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/*

 *  linux/kernel/fork.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 */

/*

 *  'fork.c' contains the help-routines for the 'fork' system call

 * (see also entry.S and others).

 * Fork is rather simple, once you get the hang of it, but the memory

 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'

 */

#include <linux/slab.h>

#include <linux/init.h>

#include <linux/unistd.h>

#include <linux/module.h>

#include <linux/vmalloc.h>

#include <linux/completion.h>

#include <linux/mnt_namespace.h>

#include <linux/personality.h>

#include <linux/mempolicy.h>

#include <linux/sem.h>

#include <linux/file.h>

#include <linux/key.h>

#include <linux/binfmts.h>

#include <linux/mman.h>

#include <linux/fs.h>

#include <linux/nsproxy.h>

#include <linux/capability.h>

#include <linux/cpu.h>

#include <linux/cgroup.h>

#include <linux/security.h>

#include <linux/swap.h>

#include <linux/syscalls.h>

#include <linux/jiffies.h>

#include <linux/futex.h>

#include <linux/task_io_accounting_ops.h>

#include <linux/rcupdate.h>

#include <linux/ptrace.h>

#include <linux/mount.h>

#include <linux/audit.h>

#include <linux/profile.h>

#include <linux/rmap.h>

#include <linux/acct.h>

#include <linux/tsacct_kern.h>

#include <linux/cn_proc.h>

#include <linux/freezer.h>

#include <linux/delayacct.h>

#include <linux/taskstats_kern.h>

#include <linux/random.h>

#include <linux/tty.h>

#include <linux/proc_fs.h>

#include <asm/pgtable.h>

#include <asm/pgalloc.h>

#include <asm/uaccess.h>

#include <asm/mmu_context.h>

#include <asm/cacheflush.h>

#include <asm/tlbflush.h>

/*

 * Protected counters by write_lock_irq(&tasklist_lock)

 */

unsigned long total_forks;      /* Handle normal Linux uptimes. */

int nr_threads;                 /* The idle threads do not count.. */

int max_threads;                /* tunable limit on nr_threads */

DEFINE_PER_CPU(unsigned long, process_counts) = 0;

__cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */

int nr_processes(void)

{

        int cpu;

        int total = 0;

        for_each_online_cpu(cpu)

                total += per_cpu(process_counts, cpu);

        return total;

}

#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR

# define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)

# define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))

static struct kmem_cache *task_struct_cachep;

#endif

/* SLAB cache for signal_struct structures (tsk->signal) */

static struct kmem_cache *signal_cachep;

/* SLAB cache for sighand_struct structures (tsk->sighand) */

struct kmem_cache *sighand_cachep;

/* SLAB cache for files_struct structures (tsk->files) */

struct kmem_cache *files_cachep;

/* SLAB cache for fs_struct structures (tsk->fs) */

struct kmem_cache *fs_cachep;

/* SLAB cache for vm_area_struct structures */

struct kmem_cache *vm_area_cachep;

/* SLAB cache for mm_struct structures (tsk->mm) */

static struct kmem_cache *mm_cachep;

void free_task(struct task_struct *tsk)

{

        prop_local_destroy_single(&tsk->dirties);

        free_thread_info(tsk->stack);

        rt_mutex_debug_task_free(tsk);

        free_task_struct(tsk);

}

EXPORT_SYMBOL(free_task);

void __put_task_struct(struct task_struct *tsk)

{

        WARN_ON(!tsk->exit_state);

        WARN_ON(atomic_read(&tsk->usage));

        WARN_ON(tsk == current);

        security_task_free(tsk);

        free_uid(tsk->user);

        put_group_info(tsk->group_info);

        delayacct_tsk_free(tsk);

        if (!profile_handoff_task(tsk))

                free_task(tsk);

}

void __init fork_init(unsigned long mempages)

{

#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR

#ifndef ARCH_MIN_TASKALIGN

#define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES

#endif

        /* create a slab on which task_structs can be allocated */

        task_struct_cachep =

                kmem_cache_create("task_struct", sizeof(struct task_struct),

                        ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);

#endif

        /*

         * The default maximum number of threads is set to a safe

         * value: the thread structures can take up at most half

         * of memory.

         */

        max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);

        /*

         * we need to allow at least 20 threads to boot a system

         */

        if(max_threads < 20)

                max_threads = 20;

        init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;

        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;

        init_task.signal->rlim[RLIMIT_SIGPENDING] =

                init_task.signal->rlim[RLIMIT_NPROC];

}

static struct task_struct *dup_task_struct(struct task_struct *orig)

{

        struct task_struct *tsk;

        struct thread_info *ti;

        int err;

        prepare_to_copy(orig);

        tsk = alloc_task_struct();

        if (!tsk)

                return NULL;

        ti = alloc_thread_info(tsk);

        if (!ti) {

                free_task_struct(tsk);

                return NULL;

        }

        *tsk = *orig;

        tsk->stack = ti;

        err = prop_local_init_single(&tsk->dirties);

        if (err) {

                free_thread_info(ti);

                free_task_struct(tsk);

                return NULL;

        }

        setup_thread_stack(tsk, orig);

#ifdef CONFIG_CC_STACKPROTECTOR

        tsk->stack_canary = get_random_int();

#endif

        /* One for us, one for whoever does the "release_task()" (usually parent) */

        atomic_set(&tsk->usage,2);

        atomic_set(&tsk->fs_excl, 0);

#ifdef CONFIG_BLK_DEV_IO_TRACE

        tsk->btrace_seq = 0;

#endif

        tsk->splice_pipe = NULL;

        return tsk;

}

#ifdef CONFIG_MMU

static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)

{

        struct vm_area_struct *mpnt, *tmp, **pprev;

        struct rb_node **rb_link, *rb_parent;

        int retval;

        unsigned long charge;

        struct mempolicy *pol;

        down_write(&oldmm->mmap_sem);

        flush_cache_dup_mm(oldmm);

        /*

         * Not linked in yet - no deadlock potential:

         */

        down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);

        mm->locked_vm = 0;

        mm->mmap = NULL;

        mm->mmap_cache = NULL;

        mm->free_area_cache = oldmm->mmap_base;

        mm->cached_hole_size = ~0UL;

        mm->map_count = 0;

        cpus_clear(mm->cpu_vm_mask);

        mm->mm_rb = RB_ROOT;

        rb_link = &mm->mm_rb.rb_node;

        rb_parent = NULL;

        pprev = &mm->mmap;

        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {

                struct file *file;

                if (mpnt->vm_flags & VM_DONTCOPY) {

                        long pages = vma_pages(mpnt);

                        mm->total_vm -= pages;

                        vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,

                                                                -pages);

                        continue;

                }

                charge = 0;

                if (mpnt->vm_flags & VM_ACCOUNT) {

                        unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;

                        if (security_vm_enough_memory(len))

                                goto fail_nomem;

                        charge = len;

                }

                tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);

                if (!tmp)

                        goto fail_nomem;

                *tmp = *mpnt;

                pol = mpol_copy(vma_policy(mpnt));

                retval = PTR_ERR(pol);

                if (IS_ERR(pol))

                        goto fail_nomem_policy;

                vma_set_policy(tmp, pol);

                tmp->vm_flags &= ~VM_LOCKED;

                tmp->vm_mm = mm;

                tmp->vm_next = NULL;

                anon_vma_link(tmp);

                file = tmp->vm_file;

                if (file) {

                        struct inode *inode = file->f_path.dentry->d_inode;

                        get_file(file);

                        if (tmp->vm_flags & VM_DENYWRITE)

                                atomic_dec(&inode->i_writecount);

                        /* insert tmp into the share list, just after mpnt */

                        spin_lock(&file->f_mapping->i_mmap_lock);

                        tmp->vm_truncate_count = mpnt->vm_truncate_count;

                        flush_dcache_mmap_lock(file->f_mapping);

                        vma_prio_tree_add(tmp, mpnt);

                        flush_dcache_mmap_unlock(file->f_mapping);

                        spin_unlock(&file->f_mapping->i_mmap_lock);

                }

                /*

                 * Link in the new vma and copy the page table entries.

                 */

                *pprev = tmp;

                pprev = &tmp->vm_next;

                __vma_link_rb(mm, tmp, rb_link, rb_parent);

                rb_link = &tmp->vm_rb.rb_right;

                rb_parent = &tmp->vm_rb;

                mm->map_count++;

                retval = copy_page_range(mm, oldmm, mpnt);

                if (tmp->vm_ops && tmp->vm_ops->open)

                        tmp->vm_ops->open(tmp);

                if (retval)

                        goto out;

        }

        /* a new mm has just been created */

        arch_dup_mmap(oldmm, mm);

        retval = 0;

out:

        up_write(&mm->mmap_sem);

        flush_tlb_mm(oldmm);

        up_write(&oldmm->mmap_sem);

        return retval;

fail_nomem_policy:

        kmem_cache_free(vm_area_cachep, tmp);

fail_nomem:

        retval = -ENOMEM;

        vm_unacct_memory(charge);

        goto out;

}

static inline int mm_alloc_pgd(struct mm_struct * mm)

{

        mm->pgd = pgd_alloc(mm);

        if (unlikely(!mm->pgd))

                return -ENOMEM;

        return 0;

}

static inline void mm_free_pgd(struct mm_struct * mm)

{

        pgd_free(mm->pgd);

}

#else

#define dup_mmap(mm, oldmm)     (0)

#define mm_alloc_pgd(mm)        (0)

#define mm_free_pgd(mm)

#endif /* CONFIG_MMU */

__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);

#define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))

#define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))

#include <linux/init_task.h>

static struct mm_struct * mm_init(struct mm_struct * mm)

{

        atomic_set(&mm->mm_users, 1);

        atomic_set(&mm->mm_count, 1);

        init_rwsem(&mm->mmap_sem);

        INIT_LIST_HEAD(&mm->mmlist);

        mm->flags = (current->mm) ? current->mm->flags

                                  : MMF_DUMP_FILTER_DEFAULT;

        mm->core_waiters = 0;

        mm->nr_ptes = 0;

        set_mm_counter(mm, file_rss, 0);

        set_mm_counter(mm, anon_rss, 0);

        spin_lock_init(&mm->page_table_lock);

        rwlock_init(&mm->ioctx_list_lock);

        mm->ioctx_list = NULL;

        mm->free_area_cache = TASK_UNMAPPED_BASE;

        mm->cached_hole_size = ~0UL;

        if (likely(!mm_alloc_pgd(mm))) {

                mm->def_flags = 0;

                return mm;

        }

        free_mm(mm);

        return NULL;

}

/*

 * Allocate and initialize an mm_struct.

 */

struct mm_struct * mm_alloc(void)

{

        struct mm_struct * mm;

        mm = allocate_mm();

        if (mm) {

                memset(mm, 0, sizeof(*mm));

                mm = mm_init(mm);

        }

        return mm;

}

/*

 * Called when the last reference to the mm

 * is dropped: either by a lazy thread or by

 * mmput. Free the page directory and the mm.

 */

void fastcall __mmdrop(struct mm_struct *mm)

{

        BUG_ON(mm == &init_mm);

        mm_free_pgd(mm);

        destroy_context(mm);

        free_mm(mm);

}

/*

 * Decrement the use count and release all resources for an mm.

 */

void mmput(struct mm_struct *mm)

{

        might_sleep();

        if (atomic_dec_and_test(&mm->mm_users)) {

                exit_aio(mm);

                exit_mmap(mm);

                if (!list_empty(&mm->mmlist)) {

                        spin_lock(&mmlist_lock);

                        list_del(&mm->mmlist);

                        spin_unlock(&mmlist_lock);

                }

                put_swap_token(mm);

                mmdrop(mm);

        }

}

EXPORT_SYMBOL_GPL(mmput);

/**

 * get_task_mm - acquire a reference to the task's mm

 *

 * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning

 * this kernel workthread has transiently adopted a user mm with use_mm,

 * to do its AIO) is not set and if so returns a reference to it, after

 * bumping up the use count.  User must release the mm via mmput()

 * after use.  Typically used by /proc and ptrace.

 */

struct mm_struct *get_task_mm(struct task_struct *task)

{

        struct mm_struct *mm;

        task_lock(task);

        mm = task->mm;

        if (mm) {

                if (task->flags & PF_BORROWED_MM)

                        mm = NULL;

                else

                        atomic_inc(&mm->mm_users);

        }

        task_unlock(task);

        return mm;

}

EXPORT_SYMBOL_GPL(get_task_mm);

/* Please note the differences between mmput and mm_release.

 * mmput is called whenever we stop holding onto a mm_struct,

 * error success whatever.

 *

 * mm_release is called after a mm_struct has been removed

 * from the current process.

 *

 * This difference is important for error handling, when we

 * only half set up a mm_struct for a new process and need to restore

 * the old one.  Because we mmput the new mm_struct before

 * restoring the old one. . .

 * Eric Biederman 10 January 1998

 */

void mm_release(struct task_struct *tsk, struct mm_struct *mm)

{

        struct completion *vfork_done = tsk->vfork_done;

        /* Get rid of any cached register state */

        deactivate_mm(tsk, mm);

        /* notify parent sleeping on vfork() */

        if (vfork_done) {

                tsk->vfork_done = NULL;

                complete(vfork_done);

        }

        /*

         * If we're exiting normally, clear a user-space tid field if

         * requested.  We leave this alone when dying by signal, to leave

         * the value intact in a core dump, and to save the unnecessary

         * trouble otherwise.  Userland only wants this done for a sys_exit.

         */

        if (tsk->clear_child_tid

            && !(tsk->flags & PF_SIGNALED)

            && atomic_read(&mm->mm_users) > 1) {

                u32 __user * tidptr = tsk->clear_child_tid;

                tsk->clear_child_tid = NULL;

                /*

                 * We don't check the error code - if userspace has

                 * not set up a proper pointer then tough luck.

                 */

                put_user(0, tidptr);

                sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);

        }

}

/*

 * Allocate a new mm structure and copy contents from the

 * mm structure of the passed in task structure.

 */

static struct mm_struct *dup_mm(struct task_struct *tsk)

{

        struct mm_struct *mm, *oldmm = current->mm;

        int err;

        if (!oldmm)

                return NULL;

        mm = allocate_mm();

        if (!mm)

                goto fail_nomem;

        memcpy(mm, oldmm, sizeof(*mm));

        /* Initializing for Swap token stuff */

        mm->token_priority = 0;

        mm->last_interval = 0;

        if (!mm_init(mm))

                goto fail_nomem;

        if (init_new_context(tsk, mm))

                goto fail_nocontext;

        err = dup_mmap(mm, oldmm);

        if (err)

                goto free_pt;

        mm->hiwater_rss = get_mm_rss(mm);

        mm->hiwater_vm = mm->total_vm;

        return mm;

free_pt:

        mmput(mm);

fail_nomem:

        return NULL;

fail_nocontext:

        /*

         * If init_new_context() failed, we cannot use mmput() to free the mm

         * because it calls destroy_context()

         */

        mm_free_pgd(mm);

        free_mm(mm);

        return NULL;

}

static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)

{

        struct mm_struct * mm, *oldmm;

        int retval;

        tsk->min_flt = tsk->maj_flt = 0;

        tsk->nvcsw = tsk->nivcsw = 0;

        tsk->mm = NULL;

        tsk->active_mm = NULL;

        /*

         * Are we cloning a kernel thread?

         *

         * We need to steal a active VM for that..

         */

        oldmm = current->mm;

        if (!oldmm)

                return 0;

        if (clone_flags & CLONE_VM) {

                atomic_inc(&oldmm->mm_users);

                mm = oldmm;

                goto good_mm;

        }

        retval = -ENOMEM;

        mm = dup_mm(tsk);

        if (!mm)

                goto fail_nomem;

good_mm:

        /* Initializing for Swap token stuff */

        mm->token_priority = 0;

        mm->last_interval = 0;

        tsk->mm = mm;

        tsk->active_mm = mm;

        return 0;

fail_nomem:

        return retval;

}

static struct fs_struct *__copy_fs_struct(struct fs_struct *old)

{

        struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);

        /* We don't need to lock fs - think why ;-) */

        if (fs) {

                atomic_set(&fs->count, 1);

                rwlock_init(&fs->lock);

                fs->umask = old->umask;

                read_lock(&old->lock);

                fs->rootmnt = mntget(old->rootmnt);

                fs->root = dget(old->root);

                fs->pwdmnt = mntget(old->pwdmnt);

                fs->pwd = dget(old->pwd);

                if (old->altroot) {

                        fs->altrootmnt = mntget(old->altrootmnt);

                        fs->altroot = dget(old->altroot);

                } else {

                        fs->altrootmnt = NULL;

                        fs->altroot = NULL;

                }

                read_unlock(&old->lock);

        }

        return fs;

}

struct fs_struct *copy_fs_struct(struct fs_struct *old)

{

        return __copy_fs_struct(old);

}

EXPORT_SYMBOL_GPL(copy_fs_struct);

static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)

{

        if (clone_flags & CLONE_FS) {

                atomic_inc(&current->fs->count);

                return 0;

        }

        tsk->fs = __copy_fs_struct(current->fs);

        if (!tsk->fs)

                return -ENOMEM;

        return 0;

}

static int count_open_files(struct fdtable *fdt)

{

        int size = fdt->max_fds;

        int i;

        /* Find the last open fd */

        for (i = size/(8*sizeof(long)); i > 0; ) {

                if (fdt->open_fds->fds_bits[--i])

                        break;

        }

        i = (i+1) * 8 * sizeof(long);

        return i;

}

static struct files_struct *alloc_files(void)

{

        struct files_struct *newf;

        struct fdtable *fdt;

        newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);

        if (!newf)

                goto out;

        atomic_set(&newf->count, 1);

        spin_lock_init(&newf->file_lock);

        newf->next_fd = 0;

        fdt = &newf->fdtab;

        fdt->max_fds = NR_OPEN_DEFAULT;

        fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;

        fdt->open_fds = (fd_set *)&newf->open_fds_init;

        fdt->fd = &newf->fd_array[0];

        INIT_RCU_HEAD(&fdt->rcu);

        fdt->next = NULL;

        rcu_assign_pointer(newf->fdt, fdt);

out:

        return newf;

}

/*

 * Allocate a new files structure and copy contents from the

 * passed in files structure.

 * errorp will be valid only when the returned files_struct is NULL.

 */

static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)

{

        struct files_struct *newf;

        struct file **old_fds, **new_fds;

        int open_files, size, i;

        struct fdtable *old_fdt, *new_fdt;

        *errorp = -ENOMEM;

        newf = alloc_files();

        if (!newf)

                goto out;

        spin_lock(&oldf->file_lock);

        old_fdt = files_fdtable(oldf);

        new_fdt = files_fdtable(newf);

        open_files = count_open_files(old_fdt);

        /*

         * Check whether we need to allocate a larger fd array and fd set.

         * Note: we're not a clone task, so the open count won't change.

         */