv,
> - int index)
> +static int tegra114_enter_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index)
> {
> tegra_cpuidle_enter(dev, drv, index);
> +
> + return 0;
> }
>
> /*
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index f449584..b178da3 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -175,13 +175,15 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
> * Invoked as a suspend-to-idle callback routine with frozen user space, frozen
> * scheduler tick and suspended scheduler clock on the target CPU.
> */
> -static __cpuidle void intel_idle_s2idle(struct cpuidle_device *dev,
> - struct cpuidle_driver *drv, int index)
> +static __cpuidle int intel_idle_s2idle(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv, int index)
> {
> unsigned long eax = flg2MWAIT(drv->states[index].flags);
> unsigned long ecx = 1; /* break on interrupt flag */
>
> mwait_idle_with_hints(eax, ecx);
> +
> + return 0;
> }
>
> /*
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index ec2ef63..bee10c0 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -66,9 +66,9 @@ struct cpuidle_state {
> * suspended, so it must not re-enable interrupts at any point (even
> * temporarily) or attempt to change states of clock event devices.
> */
> - void (*enter_s2idle) (struct cpuidle_device *dev,
> - struct cpuidle_driver *drv,
> - int index);
> + int (*enter_s2idle)(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index);
> };
>
> /* Idle State Flags */
> --
> 1.7.9.5
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