Merge tag 'drm-misc-next-fixes-2018-10-03' of git://anongit.freedesktop.org/drm/drm-misc into drm-next

- Add EXPERT config option to allow phys mem leak from fbdev for blob drivers (Neil)

Cc: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20181003195957.GA64584@art_vandelay

2 files changed, 51 insertions, 2 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 736b7e67e4ec..4385f00e1d05 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -110,6 +110,26 @@ config DRM_FBDEV_OVERALLOC
           is 100. Typical values for double buffering will be 200,
           triple buffering 300.
 
+config DRM_FBDEV_LEAK_PHYS_SMEM
+        bool "Shamelessly allow leaking of fbdev physical address (DANGEROUS)"
+        depends on DRM_FBDEV_EMULATION && EXPERT
+        default n
+        help
+          In order to keep user-space compatibility, we want in certain
+          use-cases to keep leaking the fbdev physical address to the
+          user-space program handling the fbdev buffer.
+          This affects, not only, Amlogic, Allwinner or Rockchip devices
+          with ARM Mali GPUs using an userspace Blob.
+          This option is not supported by upstream developers and should be
+          removed as soon as possible and be considered as a broken and
+          legacy behaviour from a modern fbdev device driver.
+
+          Please send any bug reports when using this to your proprietary
+          software vendor that requires this.
+
+          If in doubt, say "N" or spread the word to your closed source
+          library vendor.
+
 config DRM_LOAD_EDID_FIRMWARE
         bool "Allow to specify an EDID data set instead of probing for it"
         depends on DRM
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a504a5e05676..9b111e846847 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -56,6 +56,25 @@ MODULE_PARM_DESC(drm_fbdev_overalloc,
                  "Overallocation of the fbdev buffer (%) [default="
                  __MODULE_STRING(CONFIG_DRM_FBDEV_OVERALLOC) "]");
 
+/*
+ * In order to keep user-space compatibility, we want in certain use-cases
+ * to keep leaking the fbdev physical address to the user-space program
+ * handling the fbdev buffer.
+ * This is a bad habit essentially kept into closed source opengl driver
+ * that should really be moved into open-source upstream projects instead
+ * of using legacy physical addresses in user space to communicate with
+ * other out-of-tree kernel modules.
+ *
+ * This module_param *should* be removed as soon as possible and be
+ * considered as a broken and legacy behaviour from a modern fbdev device.
+ */
+#if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
+static bool drm_leak_fbdev_smem = false;
+module_param_unsafe(drm_leak_fbdev_smem, bool, 0600);
+MODULE_PARM_DESC(fbdev_emulation,
+                 "Allow unsafe leaking fbdev physical smem address [default=false]");
+#endif
+
 static LIST_HEAD(kernel_fb_helper_list);
 static DEFINE_MUTEX(kernel_fb_helper_lock);
 
@@ -2670,8 +2689,12 @@ __drm_fb_helper_initial_config_and_unlock(struct drm_fb_helper *fb_helper,
 
         info = fb_helper->fbdev;
         info->var.pixclock = 0;
-        /* don't leak any physical addresses to userspace */
-        info->flags |= FBINFO_HIDE_SMEM_START;
+        /* Shamelessly allow physical address leaking to userspace */
+#if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
+        if (!drm_leak_fbdev_smem)
+#endif
+                /* don't leak any physical addresses to userspace */
+                info->flags |= FBINFO_HIDE_SMEM_START;
 
         /* Need to drop locks to avoid recursive deadlock in
          * register_framebuffer. This is ok because the only thing left to do is
@@ -3081,6 +3104,12 @@ int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
         fbi->screen_size = fb->height * fb->pitches[0];
         fbi->fix.smem_len = fbi->screen_size;
         fbi->screen_buffer = buffer->vaddr;
+        /* Shamelessly leak the physical address to user-space */
+#if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
+        if (drm_leak_fbdev_smem && fbi->fix.smem_start == 0)
+                fbi->fix.smem_start =
+                        page_to_phys(virt_to_page(fbi->screen_buffer));
+#endif
         strcpy(fbi->fix.id, "DRM emulated");
 
         drm_fb_helper_fill_fix(fbi, fb->pitches[0], fb->format->depth);