1 files changed, 524 insertions, 0 deletions
diff --git a/sys/kern/sys_procdesc.c b/sys/kern/sys_procdesc.c
new file mode 100644
index 0000000..9993732
--- /dev/null
+++ b/sys/kern/sys_procdesc.c
@@ -0,0 +1,524 @@
+/*-
+ * Copyright (c) 2009 Robert N. M. Watson
+ * All rights reserved.
+ *
+ * This software was developed at the University of Cambridge Computer
+ * Laboratory with support from a grant from Google, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*-
+ * FreeBSD process descriptor facility.
+ *
+ * Some processes are represented by a file descriptor, which will be used in
+ * preference to signaling and pids for the purposes of process management,
+ * and is, in effect, a form of capability.  When a process descriptor is
+ * used with a process, it ceases to be visible to certain traditional UNIX
+ * process facilities, such as waitpid(2).
+ *
+ * Some semantics:
+ *
+ * - At most one process descriptor will exist for any process, although
+ *   references to that descriptor may be held from many processes (or even
+ *   be in flight between processes over a local domain socket).
+ * - Last close on the process descriptor will terminate the process using
+ *   SIGKILL and reparent it to init so that there's a process to reap it
+ *   when it's done exiting.
+ * - If the process exits before the descriptor is closed, it will not
+ *   generate SIGCHLD on termination, or be picked up by waitpid().
+ * - The pdkill(2) system call may be used to deliver a signal to the process
+ *   using its process descriptor.
+ * - The pdwait4(2) system call may be used to block (or not) on a process
+ *   descriptor to collect termination information.
+ *
+ * Open questions:
+ *
+ * - How to handle ptrace(2)?
+ * - Will we want to add a pidtoprocdesc(2) system call to allow process
+ *   descriptors to be created for processes without pfork(2)?
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_procdesc.h"
+
+#include <sys/param.h>
+#include <sys/capability.h>
+#include <sys/fcntl.h>
+#include <sys/file.h>
+#include <sys/filedesc.h>
+#include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/poll.h>
+#include <sys/proc.h>
+#include <sys/procdesc.h>
+#include <sys/resourcevar.h>
+#include <sys/stat.h>
+#include <sys/sysproto.h>
+#include <sys/sysctl.h>
+#include <sys/systm.h>
+#include <sys/ucred.h>
+
+#include <security/audit/audit.h>
+
+#include <vm/uma.h>
+
+#ifdef PROCDESC
+
+FEATURE(process_descriptors, "Process Descriptors");
+
+static uma_zone_t procdesc_zone;
+
+static fo_rdwr_t	procdesc_read;
+static fo_rdwr_t	procdesc_write;
+static fo_truncate_t	procdesc_truncate;
+static fo_ioctl_t	procdesc_ioctl;
+static fo_poll_t	procdesc_poll;
+static fo_kqfilter_t	procdesc_kqfilter;
+static fo_stat_t	procdesc_stat;
+static fo_close_t	procdesc_close;
+static fo_chmod_t	procdesc_chmod;
+static fo_chown_t	procdesc_chown;
+
+static struct fileops procdesc_ops = {
+	.fo_read = procdesc_read,
+	.fo_write = procdesc_write,
+	.fo_truncate = procdesc_truncate,
+	.fo_ioctl = procdesc_ioctl,
+	.fo_poll = procdesc_poll,
+	.fo_kqfilter = procdesc_kqfilter,
+	.fo_stat = procdesc_stat,
+	.fo_close = procdesc_close,
+	.fo_chmod = procdesc_chmod,
+	.fo_chown = procdesc_chown,
+	.fo_flags = DFLAG_PASSABLE,
+};
+
+/*
+ * Initialize with VFS so that process descriptors are available along with
+ * other file descriptor types.  As long as it runs before init(8) starts,
+ * there shouldn't be a problem.
+ */
+static void
+procdesc_init(void *dummy __unused)
+{
+
+	procdesc_zone = uma_zcreate("procdesc", sizeof(struct procdesc),
+	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
+	if (procdesc_zone == NULL)
+		panic("procdesc_init: procdesc_zone not initialized");
+}
+SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, procdesc_init, NULL);
+
+/*
+ * Return a locked process given a process descriptor, or ESRCH if it has
+ * died.
+ */
+int
+procdesc_find(struct thread *td, int fd, cap_rights_t rights,
+    struct proc **p)
+{
+	struct procdesc *pd;
+	struct file *fp;
+	int error;
+
+	error = fget(td, fd, rights, &fp);
+	if (error)
+		return (error);
+	if (fp->f_type != DTYPE_PROCDESC) {
+		error = EBADF;
+		goto out;
+	}
+	pd = fp->f_data;
+	sx_slock(&proctree_lock);
+	if (pd->pd_proc != NULL) {
+		*p = pd->pd_proc;
+		PROC_LOCK(*p);
+	} else
+		error = ESRCH;
+	sx_sunlock(&proctree_lock);
+out:
+	fdrop(fp, td);
+	return (error);
+}
+
+/*
+ * Function to be used by procstat(1) sysctls when returning procdesc
+ * information.
+ */
+pid_t
+procdesc_pid(struct file *fp_procdesc)
+{
+	struct procdesc *pd;
+
+	KASSERT(fp_procdesc->f_type == DTYPE_PROCDESC,
+	   ("procdesc_pid: !procdesc"));
+
+	pd = fp_procdesc->f_data;
+	return (pd->pd_pid);
+}
+
+/*
+ * Retrieve the PID associated with a process descriptor.
+ */
+int
+kern_pdgetpid(struct thread *td, int fd, cap_rights_t rights, pid_t *pidp)
+{
+	struct file *fp;
+	int error;
+
+	error = fget(td, fd, rights, &fp);
+	if (error)
+		return (error);
+	if (fp->f_type != DTYPE_PROCDESC) {
+		error = EBADF;
+		goto out;
+	}
+	*pidp = procdesc_pid(fp);
+out:
+	fdrop(fp, td);
+	return (error);
+}
+
+/*
+ * System call to return the pid of a process given its process descriptor.
+ */
+int
+pdgetpid(struct thread *td, struct pdgetpid_args *uap)
+{
+	pid_t pid;
+	int error;
+
+	AUDIT_ARG_FD(uap->fd);
+	error = kern_pdgetpid(td, uap->fd, CAP_PDGETPID, &pid);
+	if (error == 0)
+		error = copyout(&pid, uap->pidp, sizeof(pid));
+	return (error);
+}
+
+/*
+ * When a new process is forked by pdfork(), a file descriptor is allocated
+ * by the fork code first, then the process is forked, and then we get a
+ * chance to set up the process descriptor.  Failure is not permitted at this
+ * point, so procdesc_new() must succeed.
+ */
+void
+procdesc_new(struct proc *p, int flags)
+{
+	struct procdesc *pd;
+
+	pd = uma_zalloc(procdesc_zone, M_WAITOK | M_ZERO);
+	pd->pd_proc = p;
+	pd->pd_pid = p->p_pid;
+	p->p_procdesc = pd;
+	pd->pd_flags = 0;
+	if (flags & PD_DAEMON)
+		pd->pd_flags |= PDF_DAEMON;
+	PROCDESC_LOCK_INIT(pd);
+
+	/*
+	 * Process descriptors start out with two references: one from their
+	 * struct file, and the other from their struct proc.
+	 */
+	refcount_init(&pd->pd_refcount, 2);
+}
+
+/*
+ * Initialize a file with a process descriptor.
+ */
+void
+procdesc_finit(struct procdesc *pdp, struct file *fp)
+{
+
+	finit(fp, FREAD | FWRITE, DTYPE_PROCDESC, pdp, &procdesc_ops);
+}
+
+static void
+procdesc_free(struct procdesc *pd)
+{
+
+	/*
+	 * When the last reference is released, we assert that the descriptor
+	 * has been closed, but not that the process has exited, as we will
+	 * detach the descriptor before the process dies if the descript is
+	 * closed, as we can't wait synchronously.
+	 */
+	if (refcount_release(&pd->pd_refcount)) {
+		KASSERT(pd->pd_proc == NULL,
+		    ("procdesc_free: pd_proc != NULL"));
+		KASSERT((pd->pd_flags & PDF_CLOSED),
+		    ("procdesc_free: !PDF_CLOSED"));
+
+		PROCDESC_LOCK_DESTROY(pd);
+		uma_zfree(procdesc_zone, pd);
+	}
+}
+
+/*
+ * procdesc_exit() - notify a process descriptor that its process is exiting.
+ * We use the proctree_lock to ensure that process exit either happens
+ * strictly before or strictly after a concurrent call to procdesc_close().
+ */
+int
+procdesc_exit(struct proc *p)
+{
+	struct procdesc *pd;
+
+	sx_assert(&proctree_lock, SA_XLOCKED);
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	KASSERT(p->p_procdesc != NULL, ("procdesc_exit: p_procdesc NULL"));
+
+	pd = p->p_procdesc;
+
+	PROCDESC_LOCK(pd);
+	KASSERT((pd->pd_flags & PDF_CLOSED) == 0 || p->p_pptr == initproc,
+	    ("procdesc_exit: closed && parent not init"));
+
+	pd->pd_flags |= PDF_EXITED;
+
+	/*
+	 * If the process descriptor has been closed, then we have nothing
+	 * to do; return 1 so that init will get SIGCHLD and do the reaping.
+	 * Clean up the procdesc now rather than letting it happen during
+	 * that reap.
+	 */
+	if (pd->pd_flags & PDF_CLOSED) {
+		PROCDESC_UNLOCK(pd);
+		pd->pd_proc = NULL;
+		p->p_procdesc = NULL;
+		procdesc_free(pd);
+		return (1);
+	}
+	if (pd->pd_flags & PDF_SELECTED) {
+		pd->pd_flags &= ~PDF_SELECTED;
+		selwakeup(&pd->pd_selinfo);
+	}
+	PROCDESC_UNLOCK(pd);
+	return (0);
+}
+
+/*
+ * When a process descriptor is reaped, perhaps as a result of close() or
+ * pdwait4(), release the process's reference on the process descriptor.
+ */
+void
+procdesc_reap(struct proc *p)
+{
+	struct procdesc *pd;
+
+	sx_assert(&proctree_lock, SA_XLOCKED);
+	KASSERT(p->p_procdesc != NULL, ("procdesc_reap: p_procdesc == NULL"));
+
+	pd = p->p_procdesc;
+	pd->pd_proc = NULL;
+	procdesc_free(pd);
+}
+
+/*
+ * procdesc_close() - last close on a process descriptor.  If the process is
+ * still running, terminate with SIGKILL (unless PD_DAEMON is set) and let
+ * init(8) clean up the mess; if not, we have to clean up the zombie ourselves.
+ */
+static int
+procdesc_close(struct file *fp, struct thread *td)
+{
+	struct procdesc *pd;
+	struct proc *p;
+
+	KASSERT(fp->f_type == DTYPE_PROCDESC, ("procdesc_close: !procdesc"));
+
+	pd = fp->f_data;
+	fp->f_ops = &badfileops;
+	fp->f_data = NULL;
+
+	sx_xlock(&proctree_lock);
+	PROCDESC_LOCK(pd);
+	pd->pd_flags |= PDF_CLOSED;
+	PROCDESC_UNLOCK(pd);
+	p = pd->pd_proc;
+	PROC_LOCK(p);
+	if (p->p_state == PRS_ZOMBIE) {
+		/*
+		 * If the process is already dead and just awaiting reaping,
+		 * do that now.  This will release the process's reference to
+		 * the process descriptor when it calls back into
+		 * procdesc_reap().
+		 */
+		PROC_SLOCK(p);
+		proc_reap(curthread, p, NULL, 0, NULL);
+	} else {
+		/*
+		 * If the process is not yet dead, we need to kill it, but we
+		 * can't wait around synchronously for it to go away, as that
+		 * path leads to madness (and deadlocks).  First, detach the
+		 * process from its descriptor so that its exit status will
+		 * be reported normally.
+		 */
+		pd->pd_proc = NULL;
+		p->p_procdesc = NULL;
+		procdesc_free(pd);
+
+		/*
+		 * Next, reparent it to init(8) so that there's someone to
+		 * pick up the pieces; finally, terminate with prejudice.
+		 */
+		p->p_sigparent = SIGCHLD;
+		proc_reparent(p, initproc);
+		if ((pd->pd_flags & PD_DAEMON) == 0)
+			psignal(p, SIGKILL);
+		PROC_UNLOCK(p);
+		sx_xunlock(&proctree_lock);
+	}
+
+	/*
+	 * Release the file descriptor's reference on the process descriptor.
+	 */
+	procdesc_free(pd);
+	return (0);
+}
+
+static int
+procdesc_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
+    int flags, struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
+    int flags, struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_truncate(struct file *fp, off_t length, struct ucred *active_cred,
+    struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_ioctl(struct file *fp, u_long com, void *data,
+    struct ucred *active_cred, struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_poll(struct file *fp, int events, struct ucred *active_cred,
+    struct thread *td)
+{
+	struct procdesc *pd;
+	int revents;
+
+	revents = 0;
+	pd = fp->f_data;
+	PROCDESC_LOCK(pd);
+	if (pd->pd_flags & PDF_EXITED)
+		revents |= POLLHUP;
+	if (revents == 0) {
+		selrecord(td, &pd->pd_selinfo);
+		pd->pd_flags |= PDF_SELECTED;
+	}
+	PROCDESC_UNLOCK(pd);
+	return (revents);
+}
+
+static int
+procdesc_kqfilter(struct file *fp, struct knote *kn)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
+    struct thread *td)
+{
+	struct procdesc *pd;
+	struct timeval pstart;
+
+	/*
+	 * XXXRW: Perhaps we should cache some more information from the
+	 * process so that we can return it reliably here even after it has
+	 * died.  For example, caching its credential data.
+	 */
+	bzero(sb, sizeof(*sb));
+	pd = fp->f_data;
+	sx_slock(&proctree_lock);
+	if (pd->pd_proc != NULL) {
+		PROC_LOCK(pd->pd_proc);
+
+		/* Set birth and [acm] times to process start time. */
+		pstart = pd->pd_proc->p_stats->p_start;
+		timevaladd(&pstart, &boottime);
+		TIMEVAL_TO_TIMESPEC(&pstart, &sb->st_birthtim);
+		sb->st_atim = sb->st_birthtim;
+		sb->st_ctim = sb->st_birthtim;
+		sb->st_mtim = sb->st_birthtim;
+		if (pd->pd_proc->p_state != PRS_ZOMBIE)
+			sb->st_mode = S_IFREG | S_IRWXU;
+		else
+			sb->st_mode = S_IFREG;
+		sb->st_uid = pd->pd_proc->p_ucred->cr_ruid;
+		sb->st_gid = pd->pd_proc->p_ucred->cr_rgid;
+		PROC_UNLOCK(pd->pd_proc);
+	} else
+		sb->st_mode = S_IFREG;
+	sx_sunlock(&proctree_lock);
+	return (0);
+}
+
+static int
+procdesc_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
+    struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+static int
+procdesc_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
+    struct thread *td)
+{
+
+	return (EOPNOTSUPP);
+}
+
+#else /* !PROCDESC */
+
+int
+pdgetpid(struct thread *td, struct pdgetpid_args *uap)
+{
+
+	return (ENOSYS);
+}
+
+#endif /* PROCDESC */