sh: intc - mark data structures as __initdata

[linux-2.6/linux-2.6-openrd.git] / fs / exec.c

/*
 *  linux/fs/exec.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * #!-checking implemented by tytso.
 */
/*
 * Demand-loading implemented 01.12.91 - no need to read anything but
 * the header into memory. The inode of the executable is put into
 * "current->executable", and page faults do the actual loading. Clean.
 *
 * Once more I can proudly say that linux stood up to being changed: it
 * was less than 2 hours work to get demand-loading completely implemented.
 *
 * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
 * current->executable is only used by the procfs.  This allows a dispatch
 * table to check for several different types  of binary formats.  We keep
 * trying until we recognize the file or we run out of supported binary
 * formats. 
 */

#include <linux/slab.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/a.out.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/swap.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/proc_fs.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/rmap.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

int core_uses_pid;
char core_pattern[CORENAME_MAX_SIZE] = "core";
int suid_dumpable = 0;

EXPORT_SYMBOL(suid_dumpable);
/* The maximal length of core_pattern is also specified in sysctl.c */

static struct linux_binfmt *formats;
static DEFINE_RWLOCK(binfmt_lock);

int register_binfmt(struct linux_binfmt * fmt)
{
        struct linux_binfmt ** tmp = &formats;

        if (!fmt)
                return -EINVAL;
        if (fmt->next)
                return -EBUSY;
        write_lock(&binfmt_lock);
        while (*tmp) {
                if (fmt == *tmp) {
                        write_unlock(&binfmt_lock);
                        return -EBUSY;
                }
                tmp = &(*tmp)->next;
        }
        fmt->next = formats;
        formats = fmt;
        write_unlock(&binfmt_lock);
        return 0;       
}

EXPORT_SYMBOL(register_binfmt);

int unregister_binfmt(struct linux_binfmt * fmt)
{
        struct linux_binfmt ** tmp = &formats;

        write_lock(&binfmt_lock);
        while (*tmp) {
                if (fmt == *tmp) {
                        *tmp = fmt->next;
                        fmt->next = NULL;
                        write_unlock(&binfmt_lock);
                        return 0;
                }
                tmp = &(*tmp)->next;
        }
        write_unlock(&binfmt_lock);
        return -EINVAL;
}

EXPORT_SYMBOL(unregister_binfmt);

static inline void put_binfmt(struct linux_binfmt * fmt)
{
        module_put(fmt->module);
}

/*
 * Note that a shared library must be both readable and executable due to
 * security reasons.
 *
 * Also note that we take the address to load from from the file itself.
 */
asmlinkage long sys_uselib(const char __user * library)
{
        struct file * file;
        struct nameidata nd;
        int error;

        error = __user_path_lookup_open(library, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
        if (error)
                goto out;

        error = -EACCES;
        if (nd.mnt->mnt_flags & MNT_NOEXEC)
                goto exit;
        error = -EINVAL;
        if (!S_ISREG(nd.dentry->d_inode->i_mode))
                goto exit;

        error = vfs_permission(&nd, MAY_READ | MAY_EXEC);
        if (error)
                goto exit;

        file = nameidata_to_filp(&nd, O_RDONLY);
        error = PTR_ERR(file);
        if (IS_ERR(file))
                goto out;

        error = -ENOEXEC;
        if(file->f_op) {
                struct linux_binfmt * fmt;

                read_lock(&binfmt_lock);
                for (fmt = formats ; fmt ; fmt = fmt->next) {
                        if (!fmt->load_shlib)
                                continue;
                        if (!try_module_get(fmt->module))
                                continue;
                        read_unlock(&binfmt_lock);
                        error = fmt->load_shlib(file);
                        read_lock(&binfmt_lock);
                        put_binfmt(fmt);
                        if (error != -ENOEXEC)
                                break;
                }
                read_unlock(&binfmt_lock);
        }
        fput(file);
out:
        return error;
exit:
        release_open_intent(&nd);
        path_release(&nd);
        goto out;
}

#ifdef CONFIG_MMU

static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
                int write)
{
        struct page *page;
        int ret;

#ifdef CONFIG_STACK_GROWSUP
        if (write) {
                ret = expand_stack_downwards(bprm->vma, pos);
                if (ret < 0)
                        return NULL;
        }
#endif
        ret = get_user_pages(current, bprm->mm, pos,
                        1, write, 1, &page, NULL);
        if (ret <= 0)
                return NULL;

        if (write) {
                struct rlimit *rlim = current->signal->rlim;
                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;

                /*
                 * Limit to 1/4-th the stack size for the argv+env strings.
                 * This ensures that:
                 *  - the remaining binfmt code will not run out of stack space,
                 *  - the program will have a reasonable amount of stack left
                 *    to work from.
                 */
                if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
                        put_page(page);
                        return NULL;
                }
        }

        return page;
}

static void put_arg_page(struct page *page)
{
        put_page(page);
}

static void free_arg_page(struct linux_binprm *bprm, int i)
{
}

static void free_arg_pages(struct linux_binprm *bprm)
{
}

static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
                struct page *page)
{
        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
}

static int __bprm_mm_init(struct linux_binprm *bprm)
{
        int err = -ENOMEM;
        struct vm_area_struct *vma = NULL;
        struct mm_struct *mm = bprm->mm;

        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
        if (!vma)
                goto err;

        down_write(&mm->mmap_sem);
        vma->vm_mm = mm;

        /*
         * Place the stack at the largest stack address the architecture
         * supports. Later, we'll move this to an appropriate place. We don't
         * use STACK_TOP because that can depend on attributes which aren't
         * configured yet.
         */
        vma->vm_end = STACK_TOP_MAX;
        vma->vm_start = vma->vm_end - PAGE_SIZE;

        vma->vm_flags = VM_STACK_FLAGS;
        vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
        err = insert_vm_struct(mm, vma);
        if (err) {
                up_write(&mm->mmap_sem);
                goto err;
        }

        mm->stack_vm = mm->total_vm = 1;
        up_write(&mm->mmap_sem);

        bprm->p = vma->vm_end - sizeof(void *);

        return 0;

err:
        if (vma) {
                bprm->vma = NULL;
                kmem_cache_free(vm_area_cachep, vma);
        }

        return err;
}

static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
        return len <= MAX_ARG_STRLEN;
}

#else

static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
                int write)
{
        struct page *page;

        page = bprm->page[pos / PAGE_SIZE];
        if (!page && write) {
                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
                if (!page)
                        return NULL;
                bprm->page[pos / PAGE_SIZE] = page;
        }

        return page;
}

static void put_arg_page(struct page *page)
{
}

static void free_arg_page(struct linux_binprm *bprm, int i)
{
        if (bprm->page[i]) {
                __free_page(bprm->page[i]);
                bprm->page[i] = NULL;
        }
}

static void free_arg_pages(struct linux_binprm *bprm)
{
        int i;

        for (i = 0; i < MAX_ARG_PAGES; i++)
                free_arg_page(bprm, i);
}

static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
                struct page *page)
{
}

static int __bprm_mm_init(struct linux_binprm *bprm)
{
        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
        return 0;
}

static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
        return len <= bprm->p;
}

#endif /* CONFIG_MMU */

/*
 * Create a new mm_struct and populate it with a temporary stack
 * vm_area_struct.  We don't have enough context at this point to set the stack
 * flags, permissions, and offset, so we use temporary values.  We'll update
 * them later in setup_arg_pages().
 */
int bprm_mm_init(struct linux_binprm *bprm)
{
        int err;
        struct mm_struct *mm = NULL;

        bprm->mm = mm = mm_alloc();
        err = -ENOMEM;
        if (!mm)
                goto err;

        err = init_new_context(current, mm);
        if (err)
                goto err;

        err = __bprm_mm_init(bprm);
        if (err)
                goto err;

        return 0;

err:
        if (mm) {
                bprm->mm = NULL;
                mmdrop(mm);
        }

        return err;
}

/*
 * count() counts the number of strings in array ARGV.
 */
static int count(char __user * __user * argv, int max)
{
        int i = 0;

        if (argv != NULL) {
                for (;;) {
                        char __user * p;

                        if (get_user(p, argv))
                                return -EFAULT;
                        if (!p)
                                break;
                        argv++;
                        if(++i > max)
                                return -E2BIG;
                        cond_resched();
                }
        }
        return i;
}

/*
 * 'copy_strings()' copies argument/environment strings from the old
 * processes's memory to the new process's stack.  The call to get_user_pages()
 * ensures the destination page is created and not swapped out.
 */
static int copy_strings(int argc, char __user * __user * argv,
                        struct linux_binprm *bprm)
{
        struct page *kmapped_page = NULL;
        char *kaddr = NULL;
        unsigned long kpos = 0;
        int ret;

        while (argc-- > 0) {
                char __user *str;
                int len;
                unsigned long pos;

                if (get_user(str, argv+argc) ||
                                !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
                        ret = -EFAULT;
                        goto out;
                }

                if (!valid_arg_len(bprm, len)) {
                        ret = -E2BIG;
                        goto out;
                }

                /* We're going to work our way backwords. */
                pos = bprm->p;
                str += len;
                bprm->p -= len;

                while (len > 0) {
                        int offset, bytes_to_copy;

                        offset = pos % PAGE_SIZE;
                        if (offset == 0)
                                offset = PAGE_SIZE;

                        bytes_to_copy = offset;
                        if (bytes_to_copy > len)
                                bytes_to_copy = len;

                        offset -= bytes_to_copy;
                        pos -= bytes_to_copy;
                        str -= bytes_to_copy;
                        len -= bytes_to_copy;

                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
                                struct page *page;

                                page = get_arg_page(bprm, pos, 1);
                                if (!page) {
                                        ret = -E2BIG;
                                        goto out;
                                }

                                if (kmapped_page) {
                                        flush_kernel_dcache_page(kmapped_page);
                                        kunmap(kmapped_page);
                                        put_arg_page(kmapped_page);
                                }
                                kmapped_page = page;
                                kaddr = kmap(kmapped_page);
                                kpos = pos & PAGE_MASK;
                                flush_arg_page(bprm, kpos, kmapped_page);
                        }
                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
                                ret = -EFAULT;
                                goto out;
                        }
                }
        }
        ret = 0;
out:
        if (kmapped_page) {
                flush_kernel_dcache_page(kmapped_page);
                kunmap(kmapped_page);
                put_arg_page(kmapped_page);
        }
        return ret;
}

/*
 * Like copy_strings, but get argv and its values from kernel memory.
 */
int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
{
        int r;
        mm_segment_t oldfs = get_fs();
        set_fs(KERNEL_DS);
        r = copy_strings(argc, (char __user * __user *)argv, bprm);
        set_fs(oldfs);
        return r;
}
EXPORT_SYMBOL(copy_strings_kernel);

#ifdef CONFIG_MMU

/*
 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 * the binfmt code determines where the new stack should reside, we shift it to
 * its final location.  The process proceeds as follows:
 *
 * 1) Use shift to calculate the new vma endpoints.
 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 *    arguments passed to subsequent functions are consistent.
 * 3) Move vma's page tables to the new range.
 * 4) Free up any cleared pgd range.
 * 5) Shrink the vma to cover only the new range.
 */
static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
{
        struct mm_struct *mm = vma->vm_mm;
        unsigned long old_start = vma->vm_start;
        unsigned long old_end = vma->vm_end;
        unsigned long length = old_end - old_start;
        unsigned long new_start = old_start - shift;
        unsigned long new_end = old_end - shift;
        struct mmu_gather *tlb;

        BUG_ON(new_start > new_end);

        /*
         * ensure there are no vmas between where we want to go
         * and where we are
         */
        if (vma != find_vma(mm, new_start))
                return -EFAULT;

        /*
         * cover the whole range: [new_start, old_end)
         */
        vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);

        /*
         * move the page tables downwards, on failure we rely on
         * process cleanup to remove whatever mess we made.
         */
        if (length != move_page_tables(vma, old_start,
                                       vma, new_start, length))
                return -ENOMEM;

        lru_add_drain();
        tlb = tlb_gather_mmu(mm, 0);
        if (new_end > old_start) {
                /*
                 * when the old and new regions overlap clear from new_end.
                 */
                free_pgd_range(&tlb, new_end, old_end, new_end,
                        vma->vm_next ? vma->vm_next->vm_start : 0);
        } else {
                /*
                 * otherwise, clean from old_start; this is done to not touch
                 * the address space in [new_end, old_start) some architectures
                 * have constraints on va-space that make this illegal (IA64) -
                 * for the others its just a little faster.
                 */
                free_pgd_range(&tlb, old_start, old_end, new_end,
                        vma->vm_next ? vma->vm_next->vm_start : 0);
        }
        tlb_finish_mmu(tlb, new_end, old_end);

        /*
         * shrink the vma to just the new range.
         */
        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);

        return 0;
}

#define EXTRA_STACK_VM_PAGES    20      /* random */

/*
 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 * the stack is optionally relocated, and some extra space is added.
 */
int setup_arg_pages(struct linux_binprm *bprm,
                    unsigned long stack_top,
                    int executable_stack)
{
        unsigned long ret;
        unsigned long stack_shift;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma = bprm->vma;
        struct vm_area_struct *prev = NULL;
        unsigned long vm_flags;
        unsigned long stack_base;

#ifdef CONFIG_STACK_GROWSUP
        /* Limit stack size to 1GB */
        stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
        if (stack_base > (1 << 30))
                stack_base = 1 << 30;

        /* Make sure we didn't let the argument array grow too large. */
        if (vma->vm_end - vma->vm_start > stack_base)
                return -ENOMEM;

        stack_base = PAGE_ALIGN(stack_top - stack_base);

        stack_shift = vma->vm_start - stack_base;
        mm->arg_start = bprm->p - stack_shift;
        bprm->p = vma->vm_end - stack_shift;
#else
        stack_top = arch_align_stack(stack_top);
        stack_top = PAGE_ALIGN(stack_top);
        stack_shift = vma->vm_end - stack_top;

        bprm->p -= stack_shift;
        mm->arg_start = bprm->p;
#endif

        if (bprm->loader)
                bprm->loader -= stack_shift;
        bprm->exec -= stack_shift;

        down_write(&mm->mmap_sem);
        vm_flags = vma->vm_flags;

        /*
         * Adjust stack execute permissions; explicitly enable for
         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
         * (arch default) otherwise.
         */
        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
                vm_flags |= VM_EXEC;
        else if (executable_stack == EXSTACK_DISABLE_X)
                vm_flags &= ~VM_EXEC;
        vm_flags |= mm->def_flags;

        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
                        vm_flags);
        if (ret)
                goto out_unlock;
        BUG_ON(prev != vma);

        /* Move stack pages down in memory. */
        if (stack_shift) {
                ret = shift_arg_pages(vma, stack_shift);
                if (ret) {
                        up_write(&mm->mmap_sem);
                        return ret;
                }
        }

#ifdef CONFIG_STACK_GROWSUP
        stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#else
        stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#endif
        ret = expand_stack(vma, stack_base);
        if (ret)
                ret = -EFAULT;

out_unlock:
        up_write(&mm->mmap_sem);
        return 0;
}
EXPORT_SYMBOL(setup_arg_pages);

#endif /* CONFIG_MMU */

struct file *open_exec(const char *name)
{
        struct nameidata nd;
        int err;
        struct file *file;

        err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd, FMODE_READ|FMODE_EXEC);
        file = ERR_PTR(err);

        if (!err) {
                struct inode *inode = nd.dentry->d_inode;
                file = ERR_PTR(-EACCES);
                if (!(nd.mnt->mnt_flags & MNT_NOEXEC) &&
                    S_ISREG(inode->i_mode)) {
                        int err = vfs_permission(&nd, MAY_EXEC);
                        file = ERR_PTR(err);
                        if (!err) {
                                file = nameidata_to_filp(&nd, O_RDONLY);
                                if (!IS_ERR(file)) {
                                        err = deny_write_access(file);
                                        if (err) {
                                                fput(file);
                                                file = ERR_PTR(err);
                                        }
                                }
out:
                                return file;
                        }
                }
                release_open_intent(&nd);
                path_release(&nd);
        }
        goto out;
}

EXPORT_SYMBOL(open_exec);

int kernel_read(struct file *file, unsigned long offset,
        char *addr, unsigned long count)
{
        mm_segment_t old_fs;
        loff_t pos = offset;
        int result;

        old_fs = get_fs();
        set_fs(get_ds());
        /* The cast to a user pointer is valid due to the set_fs() */
        result = vfs_read(file, (void __user *)addr, count, &pos);
        set_fs(old_fs);
        return result;
}

EXPORT_SYMBOL(kernel_read);

static int exec_mmap(struct mm_struct *mm)
{
        struct task_struct *tsk;
        struct mm_struct * old_mm, *active_mm;

        /* Notify parent that we're no longer interested in the old VM */
        tsk = current;
        old_mm = current->mm;
        mm_release(tsk, old_mm);

        if (old_mm) {
                /*
                 * Make sure that if there is a core dump in progress
                 * for the old mm, we get out and die instead of going
                 * through with the exec.  We must hold mmap_sem around
                 * checking core_waiters and changing tsk->mm.  The
                 * core-inducing thread will increment core_waiters for
                 * each thread whose ->mm == old_mm.
                 */
                down_read(&old_mm->mmap_sem);
                if (unlikely(old_mm->core_waiters)) {
                        up_read(&old_mm->mmap_sem);
                        return -EINTR;
                }
        }
        task_lock(tsk);
        active_mm = tsk->active_mm;
        tsk->mm = mm;
        tsk->active_mm = mm;
        activate_mm(active_mm, mm);
        task_unlock(tsk);
        arch_pick_mmap_layout(mm);
        if (old_mm) {
                up_read(&old_mm->mmap_sem);
                BUG_ON(active_mm != old_mm);
                mmput(old_mm);
                return 0;
        }
        mmdrop(active_mm);
        return 0;
}

/*
 * This function makes sure the current process has its own signal table,
 * so that flush_signal_handlers can later reset the handlers without
 * disturbing other processes.  (Other processes might share the signal
 * table via the CLONE_SIGHAND option to clone().)
 */
static int de_thread(struct task_struct *tsk)
{
        struct signal_struct *sig = tsk->signal;
        struct sighand_struct *newsighand, *oldsighand = tsk->sighand;
        spinlock_t *lock = &oldsighand->siglock;
        struct task_struct *leader = NULL;
        int count;

        /*
         * If we don't share sighandlers, then we aren't sharing anything
         * and we can just re-use it all.
         */
        if (atomic_read(&oldsighand->count) <= 1) {
                exit_itimers(sig);
                return 0;
        }

        newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
        if (!newsighand)
                return -ENOMEM;

        if (thread_group_empty(tsk))
                goto no_thread_group;

        /*
         * Kill all other threads in the thread group.
         * We must hold tasklist_lock to call zap_other_threads.
         */
        read_lock(&tasklist_lock);
        spin_lock_irq(lock);
        if (sig->flags & SIGNAL_GROUP_EXIT) {
                /*
                 * Another group action in progress, just
                 * return so that the signal is processed.
                 */
                spin_unlock_irq(lock);
                read_unlock(&tasklist_lock);
                kmem_cache_free(sighand_cachep, newsighand);
                return -EAGAIN;
        }

        /*
         * child_reaper ignores SIGKILL, change it now.
         * Reparenting needs write_lock on tasklist_lock,
         * so it is safe to do it under read_lock.
         */
        if (unlikely(tsk->group_leader == child_reaper(tsk)))
                tsk->nsproxy->pid_ns->child_reaper = tsk;

        zap_other_threads(tsk);
        read_unlock(&tasklist_lock);

        /*
         * Account for the thread group leader hanging around:
         */
        count = 1;
        if (!thread_group_leader(tsk)) {
                count = 2;
                /*
                 * The SIGALRM timer survives the exec, but needs to point
                 * at us as the new group leader now.  We have a race with
                 * a timer firing now getting the old leader, so we need to
                 * synchronize with any firing (by calling del_timer_sync)
                 * before we can safely let the old group leader die.
                 */
                sig->tsk = tsk;
                spin_unlock_irq(lock);
                if (hrtimer_cancel(&sig->real_timer))
                        hrtimer_restart(&sig->real_timer);
                spin_lock_irq(lock);
        }
        while (atomic_read(&sig->count) > count) {
                sig->group_exit_task = tsk;
                sig->notify_count = count;
                __set_current_state(TASK_UNINTERRUPTIBLE);
                spin_unlock_irq(lock);
                schedule();
                spin_lock_irq(lock);
        }
        sig->group_exit_task = NULL;
        sig->notify_count = 0;
        spin_unlock_irq(lock);

        /*
         * At this point all other threads have exited, all we have to
         * do is to wait for the thread group leader to become inactive,
         * and to assume its PID:
         */
        if (!thread_group_leader(tsk)) {
                /*
                 * Wait for the thread group leader to be a zombie.
                 * It should already be zombie at this point, most
                 * of the time.
                 */
                leader = tsk->group_leader;
                while (leader->exit_state != EXIT_ZOMBIE)
                        yield();

                /*
                 * The only record we have of the real-time age of a
                 * process, regardless of execs it's done, is start_time.
                 * All the past CPU time is accumulated in signal_struct
                 * from sister threads now dead.  But in this non-leader
                 * exec, nothing survives from the original leader thread,
                 * whose birth marks the true age of this process now.
                 * When we take on its identity by switching to its PID, we
                 * also take its birthdate (always earlier than our own).
                 */
                tsk->start_time = leader->start_time;

                write_lock_irq(&tasklist_lock);

                BUG_ON(leader->tgid != tsk->tgid);
                BUG_ON(tsk->pid == tsk->tgid);
                /*
                 * An exec() starts a new thread group with the
                 * TGID of the previous thread group. Rehash the
                 * two threads with a switched PID, and release
                 * the former thread group leader:
                 */

                /* Become a process group leader with the old leader's pid.
                 * The old leader becomes a thread of the this thread group.
                 * Note: The old leader also uses this pid until release_task
                 *       is called.  Odd but simple and correct.
                 */
                detach_pid(tsk, PIDTYPE_PID);
                tsk->pid = leader->pid;
                attach_pid(tsk, PIDTYPE_PID,  find_pid(tsk->pid));
                transfer_pid(leader, tsk, PIDTYPE_PGID);
                transfer_pid(leader, tsk, PIDTYPE_SID);
                list_replace_rcu(&leader->tasks, &tsk->tasks);

                tsk->group_leader = tsk;
                leader->group_leader = tsk;

                tsk->exit_signal = SIGCHLD;

                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
                leader->exit_state = EXIT_DEAD;

                write_unlock_irq(&tasklist_lock);
        }

        /*
         * There may be one thread left which is just exiting,
         * but it's safe to stop telling the group to kill themselves.
         */
        sig->flags = 0;

no_thread_group:
        exit_itimers(sig);
        if (leader)
                release_task(leader);

        if (atomic_read(&oldsighand->count) == 1) {
                /*
                 * Now that we nuked the rest of the thread group,
                 * it turns out we are not sharing sighand any more either.
                 * So we can just keep it.
                 */
                kmem_cache_free(sighand_cachep, newsighand);
        } else {
                /*
                 * Move our state over to newsighand and switch it in.
                 */
                atomic_set(&newsighand->count, 1);
                memcpy(newsighand->action, oldsighand->action,
                       sizeof(newsighand->action));

                write_lock_irq(&tasklist_lock);
                spin_lock(&oldsighand->siglock);
                spin_lock_nested(&newsighand->siglock, SINGLE_DEPTH_NESTING);

                rcu_assign_pointer(tsk->sighand, newsighand);
                recalc_sigpending();

                spin_unlock(&newsighand->siglock);
                spin_unlock(&oldsighand->siglock);
                write_unlock_irq(&tasklist_lock);

                __cleanup_sighand(oldsighand);
        }

        BUG_ON(!thread_group_leader(tsk));
        return 0;
}
        
/*
 * These functions flushes out all traces of the currently running executable
 * so that a new one can be started
 */

static void flush_old_files(struct files_struct * files)
{
        long j = -1;
        struct fdtable *fdt;

        spin_lock(&files->file_lock);
        for (;;) {
                unsigned long set, i;

                j++;
                i = j * __NFDBITS;
                fdt = files_fdtable(files);
                if (i >= fdt->max_fds)
                        break;
                set = fdt->close_on_exec->fds_bits[j];
                if (!set)
                        continue;
                fdt->close_on_exec->fds_bits[j] = 0;
                spin_unlock(&files->file_lock);
                for ( ; set ; i++,set >>= 1) {
                        if (set & 1) {
                                sys_close(i);
                        }
                }
                spin_lock(&files->file_lock);

        }
        spin_unlock(&files->file_lock);
}

void get_task_comm(char *buf, struct task_struct *tsk)
{
        /* buf must be at least sizeof(tsk->comm) in size */
        task_lock(tsk);
        strncpy(buf, tsk->comm, sizeof(tsk->comm));
        task_unlock(tsk);
}

void set_task_comm(struct task_struct *tsk, char *buf)
{
        task_lock(tsk);
        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
        task_unlock(tsk);
}

int flush_old_exec(struct linux_binprm * bprm)
{
        char * name;
        int i, ch, retval;
        struct files_struct *files;
        char tcomm[sizeof(current->comm)];

        /*
         * Make sure we have a private signal table and that
         * we are unassociated from the previous thread group.
         */
        retval = de_thread(current);
        if (retval)
                goto out;

        /*
         * Make sure we have private file handles. Ask the
         * fork helper to do the work for us and the exit
         * helper to do the cleanup of the old one.
         */
        files = current->files;         /* refcounted so safe to hold */
        retval = unshare_files();
        if (retval)
                goto out;
        /*
         * Release all of the old mmap stuff
         */
        retval = exec_mmap(bprm->mm);
        if (retval)
                goto mmap_failed;

        bprm->mm = NULL;                /* We're using it now */

        /* This is the point of no return */
        put_files_struct(files);

        current->sas_ss_sp = current->sas_ss_size = 0;

        if (current->euid == current->uid && current->egid == current->gid)
                set_dumpable(current->mm, 1);
        else
                set_dumpable(current->mm, suid_dumpable);

        name = bprm->filename;

        /* Copies the binary name from after last slash */
        for (i=0; (ch = *(name++)) != '\0';) {
                if (ch == '/')
                        i = 0; /* overwrite what we wrote */
                else
                        if (i < (sizeof(tcomm) - 1))
                                tcomm[i++] = ch;
        }
        tcomm[i] = '\0';
        set_task_comm(current, tcomm);

        current->flags &= ~PF_RANDOMIZE;
        flush_thread();

        /* Set the new mm task size. We have to do that late because it may
         * depend on TIF_32BIT which is only updated in flush_thread() on
         * some architectures like powerpc
         */
        current->mm->task_size = TASK_SIZE;

        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
                suid_keys(current);
                set_dumpable(current->mm, suid_dumpable);
                current->pdeath_signal = 0;
        } else if (file_permission(bprm->file, MAY_READ) ||
                        (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
                suid_keys(current);
                set_dumpable(current->mm, suid_dumpable);
        }

        /* An exec changes our domain. We are no longer part of the thread
           group */

        current->self_exec_id++;
                        
        flush_signal_handlers(current, 0);
        flush_old_files(current->files);

        return 0;

mmap_failed:
        reset_files_struct(current, files);
out:
        return retval;
}

EXPORT_SYMBOL(flush_old_exec);

/* 
 * Fill the binprm structure from the inode. 
 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
 */
int prepare_binprm(struct linux_binprm *bprm)
{
        int mode;
        struct inode * inode = bprm->file->f_path.dentry->d_inode;
        int retval;

        mode = inode->i_mode;
        if (bprm->file->f_op == NULL)
                return -EACCES;

        bprm->e_uid = current->euid;
        bprm->e_gid = current->egid;

        if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
                /* Set-uid? */
                if (mode & S_ISUID) {
                        current->personality &= ~PER_CLEAR_ON_SETID;
                        bprm->e_uid = inode->i_uid;
                }

                /* Set-gid? */
                /*
                 * If setgid is set but no group execute bit then this
                 * is a candidate for mandatory locking, not a setgid
                 * executable.
                 */
                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
                        current->personality &= ~PER_CLEAR_ON_SETID;
                        bprm->e_gid = inode->i_gid;
                }
        }

        /* fill in binprm security blob */
        retval = security_bprm_set(bprm);
        if (retval)
                return retval;

        memset(bprm->buf,0,BINPRM_BUF_SIZE);
        return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
}

EXPORT_SYMBOL(prepare_binprm);

static int unsafe_exec(struct task_struct *p)
{
        int unsafe = 0;
        if (p->ptrace & PT_PTRACED) {
                if (p->ptrace & PT_PTRACE_CAP)
                        unsafe |= LSM_UNSAFE_PTRACE_CAP;
                else
                        unsafe |= LSM_UNSAFE_PTRACE;
        }
        if (atomic_read(&p->fs->count) > 1 ||
            atomic_read(&p->files->count) > 1 ||
            atomic_read(&p->sighand->count) > 1)
                unsafe |= LSM_UNSAFE_SHARE;

        return unsafe;
}

void compute_creds(struct linux_binprm *bprm)
{
        int unsafe;

        if (bprm->e_uid != current->uid) {
                suid_keys(current);
                current->pdeath_signal = 0;
        }
        exec_keys(current);

        task_lock(current);
        unsafe = unsafe_exec(current);
        security_bprm_apply_creds(bprm, unsafe);
        task_unlock(current);
        security_bprm_post_apply_creds(bprm);
}
EXPORT_SYMBOL(compute_creds);

/*
 * Arguments are '\0' separated strings found at the location bprm->p
 * points to; chop off the first by relocating brpm->p to right after
 * the first '\0' encountered.
 */
int remove_arg_zero(struct linux_binprm *bprm)
{
        int ret = 0;
        unsigned long offset;
        char *kaddr;
        struct page *page;

        if (!bprm->argc)
                return 0;

        do {
                offset = bprm->p & ~PAGE_MASK;
                page = get_arg_page(bprm, bprm->p, 0);
                if (!page) {
                        ret = -EFAULT;
                        goto out;
                }
                kaddr = kmap_atomic(page, KM_USER0);

                for (; offset < PAGE_SIZE && kaddr[offset];
                                offset++, bprm->p++)
                        ;

                kunmap_atomic(kaddr, KM_USER0);
                put_arg_page(page);

                if (offset == PAGE_SIZE)
                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
        } while (offset == PAGE_SIZE);

        bprm->p++;
        bprm->argc--;
        ret = 0;

out:
        return ret;
}
EXPORT_SYMBOL(remove_arg_zero);

/*
 * cycle the list of binary formats handler, until one recognizes the image
 */
int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
{
        int try,retval;
        struct linux_binfmt *fmt;
#ifdef __alpha__
        /* handle /sbin/loader.. */
        {
            struct exec * eh = (struct exec *) bprm->buf;

            if (!bprm->loader && eh->fh.f_magic == 0x183 &&
                (eh->fh.f_flags & 0x3000) == 0x3000)
            {
                struct file * file;
                unsigned long loader;

                allow_write_access(bprm->file);
                fput(bprm->file);
                bprm->file = NULL;

                loader = bprm->vma->vm_end - sizeof(void *);

                file = open_exec("/sbin/loader");
                retval = PTR_ERR(file);
                if (IS_ERR(file))
                        return retval;

                /* Remember if the application is TASO.  */
                bprm->sh_bang = eh->ah.entry < 0x100000000UL;

                bprm->file = file;
                bprm->loader = loader;
                retval = prepare_binprm(bprm);
                if (retval<0)
                        return retval;
                /* should call search_binary_handler recursively here,
                   but it does not matter */
            }
        }
#endif
        retval = security_bprm_check(bprm);
        if (retval)
                return retval;

        /* kernel module loader fixup */
        /* so we don't try to load run modprobe in kernel space. */
        set_fs(USER_DS);

        retval = audit_bprm(bprm);
        if (retval)
                return retval;

        retval = -ENOENT;
        for (try=0; try<2; try++) {
                read_lock(&binfmt_lock);
                for (fmt = formats ; fmt ; fmt = fmt->next) {
                        int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
                        if (!fn)
                                continue;
                        if (!try_module_get(fmt->module))
                                continue;
                        read_unlock(&binfmt_lock);
                        retval = fn(bprm, regs);
                        if (retval >= 0) {
                                put_binfmt(fmt);
                                allow_write_access(bprm->file);
                                if (bprm->file)
                                        fput(bprm->file);
                                bprm->file = NULL;
                                current->did_exec = 1;
                                proc_exec_connector(current);
                                return retval;
                        }
                        read_lock(&binfmt_lock);
                        put_binfmt(fmt);
                        if (retval != -ENOEXEC || bprm->mm == NULL)
                                break;
                        if (!bprm->file) {
                                read_unlock(&binfmt_lock);
                                return retval;
                        }
                }
                read_unlock(&binfmt_lock);
                if (retval != -ENOEXEC || bprm->mm == NULL) {
                        break;
#ifdef CONFIG_KMOD
                }else{
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
                        if (printable(bprm->buf[0]) &&
                            printable(bprm->buf[1]) &&
                            printable(bprm->buf[2]) &&
                            printable(bprm->buf[3]))
                                break; /* -ENOEXEC */
                        request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
#endif
                }
        }
        return retval;
}

EXPORT_SYMBOL(search_binary_handler);

/*
 * sys_execve() executes a new program.
 */
int do_execve(char * filename,
        char __user *__user *argv,
        char __user *__user *envp,
        struct pt_regs * regs)
{
        struct linux_binprm *bprm;
        struct file *file;
        unsigned long env_p;
        int retval;

        retval = -ENOMEM;
        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
        if (!bprm)
                goto out_ret;

        file = open_exec(filename);
        retval = PTR_ERR(file);
        if (IS_ERR(file))
                goto out_kfree;

        sched_exec();

        bprm->file = file;
        bprm->filename = filename;
        bprm->interp = filename;

        retval = bprm_mm_init(bprm);
        if (retval)
                goto out_file;

        bprm->argc = count(argv, MAX_ARG_STRINGS);
        if ((retval = bprm->argc) < 0)
                goto out_mm;

        bprm->envc = count(envp, MAX_ARG_STRINGS);
        if ((retval = bprm->envc) < 0)
                goto out_mm;

        retval = security_bprm_alloc(bprm);
        if (retval)
                goto out;

        retval = prepare_binprm(bprm);
        if (retval < 0)
                goto out;

        retval = copy_strings_kernel(1, &bprm->filename, bprm);
        if (retval < 0)
                goto out;

        bprm->exec = bprm->p;
        retval = copy_strings(bprm->envc, envp, bprm);
        if (retval < 0)
                goto out;

        env_p = bprm->p;
        retval = copy_strings(bprm->argc, argv, bprm);
        if (retval < 0)
                goto out;
        bprm->argv_len = env_p - bprm->p;

        retval = search_binary_handler(bprm,regs);
        if (retval >= 0) {
                /* execve success */
                free_arg_pages(bprm);
                security_bprm_free(bprm);
                acct_update_integrals(current);
                kfree(bprm);
                return retval;
        }

out:
        free_arg_pages(bprm);
        if (bprm->security)
                security_bprm_free(bprm);

out_mm:
        if (bprm->mm)
                mmput (bprm->mm);

out_file:
        if (bprm->file) {
                allow_write_access(bprm->file);
                fput(bprm->file);
        }
out_kfree:
        kfree(bprm);

out_ret:
        return retval;
}

int set_binfmt(struct linux_binfmt *new)
{
        struct linux_binfmt *old = current->binfmt;

        if (new) {
                if (!try_module_get(new->module))
                        return -1;
        }
        current->binfmt = new;
        if (old)
                module_put(old->module);
        return 0;
}

EXPORT_SYMBOL(set_binfmt);

/* format_corename will inspect the pattern parameter, and output a
 * name into corename, which must have space for at least
 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 */
static int format_corename(char *corename, const char *pattern, long signr)
{
        const char *pat_ptr = pattern;
        char *out_ptr = corename;
        char *const out_end = corename + CORENAME_MAX_SIZE;
        int rc;
        int pid_in_pattern = 0;
        int ispipe = 0;

        if (*pattern == '|')
                ispipe = 1;

        /* Repeat as long as we have more pattern to process and more output
           space */
        while (*pat_ptr) {
                if (*pat_ptr != '%') {
                        if (out_ptr == out_end)
                                goto out;
                        *out_ptr++ = *pat_ptr++;
                } else {
                        switch (*++pat_ptr) {
                        case 0:
                                goto out;
                        /* Double percent, output one percent */
                        case '%':
                                if (out_ptr == out_end)
                                        goto out;
                                *out_ptr++ = '%';
                                break;
                        /* pid */
                        case 'p':
                                pid_in_pattern = 1;
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%d", current->tgid);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        /* uid */
                        case 'u':
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%d", current->uid);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        /* gid */
                        case 'g':
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%d", current->gid);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        /* signal that caused the coredump */
                        case 's':
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%ld", signr);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        /* UNIX time of coredump */
                        case 't': {
                                struct timeval tv;
                                do_gettimeofday(&tv);
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%lu", tv.tv_sec);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        }
                        /* hostname */
                        case 'h':
                                down_read(&uts_sem);
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%s", utsname()->nodename);
                                up_read(&uts_sem);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        /* executable */
                        case 'e':
                                rc = snprintf(out_ptr, out_end - out_ptr,
                                              "%s", current->comm);
                                if (rc > out_end - out_ptr)
                                        goto out;
                                out_ptr += rc;
                                break;
                        default:
                                break;
                        }
                        ++pat_ptr;
                }
        }
        /* Backward compatibility with core_uses_pid:
         *
         * If core_pattern does not include a %p (as is the default)
         * and core_uses_pid is set, then .%pid will be appended to
         * the filename. Do not do this for piped commands. */
        if (!ispipe && !pid_in_pattern
            && (core_uses_pid || atomic_read(&current->mm->mm_users) != 1)) {
                rc = snprintf(out_ptr, out_end - out_ptr,
                              ".%d", current->tgid);
                if (rc > out_end - out_ptr)
                        goto out;
                out_ptr += rc;
        }
out:
        *out_ptr = 0;
        return ispipe;
}

static void zap_process(struct task_struct *start)
{
        struct task_struct *t;

        start->signal->flags = SIGNAL_GROUP_EXIT;
        start->signal->group_stop_count = 0;

        t = start;
        do {
                if (t != current && t->mm) {
                        t->mm->core_waiters++;
                        sigaddset(&t->pending.signal, SIGKILL);
                        signal_wake_up(t, 1);
                }
        } while ((t = next_thread(t)) != start);
}

static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
                                int exit_code)
{
        struct task_struct *g, *p;
        unsigned long flags;
        int err = -EAGAIN;

        spin_lock_irq(&tsk->sighand->siglock);
        if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) {
                tsk->signal->group_exit_code = exit_code;
                zap_process(tsk);
                err = 0;
        }
        spin_unlock_irq(&tsk->sighand->siglock);
        if (err)
                return err;

        if (atomic_read(&mm->mm_users) == mm->core_waiters + 1)
                goto done;

        rcu_read_lock();
        for_each_process(g) {
                if (g == tsk->group_leader)
                        continue;

                p = g;
                do {
                        if (p->mm) {
                                if (p->mm == mm) {
                                        /*
                                         * p->sighand can't disappear, but
                                         * may be changed by de_thread()
                                         */
                                        lock_task_sighand(p, &flags);
                                        zap_process(p);
                                        unlock_task_sighand(p, &flags);
                                }
                                break;
                        }
                } while ((p = next_thread(p)) != g);
        }
        rcu_read_unlock();
done:
        return mm->core_waiters;
}

static int coredump_wait(int exit_code)
{
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        struct completion startup_done;
        struct completion *vfork_done;
        int core_waiters;

        init_completion(&mm->core_done);
        init_completion(&startup_done);
        mm->core_startup_done = &startup_done;

        core_waiters = zap_threads(tsk, mm, exit_code);
        up_write(&mm->mmap_sem);

        if (unlikely(core_waiters < 0))
                goto fail;

        /*
         * Make sure nobody is waiting for us to release the VM,
         * otherwise we can deadlock when we wait on each other
         */
        vfork_done = tsk->vfork_done;
        if (vfork_done) {
                tsk->vfork_done = NULL;
                complete(vfork_done);
        }

        if (core_waiters)
                wait_for_completion(&startup_done);
fail:
        BUG_ON(mm->core_waiters);
        return core_waiters;
}

/*
 * set_dumpable converts traditional three-value dumpable to two flags and
 * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
 * these bits are not changed atomically.  So get_dumpable can observe the
 * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
 * return either old dumpable or new one by paying attention to the order of
 * modifying the bits.
 *
 * dumpable |   mm->flags (binary)
 * old  new | initial interim  final
 * ---------+-----------------------
 *  0    1  |   00      01      01
 *  0    2  |   00      10(*)   11
 *  1    0  |   01      00      00
 *  1    2  |   01      11      11
 *  2    0  |   11      10(*)   00
 *  2    1  |   11      11      01
 *
 * (*) get_dumpable regards interim value of 10 as 11.
 */
void set_dumpable(struct mm_struct *mm, int value)
{
        switch (value) {
        case 0:
                clear_bit(MMF_DUMPABLE, &mm->flags);
                smp_wmb();
                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
                break;
        case 1:
                set_bit(MMF_DUMPABLE, &mm->flags);
                smp_wmb();
                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
                break;
        case 2:
                set_bit(MMF_DUMP_SECURELY, &mm->flags);
                smp_wmb();
                set_bit(MMF_DUMPABLE, &mm->flags);
                break;
        }
}
EXPORT_SYMBOL_GPL(set_dumpable);

int get_dumpable(struct mm_struct *mm)
{
        int ret;

        ret = mm->flags & 0x3;
        return (ret >= 2) ? 2 : ret;
}

int do_coredump(long signr, int exit_code, struct pt_regs * regs)
{
        char corename[CORENAME_MAX_SIZE + 1];
        struct mm_struct *mm = current->mm;
        struct linux_binfmt * binfmt;
        struct inode * inode;
        struct file * file;
        int retval = 0;
        int fsuid = current->fsuid;
        int flag = 0;
        int ispipe = 0;

        audit_core_dumps(signr);

        binfmt = current->binfmt;
        if (!binfmt || !binfmt->core_dump)
                goto fail;
        down_write(&mm->mmap_sem);
        if (!get_dumpable(mm)) {
                up_write(&mm->mmap_sem);
                goto fail;
        }

        /*
         *      We cannot trust fsuid as being the "true" uid of the
         *      process nor do we know its entire history. We only know it
         *      was tainted so we dump it as root in mode 2.
         */
        if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
                flag = O_EXCL;          /* Stop rewrite attacks */
                current->fsuid = 0;     /* Dump root private */
        }
        set_dumpable(mm, 0);

        retval = coredump_wait(exit_code);
        if (retval < 0)
                goto fail;

        /*
         * Clear any false indication of pending signals that might
         * be seen by the filesystem code called to write the core file.
         */
        clear_thread_flag(TIF_SIGPENDING);

        if (current->signal->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump)
                goto fail_unlock;

        /*
         * lock_kernel() because format_corename() is controlled by sysctl, which
         * uses lock_kernel()
         */
        lock_kernel();
        ispipe = format_corename(corename, core_pattern, signr);
        unlock_kernel();
        if (ispipe) {
                /* SIGPIPE can happen, but it's just never processed */
                if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) {
                        printk(KERN_INFO "Core dump to %s pipe failed\n",
                               corename);
                        goto fail_unlock;
                }
        } else
                file = filp_open(corename,
                                 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
                                 0600);
        if (IS_ERR(file))
                goto fail_unlock;
        inode = file->f_path.dentry->d_inode;
        if (inode->i_nlink > 1)
                goto close_fail;        /* multiple links - don't dump */
        if (!ispipe && d_unhashed(file->f_path.dentry))
                goto close_fail;

        /* AK: actually i see no reason to not allow this for named pipes etc.,
           but keep the previous behaviour for now. */
        if (!ispipe && !S_ISREG(inode->i_mode))
                goto close_fail;
        if (!file->f_op)
                goto close_fail;
        if (!file->f_op->write)
                goto close_fail;
        if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
                goto close_fail;

        retval = binfmt->core_dump(signr, regs, file);

        if (retval)
                current->signal->group_exit_code |= 0x80;
close_fail:
        filp_close(file, NULL);
fail_unlock:
        current->fsuid = fsuid;
        complete_all(&mm->core_done);
fail:
        return retval;
}