/*
 *  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/swap.h>
#include <linux/utsname.h>
#define __NO_VERSION__
#include <linux/module.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";
int core_setuid_ok = 0;
/* 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;       
}

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;
}

static inline void put_binfmt(struct linux_binfmt * fmt)
{
        if (fmt->module)
                __MOD_DEC_USE_COUNT(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 * library)
{
        struct file * file;
        struct nameidata nd;
        int error;

        error = user_path_walk(library, &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);
        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 && file->f_op->read) {
                struct linux_binfmt * fmt;

                read_lock(&binfmt_lock);
                for (fmt = formats ; fmt ; fmt = fmt->next) {
                        if (!fmt->load_shlib)
                                continue;
                        if (!try_inc_mod_count(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 arguments/envelopes
 */
static int count(char ** argv, int max)
{
        int i = 0;

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

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

/*
 * 'copy_strings()' copies argument/envelope 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 ** argv, struct linux_binprm *bprm) 
{
        struct page *kmapped_page = NULL;
        char *kaddr = NULL;
        int ret;

        while (argc-- > 0) {
                char *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, argv, bprm);
        set_fs(oldfs);
        return r; 
}

/*
 * This routine is used to map in a page into an address space: needed by
 * execve() for the initial stack and environment pages.
 *
 * tsk->mmap_sem is held for writing.
 */
void put_dirty_page(struct task_struct * tsk, struct page *page, unsigned long address)
{
        pgd_t * pgd;
        pmd_t * pmd;
        pte_t * pte;
        struct vm_area_struct *vma; 
        pgprot_t prot = PAGE_COPY; 

        if (page_count(page) != 1)
                printk(KERN_ERR "mem_map disagrees with %p at %08lx\n", page, address);
        pgd = pgd_offset(tsk->mm, address);

        spin_lock(&tsk->mm->page_table_lock);
        pmd = pmd_alloc(tsk->mm, pgd, address);
        if (!pmd)
                goto out;
        pte = pte_alloc(tsk->mm, pmd, address);
        if (!pte)
                goto out;
        if (!pte_none(*pte))
                goto out;
        lru_cache_add(page);
        flush_dcache_page(page);
        flush_page_to_ram(page);
        /* lookup is cheap because there is only a single entry in the list */
        vma = find_vma(tsk->mm, address); 
        if (vma) 
                prot = vma->vm_page_prot;
        set_pte(pte, pte_mkdirty(pte_mkwrite(mk_pte(page, prot))));
        tsk->mm->rss++;
        spin_unlock(&tsk->mm->page_table_lock);

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

int setup_arg_pages(struct linux_binprm *bprm)
{
        unsigned long stack_base;
        struct vm_area_struct *mpnt;
        int i, ret;

        stack_base = STACK_TOP - MAX_ARG_PAGES*PAGE_SIZE;

        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; 
        
        down_write(&current->mm->mmap_sem);
        {
                mpnt->vm_mm = current->mm;
                mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
                mpnt->vm_end = STACK_TOP;
                mpnt->vm_flags = VM_STACK_FLAGS;
                mpnt->vm_page_prot = protection_map[VM_STACK_FLAGS & 0x7];
                mpnt->vm_ops = NULL;
                mpnt->vm_pgoff = 0;
                mpnt->vm_file = NULL;
                mpnt->vm_private_data = (void *) 0;
                if ((ret = insert_vm_struct(current->mm, mpnt))) {
                        up_write(&current->mm->mmap_sem);
                        kmem_cache_free(vm_area_cachep, mpnt);
                        return ret;
                }
                current->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;
                        put_dirty_page(current,page,stack_base);
                }
                stack_base += PAGE_SIZE;
        }
        up_write(&current->mm->mmap_sem);
        
        return 0;
}

struct file *open_exec(const char *name)
{
        struct nameidata nd;
        struct inode *inode;
        struct file *file;
        int err = 0;

        err = path_lookup(name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd);
        file = ERR_PTR(err);
        if (!err) {
                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);
                        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;
}

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 = -ENOSYS;

        if (!file->f_op->read)
                goto fail;
        old_fs = get_fs();
        set_fs(get_ds());
        result = file->f_op->read(file, addr, count, &pos);
        set_fs(old_fs);
fail:
        return result;
}

static int exec_mmap(void)
{
        struct mm_struct * mm, * old_mm;

        old_mm = current->mm;

        if (old_mm && atomic_read(&old_mm->mm_users) == 1) {
                mm_release();
                down_write(&old_mm->mmap_sem);
                exit_mmap(old_mm);
                up_write(&old_mm->mmap_sem);
                return 0;
        }


        mm = mm_alloc();
        if (mm) {
                struct mm_struct *active_mm;

                if (init_new_context(current, mm)) {
                        mmdrop(mm);
                        return -ENOMEM;
                }

                /* 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);

                task_lock(current);
                active_mm = current->active_mm;
                current->mm = mm;
                current->active_mm = mm;
                task_unlock(current);
                activate_mm(active_mm, mm);
                mm_release();
                if (old_mm) {
                        if (active_mm != old_mm) BUG();
                        mmput(old_mm);
                        return 0;
                }
                mmdrop(active_mm);
                return 0;
        }
        return -ENOMEM;
}

/*
 * 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_SIGNAL option to clone().)
 */
 
static inline int make_private_signals(void)
{
        struct signal_struct * newsig;

        if (atomic_read(&current->sig->count) <= 1)
                return 0;
        newsig = kmem_cache_alloc(sigact_cachep, GFP_KERNEL);
        if (newsig == NULL)
                return -ENOMEM;
        spin_lock_init(&newsig->siglock);
        atomic_set(&newsig->count, 1);
        memcpy(newsig->action, current->sig->action, sizeof(newsig->action));
        spin_lock_irq(&current->sigmask_lock);
        current->sig = newsig;
        spin_unlock_irq(&current->sigmask_lock);
        return 0;
}
        
/*
 * If make_private_signals() made a copy of the signal table, decrement the
 * refcount of the original table, and free it if necessary.
 * We don't do that in make_private_signals() so that we can back off
 * in flush_old_exec() if an error occurs after calling make_private_signals().
 */

static inline void release_old_signals(struct signal_struct * oldsig)
{
        if (current->sig == oldsig)
                return;
        if (atomic_dec_and_test(&oldsig->count))
                kmem_cache_free(sigact_cachep, oldsig);
}

/*
 * 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;

        write_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;
                write_unlock(&files->file_lock);
                for ( ; set ; i++,set >>= 1) {
                        if (set & 1) {
                                sys_close(i);
                        }
                }
                write_lock(&files->file_lock);

        }
        write_unlock(&files->file_lock);
}

/*
 * An execve() will automatically "de-thread" the process.
 * Note: we don't have to hold the tasklist_lock to test
 * whether we migth need to do this. If we're not part of
 * a thread group, there is no way we can become one
 * dynamically. And if we are, we only need to protect the
 * unlink - even if we race with the last other thread exit,
 * at worst the list_del_init() might end up being a no-op.
 */
static inline void de_thread(struct task_struct *tsk)
{
        if (!list_empty(&tsk->thread_group)) {
                write_lock_irq(&tasklist_lock);
                list_del_init(&tsk->thread_group);
                write_unlock_irq(&tasklist_lock);
        }

        /* Minor oddity: this might stay the same. */
        tsk->tgid = tsk->pid;
}

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

void set_task_comm(struct task_struct *tsk, char *buf)
{
        task_lock(tsk);
        strncpy(tsk->comm, buf, sizeof(tsk->comm));
        tsk->comm[sizeof(tsk->comm)-1]='\0';
        task_unlock(tsk);
}

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

        /*
         * Make sure we have a private signal table
         */
        oldsig = current->sig;
        retval = make_private_signals();
        if (retval) goto flush_failed;

        /*
         * 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 flush_failed;
        
        /* 
         * Release all of the old mmap stuff
         */
        retval = exec_mmap();
        if (retval) goto mmap_failed;

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

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

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

        flush_thread();

        de_thread(current);

        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 
            permission(bprm->file->f_dentry->d_inode,MAY_READ))
                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);
        flush_old_files(current->files);

        return 0;

mmap_failed:
        put_files_struct(current->files);
        current->files = files;
flush_failed:
        spin_lock_irq(&current->sigmask_lock);
        if (current->sig != oldsig) {
                kmem_cache_free(sigact_cachep, current->sig);
                current->sig = oldsig;
        }
        spin_unlock_irq(&current->sigmask_lock);
        return retval;
}

/*
 * We mustn't allow tracing of suid binaries, unless
 * the tracer has the capability to trace anything..
 */
static inline int must_not_trace_exec(struct task_struct * p)
{
        return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
}

/* 
 * 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;

        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;
        }

        /* We don't have VFS support for capabilities yet */
        cap_clear(bprm->cap_inheritable);
        cap_clear(bprm->cap_permitted);
        cap_clear(bprm->cap_effective);

        /*  To support inheritance of root-permissions and suid-root
         *  executables under compatibility mode, we raise all three
         *  capability sets for the file.
         *
         *  If only the real uid is 0, we only raise the inheritable
         *  and permitted sets of the executable file.
         */

        if (!issecure(SECURE_NOROOT)) {
                if (bprm->e_uid == 0 || current->uid == 0) {
                        cap_set_full(bprm->cap_inheritable);
                        cap_set_full(bprm->cap_permitted);
                }
                if (bprm->e_uid == 0) 
                        cap_set_full(bprm->cap_effective);
        }

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

/*
 * This function is used to produce the new IDs and capabilities
 * from the old ones and the file's capabilities.
 *
 * The formula used for evolving capabilities is:
 *
 *       pI' = pI
 * (***) pP' = (fP & X) | (fI & pI)
 *       pE' = pP' & fE          [NB. fE is 0 or ~0]
 *
 * I=Inheritable, P=Permitted, E=Effective // p=process, f=file
 * ' indicates post-exec(), and X is the global 'cap_bset'.
 *
 */

void compute_creds(struct linux_binprm *bprm) 
{
        kernel_cap_t new_permitted, working;
        int do_unlock = 0;

        new_permitted = cap_intersect(bprm->cap_permitted, cap_bset);
        working = cap_intersect(bprm->cap_inheritable,
                                current->cap_inheritable);
        new_permitted = cap_combine(new_permitted, working);

        if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
            !cap_issubset(new_permitted, current->cap_permitted)) {
                current->mm->dumpable = 0;
                
                lock_kernel();
                if (must_not_trace_exec(current)
                    || atomic_read(&current->fs->count) > 1
                    || atomic_read(&current->files->count) > 1
                    || atomic_read(&current->sig->count) > 1) {
                        if(!capable(CAP_SETUID)) {
                                bprm->e_uid = current->uid;
                                bprm->e_gid = current->gid;
                        }
                        if(!capable(CAP_SETPCAP)) {
                                new_permitted = cap_intersect(new_permitted,
                                                        current->cap_permitted);
                        }
                }
                do_unlock = 1;
        }


        /* For init, we want to retain the capabilities set
         * in the init_task struct. Thus we skip the usual
         * capability rules */
        if (current->pid != 1) {
                current->cap_permitted = new_permitted;
                current->cap_effective =
                        cap_intersect(new_permitted, bprm->cap_effective);
        }
        
        /* AUD: Audit candidate if current->cap_effective is set */

        current->suid = current->euid = current->fsuid = bprm->e_uid;
        current->sgid = current->egid = current->fsgid = bprm->e_gid;

        if(do_unlock)
                unlock_kernel();
        current->keep_capabilities = 0;
}


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(page);
inside:
                        page = bprm->page[bprm->p/PAGE_SIZE];
                        kaddr = kmap(page);
                }
                kunmap(page);
                bprm->argc--;
        }
}

/*
 * 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 < 0x100000000;

                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
        /* 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_inc_mod_count(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)
                                break;
                        if (!bprm->file) {
                                read_unlock(&binfmt_lock);
                                return retval;
                        }
                }
                read_unlock(&binfmt_lock);
                if (retval != -ENOEXEC) {
                        break;
#ifdef CONFIG_KMOD
                }else{
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
                        char modname[20];
                        if (printable(bprm->buf[0]) &&
                            printable(bprm->buf[1]) &&
                            printable(bprm->buf[2]) &&
                            printable(bprm->buf[3]))
                                break; /* -ENOEXEC */
                        sprintf(modname, "binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
                        request_module(modname);
#endif
                }
        }
        return retval;
}


/*
 * sys_execve() executes a new program.
 */
int do_execve(char * filename, char ** argv, char ** 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;

        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.sh_bang = 0;
        bprm.loader = 0;
        bprm.exec = 0;
        if ((bprm.argc = count(argv, bprm.p / sizeof(void *))) < 0) {
                allow_write_access(file);
                fput(file);
                return bprm.argc;
        }

        if ((bprm.envc = count(envp, bprm.p / sizeof(void *))) < 0) {
                allow_write_access(file);
                fput(file);
                return bprm.envc;
        }

        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)
                /* execve success */
                return retval;

out:
        /* Something went wrong, return the inode and free the argument pages*/
        allow_write_access(bprm.file);
        if (bprm.file)
                fput(bprm.file);

        for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
                struct page * page = bprm.page[i];
                if (page)
                        __free_page(page);
        }

        return retval;
}

void set_binfmt(struct linux_binfmt *new)
{
        struct linux_binfmt *old = current->binfmt;
        if (new && new->module)
                __MOD_INC_USE_COUNT(new->module);
        current->binfmt = new;
        if (old && old->module)
                __MOD_DEC_USE_COUNT(old->module);
}

#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->pid);
                                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,
                                              "%ld", 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->pid);
                if (rc > out_end - out_ptr)
                        goto out;
                out_ptr += rc;
        }
      out:
        *out_ptr = 0;
}

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

        lock_kernel();
        binfmt = current->binfmt;
        if (!binfmt || !binfmt->core_dump)
                goto fail;
        if (!is_dumpable(current))
        {
                if(!core_setuid_ok || !current->task_dumpable)
                        goto fail;
                current->fsuid = 0;
        }
        current->mm->dumpable = 0;
        if (current->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump)
                goto fail;

        format_corename(corename, core_pattern, signr);
        file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW, 0600);
        if (IS_ERR(file))
                goto fail;
        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);

close_fail:
        filp_close(file, NULL);
fail:
        if (fsuid != current->fsuid)
                current->fsuid = fsuid;
        unlock_kernel();
        return retval;
}