/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */

/* Copyright (C) 2014 Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * shim_sigaction.c
 *
 * Implementation of system call "sigaction", "sigreturn", "sigprocmask",
 * "kill", "tkill" and "tgkill".
 */

#include <shim_internal.h>
#include <shim_utils.h>
#include <shim_table.h>
#include <shim_thread.h>
#include <shim_ipc.h>
#include <shim_profile.h>

#include <pal.h>
#include <pal_error.h>

#include <errno.h>

#include <linux/signal.h>

int shim_do_sigaction (int signum, const struct __kernel_sigaction * act,
                       struct __kernel_sigaction * oldact, size_t sigsetsize)
{
    /* SIGKILL and SIGSTOP cannot be caught or ignored */
    if (signum == SIGKILL || signum == SIGSTOP ||
        signum <= 0 || signum > NUM_SIGS ||
        sigsetsize != sizeof(__sigset_t))
        return -EINVAL;

    struct shim_thread * cur = get_cur_thread();
    int err = 0;

    assert(!act || (void *) act->k_sa_handler != (void *) 0x11);

    struct shim_signal_handle * sighdl = &cur->signal_handles[signum - 1];

    lock(cur->lock);

    if (oldact) {
        if (sighdl->action) {
            memcpy(oldact, sighdl->action, sizeof(struct __kernel_sigaction));
        } else {
            memset(oldact, 0, sizeof(struct __kernel_sigaction));
            oldact->k_sa_handler = SIG_DFL;
        }
    }

    if (act) {
        if (!(sighdl->action))
            sighdl->action = malloc(sizeof(struct __kernel_sigaction));

        if (!(sighdl->action)) {
            err = -ENOMEM;
            goto out;
        }

        memcpy(sighdl->action, act, sizeof(struct __kernel_sigaction));
    }

    err = 0;
out:
    unlock(cur->lock);
    return err;
}

int shim_do_sigreturn (int __unused)
{
    /* do nothing */
    return 0;
}

int shim_do_sigprocmask (int how, const __sigset_t * set, __sigset_t * oldset)
{
    __sigset_t * old, tmp, set_tmp;

    if (how != SIG_BLOCK && how != SIG_UNBLOCK &&
        how != SIG_SETMASK)
        return -EINVAL;

    struct shim_thread * cur = get_cur_thread();
    int err = 0;

    lock(cur->lock);

    old = get_sig_mask(cur);
    if (oldset) {
        memcpy(&tmp, old, sizeof(__sigset_t));
        old = &tmp;
    }

    /* if set is NULL, then the signal mask is unchanged, but the current
       value of the signal mask is nevertheless returned in oldset */
    if (!set)
        goto out;

    memcpy(&set_tmp, old, sizeof(__sigset_t));

    switch (how) {
        case SIG_BLOCK:
            __sigorset(&set_tmp, &set_tmp, set);
            break;

        case SIG_UNBLOCK:
            __signotset(&set_tmp, &set_tmp, set);
            break;

        case SIG_SETMASK:
            memcpy(&set_tmp, set, sizeof(__sigset_t));
            break;
    }

    set_sig_mask(cur, &set_tmp);

out:
    unlock(cur->lock);

    if (!err && oldset)
        memcpy(oldset, old, sizeof(__sigset_t));

    return err;
}

int shim_do_sigaltstack (const stack_t * ss, stack_t * oss)
{
    if (ss && (ss->ss_flags & ~SS_DISABLE))
        return -EINVAL;

    struct shim_thread * cur = get_cur_thread();
    lock(cur->lock);

    if (oss)
        *oss = cur->signal_altstack;

    if (ss) {
        if (ss->ss_size < MINSIGSTKSZ) {
            unlock(cur->lock);
            return -ENOMEM;
        }

        cur->signal_altstack = *ss;
    }

    unlock(cur->lock);
    return 0;
}

int shim_do_sigsuspend (const __sigset_t * mask)
{
    __sigset_t * old, tmp;
    struct shim_thread * cur = get_cur_thread();

    lock(cur->lock);

    old = get_sig_mask(cur);
    memcpy(&tmp, old, sizeof(__sigset_t));
    old = &tmp;

    set_sig_mask(cur, mask);
    cur->suspend_on_signal = true;
    thread_setwait(NULL, NULL);
    thread_sleep(NO_TIMEOUT);

    unlock(cur->lock);
    set_sig_mask(cur, old);
    return -EINTR;
}

int shim_do_sigpending (__sigset_t * set, size_t sigsetsize)
{
    struct shim_thread * cur = get_cur_thread();

    __sigemptyset(set);

    if (!cur->signal_logs)
        return 0;

    for (int sig = 1 ; sig <= NUM_SIGS ; sig++) {
        if (atomic_read(&cur->signal_logs[sig - 1].head) !=
            atomic_read(&cur->signal_logs[sig - 1].tail))
            __sigaddset(set, sig);
    }

    return 0;
}

struct walk_arg {
    struct shim_thread * current;
    IDTYPE sender;
    IDTYPE id;
    int sig;
    bool use_ipc;
};

static inline void __append_signal (struct shim_thread * thread, int sig,
                                    IDTYPE sender)
{
    debug("Thread %d killed by signal %d\n", thread->tid, sig);
    siginfo_t info;
    memset(&info, 0, sizeof(siginfo_t));
    info.si_signo = sig;
    info.si_pid   = sender;
    append_signal(thread, sig, &info, true);
}

static int __kill_proc (struct shim_thread * thread, void * arg,
                        bool * unlocked)
{
    struct walk_arg * warg = (struct walk_arg *) arg;
    int srched = 0;

    if (!warg->use_ipc && !thread->in_vm)
        return 0;

    if (thread->tgid != warg->id)
        return 0;

    if (warg->current == thread)
        return 1;

    /* DEP: Let's do a racy read of is_alive and in_vm.
     * If either of these are zero it is a stable condition, 
     * and we can elide the lock acquire (which helps perf).
     */
    if (!thread->is_alive)
        goto out;

    if (!thread->in_vm) {
        unlock(thread_list_lock);
        *unlocked = true;
        return (!ipc_pid_kill_send(warg->sender, warg->id, KILL_PROCESS,
                                   warg->sig)) ? 1 : 0;
    } else {
        lock(thread->lock);

        if (!thread->is_alive)
            goto out_locked;

        if (thread->in_vm) {
            if (warg->sig > 0)
                __append_signal(thread, warg->sig, warg->sender);
            srched = 1;
        } else {
            /* This double-check case is probably unnecessary, but keep it for now */
            unlock(thread->lock);
            unlock(thread_list_lock);
            *unlocked = true;
            return (!ipc_pid_kill_send(warg->sender, warg->id, KILL_PROCESS,
                                   warg->sig)) ? 1 : 0;
        }
    }
out_locked:
    unlock(thread->lock);
out:
    return srched;
}

static int __kill_proc_simple (struct shim_simple_thread * sthread,
                               void * arg, bool * unlocked)
{
    struct walk_arg * warg = (struct walk_arg *) arg;
    int srched = 0;

    if (sthread->tgid != warg->id)
        return 0;

    lock(sthread->lock);

    if (sthread->is_alive) {
        unlock(sthread->lock);
        unlock(thread_list_lock);
        *unlocked = true;
        return (!ipc_pid_kill_send(warg->sender, warg->id, KILL_PROCESS,
                                   warg->sig)) ? 1 : 0;
    }

    unlock(sthread->lock);
    return srched;
}

int do_kill_proc (IDTYPE sender, IDTYPE tgid, int sig, bool use_ipc)
{
   struct shim_thread * cur = get_cur_thread();

    if (!tgid) {
        /* DEP: cur->tgid never changes.  No lock needed */
        tgid = cur->tgid;
    }

    struct walk_arg arg;
    arg.current = cur;
    arg.sender  = sender;
    arg.id      = tgid;
    arg.sig     = sig;
    arg.use_ipc = use_ipc;

    bool srched = false;

    if (!walk_thread_list(__kill_proc, &arg, false))
        srched = true;

    if (!use_ipc || srched)
        goto out;

    if (!walk_simple_thread_list(__kill_proc_simple, &arg, false))
        srched = true;

    if (!srched && !ipc_pid_kill_send(sender, tgid, KILL_PROCESS, sig))
        srched = true;

out:
    return srched ? 0 : -ESRCH;
}

static int __kill_pgroup (struct shim_thread * thread, void * arg,
                          bool * unlocked)
{
    struct walk_arg * warg = (struct walk_arg *) arg;
    int srched = 0;

    if (!warg->use_ipc && !thread->in_vm)
        return 0;

    if (thread->pgid != warg->id)
        return 0;

    if (warg->current == thread)
        return 1;

    lock(thread->lock);

    if (!thread->is_alive)
        goto out;

    if (thread->in_vm) {
        if (warg->sig > 0)
            __append_signal(thread, warg->sig, warg->sender);

        srched = 1;
    } else {
        unlock(thread->lock);
        unlock(thread_list_lock);
        *unlocked = true;
        return (!ipc_pid_kill_send(warg->sender, warg->id, KILL_PGROUP,
                                   warg->sig)) ? 1 : 0;
    }

out:
    unlock(thread->lock);
    return srched;
}

static int __kill_pgroup_simple (struct shim_simple_thread * sthread,
                                 void * arg, bool * unlocked)
{
    struct walk_arg * warg = (struct walk_arg *) arg;
    int srched = 0;

    if (sthread->pgid != warg->id)
        return 0;

    lock(sthread->lock);

    if (sthread->is_alive) {
        unlock(sthread->lock);
        unlock(thread_list_lock);
        *unlocked = true;
        return (!ipc_pid_kill_send(warg->sender, warg->id, KILL_PGROUP,
                                   warg->sig)) ? 1 : 0;
    }

    unlock(sthread->lock);
    return srched;
}

int do_kill_pgroup (IDTYPE sender, IDTYPE pgid, int sig, bool use_ipc)
{
    struct shim_thread * cur = get_cur_thread();

    if (!pgid) {
        pgid = cur->pgid;
    }

    struct walk_arg arg;
    arg.current = cur;
    arg.sender  = sender;
    arg.id      = pgid;
    arg.sig     = sig;
    arg.use_ipc = use_ipc;

    bool srched = false;

    if (!walk_thread_list(__kill_pgroup, &arg, false))
        srched = true;

    if (!use_ipc || srched)
        goto out;

    if (!walk_simple_thread_list(__kill_pgroup_simple, &arg, false))
        srched = true;

    if (!srched && !ipc_pid_kill_send(sender, pgid, KILL_PGROUP, sig))
        srched = true;

out:
    return srched ? 0 : -ESRCH;
}

static int __kill_all_threads (struct shim_thread * thread, void * arg,
                               bool * unlocked)
{
    int srched = 0;
    struct walk_arg * warg = (struct walk_arg *) arg;

    if (thread->tgid != thread->tid)
        return 0;

    if (warg->current == thread)
        return 1;

    lock(thread->lock);

    if (thread->in_vm) {
        __append_signal(thread, warg->sig, warg->sender);
        srched = 1;
    }

    unlock(thread->lock);
    return srched;
}

int broadcast_signal (IDTYPE sender, int sig);

int kill_all_threads (struct shim_thread * cur, IDTYPE sender, int sig)
{
    struct walk_arg arg;
    arg.current = cur;
    arg.sender  = sender;
    arg.id      = 0;
    arg.sig     = sig;
    arg.use_ipc = false;
    walk_thread_list(__kill_all_threads, &arg, false);
    return 0;
}

int shim_do_kill (pid_t pid, int sig)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);

    if (sig < 0 || sig > NUM_SIGS)
        return -EINVAL;

    struct shim_thread * cur = get_cur_thread();
    int ret = 0;
    bool send_to_self = false;

    /* If pid equals 0, then sig is sent to every process in the process group
       of the calling process. */
    if (pid == 0) {
        ret = do_kill_pgroup(cur->tgid, 0, sig, true);
        send_to_self = true;
    }

    /* If pid equals -1, then sig is sent to every process for which the
       calling process has permission to send */
    else if (pid == -1) {
        broadcast_signal(cur->tid, sig);
        kill_all_threads(cur, cur->tid, sig);
        send_to_self = true;
    }

    /* If pid is positive, then signal sig is sent to the process with the ID
       specified by pid. */
    else if (pid > 0) {
        ret = do_kill_proc(cur->tid, pid, sig, true);
        send_to_self = (pid == cur->tgid);
    }

    /* If pid is less than -1, then sig is sent to every process in the
       process group whose id is -pid */
    else {
        ret = do_kill_pgroup(cur->tid, -pid, sig, true);
        send_to_self = (-pid == cur->pgid);
    }

    if (send_to_self) {
        if (ret == -ESRCH)
            ret = 0;
        if (sig) {
            siginfo_t info;
            memset(&info, 0, sizeof(siginfo_t));
            info.si_signo = sig;
            info.si_pid   = cur->tid;
            deliver_signal(&info, NULL);
        }
    }

    return ret < 0 ? ret : 0;
}

int do_kill_thread (IDTYPE sender, IDTYPE tgid, IDTYPE tid, int sig,
                    bool use_ipc)
{
    if (sig < 0 || sig > NUM_SIGS)
        return -EINVAL;

    struct shim_thread * thread = lookup_thread(tid);
    int ret = 0;

    if (thread) {
        lock(thread->lock);

        if (thread->in_vm) {
            if (!tgid || thread->tgid == tgid)
                __append_signal(thread, sig, sender);
            else
                ret = -ESRCH;
        } else {
            unlock(thread->lock);
            return ipc_pid_kill_send(sender, tid, KILL_THREAD, sig);
        }

        unlock(thread->lock);
        return ret;
    }

    if (!use_ipc)
        return -ESRCH;

    return ipc_pid_kill_send(sender, tid, KILL_THREAD, sig);
}

int shim_do_tkill (pid_t tid, int sig)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);

    if (tid <= 0)
        return -EINVAL;

    struct shim_thread * cur = get_cur_thread();

    if (tid == cur->tid) {
        if (sig) {
            siginfo_t info;
            memset(&info, 0, sizeof(siginfo_t));
            info.si_signo = sig;
            info.si_pid   = cur->tid;
            deliver_signal(&info, NULL);
        }
        return 0;
    }

    return do_kill_thread(cur->tgid, 0, tid, sig, true);
}

int shim_do_tgkill (pid_t tgid, pid_t tid, int sig)
{
    INC_PROFILE_OCCURENCE(syscall_use_ipc);

    if (tgid < -1 || tgid == 0 || tid <= 0)
        return -EINVAL;

    if (tgid == -1)
        tgid = 0;

    struct shim_thread * cur = get_cur_thread();

    if (tid == cur->tid) {
        if (sig) {
            siginfo_t info;
            memset(&info, 0, sizeof(siginfo_t));
            info.si_signo = sig;
            info.si_pid   = cur->tid;
            deliver_signal(&info, NULL);
        }
        return 0;
    }

    return do_kill_thread(cur->tgid, tgid, tid, sig, true);
}