// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <pthread.h>
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>
#include "include/liblockdep/mutex.h"
#include "../../include/linux/rbtree.h"

/**
 * struct lock_lookup - liblockdep's view of a single unique lock
 * @orig: pointer to the original pthread lock, used for lookups
 * @dep_map: lockdep's dep_map structure
 * @key: lockdep's key structure
 * @node: rb-tree node used to store the lock in a global tree
 * @name: a unique name for the lock
 */
struct lock_lookup {
        void *orig; /* Original pthread lock, used for lookups */
        struct lockdep_map dep_map; /* Since all locks are dynamic, we need
                                     * a dep_map and a key for each lock */
        /*
         * Wait, there's no support for key classes? Yup :(
         * Most big projects wrap the pthread api with their own calls to
         * be compatible with different locking methods. This means that
         * "classes" will be brokes since the function that creates all
         * locks will point to a generic locking function instead of the
         * actual code that wants to do the locking.
         */
        struct lock_class_key key;
        struct rb_node node;
#define LIBLOCKDEP_MAX_LOCK_NAME 22
        char name[LIBLOCKDEP_MAX_LOCK_NAME];
};

/* This is where we store our locks */
static struct rb_root locks = RB_ROOT;
static pthread_rwlock_t locks_rwlock = PTHREAD_RWLOCK_INITIALIZER;

/* pthread mutex API */

#ifdef __GLIBC__
extern int __pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr);
extern int __pthread_mutex_lock(pthread_mutex_t *mutex);
extern int __pthread_mutex_trylock(pthread_mutex_t *mutex);
extern int __pthread_mutex_unlock(pthread_mutex_t *mutex);
extern int __pthread_mutex_destroy(pthread_mutex_t *mutex);
#else
#define __pthread_mutex_init    NULL
#define __pthread_mutex_lock    NULL
#define __pthread_mutex_trylock NULL
#define __pthread_mutex_unlock  NULL
#define __pthread_mutex_destroy NULL
#endif
static int (*ll_pthread_mutex_init)(pthread_mutex_t *mutex,
                        const pthread_mutexattr_t *attr)        = __pthread_mutex_init;
static int (*ll_pthread_mutex_lock)(pthread_mutex_t *mutex)     = __pthread_mutex_lock;
static int (*ll_pthread_mutex_trylock)(pthread_mutex_t *mutex)  = __pthread_mutex_trylock;
static int (*ll_pthread_mutex_unlock)(pthread_mutex_t *mutex)   = __pthread_mutex_unlock;
static int (*ll_pthread_mutex_destroy)(pthread_mutex_t *mutex)  = __pthread_mutex_destroy;

/* pthread rwlock API */

#ifdef __GLIBC__
extern int __pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr);
extern int __pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
#else
#define __pthread_rwlock_init           NULL
#define __pthread_rwlock_destroy        NULL
#define __pthread_rwlock_wrlock         NULL
#define __pthread_rwlock_trywrlock      NULL
#define __pthread_rwlock_rdlock         NULL
#define __pthread_rwlock_tryrdlock      NULL
#define __pthread_rwlock_unlock         NULL
#endif

static int (*ll_pthread_rwlock_init)(pthread_rwlock_t *rwlock,
                        const pthread_rwlockattr_t *attr)               = __pthread_rwlock_init;
static int (*ll_pthread_rwlock_destroy)(pthread_rwlock_t *rwlock)       = __pthread_rwlock_destroy;
static int (*ll_pthread_rwlock_rdlock)(pthread_rwlock_t *rwlock)        = __pthread_rwlock_rdlock;
static int (*ll_pthread_rwlock_tryrdlock)(pthread_rwlock_t *rwlock)     = __pthread_rwlock_tryrdlock;
static int (*ll_pthread_rwlock_trywrlock)(pthread_rwlock_t *rwlock)     = __pthread_rwlock_trywrlock;
static int (*ll_pthread_rwlock_wrlock)(pthread_rwlock_t *rwlock)        = __pthread_rwlock_wrlock;
static int (*ll_pthread_rwlock_unlock)(pthread_rwlock_t *rwlock)        = __pthread_rwlock_unlock;

enum { none, prepare, done, } __init_state;
static void init_preload(void);
static void try_init_preload(void)
{
        if (__init_state != done)
                init_preload();
}

static struct rb_node **__get_lock_node(void *lock, struct rb_node **parent)
{
        struct rb_node **node = &locks.rb_node;
        struct lock_lookup *l;

        *parent = NULL;

        while (*node) {
                l = rb_entry(*node, struct lock_lookup, node);

                *parent = *node;
                if (lock < l->orig)
                        node = &l->node.rb_left;
                else if (lock > l->orig)
                        node = &l->node.rb_right;
                else
                        return node;
        }

        return node;
}

#ifndef LIBLOCKDEP_STATIC_ENTRIES
#define LIBLOCKDEP_STATIC_ENTRIES       1024
#endif

static struct lock_lookup __locks[LIBLOCKDEP_STATIC_ENTRIES];
static int __locks_nr;

static inline bool is_static_lock(struct lock_lookup *lock)
{
        return lock >= __locks && lock < __locks + ARRAY_SIZE(__locks);
}

static struct lock_lookup *alloc_lock(void)
{
        if (__init_state != done) {
                /*
                 * Some programs attempt to initialize and use locks in their
                 * allocation path. This means that a call to malloc() would
                 * result in locks being initialized and locked.
                 *
                 * Why is it an issue for us? dlsym() below will try allocating
                 * to give us the original function. Since this allocation will
                 * result in a locking operations, we have to let pthread deal
                 * with it, but we can't! we don't have the pointer to the
                 * original API since we're inside dlsym() trying to get it
                 */

                int idx = __locks_nr++;
                if (idx >= ARRAY_SIZE(__locks)) {
                        dprintf(STDERR_FILENO,
                "LOCKDEP error: insufficient LIBLOCKDEP_STATIC_ENTRIES\n");
                        exit(EX_UNAVAILABLE);
                }
                return __locks + idx;
        }

        return malloc(sizeof(struct lock_lookup));
}

static inline void free_lock(struct lock_lookup *lock)
{
        if (likely(!is_static_lock(lock)))
                free(lock);
}

/**
 * __get_lock - find or create a lock instance
 * @lock: pointer to a pthread lock function
 *
 * Try to find an existing lock in the rbtree using the provided pointer. If
 * one wasn't found - create it.
 */
static struct lock_lookup *__get_lock(void *lock)
{
        struct rb_node **node, *parent;
        struct lock_lookup *l;

        ll_pthread_rwlock_rdlock(&locks_rwlock);
        node = __get_lock_node(lock, &parent);
        ll_pthread_rwlock_unlock(&locks_rwlock);
        if (*node) {
                return rb_entry(*node, struct lock_lookup, node);
        }

        /* We didn't find the lock, let's create it */
        l = alloc_lock();
        if (l == NULL)
                return NULL;

        l->orig = lock;
        /*
         * Currently the name of the lock is the ptr value of the pthread lock,
         * while not optimal, it makes debugging a bit easier.
         *
         * TODO: Get the real name of the lock using libdwarf
         */
        sprintf(l->name, "%p", lock);
        lockdep_init_map(&l->dep_map, l->name, &l->key, 0);

        ll_pthread_rwlock_wrlock(&locks_rwlock);
        /* This might have changed since the last time we fetched it */
        node = __get_lock_node(lock, &parent);
        rb_link_node(&l->node, parent, node);
        rb_insert_color(&l->node, &locks);
        ll_pthread_rwlock_unlock(&locks_rwlock);

        return l;
}

static void __del_lock(struct lock_lookup *lock)
{
        ll_pthread_rwlock_wrlock(&locks_rwlock);
        rb_erase(&lock->node, &locks);
        ll_pthread_rwlock_unlock(&locks_rwlock);
        free_lock(lock);
}

int pthread_mutex_init(pthread_mutex_t *mutex,
                        const pthread_mutexattr_t *attr)
{
        int r;

        /*
         * We keep trying to init our preload module because there might be
         * code in init sections that tries to touch locks before we are
         * initialized, in that case we'll need to manually call preload
         * to get us going.
         *
         * Funny enough, kernel's lockdep had the same issue, and used
         * (almost) the same solution. See look_up_lock_class() in
         * kernel/locking/lockdep.c for details.
         */
        try_init_preload();

        r = ll_pthread_mutex_init(mutex, attr);
        if (r == 0)
                /*
                 * We do a dummy initialization here so that lockdep could
                 * warn us if something fishy is going on - such as
                 * initializing a held lock.
                 */
                __get_lock(mutex);

        return r;
}

int pthread_mutex_lock(pthread_mutex_t *mutex)
{
        int r;

        try_init_preload();

        lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 1, NULL,
                        (unsigned long)_RET_IP_);
        /*
         * Here's the thing with pthread mutexes: unlike the kernel variant,
         * they can fail.
         *
         * This means that the behaviour here is a bit different from what's
         * going on in the kernel: there we just tell lockdep that we took the
         * lock before actually taking it, but here we must deal with the case
         * that locking failed.
         *
         * To do that we'll "release" the lock if locking failed - this way
         * we'll get lockdep doing the correct checks when we try to take
         * the lock, and if that fails - we'll be back to the correct
         * state by releasing it.
         */
        r = ll_pthread_mutex_lock(mutex);
        if (r)
                lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
        int r;

        try_init_preload();

        lock_acquire(&__get_lock(mutex)->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
        r = ll_pthread_mutex_trylock(mutex);
        if (r)
                lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        int r;

        try_init_preload();

        lock_release(&__get_lock(mutex)->dep_map, 0, (unsigned long)_RET_IP_);
        /*
         * Just like taking a lock, only in reverse!
         *
         * If we fail releasing the lock, tell lockdep we're holding it again.
         */
        r = ll_pthread_mutex_unlock(mutex);
        if (r)
                lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);

        return r;
}

int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
        try_init_preload();

        /*
         * Let's see if we're releasing a lock that's held.
         *
         * TODO: Hook into free() and add that check there as well.
         */
        debug_check_no_locks_freed(mutex, sizeof(*mutex));
        __del_lock(__get_lock(mutex));
        return ll_pthread_mutex_destroy(mutex);
}

/* This is the rwlock part, very similar to what happened with mutex above */
int pthread_rwlock_init(pthread_rwlock_t *rwlock,
                        const pthread_rwlockattr_t *attr)
{
        int r;

        try_init_preload();

        r = ll_pthread_rwlock_init(rwlock, attr);
        if (r == 0)
                __get_lock(rwlock);

        return r;
}

int pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
{
        try_init_preload();

        debug_check_no_locks_freed(rwlock, sizeof(*rwlock));
        __del_lock(__get_lock(rwlock));
        return ll_pthread_rwlock_destroy(rwlock);
}

int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
{
        int r;

        init_preload();

        lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 2, 1, NULL, (unsigned long)_RET_IP_);
        r = ll_pthread_rwlock_rdlock(rwlock);
        if (r)
                lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
{
        int r;

        init_preload();

        lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 2, 1, NULL, (unsigned long)_RET_IP_);
        r = ll_pthread_rwlock_tryrdlock(rwlock);
        if (r)
                lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
{
        int r;

        init_preload();

        lock_acquire(&__get_lock(rwlock)->dep_map, 0, 1, 0, 1, NULL, (unsigned long)_RET_IP_);
        r = ll_pthread_rwlock_trywrlock(rwlock);
        if (r)
                lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
{
        int r;

        init_preload();

        lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);
        r = ll_pthread_rwlock_wrlock(rwlock);
        if (r)
                lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);

        return r;
}

int pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
{
        int r;

        init_preload();

        lock_release(&__get_lock(rwlock)->dep_map, 0, (unsigned long)_RET_IP_);
        r = ll_pthread_rwlock_unlock(rwlock);
        if (r)
                lock_acquire(&__get_lock(rwlock)->dep_map, 0, 0, 0, 1, NULL, (unsigned long)_RET_IP_);

        return r;
}

__attribute__((constructor)) static void init_preload(void)
{
        if (__init_state == done)
                return;

#ifndef __GLIBC__
        __init_state = prepare;

        ll_pthread_mutex_init = dlsym(RTLD_NEXT, "pthread_mutex_init");
        ll_pthread_mutex_lock = dlsym(RTLD_NEXT, "pthread_mutex_lock");
        ll_pthread_mutex_trylock = dlsym(RTLD_NEXT, "pthread_mutex_trylock");
        ll_pthread_mutex_unlock = dlsym(RTLD_NEXT, "pthread_mutex_unlock");
        ll_pthread_mutex_destroy = dlsym(RTLD_NEXT, "pthread_mutex_destroy");

        ll_pthread_rwlock_init = dlsym(RTLD_NEXT, "pthread_rwlock_init");
        ll_pthread_rwlock_destroy = dlsym(RTLD_NEXT, "pthread_rwlock_destroy");
        ll_pthread_rwlock_rdlock = dlsym(RTLD_NEXT, "pthread_rwlock_rdlock");
        ll_pthread_rwlock_tryrdlock = dlsym(RTLD_NEXT, "pthread_rwlock_tryrdlock");
        ll_pthread_rwlock_wrlock = dlsym(RTLD_NEXT, "pthread_rwlock_wrlock");
        ll_pthread_rwlock_trywrlock = dlsym(RTLD_NEXT, "pthread_rwlock_trywrlock");
        ll_pthread_rwlock_unlock = dlsym(RTLD_NEXT, "pthread_rwlock_unlock");
#endif

        __init_state = done;
}