/* * 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/config.h> #include <linux/slab.h> #include <linux/init.h> #include <linux/unistd.h> #include <linux/smp_lock.h> #include <linux/module.h> #include <linux/vmalloc.h> #include <linux/completion.h> #include <linux/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/capability.h> #include <linux/cpu.h> #include <linux/cpuset.h> #include <linux/security.h> #include <linux/swap.h> #include <linux/syscalls.h> #include <linux/jiffies.h> #include <linux/futex.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/cn_proc.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 */ EXPORT_SYMBOL(tasklist_lock); 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 kmem_cache_t *task_struct_cachep; #endif /* SLAB cache for signal_struct structures (tsk->signal) */ static kmem_cache_t *signal_cachep; /* SLAB cache for sighand_struct structures (tsk->sighand) */ kmem_cache_t *sighand_cachep; /* SLAB cache for files_struct structures (tsk->files) */ kmem_cache_t *files_cachep; /* SLAB cache for fs_struct structures (tsk->fs) */ kmem_cache_t *fs_cachep; /* SLAB cache for vm_area_struct structures */ kmem_cache_t *vm_area_cachep; /* SLAB cache for mm_struct structures (tsk->mm) */ static kmem_cache_t *mm_cachep; void free_task(struct task_struct *tsk) { free_thread_info(tsk->thread_info); free_task_struct(tsk); } EXPORT_SYMBOL(free_task); void __put_task_struct(struct task_struct *tsk) { WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); WARN_ON(atomic_read(&tsk->usage)); WARN_ON(tsk == current); security_task_free(tsk); free_uid(tsk->user); put_group_info(tsk->group_info); 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, 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; 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->thread_info = ti; setup_thread_stack(tsk, orig); /* One for us, one for whoever does the "release_task()" (usually parent) */ atomic_set(&tsk->usage,2); atomic_set(&tsk->fs_excl, 0); tsk->btrace_seq = 0; tsk->splice_pipe = NULL; return tsk; } #ifdef CONFIG_MMU static inline 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_mm(oldmm); down_write(&mm->mmap_sem); 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, SLAB_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_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; } 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, SLAB_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->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 (tsk->clear_child_tid && 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)); 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: tsk->mm = mm; tsk->active_mm = mm; return 0; fail_nomem: return retval; } static inline 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 inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) { if (clone_flags & CLONE_FS) { atomic_inc(¤t->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_fdset; 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, SLAB_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->max_fdset = EMBEDDED_FD_SET_SIZE; 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->free_files = NULL; 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, expand; 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); size = old_fdt->max_fdset; open_files = count_open_files(old_fdt); expand = 0; /* * Check whether we need to allocate a larger fd array or fd set. * Note: we're not a clone task, so the open count won't change. */ if (open_files > new_fdt->max_fdset) { new_fdt->max_fdset = 0; expand = 1; } if (open_files > new_fdt->max_fds) { new_fdt->max_fds = 0; expand = 1; } /* if the old fdset gets grown now, we'll only copy up to "size" fds */ if (expand) { spin_unlock(&oldf->file_lock); spin_lock(&newf->file_lock); *errorp = expand_files(newf, open_files-1); spin_unlock(&newf->file_lock); if (*errorp < 0) goto out_release; new_fdt = files_fdtable(newf); /* * Reacquire the oldf lock and a pointer to its fd table * who knows it may have a new bigger fd table. We need * the latest pointer. */ spin_lock(&oldf->file_lock); old_fdt = files_fdtable(oldf); } old_fds = old_fdt->fd; new_fds = new_fdt->fd; memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); for (i = open_files; i != 0; i--) { struct file *f = *old_fds++; if (f) { get_file(f); } else { /* * The fd may be claimed in the fd bitmap but not yet * instantiated in the files array if a sibling thread * is partway through open(). So make sure that this * fd is available to the new process. */ FD_CLR(open_files - i, new_fdt->open_fds); } rcu_assign_pointer(*new_fds++, f); } spin_unlock(&oldf->file_lock); /* compute the remainder to be cleared */ size = (new_fdt->max_fds - open_files) * sizeof(struct file *); /* This is long word aligned thus could use a optimized version */ memset(new_fds, 0, size); if (new_fdt->max_fdset > open_files) { int left = (new_fdt->max_fdset-open_files)/8; int start = open_files / (8 * sizeof(unsigned long)); memset(&new_fdt->open_fds->fds_bits[start], 0, left); memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); } out: return newf; out_release: free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); free_fdset (new_fdt->open_fds, new_fdt->max_fdset); free_fd_array(new_fdt->fd, new_fdt->max_fds); kmem_cache_free(files_cachep, newf); return NULL; } 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; } /* * Note: we may be using current for both targets (See exec.c) * This works because we cache current->files (old) as oldf. Don't * break this. */ tsk->files = NULL; newf = dup_fd(oldf, &error); if (!newf) goto out; tsk->files = newf; error = 0; out: return error; } /* * 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(void) { struct files_struct *files = current->files; int rc; BUG_ON(!files); /* This can race but the race causes us to copy when we don't need to and drop the copy */ if(atomic_read(&files->count) == 1) { atomic_inc(&files->count); return 0; } rc = copy_files(0, current); if(rc) current->files = files; return rc; } EXPORT_SYMBOL(unshare_files); static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) { struct sighand_struct *sig; if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 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)) kmem_cache_free(sighand_cachep, sighand); } static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) { struct signal_struct *sig; int ret; if (clone_flags & CLONE_THREAD) { atomic_inc(¤t->signal->count); atomic_inc(¤t->signal->live); return 0; } sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); tsk->signal = sig; if (!sig) return -ENOMEM; ret = copy_thread_group_keys(tsk); if (ret < 0) { kmem_cache_free(signal_cachep, sig); return ret; } atomic_set(&sig->count, 1); atomic_set(&sig->live, 1); init_waitqueue_head(&sig->wait_chldexit); sig->flags = 0; sig->group_exit_code = 0; sig->group_exit_task = NULL; sig->group_stop_count = 0; sig->curr_target = NULL; init_sigpending(&sig->shared_pending); INIT_LIST_HEAD(&sig->posix_timers); hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL); sig->it_real_incr.tv64 = 0; sig->real_timer.function = it_real_fn; sig->tsk = tsk; sig->it_virt_expires = cputime_zero; sig->it_virt_incr = cputime_zero; sig->it_prof_expires = cputime_zero; sig->it_prof_incr = cputime_zero; sig->leader = 0; /* session leadership doesn't inherit */ sig->tty_old_pgrp = 0; sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; sig->sched_time = 0; INIT_LIST_HEAD(&sig->cpu_timers[0]); INIT_LIST_HEAD(&sig->cpu_timers[1]); INIT_LIST_HEAD(&sig->cpu_timers[2]); task_lock(current->group_leader); memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); task_unlock(current->group_leader); if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { /* * New sole thread in the process gets an expiry time * of the whole CPU time limit. */ tsk->it_prof_expires = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); } acct_init_pacct(&sig->pacct); return 0; } void __cleanup_signal(struct signal_struct *sig) { exit_thread_group_keys(sig); kmem_cache_free(signal_cachep, sig); } static inline void cleanup_signal(struct task_struct *tsk) { struct signal_struct *sig = tsk->signal; atomic_dec(&sig->live); if (atomic_dec_and_test(&sig->count)) __cleanup_signal(sig); } static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) { unsigned long new_flags = p->flags; new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); new_flags |= PF_FORKNOEXEC; if (!(clone_flags & CLONE_PTRACE)) p->ptrace = 0; p->flags = new_flags; } asmlinkage long sys_set_tid_address(int __user *tidptr) { current->clear_child_tid = tidptr; return current->pid; } /* * 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 task_t *copy_process(unsigned long clone_flags, unsigned long stack_start, struct pt_regs *regs, unsigned long stack_size, int __user *parent_tidptr, int __user *child_tidptr, int pid) { int retval; struct task_struct *p = NULL; 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); retval = security_task_create(clone_flags); if (retval) goto fork_out; retval = -ENOMEM; p = dup_task_struct(current); if (!p) goto fork_out; retval = -EAGAIN; if (atomic_read(&p->user->processes) >= p->signal->rlim[RLIMIT_NPROC].rlim_cur) { if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && p->user != &root_user) goto bad_fork_free; } atomic_inc(&p->user->__count); atomic_inc(&p->user->processes); get_group_info(p->group_info); /* * 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. */ 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; if (p->binfmt && !try_module_get(p->binfmt->module)) goto bad_fork_cleanup_put_domain; p->did_exec = 0; copy_flags(clone_flags, p); p->pid = pid; retval = -EFAULT; if (clone_flags & CLONE_PARENT_SETTID) if (put_user(p->pid, parent_tidptr)) goto bad_fork_cleanup; INIT_LIST_HEAD(&p->children); INIT_LIST_HEAD(&p->sibling); p->vfork_done = NULL; spin_lock_init(&p->alloc_lock); clear_tsk_thread_flag(p, TIF_SIGPENDING); init_sigpending(&p->pending); p->utime = cputime_zero; p->stime = cputime_zero; p->sched_time = 0; p->rchar = 0; /* I/O counter: bytes read */ p->wchar = 0; /* I/O counter: bytes written */ p->syscr = 0; /* I/O counter: read syscalls */ p->syscw = 0; /* I/O counter: write syscalls */ acct_clear_integrals(p); p->it_virt_expires = cputime_zero; p->it_prof_expires = cputime_zero; p->it_sched_expires = 0; INIT_LIST_HEAD(&p->cpu_timers[0]); INIT_LIST_HEAD(&p->cpu_timers[1]); INIT_LIST_HEAD(&p->cpu_timers[2]); p->lock_depth = -1; /* -1 = no lock */ do_posix_clock_monotonic_gettime(&p->start_time); p->security = NULL; p->io_context = NULL; p->io_wait = NULL; p->audit_context = NULL; cpuset_fork(p); #ifdef CONFIG_NUMA p->mempolicy = mpol_copy(p->mempolicy); if (IS_ERR(p->mempolicy)) { retval = PTR_ERR(p->mempolicy); p->mempolicy = NULL; goto bad_fork_cleanup_cpuset; } mpol_fix_fork_child_flag(p); #endif #ifdef CONFIG_DEBUG_MUTEXES p->blocked_on = NULL; /* not blocked yet */ #endif p->tgid = p->pid; if (clone_flags & CLONE_THREAD) p->tgid = current->tgid; if ((retval = security_task_alloc(p))) goto bad_fork_cleanup_policy; if ((retval = audit_alloc(p))) goto bad_fork_cleanup_security; /* 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_keys(clone_flags, p))) goto bad_fork_cleanup_mm; if ((retval = copy_namespace(clone_flags, p))) goto bad_fork_cleanup_keys; retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); if (retval) goto bad_fork_cleanup_namespace; 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; p->robust_list = NULL; #ifdef CONFIG_COMPAT p->compat_robust_list = 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 should be turned off in the child regardless * of CLONE_PTRACE. */ clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); #ifdef TIF_SYSCALL_EMU clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); #endif /* Our parent execution domain becomes current domain These must match for thread signalling to apply */ p->parent_exec_id = p->self_exec_id; /* 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); INIT_LIST_HEAD(&p->ptrace_children); INIT_LIST_HEAD(&p->ptrace_list); /* Perform scheduler related setup. Assign this task to a CPU. */ sched_fork(p, clone_flags); /* Need tasklist lock for parent etc handling! */ write_lock_irq(&tasklist_lock); /* * The task hasn't been attached yet, so its cpus_allowed mask will * not be changed, nor will its assigned CPU. * * The cpus_allowed mask of the parent may have changed after it was * copied first time - so re-copy it here, then check the child's CPU * to ensure it is on a valid CPU (and if not, just force it back to * parent's CPU). This avoids alot of nasty races. */ p->cpus_allowed = current->cpus_allowed; if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || !cpu_online(task_cpu(p)))) set_task_cpu(p, smp_processor_id()); /* CLONE_PARENT re-uses the old parent */ if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) p->real_parent = current->real_parent; else p->real_parent = current; p->parent = p->real_parent; 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_cleanup_namespace; } if (clone_flags & CLONE_THREAD) { p->group_leader = current->group_leader; list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); if (!cputime_eq(current->signal->it_virt_expires, cputime_zero) || !cputime_eq(current->signal->it_prof_expires, cputime_zero) || current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || !list_empty(¤t->signal->cpu_timers[0]) || !list_empty(¤t->signal->cpu_timers[1]) || !list_empty(¤t->signal->cpu_timers[2])) { /* * Have child wake up on its first tick to check * for process CPU timers. */ p->it_prof_expires = jiffies_to_cputime(1); } } /* * inherit ioprio */ p->ioprio = current->ioprio; if (likely(p->pid)) { add_parent(p); if (unlikely(p->ptrace & PT_PTRACED)) __ptrace_link(p, current->parent); if (thread_group_leader(p)) { p->signal->tty = current->signal->tty; p->signal->pgrp = process_group(current); p->signal->session = current->signal->session; attach_pid(p, PIDTYPE_PGID, process_group(p)); attach_pid(p, PIDTYPE_SID, p->signal->session); list_add_tail_rcu(&p->tasks, &init_task.tasks); __get_cpu_var(process_counts)++; } attach_pid(p, PIDTYPE_PID, p->pid); nr_threads++; } total_forks++; spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); proc_fork_connector(p); return p; bad_fork_cleanup_namespace: exit_namespace(p); bad_fork_cleanup_keys: exit_keys(p); bad_fork_cleanup_mm: if (p->mm) mmput(p->mm); bad_fork_cleanup_signal: cleanup_signal(p); 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_security: security_task_free(p); bad_fork_cleanup_policy: #ifdef CONFIG_NUMA mpol_free(p->mempolicy); bad_fork_cleanup_cpuset: #endif cpuset_exit(p); bad_fork_cleanup: if (p->binfmt) module_put(p->binfmt->module); bad_fork_cleanup_put_domain: module_put(task_thread_info(p)->exec_domain->module); bad_fork_cleanup_count: put_group_info(p->group_info); atomic_dec(&p->user->processes); free_uid(p->user); bad_fork_free: free_task(p); fork_out: return ERR_PTR(retval); } struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) { memset(regs, 0, sizeof(struct pt_regs)); return regs; } task_t * __devinit fork_idle(int cpu) { task_t *task; struct pt_regs regs; task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); if (!task) return ERR_PTR(-ENOMEM); init_idle(task, cpu); return task; } static inline int fork_traceflag (unsigned clone_flags) { if (clone_flags & CLONE_UNTRACED) return 0; else if (clone_flags & CLONE_VFORK) { if (current->ptrace & PT_TRACE_VFORK) return PTRACE_EVENT_VFORK; } else if ((clone_flags & CSIGNAL) != SIGCHLD) { if (current->ptrace & PT_TRACE_CLONE) return PTRACE_EVENT_CLONE; } else if (current->ptrace & PT_TRACE_FORK) return PTRACE_EVENT_FORK; return 0; } /* * 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; struct pid *pid = alloc_pid(); long nr; if (!pid) return -EAGAIN; nr = pid->nr; if (unlikely(current->ptrace)) { trace = fork_traceflag (clone_flags); if (trace) clone_flags |= CLONE_PTRACE; } p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr); /* * 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; if (clone_flags & CLONE_VFORK) { p->vfork_done = &vfork; init_completion(&vfork); } if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { /* * We'll start up with an immediate SIGSTOP. */ sigaddset(&p->pending.signal, SIGSTOP); set_tsk_thread_flag(p, TIF_SIGPENDING); } if (!(clone_flags & CLONE_STOPPED)) wake_up_new_task(p, clone_flags); else p->state = TASK_STOPPED; if (unlikely (trace)) { current->ptrace_message = nr; ptrace_notify ((trace << 8) | SIGTRAP); } if (clone_flags & CLONE_VFORK) { wait_for_completion(&vfork); if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); } } else { free_pid(pid); nr = PTR_ERR(p); } return nr; } #ifndef ARCH_MIN_MMSTRUCT_ALIGN #define ARCH_MIN_MMSTRUCT_ALIGN 0 #endif static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags) { struct sighand_struct *sighand = data; if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) == SLAB_CTOR_CONSTRUCTOR) spin_lock_init(&sighand->siglock); } 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, sighand_ctor, NULL); signal_cachep = kmem_cache_create("signal_cache", sizeof(struct signal_struct), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); files_cachep = kmem_cache_create("files_cache", sizeof(struct files_struct), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); fs_cachep = kmem_cache_create("fs_cache", sizeof(struct fs_struct), 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); vm_area_cachep = kmem_cache_create("vm_area_struct", sizeof(struct vm_area_struct), 0, SLAB_PANIC, NULL, NULL); mm_cachep = kmem_cache_create("mm_struct", sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); } /* * Check constraints on flags passed to the unshare system call and * force unsharing of additional process context as appropriate. */ static inline void check_unshare_flags(unsigned long *flags_ptr) { /* * If unsharing a thread from a thread group, must also * unshare vm. */ if (*flags_ptr & CLONE_THREAD) *flags_ptr |= CLONE_VM; /* * If unsharing vm, must also unshare signal handlers. */ if (*flags_ptr & CLONE_VM) *flags_ptr |= CLONE_SIGHAND; /* * If unsharing signal handlers and the task was created * using CLONE_THREAD, then must unshare the thread */ if ((*flags_ptr & CLONE_SIGHAND) && (atomic_read(¤t->signal->count) > 1)) *flags_ptr |= CLONE_THREAD; /* * If unsharing namespace, must also unshare filesystem information. */ if (*flags_ptr & CLONE_NEWNS) *flags_ptr |= CLONE_FS; } /* * Unsharing of tasks created with CLONE_THREAD is not supported yet */ static int unshare_thread(unsigned long unshare_flags) { if (unshare_flags & CLONE_THREAD) 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 && atomic_read(&fs->count) > 1)) { *new_fsp = __copy_fs_struct(current->fs); if (!*new_fsp) return -ENOMEM; } return 0; } /* * Unshare the namespace structure if it is being shared */ static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs) { struct namespace *ns = current->namespace; if ((unshare_flags & CLONE_NEWNS) && (ns && atomic_read(&ns->count) > 1)) { if (!capable(CAP_SYS_ADMIN)) return -EPERM; *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs); if (!*new_nsp) return -ENOMEM; } return 0; } /* * Unsharing of sighand for tasks created with CLONE_SIGHAND is not * supported yet */ static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) { struct sighand_struct *sigh = current->sighand; if ((unshare_flags & CLONE_SIGHAND) && (sigh && atomic_read(&sigh->count) > 1)) return -EINVAL; else return 0; } /* * Unshare vm if it is being shared */ static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) { struct mm_struct *mm = current->mm; if ((unshare_flags & CLONE_VM) && (mm && atomic_read(&mm->mm_users) > 1)) { return -EINVAL; } 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; } /* * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not * supported yet */ static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) { if (unshare_flags & CLONE_SYSVSEM) return -EINVAL; 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. */ asmlinkage long sys_unshare(unsigned long unshare_flags) { int err = 0; struct fs_struct *fs, *new_fs = NULL; struct namespace *ns, *new_ns = NULL; struct sighand_struct *sigh, *new_sigh = NULL; struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; struct files_struct *fd, *new_fd = NULL; struct sem_undo_list *new_ulist = NULL; check_unshare_flags(&unshare_flags); /* Return -EINVAL for all unsupported flags */ err = -EINVAL; if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| CLONE_VM|CLONE_FILES|CLONE_SYSVSEM)) goto bad_unshare_out; if ((err = unshare_thread(unshare_flags))) goto bad_unshare_out; if ((err = unshare_fs(unshare_flags, &new_fs))) goto bad_unshare_cleanup_thread; if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs))) goto bad_unshare_cleanup_fs; if ((err = unshare_sighand(unshare_flags, &new_sigh))) goto bad_unshare_cleanup_ns; if ((err = unshare_vm(unshare_flags, &new_mm))) goto bad_unshare_cleanup_sigh; if ((err = unshare_fd(unshare_flags, &new_fd))) goto bad_unshare_cleanup_vm; if ((err = unshare_semundo(unshare_flags, &new_ulist))) goto bad_unshare_cleanup_fd; if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) { task_lock(current); if (new_fs) { fs = current->fs; current->fs = new_fs; new_fs = fs; } if (new_ns) { ns = current->namespace; current->namespace = new_ns; new_ns = ns; } if (new_sigh) { sigh = current->sighand; rcu_assign_pointer(current->sighand, new_sigh); new_sigh = sigh; } if (new_mm) { mm = current->mm; active_mm = current->active_mm; current->mm = new_mm; current->active_mm = new_mm; activate_mm(active_mm, new_mm); new_mm = mm; } if (new_fd) { fd = current->files; current->files = new_fd; new_fd = fd; } task_unlock(current); } bad_unshare_cleanup_fd: if (new_fd) put_files_struct(new_fd); bad_unshare_cleanup_vm: if (new_mm) mmput(new_mm); bad_unshare_cleanup_sigh: if (new_sigh) if (atomic_dec_and_test(&new_sigh->count)) kmem_cache_free(sighand_cachep, new_sigh); bad_unshare_cleanup_ns: if (new_ns) put_namespace(new_ns); bad_unshare_cleanup_fs: if (new_fs) put_fs_struct(new_fs); bad_unshare_cleanup_thread: bad_unshare_out: return err; }