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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#define pr_fmt(fmt) "devtmpfs: " fmt
#include <linux/kernel.h>#include <linux/syscalls.h>#include <linux/mount.h>#include <linux/device.h>#include <linux/blkdev.h>#include <linux/namei.h>#include <linux/fs.h>#include <linux/shmem_fs.h>#include <linux/ramfs.h>#include <linux/sched.h>#include <linux/slab.h>#include <linux/kthread.h>#include <linux/init_syscalls.h>#include <uapi/linux/mount.h>#include "base.h"
#ifdef CONFIG_DEVTMPFS_SAFE#define DEVTMPFS_MFLAGS (MS_SILENT | MS_NOEXEC | MS_NOSUID)#else#define DEVTMPFS_MFLAGS (MS_SILENT)#endif
static struct task_struct *thread;
static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT);
static DEFINE_SPINLOCK(req_lock);
static struct req { struct req *next; struct completion done; int err; const char *name; umode_t mode; /* 0 => delete */ kuid_t uid; kgid_t gid; struct device *dev;} *requests;
static int __init mount_param(char *str){ return kstrtoint(str, 0, &mount_dev) == 0;}__setup("devtmpfs.mount=", mount_param);
static struct vfsmount *mnt;
static struct file_system_type internal_fs_type = { .name = "devtmpfs",#ifdef CONFIG_TMPFS .init_fs_context = shmem_init_fs_context,#else .init_fs_context = ramfs_init_fs_context,#endif .kill_sb = kill_anon_super,};
/* Simply take a ref on the existing mount */static int devtmpfs_get_tree(struct fs_context *fc){ struct super_block *sb = mnt->mnt_sb;
atomic_inc(&sb->s_active); down_write(&sb->s_umount); fc->root = dget(sb->s_root); return 0;}
/* Ops are filled in during init depending on underlying shmem or ramfs type */static struct fs_context_operations devtmpfs_context_ops = {};
/* Call the underlying initialization and set to our ops */static int devtmpfs_init_fs_context(struct fs_context *fc){ int ret;#ifdef CONFIG_TMPFS ret = shmem_init_fs_context(fc);#else ret = ramfs_init_fs_context(fc);#endif if (ret < 0) return ret;
fc->ops = &devtmpfs_context_ops;
return 0;}
static struct file_system_type dev_fs_type = { .name = "devtmpfs", .init_fs_context = devtmpfs_init_fs_context,};
static int devtmpfs_submit_req(struct req *req, const char *tmp){ init_completion(&req->done);
spin_lock(&req_lock); req->next = requests; requests = req; spin_unlock(&req_lock);
wake_up_process(thread); wait_for_completion(&req->done);
kfree(tmp);
return req->err;}
int devtmpfs_create_node(struct device *dev){ const char *tmp = NULL; struct req req;
if (!thread) return 0;
req.mode = 0; req.uid = GLOBAL_ROOT_UID; req.gid = GLOBAL_ROOT_GID; req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp); if (!req.name) return -ENOMEM;
if (req.mode == 0) req.mode = 0600; if (is_blockdev(dev)) req.mode |= S_IFBLK; else req.mode |= S_IFCHR;
req.dev = dev;
return devtmpfs_submit_req(&req, tmp);}
int devtmpfs_delete_node(struct device *dev){ const char *tmp = NULL; struct req req;
if (!thread) return 0;
req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp); if (!req.name) return -ENOMEM;
req.mode = 0; req.dev = dev;
return devtmpfs_submit_req(&req, tmp);}
static int dev_mkdir(const char *name, umode_t mode){ struct dentry *dentry; struct path path;
dentry = start_creating_path(AT_FDCWD, name, &path, LOOKUP_DIRECTORY); if (IS_ERR(dentry)) return PTR_ERR(dentry);
dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode, NULL); if (!IS_ERR(dentry)) /* mark as kernel-created inode */ d_inode(dentry)->i_private = &thread; end_creating_path(&path, dentry); return PTR_ERR_OR_ZERO(dentry);}
static int create_path(const char *nodepath){ char *path; char *s; int err = 0;
/* parent directories do not exist, create them */ path = kstrdup(nodepath, GFP_KERNEL); if (!path) return -ENOMEM;
s = path; for (;;) { s = strchr(s, '/'); if (!s) break; s[0] = '\0'; err = dev_mkdir(path, 0755); if (err && err != -EEXIST) break; s[0] = '/'; s++; } kfree(path); return err;}
static int handle_create(const char *nodename, umode_t mode, kuid_t uid, kgid_t gid, struct device *dev){ struct dentry *dentry; struct path path; int err;
dentry = start_creating_path(AT_FDCWD, nodename, &path, 0); if (dentry == ERR_PTR(-ENOENT)) { create_path(nodename); dentry = start_creating_path(AT_FDCWD, nodename, &path, 0); } if (IS_ERR(dentry)) return PTR_ERR(dentry);
err = vfs_mknod(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode, dev->devt, NULL); if (!err) { struct iattr newattrs;
newattrs.ia_mode = mode; newattrs.ia_uid = uid; newattrs.ia_gid = gid; newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID; inode_lock(d_inode(dentry)); notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL); inode_unlock(d_inode(dentry));
/* mark as kernel-created inode */ d_inode(dentry)->i_private = &thread; } end_creating_path(&path, dentry); return err;}
static int dev_rmdir(const char *name){ struct path parent; struct dentry *dentry; int err;
dentry = start_removing_path(name, &parent); if (IS_ERR(dentry)) return PTR_ERR(dentry); if (d_inode(dentry)->i_private == &thread) err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry), dentry, NULL); else err = -EPERM;
end_removing_path(&parent, dentry); return err;}
static int delete_path(const char *nodepath){ char *path; int err = 0;
path = kstrdup(nodepath, GFP_KERNEL); if (!path) return -ENOMEM;
for (;;) { char *base;
base = strrchr(path, '/'); if (!base) break; base[0] = '\0'; err = dev_rmdir(path); if (err) break; }
kfree(path); return err;}
static int dev_mynode(struct device *dev, struct inode *inode){ /* did we create it */ if (inode->i_private != &thread) return 0;
/* does the dev_t match */ if (is_blockdev(dev)) { if (!S_ISBLK(inode->i_mode)) return 0; } else { if (!S_ISCHR(inode->i_mode)) return 0; } if (inode->i_rdev != dev->devt) return 0;
/* ours */ return 1;}
static int handle_remove(const char *nodename, struct device *dev){ struct path parent; struct dentry *dentry; struct inode *inode; int deleted = 0; int err = 0;
dentry = start_removing_path(nodename, &parent); if (IS_ERR(dentry)) return PTR_ERR(dentry);
inode = d_inode(dentry); if (dev_mynode(dev, inode)) { struct iattr newattrs; /* * before unlinking this node, reset permissions * of possible references like hardlinks */ newattrs.ia_uid = GLOBAL_ROOT_UID; newattrs.ia_gid = GLOBAL_ROOT_GID; newattrs.ia_mode = inode->i_mode & ~0777; newattrs.ia_valid = ATTR_UID|ATTR_GID|ATTR_MODE; inode_lock(d_inode(dentry)); notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL); inode_unlock(d_inode(dentry)); err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry), dentry, NULL); if (!err || err == -ENOENT) deleted = 1; } end_removing_path(&parent, dentry);
if (deleted && strchr(nodename, '/')) delete_path(nodename); return err;}
/* * If configured, or requested by the commandline, devtmpfs will be * auto-mounted after the kernel mounted the root filesystem. */int __init devtmpfs_mount(void){ int err;
if (!mount_dev) return 0;
if (!thread) return 0;
err = init_mount("devtmpfs", "dev", "devtmpfs", DEVTMPFS_MFLAGS, NULL); if (err) pr_info("error mounting %d\n", err); else pr_info("mounted\n"); return err;}
static __initdata DECLARE_COMPLETION(setup_done);
static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, struct device *dev){ if (mode) return handle_create(name, mode, uid, gid, dev); else return handle_remove(name, dev);}
static void __noreturn devtmpfs_work_loop(void){ while (1) { spin_lock(&req_lock); while (requests) { struct req *req = requests; requests = NULL; spin_unlock(&req_lock); while (req) { struct req *next = req->next; req->err = handle(req->name, req->mode, req->uid, req->gid, req->dev); complete(&req->done); req = next; } spin_lock(&req_lock); } __set_current_state(TASK_INTERRUPTIBLE); spin_unlock(&req_lock); schedule(); }}
static noinline int __init devtmpfs_setup(void *p){ int err;
err = ksys_unshare(CLONE_NEWNS); if (err) goto out; err = init_mount("devtmpfs", "/", "devtmpfs", DEVTMPFS_MFLAGS, NULL); if (err) goto out; init_chdir("/.."); /* will traverse into overmounted root */ init_chroot(".");out: *(int *)p = err; return err;}
/* * The __ref is because devtmpfs_setup needs to be __init for the routines it * calls. That call is done while devtmpfs_init, which is marked __init, * synchronously waits for it to complete. */static int __ref devtmpfsd(void *p){ int err = devtmpfs_setup(p);
complete(&setup_done); if (err) return err; devtmpfs_work_loop(); return 0;}
/* * Get the underlying (shmem/ramfs) context ops to build ours */static int devtmpfs_configure_context(void){ struct fs_context *fc;
fc = fs_context_for_reconfigure(mnt->mnt_root, mnt->mnt_sb->s_flags, MS_RMT_MASK); if (IS_ERR(fc)) return PTR_ERR(fc);
/* Set up devtmpfs_context_ops based on underlying type */ devtmpfs_context_ops.free = fc->ops->free; devtmpfs_context_ops.dup = fc->ops->dup; devtmpfs_context_ops.parse_param = fc->ops->parse_param; devtmpfs_context_ops.parse_monolithic = fc->ops->parse_monolithic; devtmpfs_context_ops.get_tree = &devtmpfs_get_tree; devtmpfs_context_ops.reconfigure = fc->ops->reconfigure;
put_fs_context(fc);
return 0;}
/* * Create devtmpfs instance, driver-core devices will add their device * nodes here. */int __init devtmpfs_init(void){ char opts[] = "mode=0755"; int err;
mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts); if (IS_ERR(mnt)) { pr_err("unable to create devtmpfs %ld\n", PTR_ERR(mnt)); return PTR_ERR(mnt); }
err = devtmpfs_configure_context(); if (err) { pr_err("unable to configure devtmpfs type %d\n", err); return err; }
err = register_filesystem(&dev_fs_type); if (err) { pr_err("unable to register devtmpfs type %d\n", err); return err; }
thread = kthread_run(devtmpfsd, &err, "kdevtmpfs"); if (!IS_ERR(thread)) { wait_for_completion(&setup_done); } else { err = PTR_ERR(thread); thread = NULL; }
if (err) { pr_err("unable to create devtmpfs %d\n", err); unregister_filesystem(&dev_fs_type); thread = NULL; return err; }
pr_info("initialized\n"); return 0;}