linux/sched/signal.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SCHED_SIGNAL_H
#define _LINUX_SCHED_SIGNAL_H

#include <linux/rculist.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/sched/jobctl.h>
#include <linux/sched/task.h>
#include <linux/cred.h>
#include <linux/refcount.h>
#include <linux/posix-timers.h>
#include <linux/mm_types.h>
#include <asm/ptrace.h>
#include <linux/android_kabi.h>

/*
 * Types defining task->signal and task->sighand and APIs using them:
 */

struct sighand_struct {
    spinlock_t siglock;
    refcount_t count;
    wait_queue_head_t signalfd_wqh;
    struct k_sigaction action[_NSIG];
};

/*
 * Per-process accounting stats:
 */
struct pacct_struct {
    int ac_flag;
    long ac_exitcode;
    unsigned long ac_mem;
    u64 ac_utime, ac_stime;
    unsigned long ac_minflt, ac_majflt;
};

struct cpu_itimer {
    u64 expires;
    u64 incr;
};

/*
 * This is the atomic variant of task_cputime, which can be used for
 * storing and updating task_cputime statistics without locking.
 */
struct task_cputime_atomic {
    atomic64_t utime;
    atomic64_t stime;
    atomic64_t sum_exec_runtime;
};

#define INIT_CPUTIME_ATOMIC                                                                                            \
    (struct task_cputime_atomic)                                                                                       \
    {                                                                                                                  \
        .utime = ATOMIC64_INIT(0), .stime = ATOMIC64_INIT(0), .sum_exec_runtime = ATOMIC64_INIT(0),                    \
    }
/**
 * struct thread_group_cputimer - thread group interval timer counts
 * @cputime_atomic:    atomic thread group interval timers.
 *
 * This structure contains the version of task_cputime, above, that is
 * used for thread group CPU timer calculations.
 */
struct thread_group_cputimer {
    struct task_cputime_atomic cputime_atomic;
};

struct multiprocess_signals {
    sigset_t signal;
    struct hlist_node node;
};

/*
 * NOTE! "signal_struct" does not have its own
 * locking, because a shared signal_struct always
 * implies a shared sighand_struct, so locking
 * sighand_struct is always a proper superset of
 * the locking of signal_struct.
 */
struct signal_struct {
    refcount_t sigcnt;
    atomic_t live;
    int nr_threads;
    struct list_head thread_head;

    wait_queue_head_t wait_chldexit; /* for wait4() */

    /* current thread group signal load-balancing target: */
    struct task_struct *curr_target;

    /* shared signal handling: */
    struct sigpending shared_pending;

    /* For collecting multiprocess signals during fork */
    struct hlist_head multiprocess;

    /* thread group exit support */
    int group_exit_code;
    /* overloaded:
     * - notify group_exit_task when ->count is equal to notify_count
     * - everyone except group_exit_task is stopped during signal delivery
     *   of fatal signals, group_exit_task processes the signal.
     */
    int notify_count;
    struct task_struct *group_exit_task;

    /* thread group stop support, overloads group_exit_code too */
    int group_stop_count;
    unsigned int flags; /* see SIGNAL_* flags below */

    /*
     * PR_SET_CHILD_SUBREAPER marks a process, like a service
     * manager, to re-parent orphan (double-forking) child processes
     * to this process instead of 'init'. The service manager is
     * able to receive SIGCHLD signals and is able to investigate
     * the process until it calls wait(). All children of this
     * process will inherit a flag if they should look for a
     * child_subreaper process at exit.
     */
    unsigned int is_child_subreaper : 1;
    unsigned int has_child_subreaper : 1;

#ifdef CONFIG_POSIX_TIMERS

    /* POSIX.1b Interval Timers */
    int posix_timer_id;
    struct list_head posix_timers;

    /* ITIMER_REAL timer for the process */
    struct hrtimer real_timer;
    ktime_t it_real_incr;

    /*
     * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
     * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
     * values are defined to 0 and 1 respectively
     */
    struct cpu_itimer it[2];

    /*
     * Thread group totals for process CPU timers.
     * See thread_group_cputimer(), et al, for details.
     */
    struct thread_group_cputimer cputimer;

#endif
    /* Empty if CONFIG_POSIX_TIMERS=n */
    struct posix_cputimers posix_cputimers;

    /* PID/PID hash table linkage. */
    struct pid *pids[PIDTYPE_MAX];

#ifdef CONFIG_NO_HZ_FULL
    atomic_t tick_dep_mask;
#endif

    struct pid *tty_old_pgrp;

    /* boolean value for session group leader */
    int leader;

    struct tty_struct *tty; /* NULL if no tty */

#ifdef CONFIG_SCHED_AUTOGROUP
    struct autogroup *autogroup;
#endif
    /*
     * Cumulative resource counters for dead threads in the group,
     * and for reaped dead child processes forked by this group.
     * Live threads maintain their own counters and add to these
     * in __exit_signal, except for the group leader.
     */
    seqlock_t stats_lock;
    u64 utime, stime, cutime, cstime;
    u64 gtime;
    u64 cgtime;
    struct prev_cputime prev_cputime;
    unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
    unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
    unsigned long inblock, oublock, cinblock, coublock;
    unsigned long maxrss, cmaxrss;
    struct task_io_accounting ioac;

    /*
     * Cumulative ns of schedule CPU time fo dead threads in the
     * group, not including a zombie group leader, (This only differs
     * from jiffies_to_ns(utime + stime) if sched_clock uses something
     * other than jiffies.)
     */
    unsigned long long sum_sched_runtime;

    /*
     * We don't bother to synchronize most readers of this at all,
     * because there is no reader checking a limit that actually needs
     * to get both rlim_cur and rlim_max atomically, and either one
     * alone is a single word that can safely be read normally.
     * getrlimit/setrlimit use task_lock(current->group_leader) to
     * protect this instead of the siglock, because they really
     * have no need to disable irqs.
     */
    struct rlimit rlim[RLIM_NLIMITS];

#ifdef CONFIG_BSD_PROCESS_ACCT
    struct pacct_struct pacct; /* per-process accounting information */
#endif
#ifdef CONFIG_TASKSTATS
    struct taskstats *stats;
#endif
#ifdef CONFIG_AUDIT
    unsigned audit_tty;
    struct tty_audit_buf *tty_audit_buf;
#endif

    /*
     * Thread is the potential origin of an oom condition; kill first on
     * oom
     */
    bool oom_flag_origin;
    short oom_score_adj;      /* OOM kill score adjustment */
    short oom_score_adj_min;  /* OOM kill score adjustment min value.
                               * Only settable by CAP_SYS_RESOURCE. */
    struct mm_struct *oom_mm; /* recorded mm when the thread group got
                               * killed by the oom killer */

    struct mutex cred_guard_mutex;        /* guard against foreign influences on
                                           * credential calculations
                                           * (notably. ptrace)
                                           * Deprecated do not use in new code.
                                           * Use exec_update_lock instead.
                                           */
    struct rw_semaphore exec_update_lock; /* Held while task_struct is
                                           * being updated during exec,
                                           * and may have inconsistent
                                           * permissions.
                                           */
} __randomize_layout;

/*
 * Bits in flags field of signal_struct.
 */
#define SIGNAL_STOP_STOPPED 0x00000001   /* job control stop in effect */
#define SIGNAL_STOP_CONTINUED 0x00000002 /* SIGCONT since WCONTINUED reap */
#define SIGNAL_GROUP_EXIT 0x00000004     /* group exit in progress */
#define SIGNAL_GROUP_COREDUMP 0x00000008 /* coredump in progress */
/*
 * Pending notifications to parent.
 */
#define SIGNAL_CLD_STOPPED 0x00000010
#define SIGNAL_CLD_CONTINUED 0x00000020
#define SIGNAL_CLD_MASK (SIGNAL_CLD_STOPPED | SIGNAL_CLD_CONTINUED)

#define SIGNAL_UNKILLABLE 0x00000040 /* for init: ignore fatal signals */

#define SIGNAL_STOP_MASK (SIGNAL_CLD_MASK | SIGNAL_STOP_STOPPED | SIGNAL_STOP_CONTINUED)

static inline void signal_set_stop_flags(struct signal_struct *sig, unsigned int flags)
{
    WARN_ON(sig->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP));
    sig->flags = (sig->flags & ~SIGNAL_STOP_MASK) | flags;
}

/* If true, all threads except ->group_exit_task have pending SIGKILL */
static inline int signal_group_exit(const struct signal_struct *sig)
{
    return (sig->flags & SIGNAL_GROUP_EXIT) || (sig->group_exit_task != NULL);
}

extern void flush_signals(struct task_struct *);
extern void ignore_signals(struct task_struct *);
extern void flush_signal_handlers(struct task_struct *, int force_default);
extern int dequeue_signal(struct task_struct *task, sigset_t *mask, kernel_siginfo_t *info);

static inline int kernel_dequeue_signal(void)
{
    struct task_struct *task = current;
    kernel_siginfo_t _info;
    int ret;

    spin_lock_irq(&task->sighand->siglock);
    ret = dequeue_signal(task, &task->blocked, &_info);
    spin_unlock_irq(&task->sighand->siglock);

    return ret;
}

static inline void kernel_signal_stop(void)
{
    spin_lock_irq(&current->sighand->siglock);
    if (current->jobctl & JOBCTL_STOP_DEQUEUED) {
        set_special_state(TASK_STOPPED);
    }
    spin_unlock_irq(&current->sighand->siglock);

    schedule();
}
#ifdef __ARCH_SI_TRAPNO
#define ___ARCH_SI_TRAPNO(_a1) (, _a1)
#else
#define ___ARCH_SI_TRAPNO(_a1)
#endif
#ifdef __ia64__
#define ___ARCH_SI_IA64(_a1, _a2, _a3) (, _a1, _a2, _a3)
#else
#define ___ARCH_SI_IA64(_a1, _a2, _a3)
#endif

int force_sig_fault_to_task(int sig, int code,
                            void __user *addr ___ARCH_SI_TRAPNO(int trapno)
                                ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr),
                            struct task_struct *t);
int force_sig_fault(int sig, int code,
                    void __user *addr ___ARCH_SI_TRAPNO(int trapno)
                        ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr));
int send_sig_fault(int sig, int code,
                   void __user *addr ___ARCH_SI_TRAPNO(int trapno)
                        ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr),
                   struct task_struct *t);

int force_sig_mceerr(int code, void __user *, short);
int send_sig_mceerr(int code, void __user *, short, struct task_struct *);

int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper);
int force_sig_pkuerr(void __user *addr, u32 pkey);

int force_sig_ptrace_errno_trap(int errno, void __user *addr);

extern int send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
extern void force_sigsegv(int sig);
extern int force_sig_info(struct kernel_siginfo *);
extern int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp);
extern int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid);
extern int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr, struct pid *, const struct cred *);
extern int kill_pgrp(struct pid *pid, int sig, int priv);
extern int kill_pid(struct pid *pid, int sig, int priv);
extern __must_check bool do_notify_parent(struct task_struct *, int);
extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
extern void force_sig(int);
extern int send_sig(int, struct task_struct *, int);
extern int zap_other_threads(struct task_struct *p);
extern struct sigqueue *sigqueue_alloc(void);
extern void sigqueue_free(struct sigqueue *);
extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);

static inline int restart_syscall(void)
{
    set_tsk_thread_flag(current, TIF_SIGPENDING);
    return -ERESTARTNOINTR;
}

static inline int task_sigpending(struct task_struct *p)
{
    return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
}

static inline int signal_pending(struct task_struct *p)
{
    /*
     * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
     * behavior in terms of ensuring that we break out of wait loops
     * so that notify signal callbacks can be processed.
     */
    if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) {
        return 1;
    }

    return task_sigpending(p);
}

static inline int __fatal_signal_pending(struct task_struct *p)
{
    return unlikely(sigismember(&p->pending.signal, SIGKILL));
}

static inline int fatal_signal_pending(struct task_struct *p)
{
    return task_sigpending(p) && __fatal_signal_pending(p);
}

static inline int signal_pending_state(long state, struct task_struct *p)
{
    if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL))) {
        return 0;
    }
    if (!signal_pending(p)) {
        return 0;
    }

    return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p);
}

/*
 * This should only be used in fault handlers to decide whether we
 * should stop the current fault routine to handle the signals
 * instead, especially with the case where we've got interrupted with
 * a VM_FAULT_RETRY.
 */
static inline bool fault_signal_pending(vm_fault_t fault_flags, struct pt_regs *regs)
{
    return unlikely((fault_flags & VM_FAULT_RETRY) &&
                    (fatal_signal_pending(current) || (user_mode(regs) && signal_pending(current))));
}

/*
 * Reevaluate whether the task has signals pending delivery.
 * Wake the task if so.
 * This is required every time the blocked sigset_t changes.
 * callers must hold sighand->siglock.
 */
extern void recalc_sigpending_and_wake(struct task_struct *t);
extern void recalc_sigpending(void);
extern void calculate_sigpending(void);

extern void signal_wake_up_state(struct task_struct *t, unsigned int state);

static inline void signal_wake_up(struct task_struct *t, bool resume)
{
    signal_wake_up_state(t, resume ? TASK_WAKEKILL : 0);
}
static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
{
    signal_wake_up_state(t, resume ? __TASK_TRACED : 0);
}

void task_join_group_stop(struct task_struct *task);

#ifdef TIF_RESTORE_SIGMASK
/*
 * Legacy restore_sigmask accessors.  These are inefficient on
 * SMP architectures because they require atomic operations.
 */

/**
 * set_restore_sigmask() - make sure saved_sigmask processing gets done
 *
 * This sets TIF_RESTORE_SIGMASK and ensures that the arch signal code
 * will run before returning to user mode, to process the flag.  For
 * all callers, TIF_SIGPENDING is already set or it's no harm to set
 * it.  TIF_RESTORE_SIGMASK need not be in the set of bits that the
 * arch code will notice on return to user mode, in case those bits
 * are scarce.  We set TIF_SIGPENDING here to ensure that the arch
 * signal code always gets run when TIF_RESTORE_SIGMASK is set.
 */
static inline void set_restore_sigmask(void)
{
    set_thread_flag(TIF_RESTORE_SIGMASK);
}

static inline void clear_tsk_restore_sigmask(struct task_struct *task)
{
    clear_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
}

static inline void clear_restore_sigmask(void)
{
    clear_thread_flag(TIF_RESTORE_SIGMASK);
}
static inline bool test_tsk_restore_sigmask(struct task_struct *task)
{
    return test_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
}
static inline bool test_restore_sigmask(void)
{
    return test_thread_flag(TIF_RESTORE_SIGMASK);
}
static inline bool test_and_clear_restore_sigmask(void)
{
    return test_and_clear_thread_flag(TIF_RESTORE_SIGMASK);
}

#else /* TIF_RESTORE_SIGMASK */

/* Higher-quality implementation, used if TIF_RESTORE_SIGMASK doesn't exist. */
static inline void set_restore_sigmask(void)
{
    current->restore_sigmask = true;
}
static inline void clear_tsk_restore_sigmask(struct task_struct *task)
{
    task->restore_sigmask = false;
}
static inline void clear_restore_sigmask(void)
{
    current->restore_sigmask = false;
}
static inline bool test_restore_sigmask(void)
{
    return current->restore_sigmask;
}
static inline bool test_tsk_restore_sigmask(struct task_struct *task)
{
    return task->restore_sigmask;
}
static inline bool test_and_clear_restore_sigmask(void)
{
    if (!current->restore_sigmask) {
        return false;
    }
    current->restore_sigmask = false;
    return true;
}
#endif

static inline void restore_saved_sigmask(void)
{
    if (test_and_clear_restore_sigmask()) {
        __set_current_blocked(&current->saved_sigmask);
    }
}

extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);

static inline void restore_saved_sigmask_unless(bool interrupted)
{
    if (interrupted) {
        WARN_ON(!signal_pending(current));
    } else {
        restore_saved_sigmask();
    }
}

static inline sigset_t *sigmask_to_save(void)
{
    sigset_t *res = &current->blocked;
    if (unlikely(test_restore_sigmask())) {
        res = &current->saved_sigmask;
    }
    return res;
}

static inline int kill_cad_pid(int sig, int priv)
{
    return kill_pid(cad_pid, sig, priv);
}

/* These can be the second arg to send_sig_info/send_group_sig_info.  */
#define SEND_SIG_NOINFO ((struct kernel_siginfo *)0)
#define SEND_SIG_PRIV ((struct kernel_siginfo *)1)

static inline int __on_sig_stack(unsigned long sp)
{
#ifdef CONFIG_STACK_GROWSUP
    return sp >= current->sas_ss_sp && sp - current->sas_ss_sp < current->sas_ss_size;
#else
    return sp > current->sas_ss_sp && sp - current->sas_ss_sp <= current->sas_ss_size;
#endif
}

/*
 * True if we are on the alternate signal stack.
 */
static inline int on_sig_stack(unsigned long sp)
{
    /*
     * If the signal stack is SS_AUTODISARM then, by construction, we
     * can't be on the signal stack unless user code deliberately set
     * SS_AUTODISARM when we were already on it.
     *
     * This improves reliability: if user state gets corrupted such that
     * the stack pointer points very close to the end of the signal stack,
     * then this check will enable the signal to be handled anyway.
     */
    if (current->sas_ss_flags & SS_AUTODISARM) {
        return 0;
    }

    return __on_sig_stack(sp);
}

static inline int sas_ss_flags(unsigned long sp)
{
    if (!current->sas_ss_size) {
        return SS_DISABLE;
    }

    return on_sig_stack(sp) ? SS_ONSTACK : 0;
}

static inline void sas_ss_reset(struct task_struct *p)
{
    p->sas_ss_sp = 0;
    p->sas_ss_size = 0;
    p->sas_ss_flags = SS_DISABLE;
}

static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
{
    if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && !sas_ss_flags(sp))
#ifdef CONFIG_STACK_GROWSUP
        return current->sas_ss_sp;
#else
        return current->sas_ss_sp + current->sas_ss_size;
#endif
    return sp;
}

extern void __cleanup_sighand(struct sighand_struct *);
extern void flush_itimer_signals(void);

#define tasklist_empty() list_empty(&init_task.tasks)

#define next_task(p) list_entry_rcu((p)->tasks.next, struct task_struct, tasks)

#define for_each_process(p) for ((p) = &init_task; ((p) = next_task(p)) != &init_task;)

extern bool current_is_single_threaded(void);

/*
 * Careful: do_each_thread/while_each_thread is a double loop so
 *          'break' will not work as expected - use goto instead.
 */
#define do_each_thread(g, t)                                                                                           \
    for ((g) = (t) = &init_task; ((g) = (t) = next_task(g)) != &init_task;)                                            \
        do

#define while_each_thread(g, t) while (((t) = next_thread(t)) != (g))

#define _for_each_thread(signal, t) list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node)

#define for_each_thread(p, t) _for_each_thread((p)->signal, t)

/* Careful: this is a double loop, 'break' won't work as expected. */
#define for_each_process_thread(p, t) for_each_process(p) for_each_thread(p, t)

typedef int (*proc_visitor)(struct task_struct *p, void *data);
void walk_process_tree(struct task_struct *top, proc_visitor, void *);

static inline struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
{
    struct pid *pid;
    if (type == PIDTYPE_PID) {
        pid = task_pid(task);
    } else {
        pid = task->signal->pids[type];
    }
    return pid;
}

static inline struct pid *task_tgid(struct task_struct *task)
{
    return task->signal->pids[PIDTYPE_TGID];
}

/*
 * Without tasklist or RCU lock it is not safe to dereference
 * the result of task_pgrp/task_session even if task == current,
 * we can race with another thread doing sys_setsid/sys_setpgid.
 */
static inline struct pid *task_pgrp(struct task_struct *task)
{
    return task->signal->pids[PIDTYPE_PGID];
}

static inline struct pid *task_session(struct task_struct *task)
{
    return task->signal->pids[PIDTYPE_SID];
}

static inline int get_nr_threads(struct task_struct *task)
{
    return task->signal->nr_threads;
}

static inline bool thread_group_leader(struct task_struct *p)
{
    return p->exit_signal >= 0;
}

static inline bool same_thread_group(struct task_struct *p1, struct task_struct *p2)
{
    return p1->signal == p2->signal;
}

static inline struct task_struct *next_thread(const struct task_struct *p)
{
    return list_entry_rcu(p->thread_group.next, struct task_struct, thread_group);
}

static inline int thread_group_empty(struct task_struct *p)
{
    return list_empty(&p->thread_group);
}

#define delay_group_leader(p) (thread_group_leader(p) && !thread_group_empty(p))

extern bool thread_group_exited(struct pid *pid);

extern struct sighand_struct *__lock_task_sighand(struct task_struct *task, unsigned long *flags);

static inline struct sighand_struct *lock_task_sighand(struct task_struct *task, unsigned long *flags)
{
    struct sighand_struct *ret;

    ret = __lock_task_sighand(task, flags);
    (void)__cond_lock(&task->sighand->siglock, ret);
    return ret;
}

static inline void unlock_task_sighand(struct task_struct *task, unsigned long *flags)
{
    spin_unlock_irqrestore(&task->sighand->siglock, *flags);
}

static inline unsigned long task_rlimit(const struct task_struct *task, unsigned int limit)
{
    return READ_ONCE(task->signal->rlim[limit].rlim_cur);
}

static inline unsigned long task_rlimit_max(const struct task_struct *task, unsigned int limit)
{
    return READ_ONCE(task->signal->rlim[limit].rlim_max);
}

static inline unsigned long rlimit(unsigned int limit)
{
    return task_rlimit(current, limit);
}

static inline unsigned long rlimit_max(unsigned int limit)
{
    return task_rlimit_max(current, limit);
}

#endif /* _LINUX_SCHED_SIGNAL_H */