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3aa42cb811
The .remove() callback for a platform driver returns an int which makes many driver authors wrongly assume it's possible to do error handling by returning an error code. However the value returned is ignored (apart from emitting a warning) and this typically results in resource leaks. To improve here there is a quest to make the remove callback return void. In the first step of this quest all drivers are converted to .remove_new(), which already returns void. Eventually after all drivers are converted, .remove_new() will be renamed to .remove(). Trivially convert this driver from always returning zero in the remove callback to the void returning variant. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/8e7179794ffbcaa4ad3d0db50cc4aa03f377fc8c.1708508896.git.u.kleine-koenig@pengutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
206 lines
5.3 KiB
C
206 lines
5.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2021 - Google LLC
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* Author: David Brazdil <dbrazdil@google.com>
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*
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* Driver for Open Profile for DICE.
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*
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* This driver takes ownership of a reserved memory region containing data
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* generated by the Open Profile for DICE measured boot protocol. The memory
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* contents are not interpreted by the kernel but can be mapped into a userspace
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* process via a misc device. Userspace can also request a wipe of the memory.
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*
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* Userspace can access the data with (w/o error handling):
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*
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* fd = open("/dev/open-dice0", O_RDWR);
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* read(fd, &size, sizeof(unsigned long));
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* data = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
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* write(fd, NULL, 0); // wipe
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* close(fd);
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*/
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#include <linux/io.h>
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#include <linux/miscdevice.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/of_reserved_mem.h>
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#include <linux/platform_device.h>
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#define DRIVER_NAME "open-dice"
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struct open_dice_drvdata {
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struct mutex lock;
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char name[16];
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struct reserved_mem *rmem;
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struct miscdevice misc;
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};
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static inline struct open_dice_drvdata *to_open_dice_drvdata(struct file *filp)
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{
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return container_of(filp->private_data, struct open_dice_drvdata, misc);
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}
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static int open_dice_wipe(struct open_dice_drvdata *drvdata)
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{
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void *kaddr;
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mutex_lock(&drvdata->lock);
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kaddr = devm_memremap(drvdata->misc.this_device, drvdata->rmem->base,
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drvdata->rmem->size, MEMREMAP_WC);
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if (IS_ERR(kaddr)) {
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mutex_unlock(&drvdata->lock);
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return PTR_ERR(kaddr);
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}
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memset(kaddr, 0, drvdata->rmem->size);
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devm_memunmap(drvdata->misc.this_device, kaddr);
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mutex_unlock(&drvdata->lock);
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return 0;
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}
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/*
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* Copies the size of the reserved memory region to the user-provided buffer.
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*/
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static ssize_t open_dice_read(struct file *filp, char __user *ptr, size_t len,
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loff_t *off)
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{
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unsigned long val = to_open_dice_drvdata(filp)->rmem->size;
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return simple_read_from_buffer(ptr, len, off, &val, sizeof(val));
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}
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/*
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* Triggers a wipe of the reserved memory region. The user-provided pointer
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* is never dereferenced.
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*/
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static ssize_t open_dice_write(struct file *filp, const char __user *ptr,
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size_t len, loff_t *off)
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{
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if (open_dice_wipe(to_open_dice_drvdata(filp)))
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return -EIO;
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/* Consume the input buffer. */
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return len;
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}
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/*
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* Creates a mapping of the reserved memory region in user address space.
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*/
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static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma)
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{
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struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp);
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if (vma->vm_flags & VM_MAYSHARE) {
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/* Do not allow userspace to modify the underlying data. */
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if (vma->vm_flags & VM_WRITE)
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return -EPERM;
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/* Ensure userspace cannot acquire VM_WRITE later. */
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vm_flags_clear(vma, VM_MAYWRITE);
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}
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/* Create write-combine mapping so all clients observe a wipe. */
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vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
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vm_flags_set(vma, VM_DONTCOPY | VM_DONTDUMP);
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return vm_iomap_memory(vma, drvdata->rmem->base, drvdata->rmem->size);
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}
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static const struct file_operations open_dice_fops = {
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.owner = THIS_MODULE,
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.read = open_dice_read,
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.write = open_dice_write,
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.mmap = open_dice_mmap,
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};
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static int __init open_dice_probe(struct platform_device *pdev)
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{
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static unsigned int dev_idx;
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struct device *dev = &pdev->dev;
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struct reserved_mem *rmem;
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struct open_dice_drvdata *drvdata;
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int ret;
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rmem = of_reserved_mem_lookup(dev->of_node);
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if (!rmem) {
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dev_err(dev, "failed to lookup reserved memory\n");
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return -EINVAL;
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}
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if (!rmem->size || (rmem->size > ULONG_MAX)) {
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dev_err(dev, "invalid memory region size\n");
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return -EINVAL;
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}
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if (!PAGE_ALIGNED(rmem->base) || !PAGE_ALIGNED(rmem->size)) {
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dev_err(dev, "memory region must be page-aligned\n");
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return -EINVAL;
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}
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drvdata = devm_kmalloc(dev, sizeof(*drvdata), GFP_KERNEL);
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if (!drvdata)
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return -ENOMEM;
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*drvdata = (struct open_dice_drvdata){
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.rmem = rmem,
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.misc = (struct miscdevice){
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.parent = dev,
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.name = drvdata->name,
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.minor = MISC_DYNAMIC_MINOR,
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.fops = &open_dice_fops,
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.mode = 0600,
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},
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};
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mutex_init(&drvdata->lock);
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/* Index overflow check not needed, misc_register() will fail. */
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snprintf(drvdata->name, sizeof(drvdata->name), DRIVER_NAME"%u", dev_idx++);
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ret = misc_register(&drvdata->misc);
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if (ret) {
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dev_err(dev, "failed to register misc device '%s': %d\n",
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drvdata->name, ret);
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return ret;
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}
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platform_set_drvdata(pdev, drvdata);
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return 0;
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}
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static void open_dice_remove(struct platform_device *pdev)
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{
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struct open_dice_drvdata *drvdata = platform_get_drvdata(pdev);
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misc_deregister(&drvdata->misc);
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}
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static const struct of_device_id open_dice_of_match[] = {
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{ .compatible = "google,open-dice" },
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{},
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};
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static struct platform_driver open_dice_driver = {
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.remove_new = open_dice_remove,
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.driver = {
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.name = DRIVER_NAME,
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.of_match_table = open_dice_of_match,
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},
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};
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static int __init open_dice_init(void)
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{
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int ret = platform_driver_probe(&open_dice_driver, open_dice_probe);
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/* DICE regions are optional. Succeed even with zero instances. */
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return (ret == -ENODEV) ? 0 : ret;
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}
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static void __exit open_dice_exit(void)
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{
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platform_driver_unregister(&open_dice_driver);
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}
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module_init(open_dice_init);
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module_exit(open_dice_exit);
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("David Brazdil <dbrazdil@google.com>");
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