A drm driver that is implementing
fb_debug_enter and fb_debug_leave
in struct fb_ops with drm fb helper functions
drm_fb_helper_debug_enter and drm_fb_helper_debug_leave
must also implement the callback 'mode_set_base_atomic' in struct
drm_crtc_helper_funcs. See Documentation/DocBook/kgdb.tmpl. The current
implementation will segfault when 'mode_set_base_atomic' is a NULL
pointer.
Before this patch at least the drm drivers armada, ast, qxl, udl and
virtio do not have a 'mode_set_base_atomic' implementation but using
drm_fb_helper_debug_(enter|leave). So these drivers may segfault when
callbacks fb_debug_(enter|leave) are called.
Avoid the issue by just checking for NULL pointers. So all drivers can
unconditionally implement fb_debug_(enter|leave) with the drm_fb_helper
functions. If callback 'mode_set_base_atomic' is not implemented, the
code in drm_fb_helper_debug_(enter|leave) does effectively nothing.
Signed-off-by: Stefan Christ <contact@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_fb_helper.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 03414bd..823fc9e 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -251,6 +251,9 @@ int drm_fb_helper_debug_enter(struct fb_info *info)
continue;
funcs = mode_set->crtc->helper_private;
+ if (funcs->mode_set_base_atomic == NULL)
+ continue;
+
drm_fb_helper_save_lut_atomic(mode_set->crtc, helper);
funcs->mode_set_base_atomic(mode_set->crtc,
mode_set->fb,
@@ -304,6 +307,9 @@ int drm_fb_helper_debug_leave(struct fb_info *info)
continue;
}
+ if (funcs->mode_set_base_atomic == NULL)
+ continue;
+
drm_fb_helper_restore_lut_atomic(mode_set->crtc);
funcs->mode_set_base_atomic(mode_set->crtc, fb, crtc->x,
crtc->y, LEAVE_ATOMIC_MODE_SET);
--
2.7.3
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