We want all iomem mmaps to consistently revoke ptes when the kernel takes over and CONFIG_IO_STRICT_DEVMEM is enabled. This includes the pci bar mmaps available through procfs and sysfs, which currently do not revoke mappings.
To prepare for this, move the code from the /dev/kmem driver to kernel/resource.c.
Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Kees Cook keescook@chromium.org Cc: Dan Williams dan.j.williams@intel.com Cc: Andrew Morton akpm@linux-foundation.org Cc: John Hubbard jhubbard@nvidia.com Cc: Jérôme Glisse jglisse@redhat.com Cc: Jan Kara jack@suse.cz Cc: Dan Williams dan.j.williams@intel.com Cc: linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-samsung-soc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: David Hildenbrand david@redhat.com Cc: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch -- v3: - add barrier for consistency and document why we don't have to check for NULL (Jason) v4 - Adjust comments to reflect the general nature of this iomem revoke code now (Dan) --- drivers/char/mem.c | 85 +--------------------------------- include/linux/ioport.h | 6 +-- kernel/resource.c | 101 ++++++++++++++++++++++++++++++++++++++++- 3 files changed, 102 insertions(+), 90 deletions(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 5502f56f3655..53338aad8d28 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -31,9 +31,6 @@ #include <linux/uio.h> #include <linux/uaccess.h> #include <linux/security.h> -#include <linux/pseudo_fs.h> -#include <uapi/linux/magic.h> -#include <linux/mount.h>
#ifdef CONFIG_IA64 # include <linux/efi.h> @@ -809,42 +806,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) return ret; }
-static struct inode *devmem_inode; - -#ifdef CONFIG_IO_STRICT_DEVMEM -void revoke_devmem(struct resource *res) -{ - /* pairs with smp_store_release() in devmem_init_inode() */ - struct inode *inode = smp_load_acquire(&devmem_inode); - - /* - * Check that the initialization has completed. Losing the race - * is ok because it means drivers are claiming resources before - * the fs_initcall level of init and prevent /dev/mem from - * establishing mappings. - */ - if (!inode) - return; - - /* - * The expectation is that the driver has successfully marked - * the resource busy by this point, so devmem_is_allowed() - * should start returning false, however for performance this - * does not iterate the entire resource range. - */ - if (devmem_is_allowed(PHYS_PFN(res->start)) && - devmem_is_allowed(PHYS_PFN(res->end))) { - /* - * *cringe* iomem=relaxed says "go ahead, what's the - * worst that can happen?" - */ - return; - } - - unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1); -} -#endif - static int open_port(struct inode *inode, struct file *filp) { int rc; @@ -864,7 +825,7 @@ static int open_port(struct inode *inode, struct file *filp) * revocations when drivers want to take over a /dev/mem mapped * range. */ - filp->f_mapping = inode->i_mapping; + filp->f_mapping = iomem_get_mapping();
return 0; } @@ -995,48 +956,6 @@ static char *mem_devnode(struct device *dev, umode_t *mode)
static struct class *mem_class;
-static int devmem_fs_init_fs_context(struct fs_context *fc) -{ - return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM; -} - -static struct file_system_type devmem_fs_type = { - .name = "devmem", - .owner = THIS_MODULE, - .init_fs_context = devmem_fs_init_fs_context, - .kill_sb = kill_anon_super, -}; - -static int devmem_init_inode(void) -{ - static struct vfsmount *devmem_vfs_mount; - static int devmem_fs_cnt; - struct inode *inode; - int rc; - - rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt); - if (rc < 0) { - pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc); - return rc; - } - - inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb); - if (IS_ERR(inode)) { - rc = PTR_ERR(inode); - pr_err("Cannot allocate inode for /dev/mem: %d\n", rc); - simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt); - return rc; - } - - /* - * Publish /dev/mem initialized. - * Pairs with smp_load_acquire() in revoke_devmem(). - */ - smp_store_release(&devmem_inode, inode); - - return 0; -} - static int __init chr_dev_init(void) { int minor; @@ -1058,8 +977,6 @@ static int __init chr_dev_init(void) */ if ((minor == DEVPORT_MINOR) && !arch_has_dev_port()) continue; - if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0) - continue;
device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), NULL, devlist[minor].name); diff --git a/include/linux/ioport.h b/include/linux/ioport.h index 6c2b06fe8beb..8ffb61b36606 100644 --- a/include/linux/ioport.h +++ b/include/linux/ioport.h @@ -302,11 +302,7 @@ struct resource *devm_request_free_mem_region(struct device *dev, struct resource *request_free_mem_region(struct resource *base, unsigned long size, const char *name);
-#ifdef CONFIG_IO_STRICT_DEVMEM -void revoke_devmem(struct resource *res); -#else -static inline void revoke_devmem(struct resource *res) { }; -#endif +extern struct address_space *iomem_get_mapping(void);
#endif /* __ASSEMBLY__ */ #endif /* _LINUX_IOPORT_H */ diff --git a/kernel/resource.c b/kernel/resource.c index 841737bbda9e..a800acbc578c 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -18,12 +18,15 @@ #include <linux/spinlock.h> #include <linux/fs.h> #include <linux/proc_fs.h> +#include <linux/pseudo_fs.h> #include <linux/sched.h> #include <linux/seq_file.h> #include <linux/device.h> #include <linux/pfn.h> #include <linux/mm.h> +#include <linux/mount.h> #include <linux/resource_ext.h> +#include <uapi/linux/magic.h> #include <asm/io.h>
@@ -1112,6 +1115,58 @@ resource_size_t resource_alignment(struct resource *res)
static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
+static struct inode *iomem_inode; + +#ifdef CONFIG_IO_STRICT_DEVMEM +static void revoke_iomem(struct resource *res) +{ + /* pairs with smp_store_release() in iomem_init_inode() */ + struct inode *inode = smp_load_acquire(&iomem_inode); + + /* + * Check that the initialization has completed. Losing the race + * is ok because it means drivers are claiming resources before + * the fs_initcall level of init and prevent iomem_get_mapping users + * from establishing mappings. + */ + if (!inode) + return; + + /* + * The expectation is that the driver has successfully marked + * the resource busy by this point, so devmem_is_allowed() + * should start returning false, however for performance this + * does not iterate the entire resource range. + */ + if (devmem_is_allowed(PHYS_PFN(res->start)) && + devmem_is_allowed(PHYS_PFN(res->end))) { + /* + * *cringe* iomem=relaxed says "go ahead, what's the + * worst that can happen?" + */ + return; + } + + unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1); +} +struct address_space *iomem_get_mapping(void) +{ + /* + * This function is only called from file open paths, hence guaranteed + * that fs_initcalls have completed and no need to check for NULL. But + * since revoke_iomem can be called before the initcall we still need + * the barrier to appease checkers. + */ + return smp_load_acquire(&iomem_inode)->i_mapping; +} +#else +static void revoke_iomem(struct resource *res) {} +struct address_space *iomem_get_mapping(void) +{ + return NULL; +} +#endif + /** * __request_region - create a new busy resource region * @parent: parent resource descriptor @@ -1179,7 +1234,7 @@ struct resource * __request_region(struct resource *parent, write_unlock(&resource_lock);
if (res && orig_parent == &iomem_resource) - revoke_devmem(res); + revoke_iomem(res);
return res; } @@ -1713,4 +1768,48 @@ static int __init strict_iomem(char *str) return 1; }
+static int iomem_fs_init_fs_context(struct fs_context *fc) +{ + return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM; +} + +static struct file_system_type iomem_fs_type = { + .name = "iomem", + .owner = THIS_MODULE, + .init_fs_context = iomem_fs_init_fs_context, + .kill_sb = kill_anon_super, +}; + +static int __init iomem_init_inode(void) +{ + static struct vfsmount *iomem_vfs_mount; + static int iomem_fs_cnt; + struct inode *inode; + int rc; + + rc = simple_pin_fs(&iomem_fs_type, &iomem_vfs_mount, &iomem_fs_cnt); + if (rc < 0) { + pr_err("Cannot mount iomem pseudo filesystem: %d\n", rc); + return rc; + } + + inode = alloc_anon_inode(iomem_vfs_mount->mnt_sb); + if (IS_ERR(inode)) { + rc = PTR_ERR(inode); + pr_err("Cannot allocate inode for iomem: %d\n", rc); + simple_release_fs(&iomem_vfs_mount, &iomem_fs_cnt); + return rc; + } + + /* + * Publish iomem revocation inode initialized. + * Pairs with smp_load_acquire() in revoke_iomem(). + */ + smp_store_release(&iomem_inode, inode); + + return 0; +} + +fs_initcall(iomem_init_inode); + __setup("iomem=", strict_iomem);