Hi Am 11.06.23 um 18:37 schrieb Sam Ravnborg:
Hi Thomas, On Mon, Jun 05, 2023 at 04:48:12PM +0200, Thomas Zimmermann wrote:Add Kconfig option CONFIG_FB_DEVICE and make the virtual fbdev device optional. If the new option has not been selected, fbdev does not create a files in devfs or sysfs.s/ a//Most modern Linux systems run a DRM-based graphics stack that uses the kernel's framebuffer console, but has otherwise deprecated fbdev support. Yet fbdev userspace interfaces are still present. The option makes it possible to use the fbdev subsystem as console implementation without support for userspace. This closes potential entry points to manipulate kernel or I/O memory via framebuffers. It also prevents the execution of driver code via ioctl or sysfs, both of which might allow malicious software to exploit bugs in the fbdev code. A small number of fbdev drivers require struct fbinfo.dev to be initialized, usually for the support of sysfs interface. Make these drivers depend on FB_DEVICE. They can later be fixed if necessary.Should that be a TODO in gpu/todo.rst? Otherwise the amount of people knowing about this is very close to 1. As an alternative add a TODO to each Kconfig file.Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> --- drivers/staging/fbtft/Kconfig | 1 + drivers/video/fbdev/Kconfig | 12 +++++++++ drivers/video/fbdev/core/Makefile | 7 +++--- drivers/video/fbdev/core/fb_internal.h | 32 ++++++++++++++++++++++++ drivers/video/fbdev/omap2/omapfb/Kconfig | 2 +- include/linux/fb.h | 2 ++ 6 files changed, 52 insertions(+), 4 deletions(-) diff --git a/drivers/staging/fbtft/Kconfig b/drivers/staging/fbtft/Kconfig index 4d29e8c1014e..5dda3c65a38e 100644 --- a/drivers/staging/fbtft/Kconfig +++ b/drivers/staging/fbtft/Kconfig @@ -2,6 +2,7 @@ menuconfig FB_TFT tristate "Support for small TFT LCD display modules" depends on FB && SPI + depends on FB_DEVICE depends on GPIOLIB || COMPILE_TEST select FB_SYS_FILLRECT select FB_SYS_COPYAREA diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig index 6df9bd09454a..48d9a14f889c 100644 --- a/drivers/video/fbdev/Kconfig +++ b/drivers/video/fbdev/Kconfig @@ -57,6 +57,15 @@ config FIRMWARE_EDID combination with certain motherboards and monitors are known to suffer from this problem.+config FB_DEVICE+ bool "Provide legacy /dev/fb* device" + depends on FB + help + Say Y here if you want the legacy /dev/fb* device file. It's + only required if you have userspace programs that depend on + fbdev for graphics output. This does not effect the framebuffer + console.tabs to spaces to indent the above correct.+ config FB_DDC tristate depends on FB @@ -1545,6 +1554,7 @@ config FB_3DFX_I2C config FB_VOODOO1 tristate "3Dfx Voodoo Graphics (sst1) support" depends on FB && PCI + depends on FB_DEVICE select FB_CFB_FILLRECT select FB_CFB_COPYAREA select FB_CFB_IMAGEBLIT @@ -1862,6 +1872,7 @@ config FB_SH_MOBILE_LCDC tristate "SuperH Mobile LCDC framebuffer support" depends on FB && HAVE_CLK && HAS_IOMEM depends on SUPERH || ARCH_RENESAS || COMPILE_TEST + depends on FB_DEVICE select FB_SYS_FILLRECT select FB_SYS_COPYAREA select FB_SYS_IMAGEBLIT @@ -1930,6 +1941,7 @@ config FB_SMSCUFX config FB_UDL tristate "Displaylink USB Framebuffer support" depends on FB && USB + depends on FB_DEVICE select FB_MODE_HELPERS select FB_SYS_FILLRECT select FB_SYS_COPYAREA diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile index 125d24f50c36..d5e8772620f8 100644 --- a/drivers/video/fbdev/core/Makefile +++ b/drivers/video/fbdev/core/Makefile @@ -2,12 +2,13 @@ obj-$(CONFIG_FB_NOTIFY) += fb_notify.o obj-$(CONFIG_FB) += fb.o fb-y := fb_backlight.o \ - fb_devfs.o \ fb_info.o \ - fb_procfs.o \ - fbmem.o fbmon.o fbcmap.o fbsysfs.o \ + fbmem.o fbmon.o fbcmap.o \ modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o fb-$(CONFIG_FB_DEFERRED_IO) += fb_defio.o +fb-$(CONFIG_FB_DEVICE) += fb_devfs.o \ + fb_procfs.o \ + fbsysfs.oMaybe change this to one line to avoid '\'?ifeq ($(CONFIG_FRAMEBUFFER_CONSOLE),y)fb-y += fbcon.o bitblit.o softcursor.o diff --git a/drivers/video/fbdev/core/fb_internal.h b/drivers/video/fbdev/core/fb_internal.h index 0b43c0cd5096..b8a28466db79 100644 --- a/drivers/video/fbdev/core/fb_internal.h +++ b/drivers/video/fbdev/core/fb_internal.h @@ -3,12 +3,22 @@ #ifndef _FB_INTERNAL_H #define _FB_INTERNAL_H+#include <linux/device.h>#include <linux/fb.h> #include <linux/mutex.h>/* fb_devfs.c */+#if defined(CONFIG_FB_DEVICE) int fb_register_chrdev(void); void fb_unregister_chrdev(void); +#else +static inline int fb_register_chrdev(void) +{ + return 0; +} +static inline void fb_unregister_chrdev(void) +{ } +#endif/* fbmem.c */extern struct class *fb_class; @@ -19,11 +29,33 @@ struct fb_info *get_fb_info(unsigned int idx); void put_fb_info(struct fb_info *fb_info);/* fb_procfs.c */+#if defined(CONFIG_FB_DEVICE) int fb_init_procfs(void); void fb_cleanup_procfs(void); +#else +static inline int fb_init_procfs(void) +{ + return 0; +} +static inline void fb_cleanup_procfs(void) +{ } +#endif/* fbsysfs.c */+#if defined(CONFIG_FB_DEVICE) int fb_device_create(struct fb_info *fb_info); void fb_device_destroy(struct fb_info *fb_info); +#else +static inline int fb_device_create(struct fb_info *fb_info) +{ + get_device(fb_info->device); // as in device_add() + + return 0; +} +static inline void fb_device_destroy(struct fb_info *fb_info) +{ + put_device(fb_info->device); // as in device_del() +} +#endifI do not see why fb_device_{create,destroy} needs to call {get,put}_device - and it is not explained. A short explanation in the commit maybe?
Ok, I'll do that.This get_device() is normally done within device_create() from within register_framebuffer(). The put is within unregister_frambuffer(). Without, someone could attempt to unplug the Linux hardware device and our pointer would go stale. So we have to hold the reference within fbdev.
Best regards Thomas
With my comments addressed: Reviewed-by: Sam Ravnborg <sam@xxxxxxxxxxxx> Note: I do not engage in the thread about the best Kconfig solution - I trust the involved people will find a good solution. Sam#endifdiff --git a/drivers/video/fbdev/omap2/omapfb/Kconfig b/drivers/video/fbdev/omap2/omapfb/Kconfig index 69f9cb03507e..21069fdb7cc2 100644 --- a/drivers/video/fbdev/omap2/omapfb/Kconfig +++ b/drivers/video/fbdev/omap2/omapfb/Kconfig @@ -5,9 +5,9 @@ config OMAP2_VRFB menuconfig FB_OMAP2 tristate "OMAP2+ frame buffer support" depends on FB + depends on FB_DEVICE depends on DRM_OMAP = n depends on GPIOLIB - select FB_OMAP2_DSS select OMAP2_VRFB if ARCH_OMAP2 || ARCH_OMAP3 select FB_CFB_FILLRECT diff --git a/include/linux/fb.h b/include/linux/fb.h index 541a0e3ce21f..40ed1028160c 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -481,7 +481,9 @@ struct fb_info {const struct fb_ops *fbops;struct device *device; /* This is the parent */ +#if defined(CONFIG_FB_DEVICE) struct device *dev; /* This is this fb device */ +#endif int class_flag; /* private sysfs flags */ #ifdef CONFIG_FB_TILEBLITTING struct fb_tile_ops *tileops; /* Tile Blitting */ -- 2.40.1
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
Attachment:
OpenPGP_signature
Description: OpenPGP digital signature
