root/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/config.h>
#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/personality.h>
#include <linux/binfmts.h>
#include <linux/swap.h>
#include <linux/utsname.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 <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/mmu_context.h>

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

int core_uses_pid;
char core_pattern[65] = "core";
/* The maximal length of core_pattern is also specified in sysctl.c */

static struct linux_binfmt *formats;
static rwlock_t binfmt_lock = RW_LOCK_UNLOCKED;

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;
                        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;

        nd.intent.open.flags = FMODE_READ;
        error = __user_walk(library, LOOKUP_FOLLOW|LOOKUP_OPEN, &nd);
        if (error)
                goto out;

        error = -EINVAL;
        if (!S_ISREG(nd.dentry->d_inode->i_mode))
                goto exit;

        error = permission(nd.dentry->d_inode, MAY_READ | MAY_EXEC, &nd);
        if (error)
                goto exit;

        file = dentry_open(nd.dentry, nd.mnt, 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:
        path_release(&nd);
        goto out;
}

/*
 * 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;
                }
        }
        return i;
}

/*
 * 'copy_strings()' copies argument/environment strings from user
 * memory to free pages in kernel mem. These are in a format ready
 * to be put directly into the top of new user memory.
 */
int copy_strings(int argc,char __user * __user * argv, struct linux_binprm *bprm)
{
        struct page *kmapped_page = NULL;
        char *kaddr = NULL;
        int ret;

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

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

                if (bprm->p < len)  {
                        ret = -E2BIG;
                        goto out;
                }

                bprm->p -= len;
                /* XXX: add architecture specific overflow check here. */
                pos = bprm->p;

                while (len > 0) {
                        int i, new, err;
                        int offset, bytes_to_copy;
                        struct page *page;

                        offset = pos % PAGE_SIZE;
                        i = pos/PAGE_SIZE;
                        page = bprm->page[i];
                        new = 0;
                        if (!page) {
                                page = alloc_page(GFP_HIGHUSER);
                                bprm->page[i] = page;
                                if (!page) {
                                        ret = -ENOMEM;
                                        goto out;
                                }
                                new = 1;
                        }

                        if (page != kmapped_page) {
                                if (kmapped_page)
                                        kunmap(kmapped_page);
                                kmapped_page = page;
                                kaddr = kmap(kmapped_page);
                        }
                        if (new && offset)
                                memset(kaddr, 0, offset);
                        bytes_to_copy = PAGE_SIZE - offset;
                        if (bytes_to_copy > len) {
                                bytes_to_copy = len;
                                if (new)
                                        memset(kaddr+offset+len, 0,
                                                PAGE_SIZE-offset-len);
                        }
                        err = copy_from_user(kaddr+offset, str, bytes_to_copy);
                        if (err) {
                                ret = -EFAULT;
                                goto out;
                        }

                        pos += bytes_to_copy;
                        str += bytes_to_copy;
                        len -= bytes_to_copy;
                }
        }
        ret = 0;
out:
        if (kmapped_page)
                kunmap(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
/*
 * This routine is used to map in a page into an address space: needed by
 * execve() for the initial stack and environment pages.
 *
 * vma->vm_mm->mmap_sem is held for writing.
 */
void install_arg_page(struct vm_area_struct *vma,
                        struct page *page, unsigned long address)
{
        struct mm_struct *mm = vma->vm_mm;
        pgd_t * pgd;
        pmd_t * pmd;
        pte_t * pte;

        if (unlikely(anon_vma_prepare(vma)))
                goto out_sig;

        flush_dcache_page(page);
        pgd = pgd_offset(mm, address);

        spin_lock(&mm->page_table_lock);
        pmd = pmd_alloc(mm, pgd, address);
        if (!pmd)
                goto out;
        pte = pte_alloc_map(mm, pmd, address);
        if (!pte)
                goto out;
        if (!pte_none(*pte)) {
                pte_unmap(pte);
                goto out;
        }
        mm->rss++;
        lru_cache_add_active(page);
        set_pte(pte, pte_mkdirty(pte_mkwrite(mk_pte(
                                        page, vma->vm_page_prot))));
        page_add_anon_rmap(page, vma, address);
        pte_unmap(pte);
        spin_unlock(&mm->page_table_lock);

        /* no need for flush_tlb */
        return;
out:
        spin_unlock(&mm->page_table_lock);
out_sig:
        __free_page(page);
        force_sig(SIGKILL, current);
}

int setup_arg_pages(struct linux_binprm *bprm, int executable_stack)
{
        unsigned long stack_base;
        struct vm_area_struct *mpnt;
        struct mm_struct *mm = current->mm;
        int i;
        long arg_size;

#ifdef CONFIG_STACK_GROWSUP
        /* Move the argument and environment strings to the bottom of the
         * stack space.
         */
        int offset, j;
        char *to, *from;

        /* Start by shifting all the pages down */
        i = 0;
        for (j = 0; j < MAX_ARG_PAGES; j++) {
                struct page *page = bprm->page[j];
                if (!page)
                        continue;
                bprm->page[i++] = page;
        }

        /* Now move them within their pages */
        offset = bprm->p % PAGE_SIZE;
        to = kmap(bprm->page[0]);
        for (j = 1; j < i; j++) {
                memmove(to, to + offset, PAGE_SIZE - offset);
                from = kmap(bprm->page[j]);
                memcpy(to + PAGE_SIZE - offset, from, offset);
                kunmap(bprm->page[j - 1]);
                to = from;
        }
        memmove(to, to + offset, PAGE_SIZE - offset);
        kunmap(bprm->page[j - 1]);

        /* Adjust bprm->p to point to the end of the strings. */
        bprm->p = PAGE_SIZE * i - offset;

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

        mm->arg_start = stack_base;
        arg_size = i << PAGE_SHIFT;

        /* zero pages that were copied above */
        while (i < MAX_ARG_PAGES)
                bprm->page[i++] = NULL;
#else
        stack_base = STACK_TOP - MAX_ARG_PAGES * PAGE_SIZE;
        mm->arg_start = bprm->p + stack_base;
        arg_size = STACK_TOP - (PAGE_MASK & (unsigned long) mm->arg_start);
#endif

        bprm->p += stack_base;
        if (bprm->loader)
                bprm->loader += stack_base;
        bprm->exec += stack_base;

        mpnt = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!mpnt)
                return -ENOMEM;

        if (security_vm_enough_memory(arg_size >> PAGE_SHIFT)) {
                kmem_cache_free(vm_area_cachep, mpnt);
                return -ENOMEM;
        }

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

        down_write(&mm->mmap_sem);
        {
                mpnt->vm_mm = mm;
#ifdef CONFIG_STACK_GROWSUP
                mpnt->vm_start = stack_base;
                mpnt->vm_end = PAGE_MASK &
                        (PAGE_SIZE - 1 + (unsigned long) bprm->p);
#else
                mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
                mpnt->vm_end = STACK_TOP;
#endif
                /* 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))
                        mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;
                else if (executable_stack == EXSTACK_DISABLE_X)
                        mpnt->vm_flags = VM_STACK_FLAGS & ~VM_EXEC;
                else
                        mpnt->vm_flags = VM_STACK_FLAGS;
                mpnt->vm_page_prot = protection_map[mpnt->vm_flags & 0x7];
                insert_vm_struct(mm, mpnt);
                mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
        }

        for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
                struct page *page = bprm->page[i];
                if (page) {
                        bprm->page[i] = NULL;
                        install_arg_page(mpnt, page, stack_base);
                }
                stack_base += PAGE_SIZE;
        }
        up_write(&mm->mmap_sem);
        
        return 0;
}

EXPORT_SYMBOL(setup_arg_pages);

#define free_arg_pages(bprm) do { } while (0)

#else

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

        for (i = 0; i < MAX_ARG_PAGES; i++) {
                if (bprm->page[i])
                        __free_page(bprm->page[i]);
                bprm->page[i] = NULL;
        }
}

#endif /* CONFIG_MMU */

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

        nd.intent.open.flags = FMODE_READ;
        err = path_lookup(name, LOOKUP_FOLLOW|LOOKUP_OPEN, &nd);
        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 = permission(inode, MAY_EXEC, &nd);
                        if (!err && !(inode->i_mode & 0111))
                                err = -EACCES;
                        file = ERR_PTR(err);
                        if (!err) {
                                file = dentry_open(nd.dentry, nd.mnt, O_RDONLY);
                                if (!IS_ERR(file)) {
                                        err = deny_write_access(file);
                                        if (err) {
                                                fput(file);
                                                file = ERR_PTR(err);
                                        }
                                }
out:
                                return file;
                        }
                }
                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;

        /* Add it to the list of mm's */
        spin_lock(&mmlist_lock);
        list_add(&mm->mmlist, &init_mm.mmlist);
        mmlist_nr++;
        spin_unlock(&mmlist_lock);

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

        task_lock(tsk);
        active_mm = tsk->active_mm;
        tsk->mm = mm;
        tsk->active_mm = mm;
        activate_mm(active_mm, mm);
        task_unlock(tsk);
        if (old_mm) {
                if (active_mm != old_mm) BUG();
                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 inline int de_thread(struct task_struct *tsk)
{
        struct signal_struct *newsig, *oldsig = tsk->signal;
        struct sighand_struct *newsighand, *oldsighand = tsk->sighand;
        spinlock_t *lock = &oldsighand->siglock;
        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)
                return 0;

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

        spin_lock_init(&newsighand->siglock);
        atomic_set(&newsighand->count, 1);
        memcpy(newsighand->action, oldsighand->action, sizeof(newsighand->action));

        /*
         * See if we need to allocate a new signal structure
         */
        newsig = NULL;
        if (atomic_read(&oldsig->count) > 1) {
                newsig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
                if (!newsig) {
                        kmem_cache_free(sighand_cachep, newsighand);
                        return -ENOMEM;
                }
                atomic_set(&newsig->count, 1);
                newsig->group_exit = 0;
                newsig->group_exit_code = 0;
                newsig->group_exit_task = NULL;
                newsig->group_stop_count = 0;
                newsig->curr_target = NULL;
                init_sigpending(&newsig->shared_pending);
                INIT_LIST_HEAD(&newsig->posix_timers);

                newsig->tty = oldsig->tty;
                newsig->pgrp = oldsig->pgrp;
                newsig->session = oldsig->session;
                newsig->leader = oldsig->leader;
                newsig->tty_old_pgrp = oldsig->tty_old_pgrp;
        }

        if (thread_group_empty(current))
                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 (oldsig->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);
                if (newsig)
                        kmem_cache_free(signal_cachep, newsig);
                return -EAGAIN;
        }
        oldsig->group_exit = 1;
        zap_other_threads(current);
        read_unlock(&tasklist_lock);

        /*
         * Account for the thread group leader hanging around:
         */
        count = 2;
        if (current->pid == current->tgid)
                count = 1;
        while (atomic_read(&oldsig->count) > count) {
                oldsig->group_exit_task = current;
                oldsig->notify_count = count;
                __set_current_state(TASK_UNINTERRUPTIBLE);
                spin_unlock_irq(lock);
                schedule();
                spin_lock_irq(lock);
        }
        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 (current->pid != current->tgid) {
                struct task_struct *leader = current->group_leader, *parent;
                struct dentry *proc_dentry1, *proc_dentry2;
                unsigned long state, ptrace;

                /*
                 * Wait for the thread group leader to be a zombie.
                 * It should already be zombie at this point, most
                 * of the time.
                 */
                while (leader->state != TASK_ZOMBIE)
                        yield();

                spin_lock(&leader->proc_lock);
                spin_lock(&current->proc_lock);
                proc_dentry1 = proc_pid_unhash(current);
                proc_dentry2 = proc_pid_unhash(leader);
                write_lock_irq(&tasklist_lock);

                if (leader->tgid != current->tgid)
                        BUG();
                if (current->pid == current->tgid)
                        BUG();
                /*
                 * 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:
                 */
                ptrace = leader->ptrace;
                parent = leader->parent;

                ptrace_unlink(current);
                ptrace_unlink(leader);
                remove_parent(current);
                remove_parent(leader);

                switch_exec_pids(leader, current);

                current->parent = current->real_parent = leader->real_parent;
                leader->parent = leader->real_parent = child_reaper;
                current->group_leader = current;
                leader->group_leader = leader;

                add_parent(current, current->parent);
                add_parent(leader, leader->parent);
                if (ptrace) {
                        current->ptrace = ptrace;
                        __ptrace_link(current, parent);
                }

                list_del(&current->tasks);
                list_add_tail(&current->tasks, &init_task.tasks);
                current->exit_signal = SIGCHLD;
                state = leader->state;

                write_unlock_irq(&tasklist_lock);
                spin_unlock(&leader->proc_lock);
                spin_unlock(&current->proc_lock);
                proc_pid_flush(proc_dentry1);
                proc_pid_flush(proc_dentry2);

                if (state != TASK_ZOMBIE)
                        BUG();
                release_task(leader);
        }

no_thread_group:

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

        if (current == oldsig->curr_target)
                oldsig->curr_target = next_thread(current);
        if (newsig)
                current->signal = newsig;
        current->sighand = newsighand;
        init_sigpending(&current->pending);
        recalc_sigpending();

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

        if (newsig && atomic_dec_and_test(&oldsig->count))
                kmem_cache_free(signal_cachep, oldsig);

        if (atomic_dec_and_test(&oldsighand->count))
                kmem_cache_free(sighand_cachep, oldsighand);

        if (!thread_group_empty(current))
                BUG();
        if (current->tgid != current->pid)
                BUG();
        return 0;
}
        
/*
 * These functions flushes out all traces of the currently running executable
 * so that a new one can be started
 */

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

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

                j++;
                i = j * __NFDBITS;
                if (i >= files->max_fds || i >= files->max_fdset)
                        break;
                set = files->close_on_exec->fds_bits[j];
                if (!set)
                        continue;
                files->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);
}

int flush_old_exec(struct linux_binprm * bprm)
{
        char * name;
        int i, ch, retval;
        struct files_struct *files;

        /*
         * 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 */
        steal_locks(files);
        put_files_struct(files);

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

        if (current->euid == current->uid && current->egid == current->gid)
                current->mm->dumpable = 1;
        name = bprm->filename;
        for (i=0; (ch = *(name++)) != '\0';) {
                if (ch == '/')
                        i = 0;
                else
                        if (i < 15)
                                current->comm[i++] = ch;
        }
        current->comm[i] = '\0';

        flush_thread();

        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 
            permission(bprm->file->f_dentry->d_inode,MAY_READ, NULL))
                current->mm->dumpable = 0;

        /* 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:
        put_files_struct(current->files);
        current->files = 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_dentry->d_inode;
        int retval;

        mode = inode->i_mode;
        /*
         * Check execute perms again - if the caller has CAP_DAC_OVERRIDE,
         * vfs_permission lets a non-executable through
         */
        if (!(mode & 0111))     /* with at least _one_ execute bit set */
                return -EACCES;
        if (bprm->file->f_op == NULL)
                return -EACCES;

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

        if(!(bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)) {
                /* Set-uid? */
                if (mode & S_ISUID)
                        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))
                        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 inline 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;
        task_lock(current);
        unsafe = unsafe_exec(current);
        security_bprm_apply_creds(bprm, unsafe);
        task_unlock(current);
}

EXPORT_SYMBOL(compute_creds);

void remove_arg_zero(struct linux_binprm *bprm)
{
        if (bprm->argc) {
                unsigned long offset;
                char * kaddr;
                struct page *page;

                offset = bprm->p % PAGE_SIZE;
                goto inside;

                while (bprm->p++, *(kaddr+offset++)) {
                        if (offset != PAGE_SIZE)
                                continue;
                        offset = 0;
                        kunmap_atomic(kaddr, KM_USER0);
inside:
                        page = bprm->page[bprm->p/PAGE_SIZE];
                        kaddr = kmap_atomic(page, KM_USER0);
                }
                kunmap_atomic(kaddr, KM_USER0);
                bprm->argc--;
        }
}

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=0;
        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 = PAGE_SIZE*MAX_ARG_PAGES-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);
        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;
                                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;
        int retval;
        int i;

        file = open_exec(filename);

        retval = PTR_ERR(file);
        if (IS_ERR(file))
                return retval;

        sched_balance_exec();

        bprm.p = PAGE_SIZE*MAX_ARG_PAGES-sizeof(void *);
        memset(bprm.page, 0, MAX_ARG_PAGES*sizeof(bprm.page[0]));

        bprm.file = file;
        bprm.filename = filename;
        bprm.interp = filename;
        bprm.sh_bang = 0;
        bprm.loader = 0;
        bprm.exec = 0;
        bprm.security = NULL;
        bprm.mm = mm_alloc();
        retval = -ENOMEM;
        if (!bprm.mm)
                goto out_file;

        retval = init_new_context(current, bprm.mm);
        if (retval < 0)
                goto out_mm;

        bprm.argc = count(argv, bprm.p / sizeof(void *));
        if ((retval = bprm.argc) < 0)
                goto out_mm;

        bprm.envc = count(envp, bprm.p / sizeof(void *));
        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;

        retval = copy_strings(bprm.argc, argv, &bprm);
        if (retval < 0)
                goto out;

        retval = search_binary_handler(&bprm,regs);
        if (retval >= 0) {
                free_arg_pages(&bprm);

                /* execve success */
                security_bprm_free(&bprm);
                return retval;
        }

out:
        /* Something went wrong, return the inode and free the argument pages*/
        for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
                struct page * page = bprm.page[i];
                if (page)
                        __free_page(page);
        }

        if (bprm.security)
                security_bprm_free(&bprm);

out_mm:
        if (bprm.mm)
                mmdrop(bprm.mm);

out_file:
        if (bprm.file) {
                allow_write_access(bprm.file);
                fput(bprm.file);
        }
        return retval;
}

EXPORT_SYMBOL(do_execve);

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);

#define CORENAME_MAX_SIZE 64

/* 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.
 */
void 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;

        /* 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", system_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 */
        if (!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;
}

static void zap_threads (struct mm_struct *mm)
{
        struct task_struct *g, *p;
        struct task_struct *tsk = current;
        struct completion *vfork_done = tsk->vfork_done;

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

        read_lock(&tasklist_lock);
        do_each_thread(g,p)
                if (mm == p->mm && p != tsk) {
                        force_sig_specific(SIGKILL, p);
                        mm->core_waiters++;
                }
        while_each_thread(g,p);

        read_unlock(&tasklist_lock);
}

static void coredump_wait(struct mm_struct *mm)
{
        DECLARE_COMPLETION(startup_done);

        mm->core_waiters++; /* let other threads block */
        mm->core_startup_done = &startup_done;

        /* give other threads a chance to run: */
        yield();

        zap_threads(mm);
        if (--mm->core_waiters) {
                up_write(&mm->mmap_sem);
                wait_for_completion(&startup_done);
        } else
                up_write(&mm->mmap_sem);
        BUG_ON(mm->core_waiters);
}

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;

        lock_kernel();
        binfmt = current->binfmt;
        if (!binfmt || !binfmt->core_dump)
                goto fail;
        down_write(&mm->mmap_sem);
        if (!mm->dumpable) {
                up_write(&mm->mmap_sem);
                goto fail;
        }
        mm->dumpable = 0;
        init_completion(&mm->core_done);
        current->signal->group_exit = 1;
        current->signal->group_exit_code = exit_code;
        coredump_wait(mm);

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

        format_corename(corename, core_pattern, signr);
        file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE, 0600);
        if (IS_ERR(file))
                goto fail_unlock;
        inode = file->f_dentry->d_inode;
        if (inode->i_nlink > 1)
                goto close_fail;        /* multiple links - don't dump */
        if (d_unhashed(file->f_dentry))
                goto close_fail;

        if (!S_ISREG(inode->i_mode))
                goto close_fail;
        if (!file->f_op)
                goto close_fail;
        if (!file->f_op->write)
                goto close_fail;
        if (do_truncate(file->f_dentry, 0) != 0)
                goto close_fail;

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

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