[PATCH] drm: msm: Fix return type of dsi_mgr_connector_mode_valid for kCFI

[PATCH] drm: msm: Fix return type of dsi_mgr_connector_mode_valid for kCFI

[John Stultz]

I was hitting kCFI crashes when building with clang, and after
some digging finally narrowed it down to the
dsi_mgr_connector_mode_valid() function being implemented as
returning an int, instead of an enum drm_mode_status.

This patch fixes it, and appeases the opaque word of the kCFI
gods (seriously, clang inlining everything makes the kCFI
backtraces only really rough estimates of where things went
wrong).

Thanks as always to Sami for his help narrowing this down.

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Alistair Delva <adelva@google.com>
Cc: Amit Pundir <amit.pundir@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: freedreno@lists.freedesktop.org
Cc: clang-built-linux@googlegroups.com
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/gpu/drm/msm/dsi/dsi_manager.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
index 271aa7bbca925..355a60b4a536f 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
@@ -336,7 +336,7 @@ static int dsi_mgr_connector_get_modes(struct drm_connector *connector)
 	return num;
 }
 
-static int dsi_mgr_connector_mode_valid(struct drm_connector *connector,
+static enum drm_mode_status dsi_mgr_connector_mode_valid(struct drm_connector *connector,
 				struct drm_display_mode *mode)
 {
 	int id = dsi_mgr_connector_get_id(connector);
-- 
2.17.1

Re: [PATCH] drm: msm: Fix return type of dsi_mgr_connector_mode_valid for kCFI

[Nick Desaulniers]

On Wed, Jan 29, 2020 at 12:12 PM John Stultz <john.stultz@linaro.org> wrote:
>
> I was hitting kCFI crashes when building with clang, and after
> some digging finally narrowed it down to the
> dsi_mgr_connector_mode_valid() function being implemented as
> returning an int, instead of an enum drm_mode_status.
>
> This patch fixes it, and appeases the opaque word of the kCFI
> gods (seriously, clang inlining everything makes the kCFI
> backtraces only really rough estimates of where things went
> wrong).
>
> Thanks as always to Sami for his help narrowing this down.
>
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Alistair Delva <adelva@google.com>
> Cc: Amit Pundir <amit.pundir@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: freedreno@lists.freedesktop.org
> Cc: clang-built-linux@googlegroups.com
> Signed-off-by: John Stultz <john.stultz@linaro.org>

John, thanks for fixing this. Our inliner is a point of pride
(inlining indirect function calls; you're welcome). ;)
Indeed, the function pointer member `mode_valid` in `struct
drm_connector_helper_funcs` in
include/drm/drm_modeset_helper_vtables.h returns an `enum
drm_mode_status`.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  drivers/gpu/drm/msm/dsi/dsi_manager.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index 271aa7bbca925..355a60b4a536f 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -336,7 +336,7 @@ static int dsi_mgr_connector_get_modes(struct drm_connector *connector)
>         return num;
>  }
>
> -static int dsi_mgr_connector_mode_valid(struct drm_connector *connector,
> +static enum drm_mode_status dsi_mgr_connector_mode_valid(struct drm_connector *connector,
>                                 struct drm_display_mode *mode)
>  {
>         int id = dsi_mgr_connector_get_id(connector);
> --

-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] drm: msm: Fix return type of dsi_mgr_connector_mode_valid for kCFI

[Amit Pundir]

On Thu, 30 Jan 2020 at 01:42, John Stultz <john.stultz@linaro.org> wrote:
>
> I was hitting kCFI crashes when building with clang, and after
> some digging finally narrowed it down to the
> dsi_mgr_connector_mode_valid() function being implemented as
> returning an int, instead of an enum drm_mode_status.
>
> This patch fixes it, and appeases the opaque word of the kCFI
> gods (seriously, clang inlining everything makes the kCFI
> backtraces only really rough estimates of where things went
> wrong).
>
> Thanks as always to Sami for his help narrowing this down.
>
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Alistair Delva <adelva@google.com>
> Cc: Amit Pundir <amit.pundir@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: freedreno@lists.freedesktop.org
> Cc: clang-built-linux@googlegroups.com
> Signed-off-by: John Stultz <john.stultz@linaro.org>

Tested-by: Amit Pundir <amit.pundir@linaro.org>
Cc: stable@vger.kernel.org # v4.4+

> ---
>  drivers/gpu/drm/msm/dsi/dsi_manager.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index 271aa7bbca925..355a60b4a536f 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -336,7 +336,7 @@ static int dsi_mgr_connector_get_modes(struct drm_connector *connector)
>         return num;
>  }
>
> -static int dsi_mgr_connector_mode_valid(struct drm_connector *connector,
> +static enum drm_mode_status dsi_mgr_connector_mode_valid(struct drm_connector *connector,
>                                 struct drm_display_mode *mode)
>  {
>         int id = dsi_mgr_connector_get_id(connector);
> --
> 2.17.1
>