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linux/drivers/gpio/gpiolib.h
Bartosz Golaszewski bdbbae241a gpiolib: protect the GPIO device against being dropped while in use by user-space 
While any of the GPIO cdev syscalls is in progress, the kernel can call
gpiochip_remove() (for instance, when a USB GPIO expander is disconnected)
which will set gdev->chip to NULL after which any subsequent access will
cause a crash.

To avoid that: use an RW-semaphore in which the syscalls take it for
reading (so that we don't needlessly prohibit the user-space from calling
syscalls simultaneously) while gpiochip_remove() takes it for writing so
that it can only happen once all syscalls return.

Fixes: d7c51b47ac ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 3c0d9c635a ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Fixes: aad955842d ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Fixes: a54756cb24 ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
Fixes: 7b8e00d981 ("gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
[Nick: fixed a build failure with CDEV_V1 disabled]
Co-authored-by: Nick Hainke <vincent@systemli.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
2022-12-07 09:35:59 +01:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Internal GPIO functions.
*
* Copyright (C) 2013, Intel Corporation
* Author: Mika Westerberg <mika.westerberg@linux.intel.com>
*/
#ifndef GPIOLIB_H
#define GPIOLIB_H
#include <linux/gpio/driver.h>
#include <linux/gpio/consumer.h> /* for enum gpiod_flags */
#include <linux/err.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/rwsem.h>
#define GPIOCHIP_NAME "gpiochip"
/**
* struct gpio_device - internal state container for GPIO devices
* @dev: the GPIO device struct
* @chrdev: character device for the GPIO device
* @id: numerical ID number for the GPIO chip
* @mockdev: class device used by the deprecated sysfs interface (may be
* NULL)
* @owner: helps prevent removal of modules exporting active GPIOs
* @chip: pointer to the corresponding gpiochip, holding static
* data for this device
* @descs: array of ngpio descriptors.
* @ngpio: the number of GPIO lines on this GPIO device, equal to the size
* of the @descs array.
* @base: GPIO base in the DEPRECATED global Linux GPIO numberspace, assigned
* at device creation time.
* @label: a descriptive name for the GPIO device, such as the part number
* or name of the IP component in a System on Chip.
* @data: per-instance data assigned by the driver
* @list: links gpio_device:s together for traversal
* @notifier: used to notify subscribers about lines being requested, released
* or reconfigured
* @sem: protects the structure from a NULL-pointer dereference of @chip by
* user-space operations when the device gets unregistered during
* a hot-unplug event
* @pin_ranges: range of pins served by the GPIO driver
*
* This state container holds most of the runtime variable data
* for a GPIO device and can hold references and live on after the
* GPIO chip has been removed, if it is still being used from
* userspace.
*/
struct gpio_device {
struct device dev;
struct cdev chrdev;
int id;
struct device *mockdev;
struct module *owner;
struct gpio_chip *chip;
struct gpio_desc *descs;
int base;
u16 ngpio;
const char *label;
void *data;
struct list_head list;
struct blocking_notifier_head notifier;
struct rw_semaphore sem;
#ifdef CONFIG_PINCTRL
/*
* If CONFIG_PINCTRL is enabled, then gpio controllers can optionally
* describe the actual pin range which they serve in an SoC. This
* information would be used by pinctrl subsystem to configure
* corresponding pins for gpio usage.
*/
struct list_head pin_ranges;
#endif
};
static inline struct gpio_device *to_gpio_device(struct device *dev)
{
return container_of(dev, struct gpio_device, dev);
}
/* gpio suffixes used for ACPI and device tree lookup */
static __maybe_unused const char * const gpio_suffixes[] = { "gpios", "gpio" };
/**
* struct gpio_array - Opaque descriptor for a structure of GPIO array attributes
*
* @desc: Array of pointers to the GPIO descriptors
* @size: Number of elements in desc
* @chip: Parent GPIO chip
* @get_mask: Get mask used in fastpath
* @set_mask: Set mask used in fastpath
* @invert_mask: Invert mask used in fastpath
*
* This structure is attached to struct gpiod_descs obtained from
* gpiod_get_array() and can be passed back to get/set array functions in order
* to activate fast processing path if applicable.
*/
struct gpio_array {
struct gpio_desc **desc;
unsigned int size;
struct gpio_chip *chip;
unsigned long *get_mask;
unsigned long *set_mask;
unsigned long invert_mask[];
};
struct gpio_desc *gpiochip_get_desc(struct gpio_chip *gc, unsigned int hwnum);
#define for_each_gpio_desc(gc, desc) \
for (unsigned int __i = 0; \
__i < gc->ngpio && (desc = gpiochip_get_desc(gc, __i)); \
__i++) \
#define for_each_gpio_desc_with_flag(gc, desc, flag) \
for_each_gpio_desc(gc, desc) \
if (!test_bit(flag, &desc->flags)) {} else
int gpiod_get_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
struct gpio_array *array_info,
unsigned long *value_bitmap);
int gpiod_set_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
struct gpio_array *array_info,
unsigned long *value_bitmap);
extern spinlock_t gpio_lock;
extern struct list_head gpio_devices;
/**
* struct gpio_desc - Opaque descriptor for a GPIO
*
* @gdev: Pointer to the parent GPIO device
* @flags: Binary descriptor flags
* @label: Name of the consumer
* @name: Line name
* @hog: Pointer to the device node that hogs this line (if any)
* @debounce_period_us: Debounce period in microseconds
*
* These are obtained using gpiod_get() and are preferable to the old
* integer-based handles.
*
* Contrary to integers, a pointer to a &struct gpio_desc is guaranteed to be
* valid until the GPIO is released.
*/
struct gpio_desc {
struct gpio_device *gdev;
unsigned long flags;
/* flag symbols are bit numbers */
#define FLAG_REQUESTED 0
#define FLAG_IS_OUT 1
#define FLAG_EXPORT 2 /* protected by sysfs_lock */
#define FLAG_SYSFS 3 /* exported via /sys/class/gpio/control */
#define FLAG_ACTIVE_LOW 6 /* value has active low */
#define FLAG_OPEN_DRAIN 7 /* Gpio is open drain type */
#define FLAG_OPEN_SOURCE 8 /* Gpio is open source type */
#define FLAG_USED_AS_IRQ 9 /* GPIO is connected to an IRQ */
#define FLAG_IRQ_IS_ENABLED 10 /* GPIO is connected to an enabled IRQ */
#define FLAG_IS_HOGGED 11 /* GPIO is hogged */
#define FLAG_TRANSITORY 12 /* GPIO may lose value in sleep or reset */
#define FLAG_PULL_UP 13 /* GPIO has pull up enabled */
#define FLAG_PULL_DOWN 14 /* GPIO has pull down enabled */
#define FLAG_BIAS_DISABLE 15 /* GPIO has pull disabled */
#define FLAG_EDGE_RISING 16 /* GPIO CDEV detects rising edge events */
#define FLAG_EDGE_FALLING 17 /* GPIO CDEV detects falling edge events */
#define FLAG_EVENT_CLOCK_REALTIME 18 /* GPIO CDEV reports REALTIME timestamps in events */
#define FLAG_EVENT_CLOCK_HTE 19 /* GPIO CDEV reports hardware timestamps in events */
/* Connection label */
const char *label;
/* Name of the GPIO */
const char *name;
#ifdef CONFIG_OF_DYNAMIC
struct device_node *hog;
#endif
#ifdef CONFIG_GPIO_CDEV
/* debounce period in microseconds */
unsigned int debounce_period_us;
#endif
};
#define gpiod_not_found(desc) (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
int gpiod_request(struct gpio_desc *desc, const char *label);
void gpiod_free(struct gpio_desc *desc);
static inline int gpiod_request_user(struct gpio_desc *desc, const char *label)
{
int ret;
ret = gpiod_request(desc, label);
if (ret == -EPROBE_DEFER)
ret = -ENODEV;
return ret;
}
int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
unsigned long lflags, enum gpiod_flags dflags);
int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce);
int gpiod_hog(struct gpio_desc *desc, const char *name,
unsigned long lflags, enum gpiod_flags dflags);
/*
* Return the GPIO number of the passed descriptor relative to its chip
*/
static inline int gpio_chip_hwgpio(const struct gpio_desc *desc)
{
return desc - &desc->gdev->descs[0];
}
/* With descriptor prefix */
#define gpiod_emerg(desc, fmt, ...) \
pr_emerg("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?",\
##__VA_ARGS__)
#define gpiod_crit(desc, fmt, ...) \
pr_crit("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
##__VA_ARGS__)
#define gpiod_err(desc, fmt, ...) \
pr_err("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
##__VA_ARGS__)
#define gpiod_warn(desc, fmt, ...) \
pr_warn("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
##__VA_ARGS__)
#define gpiod_info(desc, fmt, ...) \
pr_info("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?", \
##__VA_ARGS__)
#define gpiod_dbg(desc, fmt, ...) \
pr_debug("gpio-%d (%s): " fmt, desc_to_gpio(desc), desc->label ? : "?",\
##__VA_ARGS__)
/* With chip prefix */
#define chip_emerg(gc, fmt, ...) \
dev_emerg(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#define chip_crit(gc, fmt, ...) \
dev_crit(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#define chip_err(gc, fmt, ...) \
dev_err(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#define chip_warn(gc, fmt, ...) \
dev_warn(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#define chip_info(gc, fmt, ...) \
dev_info(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#define chip_dbg(gc, fmt, ...) \
dev_dbg(&gc->gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
#endif /* GPIOLIB_H */
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