diff options
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 1775 |
1 files changed, 1775 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c new file mode 100644 index 00000000..fa6030d9 --- /dev/null +++ b/kernel/fork.c @@ -0,0 +1,1775 @@ +/* + * 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/personality.h> +#include <linux/mempolicy.h> +#include <linux/sem.h> +#include <linux/file.h> +#include <linux/fdtable.h> +#include <linux/iocontext.h> +#include <linux/key.h> +#include <linux/binfmts.h> +#include <linux/mman.h> +#include <linux/mmu_notifier.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/hugetlb.h> +#include <linux/swap.h> +#include <linux/syscalls.h> +#include <linux/jiffies.h> +#include <linux/tracehook.h> +#include <linux/futex.h> +#include <linux/compat.h> +#include <linux/kthread.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/memcontrol.h> +#include <linux/ftrace.h> +#include <linux/proc_fs.h> +#include <linux/profile.h> +#include <linux/rmap.h> +#include <linux/ksm.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/blkdev.h> +#include <linux/fs_struct.h> +#include <linux/magic.h> +#include <linux/perf_event.h> +#include <linux/posix-timers.h> +#include <linux/user-return-notifier.h> +#include <linux/oom.h> +#include <linux/khugepaged.h> +#include <linux/signalfd.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> + +#include <trace/events/sched.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 */ + +#ifdef CONFIG_PROVE_RCU +int lockdep_tasklist_lock_is_held(void) +{ + return lockdep_is_held(&tasklist_lock); +} +EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); +#endif /* #ifdef CONFIG_PROVE_RCU */ + +int nr_processes(void) +{ + int cpu; + int total = 0; + + for_each_possible_cpu(cpu) + total += per_cpu(process_counts, cpu); + + return total; +} + +#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR +# define alloc_task_struct_node(node) \ + kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node) +# define free_task_struct(tsk) \ + kmem_cache_free(task_struct_cachep, (tsk)) +static struct kmem_cache *task_struct_cachep; +#endif + +#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR +static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, + int node) +{ +#ifdef CONFIG_DEBUG_STACK_USAGE + gfp_t mask = GFP_KERNEL | __GFP_ZERO; +#else + gfp_t mask = GFP_KERNEL; +#endif + struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER); + + return page ? page_address(page) : NULL; +} + +static inline void free_thread_info(struct thread_info *ti) +{ + free_pages((unsigned long)ti, THREAD_SIZE_ORDER); +} +#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; + +/* Notifier list called when a task struct is freed */ +static ATOMIC_NOTIFIER_HEAD(task_free_notifier); + +static void account_kernel_stack(struct thread_info *ti, int account) +{ + struct zone *zone = page_zone(virt_to_page(ti)); + + mod_zone_page_state(zone, NR_KERNEL_STACK, account); +} + +void free_task(struct task_struct *tsk) +{ + prop_local_destroy_single(&tsk->dirties); + account_kernel_stack(tsk->stack, -1); + free_thread_info(tsk->stack); + rt_mutex_debug_task_free(tsk); + ftrace_graph_exit_task(tsk); + free_task_struct(tsk); +} +EXPORT_SYMBOL(free_task); + +static inline void free_signal_struct(struct signal_struct *sig) +{ + taskstats_tgid_free(sig); + sched_autogroup_exit(sig); + kmem_cache_free(signal_cachep, sig); +} + +static inline void put_signal_struct(struct signal_struct *sig) +{ + if (atomic_dec_and_test(&sig->sigcnt)) + free_signal_struct(sig); +} + +int task_free_register(struct notifier_block *n) +{ + return atomic_notifier_chain_register(&task_free_notifier, n); +} +EXPORT_SYMBOL(task_free_register); + +int task_free_unregister(struct notifier_block *n) +{ + return atomic_notifier_chain_unregister(&task_free_notifier, n); +} +EXPORT_SYMBOL(task_free_unregister); + +void __put_task_struct(struct task_struct *tsk) +{ + WARN_ON(!tsk->exit_state); + WARN_ON(atomic_read(&tsk->usage)); + WARN_ON(tsk == current); + + exit_creds(tsk); + delayacct_tsk_free(tsk); + put_signal_struct(tsk->signal); + + atomic_notifier_call_chain(&task_free_notifier, 0, tsk); + if (!profile_handoff_task(tsk)) + free_task(tsk); +} +EXPORT_SYMBOL_GPL(__put_task_struct); + +/* + * macro override instead of weak attribute alias, to workaround + * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. + */ +#ifndef arch_task_cache_init +#define arch_task_cache_init() +#endif + +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 | SLAB_NOTRACK, NULL); +#endif + + /* do the arch specific task caches init */ + arch_task_cache_init(); + + /* + * 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]; +} + +int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, + struct task_struct *src) +{ + *dst = *src; + return 0; +} + +static struct task_struct *dup_task_struct(struct task_struct *orig) +{ + struct task_struct *tsk; + struct thread_info *ti; + unsigned long *stackend; + int node = tsk_fork_get_node(orig); + int err; + + prepare_to_copy(orig); + + tsk = alloc_task_struct_node(node); + if (!tsk) + return NULL; + + ti = alloc_thread_info_node(tsk, node); + if (!ti) { + free_task_struct(tsk); + return NULL; + } + + err = arch_dup_task_struct(tsk, orig); + if (err) + goto out; + + tsk->stack = ti; + + err = prop_local_init_single(&tsk->dirties); + if (err) + goto out; + + setup_thread_stack(tsk, orig); + clear_user_return_notifier(tsk); + clear_tsk_need_resched(tsk); + stackend = end_of_stack(tsk); + *stackend = STACK_END_MAGIC; /* for overflow detection */ + +#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; + + account_kernel_stack(ti, 1); + + return tsk; + +out: + free_thread_info(ti); + free_task_struct(tsk); + return NULL; +} + +#ifdef CONFIG_MMU +static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) +{ + struct vm_area_struct *mpnt, *tmp, *prev, **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; + cpumask_clear(mm_cpumask(mm)); + mm->mm_rb = RB_ROOT; + rb_link = &mm->mm_rb.rb_node; + rb_parent = NULL; + pprev = &mm->mmap; + retval = ksm_fork(mm, oldmm); + if (retval) + goto out; + retval = khugepaged_fork(mm, oldmm); + if (retval) + goto out; + + prev = NULL; + 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; + INIT_LIST_HEAD(&tmp->anon_vma_chain); + pol = mpol_dup(vma_policy(mpnt)); + retval = PTR_ERR(pol); + if (IS_ERR(pol)) + goto fail_nomem_policy; + vma_set_policy(tmp, pol); + tmp->vm_mm = mm; + if (anon_vma_fork(tmp, mpnt)) + goto fail_nomem_anon_vma_fork; + tmp->vm_flags &= ~VM_LOCKED; + tmp->vm_next = tmp->vm_prev = NULL; + file = tmp->vm_file; + if (file) { + struct inode *inode = file->f_path.dentry->d_inode; + struct address_space *mapping = file->f_mapping; + + get_file(file); + if (tmp->vm_flags & VM_DENYWRITE) + atomic_dec(&inode->i_writecount); + mutex_lock(&mapping->i_mmap_mutex); + if (tmp->vm_flags & VM_SHARED) + mapping->i_mmap_writable++; + flush_dcache_mmap_lock(mapping); + /* insert tmp into the share list, just after mpnt */ + vma_prio_tree_add(tmp, mpnt); + flush_dcache_mmap_unlock(mapping); + mutex_unlock(&mapping->i_mmap_mutex); + } + + /* + * Clear hugetlb-related page reserves for children. This only + * affects MAP_PRIVATE mappings. Faults generated by the child + * are not guaranteed to succeed, even if read-only + */ + if (is_vm_hugetlb_page(tmp)) + reset_vma_resv_huge_pages(tmp); + + /* + * Link in the new vma and copy the page table entries. + */ + *pprev = tmp; + pprev = &tmp->vm_next; + tmp->vm_prev = prev; + prev = tmp; + + __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_anon_vma_fork: + mpol_put(pol); +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, 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))) + +static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; + +static int __init coredump_filter_setup(char *s) +{ + default_dump_filter = + (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & + MMF_DUMP_FILTER_MASK; + return 1; +} + +__setup("coredump_filter=", coredump_filter_setup); + +#include <linux/init_task.h> + +static void mm_init_aio(struct mm_struct *mm) +{ +#ifdef CONFIG_AIO + spin_lock_init(&mm->ioctx_lock); + INIT_HLIST_HEAD(&mm->ioctx_list); +#endif +} + +static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) +{ + 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_INIT_MASK) : default_dump_filter; + mm->core_state = NULL; + mm->nr_ptes = 0; + memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); + spin_lock_init(&mm->page_table_lock); + mm->free_area_cache = TASK_UNMAPPED_BASE; + mm->cached_hole_size = ~0UL; + mm_init_aio(mm); + mm_init_owner(mm, p); + atomic_set(&mm->oom_disable_count, 0); + + if (likely(!mm_alloc_pgd(mm))) { + mm->def_flags = 0; + mmu_notifier_mm_init(mm); + 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) + return NULL; + + memset(mm, 0, sizeof(*mm)); + mm_init_cpumask(mm); + return mm_init(mm, current); +} + +/* + * 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 __mmdrop(struct mm_struct *mm) +{ + BUG_ON(mm == &init_mm); + mm_free_pgd(mm); + destroy_context(mm); + mmu_notifier_mm_destroy(mm); +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + VM_BUG_ON(mm->pmd_huge_pte); +#endif + free_mm(mm); +} +EXPORT_SYMBOL_GPL(__mmdrop); + +/* + * 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); + ksm_exit(mm); + khugepaged_exit(mm); /* must run before exit_mmap */ + exit_mmap(mm); + set_mm_exe_file(mm, NULL); + if (!list_empty(&mm->mmlist)) { + spin_lock(&mmlist_lock); + list_del(&mm->mmlist); + spin_unlock(&mmlist_lock); + } + put_swap_token(mm); + if (mm->binfmt) + module_put(mm->binfmt->module); + mmdrop(mm); + } +} +EXPORT_SYMBOL_GPL(mmput); + +/* + * We added or removed a vma mapping the executable. The vmas are only mapped + * during exec and are not mapped with the mmap system call. + * Callers must hold down_write() on the mm's mmap_sem for these + */ +void added_exe_file_vma(struct mm_struct *mm) +{ + mm->num_exe_file_vmas++; +} + +void removed_exe_file_vma(struct mm_struct *mm) +{ + mm->num_exe_file_vmas--; + if ((mm->num_exe_file_vmas == 0) && mm->exe_file){ + fput(mm->exe_file); + mm->exe_file = NULL; + } + +} + +void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) +{ + if (new_exe_file) + get_file(new_exe_file); + if (mm->exe_file) + fput(mm->exe_file); + mm->exe_file = new_exe_file; + mm->num_exe_file_vmas = 0; +} + +struct file *get_mm_exe_file(struct mm_struct *mm) +{ + struct file *exe_file; + + /* We need mmap_sem to protect against races with removal of + * VM_EXECUTABLE vmas */ + down_read(&mm->mmap_sem); + exe_file = mm->exe_file; + if (exe_file) + get_file(exe_file); + up_read(&mm->mmap_sem); + return exe_file; +} + +static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) +{ + /* It's safe to write the exe_file pointer without exe_file_lock because + * this is called during fork when the task is not yet in /proc */ + newmm->exe_file = get_mm_exe_file(oldmm); +} + +/** + * get_task_mm - acquire a reference to the task's mm + * + * Returns %NULL if the task has no mm. Checks PF_KTHREAD (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_KTHREAD) + 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 futexes when releasing the mm */ +#ifdef CONFIG_FUTEX + if (unlikely(tsk->robust_list)) { + exit_robust_list(tsk); + tsk->robust_list = NULL; + } +#ifdef CONFIG_COMPAT + if (unlikely(tsk->compat_robust_list)) { + compat_exit_robust_list(tsk); + tsk->compat_robust_list = NULL; + } +#endif + if (unlikely(!list_empty(&tsk->pi_state_list))) + exit_pi_state_list(tsk); +#endif + + /* 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) { + if (!(tsk->flags & PF_SIGNALED) && + atomic_read(&mm->mm_users) > 1) { + /* + * We don't check the error code - if userspace has + * not set up a proper pointer then tough luck. + */ + put_user(0, tsk->clear_child_tid); + sys_futex(tsk->clear_child_tid, FUTEX_WAKE, + 1, NULL, NULL, 0); + } + tsk->clear_child_tid = NULL; + } +} + +/* + * Allocate a new mm structure and copy contents from the + * mm structure of the passed in task structure. + */ +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)); + mm_init_cpumask(mm); + + /* Initializing for Swap token stuff */ + mm->token_priority = 0; + mm->last_interval = 0; + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + mm->pmd_huge_pte = NULL; +#endif + + if (!mm_init(mm, tsk)) + goto fail_nomem; + + if (init_new_context(tsk, mm)) + goto fail_nocontext; + + dup_mm_exe_file(oldmm, mm); + + err = dup_mmap(mm, oldmm); + if (err) + goto free_pt; + + mm->hiwater_rss = get_mm_rss(mm); + mm->hiwater_vm = mm->total_vm; + + if (mm->binfmt && !try_module_get(mm->binfmt->module)) + goto free_pt; + + return mm; + +free_pt: + /* don't put binfmt in mmput, we haven't got module yet */ + mm->binfmt = NULL; + 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; +#ifdef CONFIG_DETECT_HUNG_TASK + tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; +#endif + + 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; + if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) + atomic_inc(&mm->oom_disable_count); + + tsk->mm = mm; + tsk->active_mm = mm; + return 0; + +fail_nomem: + return retval; +} + +static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) +{ + struct fs_struct *fs = current->fs; + if (clone_flags & CLONE_FS) { + /* tsk->fs is already what we want */ + spin_lock(&fs->lock); + if (fs->in_exec) { + spin_unlock(&fs->lock); + return -EAGAIN; + } + fs->users++; + spin_unlock(&fs->lock); + return 0; + } + tsk->fs = copy_fs_struct(fs); + if (!tsk->fs) + return -ENOMEM; + return 0; +} + +static int copy_files(unsigned long clone_flags, struct task_struct * tsk) +{ + struct files_struct *oldf, *newf; + int error = 0; + + /* + * A background process may not have any files ... + */ + oldf = current->files; + if (!oldf) + goto out; + + if (clone_flags & CLONE_FILES) { + atomic_inc(&oldf->count); + goto out; + } + + newf = dup_fd(oldf, &error); + if (!newf) + goto out; + + tsk->files = newf; + error = 0; +out: + return error; +} + +static int copy_io(unsigned long clone_flags, struct task_struct *tsk) +{ +#ifdef CONFIG_BLOCK + struct io_context *ioc = current->io_context; + + if (!ioc) + return 0; + /* + * Share io context with parent, if CLONE_IO is set + */ + if (clone_flags & CLONE_IO) { + tsk->io_context = ioc_task_link(ioc); + if (unlikely(!tsk->io_context)) + return -ENOMEM; + } else if (ioprio_valid(ioc->ioprio)) { + tsk->io_context = alloc_io_context(GFP_KERNEL, -1); + if (unlikely(!tsk->io_context)) + return -ENOMEM; + + tsk->io_context->ioprio = ioc->ioprio; + } +#endif + return 0; +} + +static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) +{ + struct sighand_struct *sig; + + if (clone_flags & CLONE_SIGHAND) { + atomic_inc(¤t->sighand->count); + return 0; + } + sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); + rcu_assign_pointer(tsk->sighand, sig); + if (!sig) + return -ENOMEM; + atomic_set(&sig->count, 1); + memcpy(sig->action, current->sighand->action, sizeof(sig->action)); + return 0; +} + +void __cleanup_sighand(struct sighand_struct *sighand) +{ + if (atomic_dec_and_test(&sighand->count)) { + signalfd_cleanup(sighand); + kmem_cache_free(sighand_cachep, sighand); + } +} + + +/* + * Initialize POSIX timer handling for a thread group. + */ +static void posix_cpu_timers_init_group(struct signal_struct *sig) +{ + unsigned long cpu_limit; + + /* Thread group counters. */ + thread_group_cputime_init(sig); + + cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); + if (cpu_limit != RLIM_INFINITY) { + sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); + sig->cputimer.running = 1; + } + + /* The timer lists. */ + INIT_LIST_HEAD(&sig->cpu_timers[0]); + INIT_LIST_HEAD(&sig->cpu_timers[1]); + INIT_LIST_HEAD(&sig->cpu_timers[2]); +} + +static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) +{ + struct signal_struct *sig; + + if (clone_flags & CLONE_THREAD) + return 0; + + sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); + tsk->signal = sig; + if (!sig) + return -ENOMEM; + + sig->nr_threads = 1; + atomic_set(&sig->live, 1); + atomic_set(&sig->sigcnt, 1); + init_waitqueue_head(&sig->wait_chldexit); + if (clone_flags & CLONE_NEWPID) + sig->flags |= SIGNAL_UNKILLABLE; + sig->curr_target = tsk; + init_sigpending(&sig->shared_pending); + INIT_LIST_HEAD(&sig->posix_timers); + + hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + sig->real_timer.function = it_real_fn; + + task_lock(current->group_leader); + memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); + task_unlock(current->group_leader); + + posix_cpu_timers_init_group(sig); + + tty_audit_fork(sig); + sched_autogroup_fork(sig); + +#ifdef CONFIG_CGROUPS + init_rwsem(&sig->threadgroup_fork_lock); +#endif + + sig->oom_adj = current->signal->oom_adj; + sig->oom_score_adj = current->signal->oom_score_adj; + sig->oom_score_adj_min = current->signal->oom_score_adj_min; + + mutex_init(&sig->cred_guard_mutex); + + return 0; +} + +static void copy_flags(unsigned long clone_flags, struct task_struct *p) +{ + unsigned long new_flags = p->flags; + + new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); + new_flags |= PF_FORKNOEXEC; + new_flags |= PF_STARTING; + p->flags = new_flags; + clear_freeze_flag(p); +} + +SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) +{ + current->clear_child_tid = tidptr; + + return task_pid_vnr(current); +} + +static void rt_mutex_init_task(struct task_struct *p) +{ + raw_spin_lock_init(&p->pi_lock); +#ifdef CONFIG_RT_MUTEXES + plist_head_init(&p->pi_waiters); + p->pi_blocked_on = NULL; +#endif +} + +#ifdef CONFIG_MM_OWNER +void mm_init_owner(struct mm_struct *mm, struct task_struct *p) +{ + mm->owner = p; +} +#endif /* CONFIG_MM_OWNER */ + +/* + * Initialize POSIX timer handling for a single task. + */ +static void posix_cpu_timers_init(struct task_struct *tsk) +{ + tsk->cputime_expires.prof_exp = cputime_zero; + tsk->cputime_expires.virt_exp = cputime_zero; + tsk->cputime_expires.sched_exp = 0; + INIT_LIST_HEAD(&tsk->cpu_timers[0]); + INIT_LIST_HEAD(&tsk->cpu_timers[1]); + INIT_LIST_HEAD(&tsk->cpu_timers[2]); +} + +/* + * This creates a new process as a copy of the old one, + * but does not actually start it yet. + * + * It copies the registers, and all the appropriate + * parts of the process environment (as per the clone + * flags). The actual kick-off is left to the caller. + */ +static struct task_struct *copy_process(unsigned long clone_flags, + unsigned long stack_start, + struct pt_regs *regs, + unsigned long stack_size, + int __user *child_tidptr, + struct pid *pid, + int trace) +{ + int retval; + struct task_struct *p; + int cgroup_callbacks_done = 0; + + if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) + return ERR_PTR(-EINVAL); + + /* + * Thread groups must share signals as well, and detached threads + * can only be started up within the thread group. + */ + if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) + return ERR_PTR(-EINVAL); + + /* + * Shared signal handlers imply shared VM. By way of the above, + * thread groups also imply shared VM. Blocking this case allows + * for various simplifications in other code. + */ + if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) + return ERR_PTR(-EINVAL); + + /* + * Siblings of global init remain as zombies on exit since they are + * not reaped by their parent (swapper). To solve this and to avoid + * multi-rooted process trees, prevent global and container-inits + * from creating siblings. + */ + if ((clone_flags & CLONE_PARENT) && + current->signal->flags & SIGNAL_UNKILLABLE) + return ERR_PTR(-EINVAL); + + retval = security_task_create(clone_flags); + if (retval) + goto fork_out; + + retval = -ENOMEM; + p = dup_task_struct(current); + if (!p) + goto fork_out; + + ftrace_graph_init_task(p); + + rt_mutex_init_task(p); + +#ifdef CONFIG_PROVE_LOCKING + DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); + DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); +#endif + retval = -EAGAIN; + if (atomic_read(&p->real_cred->user->processes) >= + task_rlimit(p, RLIMIT_NPROC)) { + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && + p->real_cred->user != INIT_USER) + goto bad_fork_free; + } + + retval = copy_creds(p, clone_flags); + if (retval < 0) + goto bad_fork_free; + + /* + * If multiple threads are within copy_process(), then this check + * triggers too late. This doesn't hurt, the check is only there + * to stop root fork bombs. + */ + retval = -EAGAIN; + if (nr_threads >= max_threads) + goto bad_fork_cleanup_count; + + if (!try_module_get(task_thread_info(p)->exec_domain->module)) + goto bad_fork_cleanup_count; + + p->did_exec = 0; + delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ + copy_flags(clone_flags, p); + INIT_LIST_HEAD(&p->children); + INIT_LIST_HEAD(&p->sibling); + rcu_copy_process(p); + p->vfork_done = NULL; + spin_lock_init(&p->alloc_lock); + + init_sigpending(&p->pending); + + p->utime = cputime_zero; + p->stime = cputime_zero; + p->gtime = cputime_zero; + p->utimescaled = cputime_zero; + p->stimescaled = cputime_zero; +#ifndef CONFIG_VIRT_CPU_ACCOUNTING + p->prev_utime = cputime_zero; + p->prev_stime = cputime_zero; +#endif +#if defined(SPLIT_RSS_COUNTING) + memset(&p->rss_stat, 0, sizeof(p->rss_stat)); +#endif + + p->default_timer_slack_ns = current->timer_slack_ns; + + task_io_accounting_init(&p->ioac); + acct_clear_integrals(p); + + posix_cpu_timers_init(p); + + do_posix_clock_monotonic_gettime(&p->start_time); + p->real_start_time = p->start_time; + monotonic_to_bootbased(&p->real_start_time); + p->io_context = NULL; + p->audit_context = NULL; + if (clone_flags & CLONE_THREAD) + threadgroup_fork_read_lock(current); + cgroup_fork(p); +#ifdef CONFIG_NUMA + p->mempolicy = mpol_dup(p->mempolicy); + if (IS_ERR(p->mempolicy)) { + retval = PTR_ERR(p->mempolicy); + p->mempolicy = NULL; + goto bad_fork_cleanup_cgroup; + } + mpol_fix_fork_child_flag(p); +#endif +#ifdef CONFIG_TRACE_IRQFLAGS + p->irq_events = 0; +#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW + p->hardirqs_enabled = 1; +#else + p->hardirqs_enabled = 0; +#endif + p->hardirq_enable_ip = 0; + p->hardirq_enable_event = 0; + p->hardirq_disable_ip = _THIS_IP_; + p->hardirq_disable_event = 0; + p->softirqs_enabled = 1; + p->softirq_enable_ip = _THIS_IP_; + p->softirq_enable_event = 0; + p->softirq_disable_ip = 0; + p->softirq_disable_event = 0; + p->hardirq_context = 0; + p->softirq_context = 0; +#endif +#ifdef CONFIG_LOCKDEP + p->lockdep_depth = 0; /* no locks held yet */ + p->curr_chain_key = 0; + p->lockdep_recursion = 0; +#endif + +#ifdef CONFIG_DEBUG_MUTEXES + p->blocked_on = NULL; /* not blocked yet */ +#endif +#ifdef CONFIG_CGROUP_MEM_RES_CTLR + p->memcg_batch.do_batch = 0; + p->memcg_batch.memcg = NULL; +#endif + + /* Perform scheduler related setup. Assign this task to a CPU. */ + sched_fork(p); + + retval = perf_event_init_task(p); + if (retval) + goto bad_fork_cleanup_policy; + + if ((retval = audit_alloc(p))) + goto bad_fork_cleanup_policy; + /* copy all the process information */ + if ((retval = copy_semundo(clone_flags, p))) + goto bad_fork_cleanup_audit; + if ((retval = copy_files(clone_flags, p))) + goto bad_fork_cleanup_semundo; + if ((retval = copy_fs(clone_flags, p))) + goto bad_fork_cleanup_files; + if ((retval = copy_sighand(clone_flags, p))) + goto bad_fork_cleanup_fs; + if ((retval = copy_signal(clone_flags, p))) + goto bad_fork_cleanup_sighand; + if ((retval = copy_mm(clone_flags, p))) + goto bad_fork_cleanup_signal; + if ((retval = copy_namespaces(clone_flags, p))) + goto bad_fork_cleanup_mm; + if ((retval = copy_io(clone_flags, p))) + goto bad_fork_cleanup_namespaces; + retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); + if (retval) + goto bad_fork_cleanup_io; + + if (pid != &init_struct_pid) { + retval = -ENOMEM; + pid = alloc_pid(p->nsproxy->pid_ns); + if (!pid) + goto bad_fork_cleanup_io; + } + + p->pid = pid_nr(pid); + p->tgid = p->pid; + if (clone_flags & CLONE_THREAD) + p->tgid = current->tgid; + + p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; + /* + * Clear TID on mm_release()? + */ + p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; +#ifdef CONFIG_BLOCK + p->plug = NULL; +#endif +#ifdef CONFIG_FUTEX + p->robust_list = NULL; +#ifdef CONFIG_COMPAT + p->compat_robust_list = NULL; +#endif + INIT_LIST_HEAD(&p->pi_state_list); + p->pi_state_cache = NULL; +#endif + /* + * sigaltstack should be cleared when sharing the same VM + */ + if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) + p->sas_ss_sp = p->sas_ss_size = 0; + + /* + * Syscall tracing and stepping should be turned off in the + * child regardless of CLONE_PTRACE. + */ + user_disable_single_step(p); + clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); +#ifdef TIF_SYSCALL_EMU + clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); +#endif + clear_all_latency_tracing(p); + + /* ok, now we should be set up.. */ + p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); + p->pdeath_signal = 0; + p->exit_state = 0; + + /* + * Ok, make it visible to the rest of the system. + * We dont wake it up yet. + */ + p->group_leader = p; + INIT_LIST_HEAD(&p->thread_group); + + /* Now that the task is set up, run cgroup callbacks if + * necessary. We need to run them before the task is visible + * on the tasklist. */ + cgroup_fork_callbacks(p); + cgroup_callbacks_done = 1; + + /* Need tasklist lock for parent etc handling! */ + write_lock_irq(&tasklist_lock); + + /* CLONE_PARENT re-uses the old parent */ + if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { + p->real_parent = current->real_parent; + p->parent_exec_id = current->parent_exec_id; + } else { + p->real_parent = current; + p->parent_exec_id = current->self_exec_id; + } + + spin_lock(¤t->sighand->siglock); + + /* + * Process group and session signals need to be delivered to just the + * parent before the fork or both the parent and the child after the + * fork. Restart if a signal comes in before we add the new process to + * it's process group. + * A fatal signal pending means that current will exit, so the new + * thread can't slip out of an OOM kill (or normal SIGKILL). + */ + recalc_sigpending(); + if (signal_pending(current)) { + spin_unlock(¤t->sighand->siglock); + write_unlock_irq(&tasklist_lock); + retval = -ERESTARTNOINTR; + goto bad_fork_free_pid; + } + + if (clone_flags & CLONE_THREAD) { + current->signal->nr_threads++; + atomic_inc(¤t->signal->live); + atomic_inc(¤t->signal->sigcnt); + p->group_leader = current->group_leader; + list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); + } + + if (likely(p->pid)) { + tracehook_finish_clone(p, clone_flags, trace); + + if (thread_group_leader(p)) { + if (is_child_reaper(pid)) + p->nsproxy->pid_ns->child_reaper = p; + + p->signal->leader_pid = pid; + p->signal->tty = tty_kref_get(current->signal->tty); + attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); + attach_pid(p, PIDTYPE_SID, task_session(current)); + list_add_tail(&p->sibling, &p->real_parent->children); + list_add_tail_rcu(&p->tasks, &init_task.tasks); + __this_cpu_inc(process_counts); + } + attach_pid(p, PIDTYPE_PID, pid); + nr_threads++; + } + + total_forks++; + spin_unlock(¤t->sighand->siglock); + write_unlock_irq(&tasklist_lock); + proc_fork_connector(p); + cgroup_post_fork(p); + if (clone_flags & CLONE_THREAD) + threadgroup_fork_read_unlock(current); + perf_event_fork(p); + return p; + +bad_fork_free_pid: + if (pid != &init_struct_pid) + free_pid(pid); +bad_fork_cleanup_io: + if (p->io_context) + exit_io_context(p); +bad_fork_cleanup_namespaces: + if (unlikely(clone_flags & CLONE_NEWPID)) + pid_ns_release_proc(p->nsproxy->pid_ns); + exit_task_namespaces(p); +bad_fork_cleanup_mm: + if (p->mm) { + task_lock(p); + if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) + atomic_dec(&p->mm->oom_disable_count); + task_unlock(p); + mmput(p->mm); + } +bad_fork_cleanup_signal: + if (!(clone_flags & CLONE_THREAD)) + free_signal_struct(p->signal); +bad_fork_cleanup_sighand: + __cleanup_sighand(p->sighand); +bad_fork_cleanup_fs: + exit_fs(p); /* blocking */ +bad_fork_cleanup_files: + exit_files(p); /* blocking */ +bad_fork_cleanup_semundo: + exit_sem(p); +bad_fork_cleanup_audit: + audit_free(p); +bad_fork_cleanup_policy: + perf_event_free_task(p); +#ifdef CONFIG_NUMA + mpol_put(p->mempolicy); +bad_fork_cleanup_cgroup: +#endif + if (clone_flags & CLONE_THREAD) + threadgroup_fork_read_unlock(current); + cgroup_exit(p, cgroup_callbacks_done); + delayacct_tsk_free(p); + module_put(task_thread_info(p)->exec_domain->module); +bad_fork_cleanup_count: + atomic_dec(&p->cred->user->processes); + exit_creds(p); +bad_fork_free: + free_task(p); +fork_out: + return ERR_PTR(retval); +} + +noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) +{ + memset(regs, 0, sizeof(struct pt_regs)); + return regs; +} + +static inline void init_idle_pids(struct pid_link *links) +{ + enum pid_type type; + + for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { + INIT_HLIST_NODE(&links[type].node); /* not really needed */ + links[type].pid = &init_struct_pid; + } +} + +struct task_struct * __cpuinit fork_idle(int cpu) +{ + struct task_struct *task; + struct pt_regs regs; + + task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, + &init_struct_pid, 0); + if (!IS_ERR(task)) { + init_idle_pids(task->pids); + init_idle(task, cpu); + } + + return task; +} + +/* + * Ok, this is the main fork-routine. + * + * It copies the process, and if successful kick-starts + * it and waits for it to finish using the VM if required. + */ +long do_fork(unsigned long clone_flags, + unsigned long stack_start, + struct pt_regs *regs, + unsigned long stack_size, + int __user *parent_tidptr, + int __user *child_tidptr) +{ + struct task_struct *p; + int trace = 0; + long nr; + + /* + * Do some preliminary argument and permissions checking before we + * actually start allocating stuff + */ + if (clone_flags & CLONE_NEWUSER) { + if (clone_flags & CLONE_THREAD) + return -EINVAL; + /* hopefully this check will go away when userns support is + * complete + */ + if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || + !capable(CAP_SETGID)) + return -EPERM; + } + + /* + * When called from kernel_thread, don't do user tracing stuff. + */ + if (likely(user_mode(regs))) + trace = tracehook_prepare_clone(clone_flags); + + p = copy_process(clone_flags, stack_start, regs, stack_size, + child_tidptr, NULL, trace); + /* + * Do this prior waking up the new thread - the thread pointer + * might get invalid after that point, if the thread exits quickly. + */ + if (!IS_ERR(p)) { + struct completion vfork; + + trace_sched_process_fork(current, p); + + nr = task_pid_vnr(p); + + if (clone_flags & CLONE_PARENT_SETTID) + put_user(nr, parent_tidptr); + + if (clone_flags & CLONE_VFORK) { + p->vfork_done = &vfork; + init_completion(&vfork); + } + + audit_finish_fork(p); + tracehook_report_clone(regs, clone_flags, nr, p); + + /* + * We set PF_STARTING at creation in case tracing wants to + * use this to distinguish a fully live task from one that + * hasn't gotten to tracehook_report_clone() yet. Now we + * clear it and set the child going. + */ + p->flags &= ~PF_STARTING; + + wake_up_new_task(p); + + tracehook_report_clone_complete(trace, regs, + clone_flags, nr, p); + + if (clone_flags & CLONE_VFORK) { + freezer_do_not_count(); + wait_for_completion(&vfork); + freezer_count(); + tracehook_report_vfork_done(p, nr); + } + } else { + nr = PTR_ERR(p); + } + return nr; +} + +#ifndef ARCH_MIN_MMSTRUCT_ALIGN +#define ARCH_MIN_MMSTRUCT_ALIGN 0 +#endif + +static void sighand_ctor(void *data) +{ + struct sighand_struct *sighand = data; + + spin_lock_init(&sighand->siglock); + init_waitqueue_head(&sighand->signalfd_wqh); +} + +void __init proc_caches_init(void) +{ + sighand_cachep = kmem_cache_create("sighand_cache", + sizeof(struct sighand_struct), 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| + SLAB_NOTRACK, sighand_ctor); + signal_cachep = kmem_cache_create("signal_cache", + sizeof(struct signal_struct), 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); + files_cachep = kmem_cache_create("files_cache", + sizeof(struct files_struct), 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); + fs_cachep = kmem_cache_create("fs_cache", + sizeof(struct fs_struct), 0, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); + /* + * FIXME! The "sizeof(struct mm_struct)" currently includes the + * whole struct cpumask for the OFFSTACK case. We could change + * this to *only* allocate as much of it as required by the + * maximum number of CPU's we can ever have. The cpumask_allocation + * is at the end of the structure, exactly for that reason. + */ + mm_cachep = kmem_cache_create("mm_struct", + sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); + vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); + mmap_init(); +} + +/* + * Check constraints on flags passed to the unshare system call. + */ +static int check_unshare_flags(unsigned long unshare_flags) +{ + if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| + CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| + CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) + return -EINVAL; + /* + * Not implemented, but pretend it works if there is nothing to + * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND + * needs to unshare vm. + */ + if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { + /* FIXME: get_task_mm() increments ->mm_users */ + if (atomic_read(¤t->mm->mm_users) > 1) + return -EINVAL; + } + + return 0; +} + +/* + * Unshare the filesystem structure if it is being shared + */ +static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) +{ + struct fs_struct *fs = current->fs; + + if (!(unshare_flags & CLONE_FS) || !fs) + return 0; + + /* don't need lock here; in the worst case we'll do useless copy */ + if (fs->users == 1) + return 0; + + *new_fsp = copy_fs_struct(fs); + if (!*new_fsp) + return -ENOMEM; + + return 0; +} + +/* + * Unshare file descriptor table if it is being shared + */ +static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) +{ + struct files_struct *fd = current->files; + int error = 0; + + if ((unshare_flags & CLONE_FILES) && + (fd && atomic_read(&fd->count) > 1)) { + *new_fdp = dup_fd(fd, &error); + if (!*new_fdp) + return error; + } + + return 0; +} + +/* + * unshare allows a process to 'unshare' part of the process + * context which was originally shared using clone. copy_* + * functions used by do_fork() cannot be used here directly + * because they modify an inactive task_struct that is being + * constructed. Here we are modifying the current, active, + * task_struct. + */ +SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) +{ + struct fs_struct *fs, *new_fs = NULL; + struct files_struct *fd, *new_fd = NULL; + struct nsproxy *new_nsproxy = NULL; + int do_sysvsem = 0; + int err; + + err = check_unshare_flags(unshare_flags); + if (err) + goto bad_unshare_out; + + /* + * If unsharing namespace, must also unshare filesystem information. + */ + if (unshare_flags & CLONE_NEWNS) + unshare_flags |= CLONE_FS; + /* + * CLONE_NEWIPC must also detach from the undolist: after switching + * to a new ipc namespace, the semaphore arrays from the old + * namespace are unreachable. + */ + if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) + do_sysvsem = 1; + if ((err = unshare_fs(unshare_flags, &new_fs))) + goto bad_unshare_out; + if ((err = unshare_fd(unshare_flags, &new_fd))) + goto bad_unshare_cleanup_fs; + if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, + new_fs))) + goto bad_unshare_cleanup_fd; + + if (new_fs || new_fd || do_sysvsem || new_nsproxy) { + if (do_sysvsem) { + /* + * CLONE_SYSVSEM is equivalent to sys_exit(). + */ + exit_sem(current); + } + + if (new_nsproxy) { + switch_task_namespaces(current, new_nsproxy); + new_nsproxy = NULL; + } + + task_lock(current); + + if (new_fs) { + fs = current->fs; + spin_lock(&fs->lock); + current->fs = new_fs; + if (--fs->users) + new_fs = NULL; + else + new_fs = fs; + spin_unlock(&fs->lock); + } + + if (new_fd) { + fd = current->files; + current->files = new_fd; + new_fd = fd; + } + + task_unlock(current); + } + + if (new_nsproxy) + put_nsproxy(new_nsproxy); + +bad_unshare_cleanup_fd: + if (new_fd) + put_files_struct(new_fd); + +bad_unshare_cleanup_fs: + if (new_fs) + free_fs_struct(new_fs); + +bad_unshare_out: + return err; +} + +/* + * Helper to unshare the files of the current task. + * We don't want to expose copy_files internals to + * the exec layer of the kernel. + */ + +int unshare_files(struct files_struct **displaced) +{ + struct task_struct *task = current; + struct files_struct *copy = NULL; + int error; + + error = unshare_fd(CLONE_FILES, ©); + if (error || !copy) { + *displaced = NULL; + return error; + } + *displaced = task->files; + task_lock(task); + task->files = copy; + task_unlock(task); + return 0; +} |