4732e446fb
what Linux does. This is because robust futexes are mostly userspace thing which we cannot alter. Two syscalls maintain pointer to userspace list and when process exits a routine walks this list waking up processes sleeping on futexes from that list. Reviewed by: kib (mentor) MFC after: 1 month
336 lines
8.7 KiB
C
336 lines
8.7 KiB
C
/*-
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* Copyright (c) 2006 Roman Divacky
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_compat.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/imgact.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/sx.h>
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#include <sys/proc.h>
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#include <sys/syscallsubr.h>
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#include <sys/sysproto.h>
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#include <sys/unistd.h>
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#ifdef COMPAT_LINUX32
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#include <machine/../linux32/linux.h>
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#include <machine/../linux32/linux32_proto.h>
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#else
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#include <machine/../linux/linux.h>
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#include <machine/../linux/linux_proto.h>
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#endif
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#include <compat/linux/linux_emul.h>
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#include <compat/linux/linux_futex.h>
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struct sx emul_shared_lock;
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struct mtx emul_lock;
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/* this returns locked reference to the emuldata entry (if found) */
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struct linux_emuldata *
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em_find(struct proc *p, int locked)
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{
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struct linux_emuldata *em;
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if (locked == EMUL_DOLOCK)
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EMUL_LOCK(&emul_lock);
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em = p->p_emuldata;
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if (em == NULL && locked == EMUL_DOLOCK)
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EMUL_UNLOCK(&emul_lock);
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return (em);
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}
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int
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linux_proc_init(struct thread *td, pid_t child, int flags)
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{
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struct linux_emuldata *em, *p_em;
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struct proc *p;
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if (child != 0) {
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/* non-exec call */
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em = malloc(sizeof *em, M_LINUX, M_WAITOK | M_ZERO);
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em->pid = child;
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em->pdeath_signal = 0;
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em->robust_futexes = NULL;
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if (flags & LINUX_CLONE_THREAD) {
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/* handled later in the code */
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} else {
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struct linux_emuldata_shared *s;
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s = malloc(sizeof *s, M_LINUX, M_WAITOK | M_ZERO);
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s->refs = 1;
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s->group_pid = child;
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LIST_INIT(&s->threads);
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em->shared = s;
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}
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} else {
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/* lookup the old one */
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em = em_find(td->td_proc, EMUL_DOLOCK);
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KASSERT(em != NULL, ("proc_init: emuldata not found in exec case.\n"));
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}
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em->child_clear_tid = NULL;
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em->child_set_tid = NULL;
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/*
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* allocate the shared struct only in clone()/fork cases in the case
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* of clone() td = calling proc and child = pid of the newly created
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* proc
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*/
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if (child != 0) {
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if (flags & LINUX_CLONE_THREAD) {
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/* lookup the parent */
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/*
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* we dont have to lock the p_em because
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* its waiting for us in linux_clone so
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* there is no chance of it changing the
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* p_em->shared address
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*/
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p_em = em_find(td->td_proc, EMUL_DONTLOCK);
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KASSERT(p_em != NULL, ("proc_init: parent emuldata not found for CLONE_THREAD\n"));
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em->shared = p_em->shared;
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EMUL_SHARED_WLOCK(&emul_shared_lock);
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em->shared->refs++;
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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} else {
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/*
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* handled earlier to avoid malloc(M_WAITOK) with
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* rwlock held
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*/
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}
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}
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if (child != 0) {
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EMUL_SHARED_WLOCK(&emul_shared_lock);
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LIST_INSERT_HEAD(&em->shared->threads, em, threads);
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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p = pfind(child);
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KASSERT(p != NULL, ("process not found in proc_init\n"));
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p->p_emuldata = em;
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PROC_UNLOCK(p);
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} else
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EMUL_UNLOCK(&emul_lock);
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return (0);
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}
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void
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linux_proc_exit(void *arg __unused, struct proc *p)
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{
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struct linux_emuldata *em;
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int error;
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struct thread *td = FIRST_THREAD_IN_PROC(p);
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int *child_clear_tid;
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struct proc *q, *nq;
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if (__predict_true(p->p_sysent != &elf_linux_sysvec))
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return;
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release_futexes(p);
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/* find the emuldata */
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em = em_find(p, EMUL_DOLOCK);
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KASSERT(em != NULL, ("proc_exit: emuldata not found.\n"));
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/* reparent all procs that are not a thread leader to initproc */
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if (em->shared->group_pid != p->p_pid) {
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child_clear_tid = em->child_clear_tid;
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EMUL_UNLOCK(&emul_lock);
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sx_xlock(&proctree_lock);
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wakeup(initproc);
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PROC_LOCK(p);
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proc_reparent(p, initproc);
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p->p_sigparent = SIGCHLD;
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PROC_UNLOCK(p);
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sx_xunlock(&proctree_lock);
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} else {
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child_clear_tid = em->child_clear_tid;
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EMUL_UNLOCK(&emul_lock);
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}
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EMUL_SHARED_WLOCK(&emul_shared_lock);
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LIST_REMOVE(em, threads);
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em->shared->refs--;
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if (em->shared->refs == 0) {
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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free(em->shared, M_LINUX);
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} else
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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if (child_clear_tid != NULL) {
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struct linux_sys_futex_args cup;
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int null = 0;
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error = copyout(&null, child_clear_tid, sizeof(null));
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if (error) {
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free(em, M_LINUX);
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return;
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}
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/* futexes stuff */
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cup.uaddr = child_clear_tid;
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cup.op = LINUX_FUTEX_WAKE;
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cup.val = 0x7fffffff; /* Awake everyone */
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cup.timeout = NULL;
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cup.uaddr2 = NULL;
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cup.val3 = 0;
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error = linux_sys_futex(FIRST_THREAD_IN_PROC(p), &cup);
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/*
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* this cannot happen at the moment and if this happens it
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* probably means there is a user space bug
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*/
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if (error)
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printf(LMSG("futex stuff in proc_exit failed.\n"));
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}
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/* clean the stuff up */
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free(em, M_LINUX);
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/* this is a little weird but rewritten from exit1() */
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sx_xlock(&proctree_lock);
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q = LIST_FIRST(&p->p_children);
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for (; q != NULL; q = nq) {
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nq = LIST_NEXT(q, p_sibling);
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if (q->p_flag & P_WEXIT)
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continue;
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if (__predict_false(q->p_sysent != &elf_linux_sysvec))
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continue;
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em = em_find(q, EMUL_DOLOCK);
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KASSERT(em != NULL, ("linux_reparent: emuldata not found: %i\n", q->p_pid));
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if (em->pdeath_signal != 0) {
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PROC_LOCK(q);
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psignal(q, em->pdeath_signal);
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PROC_UNLOCK(q);
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}
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EMUL_UNLOCK(&emul_lock);
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}
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sx_xunlock(&proctree_lock);
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}
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/*
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* This is used in a case of transition from FreeBSD binary execing to linux binary
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* in this case we create linux emuldata proc entry with the pid of the currently running
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* process.
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*/
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void
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linux_proc_exec(void *arg __unused, struct proc *p, struct image_params *imgp)
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{
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if (__predict_false(imgp->sysent == &elf_linux_sysvec
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&& p->p_sysent != &elf_linux_sysvec))
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linux_proc_init(FIRST_THREAD_IN_PROC(p), p->p_pid, 0);
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if (__predict_false(imgp->sysent != &elf_linux_sysvec
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&& p->p_sysent == &elf_linux_sysvec)) {
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struct linux_emuldata *em;
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/*
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* XXX:There's a race because here we assign p->p_emuldata NULL
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* but the process is still counted as linux one for a short
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* time so some other process might reference it and try to
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* access its p->p_emuldata and panicing on a NULL reference.
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*/
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em = em_find(p, EMUL_DONTLOCK);
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KASSERT(em != NULL, ("proc_exec: emuldata not found.\n"));
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EMUL_SHARED_WLOCK(&emul_shared_lock);
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LIST_REMOVE(em, threads);
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PROC_LOCK(p);
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p->p_emuldata = NULL;
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PROC_UNLOCK(p);
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em->shared->refs--;
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if (em->shared->refs == 0) {
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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free(em->shared, M_LINUX);
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} else
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EMUL_SHARED_WUNLOCK(&emul_shared_lock);
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free(em, M_LINUX);
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}
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}
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void
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linux_schedtail(void *arg __unused, struct proc *p)
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{
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struct linux_emuldata *em;
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int error = 0;
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int *child_set_tid;
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if (__predict_true(p->p_sysent != &elf_linux_sysvec))
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return;
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/* find the emuldata */
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em = em_find(p, EMUL_DOLOCK);
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KASSERT(em != NULL, ("linux_schedtail: emuldata not found.\n"));
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child_set_tid = em->child_set_tid;
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EMUL_UNLOCK(&emul_lock);
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if (child_set_tid != NULL)
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error = copyout(&p->p_pid, (int *)child_set_tid,
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sizeof(p->p_pid));
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return;
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}
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int
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linux_set_tid_address(struct thread *td, struct linux_set_tid_address_args *args)
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{
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struct linux_emuldata *em;
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#ifdef DEBUG
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if (ldebug(set_tid_address))
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printf(ARGS(set_tid_address, "%p"), args->tidptr);
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#endif
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/* find the emuldata */
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em = em_find(td->td_proc, EMUL_DOLOCK);
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KASSERT(em != NULL, ("set_tid_address: emuldata not found.\n"));
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em->child_clear_tid = args->tidptr;
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td->td_retval[0] = td->td_proc->p_pid;
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EMUL_UNLOCK(&emul_lock);
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return 0;
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}
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