/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1994-1996 Søren Schmidt
 * Copyright (c) 2006 Roman Divacky
 * All rights reserved.
 * Copyright (c) 2013 Dmitry Chagin <dchagin@FreeBSD.org>
 *
 * 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.
 */

#include <sys/param.h>
#include <sys/fcntl.h>
#include <sys/imgact.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sx.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>

#include <compat/linux/linux_emul.h>
#include <compat/linux/linux_mib.h>
#include <compat/linux/linux_misc.h>
#include <compat/linux/linux_persona.h>
#include <compat/linux/linux_util.h>

#if BYTE_ORDER == LITTLE_ENDIAN
#define SHELLMAGIC      0x2123 /* #! */
#else
#define SHELLMAGIC      0x2321
#endif

/*
 * This returns reference to the thread emuldata entry (if found)
 *
 * Hold PROC_LOCK when referencing emuldata from other threads.
 */
struct linux_emuldata *
em_find(struct thread *td)
{
        struct linux_emuldata *em;

        em = td->td_emuldata;

        return (em);
}

/*
 * This returns reference to the proc pemuldata entry (if found)
 *
 * Hold PROC_LOCK when referencing proc pemuldata from other threads.
 * Hold LINUX_PEM_LOCK wher referencing pemuldata members.
 */
struct linux_pemuldata *
pem_find(struct proc *p)
{
        struct linux_pemuldata *pem;

        pem = p->p_emuldata;

        return (pem);
}

/*
 * Linux apps generally expect the soft open file limit to be set
 * to 1024, often iterating over all the file descriptors up to that
 * limit instead of using closefrom(2).  Give them what they want,
 * unless there already is a resource limit in place.
 */
static void
linux_set_default_openfiles(struct thread *td, struct proc *p)
{
        struct rlimit rlim;
        int error __diagused;

        if (linux_default_openfiles < 0)
                return;

        PROC_LOCK(p);
        lim_rlimit_proc(p, RLIMIT_NOFILE, &rlim);
        PROC_UNLOCK(p);
        if (rlim.rlim_cur != rlim.rlim_max ||
            rlim.rlim_cur <= linux_default_openfiles)
                return;
        rlim.rlim_cur = linux_default_openfiles;
        error = kern_proc_setrlimit(td, p, RLIMIT_NOFILE, &rlim);
        KASSERT(error == 0, ("kern_proc_setrlimit failed"));
}

/*
 * The default stack size limit in Linux is 8MB.
 */
static void
linux_set_default_stacksize(struct thread *td, struct proc *p)
{
        struct rlimit rlim;
        int error __diagused;

        if (linux_default_stacksize < 0)
                return;

        PROC_LOCK(p);
        lim_rlimit_proc(p, RLIMIT_STACK, &rlim);
        PROC_UNLOCK(p);
        if (rlim.rlim_cur != rlim.rlim_max ||
            rlim.rlim_cur <= linux_default_stacksize)
                return;
        rlim.rlim_cur = linux_default_stacksize;
        error = kern_proc_setrlimit(td, p, RLIMIT_STACK, &rlim);
        KASSERT(error == 0, ("kern_proc_setrlimit failed"));
}

void
linux_proc_init(struct thread *td, struct thread *newtd, bool init_thread)
{
        struct linux_emuldata *em;
        struct linux_pemuldata *pem;
        struct proc *p;

        if (newtd != NULL) {
                p = newtd->td_proc;

                /* non-exec call */
                em = malloc(sizeof(*em), M_LINUX, M_WAITOK | M_ZERO);
                if (init_thread) {
                        LINUX_CTR1(proc_init, "thread newtd(%d)",
                            newtd->td_tid);

                        em->em_tid = newtd->td_tid;
                } else {
                        LINUX_CTR1(proc_init, "fork newtd(%d)", p->p_pid);

                        em->em_tid = p->p_pid;

                        pem = malloc(sizeof(*pem), M_LINUX, M_WAITOK | M_ZERO);
                        sx_init(&pem->pem_sx, "lpemlk");
                        p->p_emuldata = pem;
                }
                newtd->td_emuldata = em;

                linux_set_default_openfiles(td, p);
                linux_set_default_stacksize(td, p);
        } else {
                p = td->td_proc;

                /* exec */
                LINUX_CTR1(proc_init, "exec newtd(%d)", p->p_pid);

                /* lookup the old one */
                em = em_find(td);
                KASSERT(em != NULL, ("proc_init: thread emuldata not found.\n"));

                em->em_tid = p->p_pid;
                em->flags = 0;
                em->robust_futexes = NULL;
                em->child_clear_tid = NULL;
                em->child_set_tid = NULL;

                pem = pem_find(p);
                KASSERT(pem != NULL, ("proc_init: proc emuldata not found.\n"));
                pem->persona = 0;
                pem->oom_score_adj = 0;
        }
}

void
linux_on_exit(struct proc *p)
{
        struct linux_pemuldata *pem;
        struct thread *td = curthread;

        MPASS(SV_CURPROC_ABI() == SV_ABI_LINUX);

        LINUX_CTR3(proc_exit, "thread(%d) proc(%d) p %p",
            td->td_tid, p->p_pid, p);

        pem = pem_find(p);
        if (pem == NULL)
                return;
        (p->p_sysent->sv_thread_detach)(td);

        p->p_emuldata = NULL;

        sx_destroy(&pem->pem_sx);
        free(pem, M_LINUX);
}

int
linux_common_execve(struct thread *td, struct image_args *eargs)
{
        struct linux_pemuldata *pem;
        struct vmspace *oldvmspace;
        struct linux_emuldata *em;
        struct proc *p;
        int error;

        p = td->td_proc;

        error = pre_execve(td, &oldvmspace);
        if (error != 0)
                return (error);

        error = kern_execve(td, eargs, NULL, oldvmspace);
        post_execve(td, error, oldvmspace);
        if (error != EJUSTRETURN)
                return (error);

        /*
         * In a case of transition from Linux binary execing to
         * FreeBSD binary we destroy Linux emuldata thread & proc entries.
         */
        if (SV_CURPROC_ABI() != SV_ABI_LINUX) {

                /* Clear ABI root directory if set. */
                linux_pwd_onexec_native(td);

                PROC_LOCK(p);
                em = em_find(td);
                KASSERT(em != NULL, ("proc_exec: thread emuldata not found.\n"));
                td->td_emuldata = NULL;

                pem = pem_find(p);
                KASSERT(pem != NULL, ("proc_exec: proc pemuldata not found.\n"));
                p->p_emuldata = NULL;
                PROC_UNLOCK(p);

                free(em, M_LINUX);
                free(pem, M_LINUX);
        }
        return (EJUSTRETURN);
}

int
linux_on_exec(struct proc *p, struct image_params *imgp)
{
        struct thread *td;
        struct thread *othertd;
#if defined(__amd64__)
        struct linux_pemuldata *pem;
#endif
        int error;

        td = curthread;
        MPASS((imgp->sysent->sv_flags & SV_ABI_MASK) == SV_ABI_LINUX);

        /*
         * When execing to Linux binary, we create Linux emuldata
         * thread entry.
         */
        if (SV_PROC_ABI(p) == SV_ABI_LINUX) {
                /*
                 * Process already was under Linuxolator
                 * before exec.  Update emuldata to reflect
                 * single-threaded cleaned state after exec.
                 */
                linux_proc_init(td, NULL, false);
        } else {
                /*
                 * We are switching the process to Linux emulator.
                 */
                linux_proc_init(td, td, false);

                /*
                 * Create a transient td_emuldata for all suspended
                 * threads, so that p->p_sysent->sv_thread_detach() ==
                 * linux_thread_detach() can find expected but unused
                 * emuldata.
                 */
                FOREACH_THREAD_IN_PROC(td->td_proc, othertd) {
                        if (othertd == td)
                                continue;
                        linux_proc_init(td, othertd, true);
                }

                /* Set ABI root directory. */
                if ((error = linux_pwd_onexec(td)) != 0)
                        return (error);
        }
#if defined(__amd64__)
        /*
         * An IA32 executable which has executable stack will have the
         * READ_IMPLIES_EXEC personality flag set automatically.
         */
        if (SV_PROC_FLAG(td->td_proc, SV_ILP32) &&
            imgp->stack_prot & VM_PROT_EXECUTE) {
                pem = pem_find(p);
                pem->persona |= LINUX_READ_IMPLIES_EXEC;
        }
#endif
        return (0);
}

void
linux_thread_dtor(struct thread *td)
{
        struct linux_emuldata *em;

        em = em_find(td);
        if (em == NULL)
                return;
        td->td_emuldata = NULL;

        LINUX_CTR1(thread_dtor, "thread(%d)", em->em_tid);

        free(em, M_LINUX);
}

void
linux_schedtail(struct thread *td)
{
        struct linux_emuldata *em;
#ifdef KTR
        int error;
#else
        int error __unused;
#endif
        int *child_set_tid;

        em = em_find(td);
        KASSERT(em != NULL, ("linux_schedtail: thread emuldata not found.\n"));
        child_set_tid = em->child_set_tid;

        if (child_set_tid != NULL) {
                error = copyout(&em->em_tid, child_set_tid,
                    sizeof(em->em_tid));
                LINUX_CTR4(schedtail, "thread(%d) %p stored %d error %d",
                    td->td_tid, child_set_tid, em->em_tid, error);
        } else
                LINUX_CTR1(schedtail, "thread(%d)", em->em_tid);
}