fbdev: Warn on incorrect framebuffer access

Test in framebuffer read, write and drawing helpers if FBINFO_VIRTFB
has been set correctly. Framebuffers in I/O memory should only be
accessed with the architecture's respective helpers. Framebuffers
in system memory should be accessed with the regular load and
store operations. Presumably not all drivers get this right, so we
now warn about it.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231127131655.4020-32-tzimmermann@suse.de

8 files changed, 33 insertions, 0 deletions

diff --git a/drivers/video/fbdev/core/cfbcopyarea.c b/drivers/video/fbdev/core/cfbcopyarea.c
index 5b80bf3dae50..a271f57d9c6c 100644
--- a/drivers/video/fbdev/core/cfbcopyarea.c
+++ b/drivers/video/fbdev/core/cfbcopyarea.c
@@ -391,6 +391,9 @@ void cfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (p->flags & FBINFO_VIRTFB)
+		fb_warn_once(p, "Framebuffer is not in I/O address space.");
+
 	/* if the beginning of the target area might overlap with the end of
 	the source area, be have to copy the area reverse. */
 	if ((dy == sy && dx > sx) || (dy > sy)) {
diff --git a/drivers/video/fbdev/core/cfbfillrect.c b/drivers/video/fbdev/core/cfbfillrect.c
index ba9f58b2a5e8..cbaa4c9e2355 100644
--- a/drivers/video/fbdev/core/cfbfillrect.c
+++ b/drivers/video/fbdev/core/cfbfillrect.c
@@ -287,6 +287,9 @@ void cfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (p->flags & FBINFO_VIRTFB)
+		fb_warn_once(p, "Framebuffer is not in I/O address space.");
+
 	if (p->fix.visual == FB_VISUAL_TRUECOLOR ||
 	    p->fix.visual == FB_VISUAL_DIRECTCOLOR )
 		fg = ((u32 *) (p->pseudo_palette))[rect->color];
diff --git a/drivers/video/fbdev/core/cfbimgblt.c b/drivers/video/fbdev/core/cfbimgblt.c
index 9ebda4e0dc7a..7d1d2f1a627d 100644
--- a/drivers/video/fbdev/core/cfbimgblt.c
+++ b/drivers/video/fbdev/core/cfbimgblt.c
@@ -326,6 +326,9 @@ void cfb_imageblit(struct fb_info *p, const struct fb_image *image)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (p->flags & FBINFO_VIRTFB)
+		fb_warn_once(p, "Framebuffer is not in I/O address space.");
+
 	bitstart = (dy * p->fix.line_length * 8) + (dx * bpp);
 	start_index = bitstart & (32 - 1);
 	pitch_index = (p->fix.line_length & (bpl - 1)) * 8;
diff --git a/drivers/video/fbdev/core/fb_io_fops.c b/drivers/video/fbdev/core/fb_io_fops.c
index 60805e43914e..3408ff1b2b7a 100644
--- a/drivers/video/fbdev/core/fb_io_fops.c
+++ b/drivers/video/fbdev/core/fb_io_fops.c
@@ -12,6 +12,9 @@ ssize_t fb_io_read(struct fb_info *info, char __user *buf, size_t count, loff_t
 	int c, cnt = 0, err = 0;
 	unsigned long total_size, trailing;
 
+	if (info->flags & FBINFO_VIRTFB)
+		fb_warn_once(info, "Framebuffer is not in I/O address space.");
+
 	if (!info->screen_base)
 		return -ENODEV;
 
@@ -73,6 +76,9 @@ ssize_t fb_io_write(struct fb_info *info, const char __user *buf, size_t count,
 	int c, cnt = 0, err = 0;
 	unsigned long total_size, trailing;
 
+	if (info->flags & FBINFO_VIRTFB)
+		fb_warn_once(info, "Framebuffer is not in I/O address space.");
+
 	if (!info->screen_base)
 		return -ENODEV;
 
@@ -138,6 +144,9 @@ int fb_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 	u32 len = info->fix.smem_len;
 	unsigned long mmio_pgoff = PAGE_ALIGN((start & ~PAGE_MASK) + len) >> PAGE_SHIFT;
 
+	if (info->flags & FBINFO_VIRTFB)
+		fb_warn_once(info, "Framebuffer is not in I/O address space.");
+
 	/*
 	 * This can be either the framebuffer mapping, or if pgoff points
 	 * past it, the mmio mapping.
diff --git a/drivers/video/fbdev/core/fb_sys_fops.c b/drivers/video/fbdev/core/fb_sys_fops.c
index 0cb0989abda6..a9aa6519a5b3 100644
--- a/drivers/video/fbdev/core/fb_sys_fops.c
+++ b/drivers/video/fbdev/core/fb_sys_fops.c
@@ -22,6 +22,9 @@ ssize_t fb_sys_read(struct fb_info *info, char __user *buf, size_t count,
 	unsigned long total_size, c;
 	ssize_t ret;
 
+	if (!(info->flags & FBINFO_VIRTFB))
+		fb_warn_once(info, "Framebuffer is not in virtual address space.");
+
 	if (!info->screen_buffer)
 		return -ENODEV;
 
@@ -64,6 +67,9 @@ ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
 	unsigned long total_size, c;
 	size_t ret;
 
+	if (!(info->flags & FBINFO_VIRTFB))
+		fb_warn_once(info, "Framebuffer is not in virtual address space.");
+
 	if (!info->screen_buffer)
 		return -ENODEV;
 
diff --git a/drivers/video/fbdev/core/syscopyarea.c b/drivers/video/fbdev/core/syscopyarea.c
index 7b8bd3a2bedc..75e7001e8450 100644
--- a/drivers/video/fbdev/core/syscopyarea.c
+++ b/drivers/video/fbdev/core/syscopyarea.c
@@ -324,6 +324,9 @@ void sys_copyarea(struct fb_info *p, const struct fb_copyarea *area)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (!(p->flags & FBINFO_VIRTFB))
+		fb_warn_once(p, "Framebuffer is not in virtual address space.");
+
 	/* if the beginning of the target area might overlap with the end of
 	the source area, be have to copy the area reverse. */
 	if ((dy == sy && dx > sx) || (dy > sy)) {
diff --git a/drivers/video/fbdev/core/sysfillrect.c b/drivers/video/fbdev/core/sysfillrect.c
index bcdcaeae6538..e49221a88ccc 100644
--- a/drivers/video/fbdev/core/sysfillrect.c
+++ b/drivers/video/fbdev/core/sysfillrect.c
@@ -242,6 +242,9 @@ void sys_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (!(p->flags & FBINFO_VIRTFB))
+		fb_warn_once(p, "Framebuffer is not in virtual address space.");
+
 	if (p->fix.visual == FB_VISUAL_TRUECOLOR ||
 	    p->fix.visual == FB_VISUAL_DIRECTCOLOR )
 		fg = ((u32 *) (p->pseudo_palette))[rect->color];
diff --git a/drivers/video/fbdev/core/sysimgblt.c b/drivers/video/fbdev/core/sysimgblt.c
index 665ef7a0a249..6949bbd51d92 100644
--- a/drivers/video/fbdev/core/sysimgblt.c
+++ b/drivers/video/fbdev/core/sysimgblt.c
@@ -296,6 +296,9 @@ void sys_imageblit(struct fb_info *p, const struct fb_image *image)
 	if (p->state != FBINFO_STATE_RUNNING)
 		return;
 
+	if (!(p->flags & FBINFO_VIRTFB))
+		fb_warn_once(p, "Framebuffer is not in virtual address space.");
+
 	bitstart = (dy * p->fix.line_length * 8) + (dx * bpp);
 	start_index = bitstart & (32 - 1);
 	pitch_index = (p->fix.line_length & (bpl - 1)) * 8;