diff options
| -rw-r--r-- | fs/Makefile | 1 | ||||
| -rw-r--r-- | fs/exec.c | 11 | ||||
| -rw-r--r-- | fs/signalfd.c | 349 | ||||
| -rw-r--r-- | include/linux/Kbuild | 1 | ||||
| -rw-r--r-- | include/linux/init_task.h | 1 | ||||
| -rw-r--r-- | include/linux/sched.h | 1 | ||||
| -rw-r--r-- | include/linux/signal.h | 1 | ||||
| -rw-r--r-- | include/linux/signalfd.h | 97 | ||||
| -rw-r--r-- | include/linux/syscalls.h | 1 | ||||
| -rw-r--r-- | init/Kconfig | 10 | ||||
| -rw-r--r-- | kernel/exit.c | 9 | ||||
| -rw-r--r-- | kernel/fork.c | 8 | ||||
| -rw-r--r-- | kernel/signal.c | 22 | ||||
| -rw-r--r-- | kernel/sys_ni.c | 3 |
14 files changed, 508 insertions, 7 deletions
diff --git a/fs/Makefile b/fs/Makefile index b5cd46a88cb0..cd8a57aeac04 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -23,6 +23,7 @@ obj-$(CONFIG_INOTIFY) += inotify.o obj-$(CONFIG_INOTIFY_USER) += inotify_user.o obj-$(CONFIG_EPOLL) += eventpoll.o obj-$(CONFIG_ANON_INODES) += anon_inodes.o +obj-$(CONFIG_SIGNALFD) += signalfd.o obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o nfsd-$(CONFIG_NFSD) := nfsctl.o diff --git a/fs/exec.c b/fs/exec.c index 2255dc72deef..955a8eb66d70 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -50,6 +50,7 @@ #include <linux/tsacct_kern.h> #include <linux/cn_proc.h> #include <linux/audit.h> +#include <linux/signalfd.h> #include <asm/uaccess.h> #include <asm/mmu_context.h> @@ -582,6 +583,13 @@ static int de_thread(struct task_struct *tsk) int count; /* + * Tell all the sighand listeners that this sighand has + * been detached. The signalfd_detach() function grabs the + * sighand lock, if signal listeners are present on the sighand. + */ + signalfd_detach(tsk); + + /* * If we don't share sighandlers, then we aren't sharing anything * and we can just re-use it all. */ @@ -757,8 +765,7 @@ no_thread_group: spin_unlock(&oldsighand->siglock); write_unlock_irq(&tasklist_lock); - if (atomic_dec_and_test(&oldsighand->count)) - kmem_cache_free(sighand_cachep, oldsighand); + __cleanup_sighand(oldsighand); } BUG_ON(!thread_group_leader(tsk)); diff --git a/fs/signalfd.c b/fs/signalfd.c new file mode 100644 index 000000000000..7cfeab412b45 --- /dev/null +++ b/fs/signalfd.c @@ -0,0 +1,349 @@ +/* + * fs/signalfd.c + * + * Copyright (C) 2003 Linus Torvalds + * + * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org> + * Changed ->read() to return a siginfo strcture instead of signal number. + * Fixed locking in ->poll(). + * Added sighand-detach notification. + * Added fd re-use in sys_signalfd() syscall. + * Now using anonymous inode source. + * Thanks to Oleg Nesterov for useful code review and suggestions. + * More comments and suggestions from Arnd Bergmann. + */ + +#include <linux/file.h> +#include <linux/poll.h> +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/signal.h> +#include <linux/list.h> +#include <linux/anon_inodes.h> +#include <linux/signalfd.h> + +struct signalfd_ctx { + struct list_head lnk; + wait_queue_head_t wqh; + sigset_t sigmask; + struct task_struct *tsk; +}; + +struct signalfd_lockctx { + struct task_struct *tsk; + unsigned long flags; +}; + +/* + * Tries to acquire the sighand lock. We do not increment the sighand + * use count, and we do not even pin the task struct, so we need to + * do it inside an RCU read lock, and we must be prepared for the + * ctx->tsk going to NULL (in signalfd_deliver()), and for the sighand + * being detached. We return 0 if the sighand has been detached, or + * 1 if we were able to pin the sighand lock. + */ +static int signalfd_lock(struct signalfd_ctx *ctx, struct signalfd_lockctx *lk) +{ + struct sighand_struct *sighand = NULL; + + rcu_read_lock(); + lk->tsk = rcu_dereference(ctx->tsk); + if (likely(lk->tsk != NULL)) + sighand = lock_task_sighand(lk->tsk, &lk->flags); + rcu_read_unlock(); + + if (sighand && !ctx->tsk) { + unlock_task_sighand(lk->tsk, &lk->flags); + sighand = NULL; + } + + return sighand != NULL; +} + +static void signalfd_unlock(struct signalfd_lockctx *lk) +{ + unlock_task_sighand(lk->tsk, &lk->flags); +} + +/* + * This must be called with the sighand lock held. + */ +void signalfd_deliver(struct task_struct *tsk, int sig) +{ + struct sighand_struct *sighand = tsk->sighand; + struct signalfd_ctx *ctx, *tmp; + + BUG_ON(!sig); + list_for_each_entry_safe(ctx, tmp, &sighand->signalfd_list, lnk) { + /* + * We use a negative signal value as a way to broadcast that the + * sighand has been orphaned, so that we can notify all the + * listeners about this. Remember the ctx->sigmask is inverted, + * so if the user is interested in a signal, that corresponding + * bit will be zero. + */ + if (sig < 0) { + if (ctx->tsk == tsk) { + ctx->tsk = NULL; + list_del_init(&ctx->lnk); + wake_up(&ctx->wqh); + } + } else { + if (!sigismember(&ctx->sigmask, sig)) + wake_up(&ctx->wqh); + } + } +} + +static void signalfd_cleanup(struct signalfd_ctx *ctx) +{ + struct signalfd_lockctx lk; + + /* + * This is tricky. If the sighand is gone, we do not need to remove + * context from the list, the list itself won't be there anymore. + */ + if (signalfd_lock(ctx, &lk)) { + list_del(&ctx->lnk); + signalfd_unlock(&lk); + } + kfree(ctx); +} + +static int signalfd_release(struct inode *inode, struct file *file) +{ + signalfd_cleanup(file->private_data); + return 0; +} + +static unsigned int signalfd_poll(struct file *file, poll_table *wait) +{ + struct signalfd_ctx *ctx = file->private_data; + unsigned int events = 0; + struct signalfd_lockctx lk; + + poll_wait(file, &ctx->wqh, wait); + + /* + * Let the caller get a POLLIN in this case, ala socket recv() when + * the peer disconnects. + */ + if (signalfd_lock(ctx, &lk)) { + if (next_signal(&lk.tsk->pending, &ctx->sigmask) > 0 || + next_signal(&lk.tsk->signal->shared_pending, + &ctx->sigmask) > 0) + events |= POLLIN; + signalfd_unlock(&lk); + } else + events |= POLLIN; + + return events; +} + +/* + * Copied from copy_siginfo_to_user() in kernel/signal.c + */ +static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, + siginfo_t const *kinfo) +{ + long err; + + BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); + + /* + * Unused memebers should be zero ... + */ + err = __clear_user(uinfo, sizeof(*uinfo)); + + /* + * If you change siginfo_t structure, please be sure + * this code is fixed accordingly. + */ + err |= __put_user(kinfo->si_signo, &uinfo->signo); + err |= __put_user(kinfo->si_errno, &uinfo->err); + err |= __put_user((short)kinfo->si_code, &uinfo->code); + switch (kinfo->si_code & __SI_MASK) { + case __SI_KILL: + err |= __put_user(kinfo->si_pid, &uinfo->pid); + err |= __put_user(kinfo->si_uid, &uinfo->uid); + break; + case __SI_TIMER: + err |= __put_user(kinfo->si_tid, &uinfo->tid); + err |= __put_user(kinfo->si_overrun, &uinfo->overrun); + err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr); + break; + case __SI_POLL: + err |= __put_user(kinfo->si_band, &uinfo->band); + err |= __put_user(kinfo->si_fd, &uinfo->fd); + break; + case __SI_FAULT: + err |= __put_user((long)kinfo->si_addr, &uinfo->addr); +#ifdef __ARCH_SI_TRAPNO + err |= __put_user(kinfo->si_trapno, &uinfo->trapno); +#endif + break; + case __SI_CHLD: + err |= __put_user(kinfo->si_pid, &uinfo->pid); + err |= __put_user(kinfo->si_uid, &uinfo->uid); + err |= __put_user(kinfo->si_status, &uinfo->status); + err |= __put_user(kinfo->si_utime, &uinfo->utime); + err |= __put_user(kinfo->si_stime, &uinfo->stime); + break; + case __SI_RT: /* This is not generated by the kernel as of now. */ + case __SI_MESGQ: /* But this is */ + err |= __put_user(kinfo->si_pid, &uinfo->pid); + err |= __put_user(kinfo->si_uid, &uinfo->uid); + err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr); + break; + default: /* this is just in case for now ... */ + err |= __put_user(kinfo->si_pid, &uinfo->pid); + err |= __put_user(kinfo->si_uid, &uinfo->uid); + break; + } + + return err ? -EFAULT: sizeof(*uinfo); +} + +/* + * Returns either the size of a "struct signalfd_siginfo", or zero if the + * sighand we are attached to, has been orphaned. The "count" parameter + * must be at least the size of a "struct signalfd_siginfo". + */ +static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, + loff_t *ppos) +{ + struct signalfd_ctx *ctx = file->private_data; + ssize_t res = 0; + int locked, signo; + siginfo_t info; + struct signalfd_lockctx lk; + DECLARE_WAITQUEUE(wait, current); + + if (count < sizeof(struct signalfd_siginfo)) + return -EINVAL; + locked = signalfd_lock(ctx, &lk); + if (!locked) + return 0; + res = -EAGAIN; + signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info); + if (signo == 0 && !(file->f_flags & O_NONBLOCK)) { + add_wait_queue(&ctx->wqh, &wait); + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info); + if (signo != 0) + break; + if (signal_pending(current)) { + res = -ERESTARTSYS; + break; + } + signalfd_unlock(&lk); + schedule(); + locked = signalfd_lock(ctx, &lk); + if (unlikely(!locked)) { + /* + * Let the caller read zero byte, ala socket + * recv() when the peer disconnect. This test + * must be done before doing a dequeue_signal(), + * because if the sighand has been orphaned, + * the dequeue_signal() call is going to crash. + */ + res = 0; + break; + } + } + remove_wait_queue(&ctx->wqh, &wait); + __set_current_state(TASK_RUNNING); + } + if (likely(locked)) + signalfd_unlock(&lk); + if (likely(signo)) + res = signalfd_copyinfo((struct signalfd_siginfo __user *) buf, + &info); + + return res; +} + +static const struct file_operations signalfd_fops = { + .release = signalfd_release, + .poll = signalfd_poll, + .read = signalfd_read, +}; + +/* + * Create a file descriptor that is associated with our signal + * state. We can pass it around to others if we want to, but + * it will always be _our_ signal state. + */ +asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask) +{ + int error; + sigset_t sigmask; + struct signalfd_ctx *ctx; + struct sighand_struct *sighand; + struct file *file; + struct inode *inode; + struct signalfd_lockctx lk; + + if (sizemask != sizeof(sigset_t) || + copy_from_user(&sigmask, user_mask, sizeof(sigmask))) + return error = -EINVAL; + sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); + signotset(&sigmask); + + if (ufd == -1) { + ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); + if (!ctx) + return -ENOMEM; + + init_waitqueue_head(&ctx->wqh); + ctx->sigmask = sigmask; + ctx->tsk = current; + + sighand = current->sighand; + /* + * Add this fd to the list of signal listeners. + */ + spin_lock_irq(&sighand->siglock); + list_add_tail(&ctx->lnk, &sighand->signalfd_list); + spin_unlock_irq(&sighand->siglock); + + /* + * When we call this, the initialization must be complete, since + * anon_inode_getfd() will install the fd. + */ + error = anon_inode_getfd(&ufd, &inode, &file, "[signalfd]", + &signalfd_fops, ctx); + if (error) + goto err_fdalloc; + } else { + file = fget(ufd); + if (!file) + return -EBADF; + ctx = file->private_data; + if (file->f_op != &signalfd_fops) { + fput(file); + return -EINVAL; + } + /* + * We need to be prepared of the fact that the sighand this fd + * is attached to, has been detched. In that case signalfd_lock() + * will return 0, and we'll just skip setting the new mask. + */ + if (signalfd_lock(ctx, &lk)) { + ctx->sigmask = sigmask; + signalfd_unlock(&lk); + } + wake_up(&ctx->wqh); + fput(file); + } + + return ufd; + +err_fdalloc: + signalfd_cleanup(ctx); + return error; +} + diff --git a/include/linux/Kbuild b/include/linux/Kbuild index 645b3b528150..bcd01f269f60 100644 --- a/include/linux/Kbuild +++ b/include/linux/Kbuild @@ -190,6 +190,7 @@ unifdef-y += errno.h unifdef-y += errqueue.h unifdef-y += ethtool.h unifdef-y += eventpoll.h +unifdef-y += signalfd.h unifdef-y += ext2_fs.h unifdef-y += ext3_fs.h unifdef-y += fb.h diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 66e2f0a70814..276ccaa2670c 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -84,6 +84,7 @@ extern struct nsproxy init_nsproxy; .count = ATOMIC_INIT(1), \ .action = { { { .sa_handler = NULL, } }, }, \ .siglock = __SPIN_LOCK_UNLOCKED(sighand.siglock), \ + .signalfd_list = LIST_HEAD_INIT(sighand.signalfd_list), \ } extern struct group_info init_groups; diff --git a/include/linux/sched.h b/include/linux/sched.h index 75f44379b7e9..97c0c7da58ef 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -391,6 +391,7 @@ struct sighand_struct { atomic_t count; struct k_sigaction action[_NSIG]; spinlock_t siglock; + struct list_head signalfd_list; }; struct pacct_struct { diff --git a/include/linux/signal.h b/include/linux/signal.h index 3fa0fab4a04b..9a5eac508e5e 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -233,6 +233,7 @@ static inline int valid_signal(unsigned long sig) return sig <= _NSIG ? 1 : 0; } +extern int next_signal(struct sigpending *pending, sigset_t *mask); extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p); extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *); extern long do_sigpending(void __user *, unsigned long); diff --git a/include/linux/signalfd.h b/include/linux/signalfd.h new file mode 100644 index 000000000000..510429495690 --- /dev/null +++ b/include/linux/signalfd.h @@ -0,0 +1,97 @@ +/* + * include/linux/signalfd.h + * + * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> + * + */ + +#ifndef _LINUX_SIGNALFD_H +#define _LINUX_SIGNALFD_H + + +struct signalfd_siginfo { + __u32 signo; + __s32 err; + __s32 code; + __u32 pid; + __u32 uid; + __s32 fd; + __u32 tid; + __u32 band; + __u32 overrun; + __u32 trapno; + __s32 status; + __s32 svint; + __u64 svptr; + __u64 utime; + __u64 stime; + __u64 addr; + + /* + * Pad strcture to 128 bytes. Remember to update the + * pad size when you add new memebers. We use a fixed + * size structure to avoid compatibility problems with + * future versions, and we leave extra space for additional + * members. We use fixed size members because this strcture + * comes out of a read(2) and we really don't want to have + * a compat on read(2). + */ + __u8 __pad[48]; +}; + + +#ifdef __KERNEL__ + +#ifdef CONFIG_SIGNALFD + +/* + * Deliver the signal to listening signalfd. This must be called + * with the sighand lock held. Same are the following that end up + * calling signalfd_deliver(). + */ +void signalfd_deliver(struct task_struct *tsk, int sig); + +/* + * No need to fall inside signalfd_deliver() if no signal listeners + * are available. + */ +static inline void signalfd_notify(struct task_struct *tsk, int sig) +{ + if (unlikely(!list_empty(&tsk->sighand->signalfd_list))) + signalfd_deliver(tsk, sig); +} + +/* + * The signal -1 is used to notify the signalfd that the sighand + * is on its way to be detached. + */ +static inline void signalfd_detach_locked(struct task_struct *tsk) +{ + if (unlikely(!list_empty(&tsk->sighand->signalfd_list))) + signalfd_deliver(tsk, -1); +} + +static inline void signalfd_detach(struct task_struct *tsk) +{ + struct sighand_struct *sighand = tsk->sighand; + + if (unlikely(!list_empty(&sighand->signalfd_list))) { + spin_lock_irq(&sighand->siglock); + signalfd_deliver(tsk, -1); + spin_unlock_irq(&sighand->siglock); + } +} + +#else /* CONFIG_SIGNALFD */ + +#define signalfd_deliver(t, s) do { } while (0) +#define signalfd_notify(t, s) do { } while (0) +#define signalfd_detach_locked(t) do { } while (0) +#define signalfd_detach(t) do { } while (0) + +#endif /* CONFIG_SIGNALFD */ + +#endif /* __KERNEL__ */ + +#endif /* _LINUX_SIGNALFD_H */ + diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 3139f4412297..e049f14a75b7 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -604,6 +604,7 @@ asmlinkage long sys_get_robust_list(int pid, asmlinkage long sys_set_robust_list(struct robust_list_head __user *head, size_t len); asmlinkage long sys_getcpu(unsigned __user *cpu, unsigned __user *node, struct getcpu_cache __user *cache); +asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask); int kernel_execve(const char *filename, char *const argv[], char *const envp[]); diff --git a/init/Kconfig b/init/Kconfig index a80bd8326bc6..db707204b751 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -492,6 +492,16 @@ config EPOLL Disabling this option will cause the kernel to be built without support for epoll family of system calls. +config SIGNALFD + bool "Enable signalfd() system call" if EMBEDDED + depends on ANON_INODES + default y + help + Enable the signalfd() system call that allows to receive signals + on a file descriptor. + + If unsure, say Y. + config SHMEM bool "Use full shmem filesystem" if EMBEDDED default y diff --git a/kernel/exit.c b/kernel/exit.c index e93691e9b325..c6d14b8008dd 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -24,6 +24,7 @@ #include <linux/pid_namespace.h> #include <linux/ptrace.h> #include <linux/profile.h> +#include <linux/signalfd.h> #include <linux/mount.h> #include <linux/proc_fs.h> #include <linux/kthread.h> @@ -83,6 +84,14 @@ static void __exit_signal(struct task_struct *tsk) sighand = rcu_dereference(tsk->sighand); spin_lock(&sighand->siglock); + /* + * Notify that this sighand has been detached. This must + * be called with the tsk->sighand lock held. Also, this + * access tsk->sighand internally, so it must be called + * before tsk->sighand is reset. + */ + signalfd_detach_locked(tsk); + posix_cpu_timers_exit(tsk); if (atomic_dec_and_test(&sig->count)) posix_cpu_timers_exit_group(tsk); diff --git a/kernel/fork.c b/kernel/fork.c index 083bf8953ce8..49530e40ea8b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1422,12 +1422,15 @@ long do_fork(unsigned long clone_flags, #define ARCH_MIN_MMSTRUCT_ALIGN 0 #endif -static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags) +static void sighand_ctor(void *data, struct kmem_cache *cachep, + unsigned long flags) { struct sighand_struct *sighand = data; - if (flags & SLAB_CTOR_CONSTRUCTOR) + if (flags & SLAB_CTOR_CONSTRUCTOR) { spin_lock_init(&sighand->siglock); + INIT_LIST_HEAD(&sighand->signalfd_list); + } } void __init proc_caches_init(void) @@ -1453,7 +1456,6 @@ void __init proc_caches_init(void) SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); } - /* * Check constraints on flags passed to the unshare system call and * force unsharing of additional process context as appropriate. diff --git a/kernel/signal.c b/kernel/signal.c index 2ac3a668d9dd..34b7d6abce8f 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -21,6 +21,7 @@ #include <linux/syscalls.h> #include <linux/ptrace.h> #include <linux/signal.h> +#include <linux/signalfd.h> #include <linux/capability.h> #include <linux/freezer.h> #include <linux/pid_namespace.h> @@ -113,8 +114,7 @@ void recalc_sigpending(void) /* Given the mask, find the first available signal that should be serviced. */ -static int -next_signal(struct sigpending *pending, sigset_t *mask) +int next_signal(struct sigpending *pending, sigset_t *mask) { unsigned long i, *s, *m, x; int sig = 0; @@ -630,6 +630,12 @@ static int send_signal(int sig, struct siginfo *info, struct task_struct *t, int ret = 0; /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(t, sig); + + /* * fast-pathed signals for kernel-internal things like SIGSTOP * or SIGKILL. */ @@ -1280,6 +1286,11 @@ int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) ret = 1; goto out; } + /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(p, sig); list_add_tail(&q->list, &p->pending.list); sigaddset(&p->pending.signal, sig); @@ -1323,6 +1334,11 @@ send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) q->info.si_overrun++; goto out; } + /* + * Deliver the signal to listening signalfds. This must be called + * with the sighand lock held. + */ + signalfd_notify(p, sig); /* * Put this signal on the shared-pending queue. @@ -1983,6 +1999,8 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from) /* * If you change siginfo_t structure, please be sure * this code is fixed accordingly. + * Please remember to update the signalfd_copyinfo() function + * inside fs/signalfd.c too, in case siginfo_t changes. * It should never copy any pad contained in the structure * to avoid security leaks, but must copy the generic * 3 ints plus the relevant union member. diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index d7306d0f3dfc..807e9bb8fcdb 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -141,3 +141,6 @@ cond_syscall(compat_sys_migrate_pages); cond_syscall(sys_bdflush); cond_syscall(sys_ioprio_set); cond_syscall(sys_ioprio_get); + +/* New file descriptors */ +cond_syscall(sys_signalfd); |
