/*-
 * Copyright (c) 2006 Roman Divacky
 * All rights reserved.
 *
 * 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
 *    in this position and unchanged.
 * 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: head/sys/compat/linux/linux_emul.c 258541 2013-11-25 07:38:45Z attilio $");

#include "opt_compat.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sdt.h>
#include <sys/sx.h>
#include <sys/proc.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/unistd.h>

#ifdef COMPAT_LINUX32
#include <machine/../linux32/linux.h>
#include <machine/../linux32/linux32_proto.h>
#else
#include <machine/../linux/linux.h>
#include <machine/../linux/linux_proto.h>
#endif

#include <compat/linux/linux_dtrace.h>
#include <compat/linux/linux_emul.h>
#include <compat/linux/linux_futex.h>
#include <compat/linux/linux_misc.h>

/**
 * Special DTrace provider for the linuxulator.
 *
 * In this file we define the provider for the entire linuxulator. All
 * modules (= files of the linuxulator) use it.
 *
 * We define a different name depending on the emulated bitsize, see
 * ../../<ARCH>/linux{,32}/linux.h, e.g.:
 *      native bitsize          = linuxulator
 *      amd64, 32bit emulation  = linuxulator32
 */
LIN_SDT_PROVIDER_DEFINE(LINUX_DTRACE);

/**
 * Special DTrace module "locks", it covers some linuxulator internal
 * locks.
 */
LIN_SDT_PROBE_DEFINE1(locks, emul_lock, locked, "struct mtx *");
LIN_SDT_PROBE_DEFINE1(locks, emul_lock, unlock, "struct mtx *");
LIN_SDT_PROBE_DEFINE1(locks, emul_shared_rlock, locked, "struct sx *");
LIN_SDT_PROBE_DEFINE1(locks, emul_shared_rlock, unlock, "struct sx *");
LIN_SDT_PROBE_DEFINE1(locks, emul_shared_wlock, locked, "struct sx *");
LIN_SDT_PROBE_DEFINE1(locks, emul_shared_wlock, unlock, "struct sx *");

/**
 * DTrace probes in this module.
 */
LIN_SDT_PROBE_DEFINE2(emul, em_find, entry, "struct proc *", "int");
LIN_SDT_PROBE_DEFINE0(emul, em_find, return);
LIN_SDT_PROBE_DEFINE3(emul, proc_init, entry, "struct thread *", "pid_t",
    "int");
LIN_SDT_PROBE_DEFINE0(emul, proc_init, create_thread);
LIN_SDT_PROBE_DEFINE0(emul, proc_init, fork);
LIN_SDT_PROBE_DEFINE0(emul, proc_init, exec);
LIN_SDT_PROBE_DEFINE0(emul, proc_init, return);
LIN_SDT_PROBE_DEFINE1(emul, proc_exit, entry, "struct proc *");
LIN_SDT_PROBE_DEFINE0(emul, proc_exit, futex_failed);
LIN_SDT_PROBE_DEFINE3(emul, proc_exit, reparent, "pid_t", "pid_t",
    "struct proc *");
LIN_SDT_PROBE_DEFINE1(emul, proc_exit, child_clear_tid_error, "int");
LIN_SDT_PROBE_DEFINE0(emul, proc_exit, return);
LIN_SDT_PROBE_DEFINE2(emul, proc_exec, entry, "struct proc *",
    "struct image_params *");
LIN_SDT_PROBE_DEFINE0(emul, proc_exec, return);
LIN_SDT_PROBE_DEFINE0(emul, linux_schedtail, entry);
LIN_SDT_PROBE_DEFINE1(emul, linux_schedtail, copyout_error, "int");
LIN_SDT_PROBE_DEFINE0(emul, linux_schedtail, return);
LIN_SDT_PROBE_DEFINE1(emul, linux_set_tid_address, entry, "int *");
LIN_SDT_PROBE_DEFINE0(emul, linux_set_tid_address, return);
LIN_SDT_PROBE_DEFINE2(emul, linux_kill_threads, entry, "struct thread *",
    "int");
LIN_SDT_PROBE_DEFINE1(emul, linux_kill_threads, kill, "pid_t");
LIN_SDT_PROBE_DEFINE0(emul, linux_kill_threads, return);

struct sx	emul_shared_lock;
struct mtx	emul_lock;

/* this returns locked reference to the emuldata entry (if found) */
struct linux_emuldata *
em_find(struct proc *p, int locked)
{
	struct linux_emuldata *em;

	LIN_SDT_PROBE2(emul, em_find, entry, p, locked);

	if (locked == EMUL_DOLOCK)
		EMUL_LOCK(&emul_lock);

	em = p->p_emuldata;

	if (em == NULL && locked == EMUL_DOLOCK)
		EMUL_UNLOCK(&emul_lock);

	LIN_SDT_PROBE1(emul, em_find, return, em);
	return (em);
}

int
linux_proc_init(struct thread *td, pid_t child, int flags)
{
	struct linux_emuldata *em, *p_em;
	struct proc *p;

	LIN_SDT_PROBE3(emul, proc_init, entry, td, child, flags);

	if (child != 0) {
		/* fork or create a thread */
		em = malloc(sizeof *em, M_LINUX, M_WAITOK | M_ZERO);
		em->pid = child;
		em->pdeath_signal = 0;
		em->flags = 0;
		em->robust_futexes = NULL;
		if (flags & LINUX_CLONE_THREAD) {
			/* handled later in the code */
			LIN_SDT_PROBE0(emul, proc_init, create_thread);
		} else {
			struct linux_emuldata_shared *s;

			LIN_SDT_PROBE0(emul, proc_init, fork);

			s = malloc(sizeof *s, M_LINUX, M_WAITOK | M_ZERO);
			s->refs = 1;
			s->group_pid = child;

			LIST_INIT(&s->threads);
			em->shared = s;
		}
	} else {
		/* exec */
		LIN_SDT_PROBE0(emul, proc_init, exec);

		/* lookup the old one */
		em = em_find(td->td_proc, EMUL_DOLOCK);
		KASSERT(em != NULL, ("proc_init: emuldata not found in exec case.\n"));
	}

	em->child_clear_tid = NULL;
	em->child_set_tid = NULL;

	/*
	 * allocate the shared struct only in clone()/fork cases in the case
	 * of clone() td = calling proc and child = pid of the newly created
	 * proc
	 */
	if (child != 0) {
		if (flags & LINUX_CLONE_THREAD) {
			/* lookup the parent */
			/* 
			 * we dont have to lock the p_em because
			 * its waiting for us in linux_clone so
			 * there is no chance of it changing the
			 * p_em->shared address
			 */
			p_em = em_find(td->td_proc, EMUL_DONTLOCK);
			KASSERT(p_em != NULL, ("proc_init: parent emuldata not found for CLONE_THREAD\n"));
			em->shared = p_em->shared;
			EMUL_SHARED_WLOCK(&emul_shared_lock);
			em->shared->refs++;
			EMUL_SHARED_WUNLOCK(&emul_shared_lock);
		} else {
			/*
			 * handled earlier to avoid malloc(M_WAITOK) with
			 * rwlock held
			 */
		}

		EMUL_SHARED_WLOCK(&emul_shared_lock);
		LIST_INSERT_HEAD(&em->shared->threads, em, threads);
		EMUL_SHARED_WUNLOCK(&emul_shared_lock);

		p = pfind(child);
		KASSERT(p != NULL, ("process not found in proc_init\n"));
		p->p_emuldata = em;
		PROC_UNLOCK(p);
	} else
		EMUL_UNLOCK(&emul_lock);

	LIN_SDT_PROBE0(emul, proc_init, return);
	return (0);
}

void
linux_proc_exit(void *arg __unused, struct proc *p)
{
	struct linux_emuldata *em;
	int error, shared_flags, shared_xstat;
	struct thread *td = FIRST_THREAD_IN_PROC(p);
	int *child_clear_tid;
	struct proc *q, *nq;

	if (__predict_true(p->p_sysent != &elf_linux_sysvec))
		return;

	LIN_SDT_PROBE1(emul, proc_exit, entry, p);

	release_futexes(p);

	/* find the emuldata */
	em = em_find(p, EMUL_DOLOCK);

	KASSERT(em != NULL, ("proc_exit: emuldata not found.\n"));

	/* reparent all procs that are not a thread leader to initproc */
	if (em->shared->group_pid != p->p_pid) {
		LIN_SDT_PROBE3(emul, proc_exit, reparent,
		    em->shared->group_pid, p->p_pid, p);

		child_clear_tid = em->child_clear_tid;
		EMUL_UNLOCK(&emul_lock);
		sx_xlock(&proctree_lock);
		wakeup(initproc);
		PROC_LOCK(p);
		proc_reparent(p, initproc);
		p->p_sigparent = SIGCHLD;
		PROC_UNLOCK(p);
		sx_xunlock(&proctree_lock);
	} else {
		child_clear_tid = em->child_clear_tid;
		EMUL_UNLOCK(&emul_lock);	
	}

	EMUL_SHARED_WLOCK(&emul_shared_lock);
	shared_flags = em->shared->flags;
	shared_xstat = em->shared->xstat;
	LIST_REMOVE(em, threads);

	em->shared->refs--;
	if (em->shared->refs == 0) {
		EMUL_SHARED_WUNLOCK(&emul_shared_lock);
		free(em->shared, M_LINUX);
	} else	
		EMUL_SHARED_WUNLOCK(&emul_shared_lock);

	if ((shared_flags & EMUL_SHARED_HASXSTAT) != 0)
		p->p_xstat = shared_xstat;

	if (child_clear_tid != NULL) {
		struct linux_sys_futex_args cup;
		int null = 0;

		error = copyout(&null, child_clear_tid, sizeof(null));
		if (error) {
			LIN_SDT_PROBE1(emul, proc_exit,
			    child_clear_tid_error, error);

			free(em, M_LINUX);

			LIN_SDT_PROBE0(emul, proc_exit, return);
			return;
		}

		/* futexes stuff */
		cup.uaddr = child_clear_tid;
		cup.op = LINUX_FUTEX_WAKE;
		cup.val = 0x7fffffff;	/* Awake everyone */
		cup.timeout = NULL;
		cup.uaddr2 = NULL;
		cup.val3 = 0;
		error = linux_sys_futex(FIRST_THREAD_IN_PROC(p), &cup);
		/*
		 * this cannot happen at the moment and if this happens it
		 * probably means there is a user space bug
		 */
		if (error) {
			LIN_SDT_PROBE0(emul, proc_exit, futex_failed);
			printf(LMSG("futex stuff in proc_exit failed.\n"));
		}
	}

	/* clean the stuff up */
	free(em, M_LINUX);

	/* this is a little weird but rewritten from exit1() */
	sx_xlock(&proctree_lock);
	q = LIST_FIRST(&p->p_children);
	for (; q != NULL; q = nq) {
		nq = LIST_NEXT(q, p_sibling);
		if (q->p_flag & P_WEXIT)
			continue;
		if (__predict_false(q->p_sysent != &elf_linux_sysvec))
			continue;
		em = em_find(q, EMUL_DOLOCK);
		KASSERT(em != NULL, ("linux_reparent: emuldata not found: %i\n", q->p_pid));
		PROC_LOCK(q);
		if ((q->p_flag & P_WEXIT) == 0 && em->pdeath_signal != 0) {
			kern_psignal(q, em->pdeath_signal);
		}
		PROC_UNLOCK(q);
		EMUL_UNLOCK(&emul_lock);
	}
	sx_xunlock(&proctree_lock);

	LIN_SDT_PROBE0(emul, proc_exit, return);
}

/*
 * This is used in a case of transition from FreeBSD binary execing to linux binary
 * in this case we create linux emuldata proc entry with the pid of the currently running
 * process.
 */
void 
linux_proc_exec(void *arg __unused, struct proc *p, struct image_params *imgp)
{
	if (__predict_false(imgp->sysent == &elf_linux_sysvec)) {
		LIN_SDT_PROBE2(emul, proc_exec, entry, p, imgp);
	}
	if (__predict_false(imgp->sysent == &elf_linux_sysvec
	    && p->p_sysent != &elf_linux_sysvec))
		linux_proc_init(FIRST_THREAD_IN_PROC(p), p->p_pid, 0);
	if (__predict_false((p->p_sysent->sv_flags & SV_ABI_MASK) ==
	    SV_ABI_LINUX))
		/* Kill threads regardless of imgp->sysent value */
		linux_kill_threads(FIRST_THREAD_IN_PROC(p), SIGKILL);
	if (__predict_false(imgp->sysent != &elf_linux_sysvec
	    && p->p_sysent == &elf_linux_sysvec)) {
		struct linux_emuldata *em;

		/* 
		 * XXX:There's a race because here we assign p->p_emuldata NULL
		 * but the process is still counted as linux one for a short
 		 * time so some other process might reference it and try to
 		 * access its p->p_emuldata and panicing on a NULL reference.
		 */
		em = em_find(p, EMUL_DONTLOCK);

		KASSERT(em != NULL, ("proc_exec: emuldata not found.\n"));

		EMUL_SHARED_WLOCK(&emul_shared_lock);
		LIST_REMOVE(em, threads);

		PROC_LOCK(p);
		p->p_emuldata = NULL;
		PROC_UNLOCK(p);

		em->shared->refs--;
		if (em->shared->refs == 0) {
			EMUL_SHARED_WUNLOCK(&emul_shared_lock);
			free(em->shared, M_LINUX);
		} else
			EMUL_SHARED_WUNLOCK(&emul_shared_lock);

		free(em, M_LINUX);
	}

	if (__predict_false(imgp->sysent == &elf_linux_sysvec)) {
		LIN_SDT_PROBE0(emul, proc_exec, return);
	}
}

void
linux_schedtail(struct thread *td)
{
	struct linux_emuldata *em;
	struct proc *p;
	int error = 0;
	int *child_set_tid;

	p = td->td_proc;

	LIN_SDT_PROBE1(emul, linux_schedtail, entry, p);

	/* find the emuldata */
	em = em_find(p, EMUL_DOLOCK);

	KASSERT(em != NULL, ("linux_schedtail: emuldata not found.\n"));
	child_set_tid = em->child_set_tid;
	EMUL_UNLOCK(&emul_lock);

	if (child_set_tid != NULL) {
		error = copyout(&p->p_pid, (int *)child_set_tid,
		    sizeof(p->p_pid));

		if (error != 0) {
			LIN_SDT_PROBE1(emul, linux_schedtail, copyout_error,
			    error);
		}
	}

	LIN_SDT_PROBE0(emul, linux_schedtail, return);

	return;
}

int
linux_set_tid_address(struct thread *td, struct linux_set_tid_address_args *args)
{
	struct linux_emuldata *em;

	LIN_SDT_PROBE1(emul, linux_set_tid_address, entry, args->tidptr);

	/* find the emuldata */
	em = em_find(td->td_proc, EMUL_DOLOCK);

	KASSERT(em != NULL, ("set_tid_address: emuldata not found.\n"));

	em->child_clear_tid = args->tidptr;
	td->td_retval[0] = td->td_proc->p_pid;

	EMUL_UNLOCK(&emul_lock);

	LIN_SDT_PROBE0(emul, linux_set_tid_address, return);
	return 0;
}

void
linux_kill_threads(struct thread *td, int sig)
{
	struct linux_emuldata *em, *td_em, *tmp_em;
	struct proc *sp;

	LIN_SDT_PROBE2(emul, linux_kill_threads, entry, td, sig);

	td_em = em_find(td->td_proc, EMUL_DONTLOCK);

	KASSERT(td_em != NULL, ("linux_kill_threads: emuldata not found.\n"));

	EMUL_SHARED_RLOCK(&emul_shared_lock);
	LIST_FOREACH_SAFE(em, &td_em->shared->threads, threads, tmp_em) {
		if (em->pid == td_em->pid)
			continue;

		sp = pfind(em->pid);
		if ((sp->p_flag & P_WEXIT) == 0)
			kern_psignal(sp, sig);
		PROC_UNLOCK(sp);

		LIN_SDT_PROBE1(emul, linux_kill_threads, kill, em->pid);
	}
	EMUL_SHARED_RUNLOCK(&emul_shared_lock);

	LIN_SDT_PROBE0(emul, linux_kill_threads, return);
}