/*
   *  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/fdtable.h>

  #include <linux/mm.h>

  #include <linux/vmacache.h>

  #include <linux/stat.h>
  #include <linux/fcntl.h>

  #include <linux/swap.h>

  #include <linux/string.h>

  #include <linux/init.h>

  #include <linux/sched/mm.h>

  #include <linux/sched/coredump.h>

  #include <linux/sched/signal.h>

  #include <linux/sched/numa_balancing.h>

  #include <linux/sched/task.h>

  #include <linux/pagemap.h>

  #include <linux/perf_event.h>

  #include <linux/highmem.h>
  #include <linux/spinlock.h>
  #include <linux/key.h>
  #include <linux/personality.h>
  #include <linux/binfmts.h>

  #include <linux/utsname.h>

  #include <linux/pid_namespace.h>

  #include <linux/module.h>
  #include <linux/namei.h>

  #include <linux/mount.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>

  #include <linux/tsacct_kern.h>

  #include <linux/cn_proc.h>

  #include <linux/audit.h>

  #include <linux/tracehook.h>

  #include <linux/kmod.h>

  #include <linux/fsnotify.h>

  #include <linux/fs_struct.h>

  #include <linux/pipe_fs_i.h>

  #include <linux/oom.h>

  #include <linux/compat.h>

  #include <linux/vmalloc.h>

  #include <linux/uaccess.h>

  #include <asm/mmu_context.h>

  #include <asm/tlb.h>

  
  #include <trace/events/task.h>

  #include "internal.h"

  #include <trace/events/sched.h>

  int suid_dumpable = 0;

  static LIST_HEAD(formats);

  static DEFINE_RWLOCK(binfmt_lock);

  void __register_binfmt(struct linux_binfmt * fmt, int insert)

  {

  	BUG_ON(!fmt);

  	if (WARN_ON(!fmt->load_binary))
  		return;

  	write_lock(&binfmt_lock);

  	insert ? list_add(&fmt->lh, &formats) :
  		 list_add_tail(&fmt->lh, &formats);

  	write_unlock(&binfmt_lock);

  }

  EXPORT_SYMBOL(__register_binfmt);

  void unregister_binfmt(struct linux_binfmt * fmt)

  {

  	write_lock(&binfmt_lock);

  	list_del(&fmt->lh);

  	write_unlock(&binfmt_lock);

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

  bool path_noexec(const struct path *path)
  {
  	return (path->mnt->mnt_flags & MNT_NOEXEC) ||
  	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
  }

  #ifdef CONFIG_USELIB

  /*
   * 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.
   */

  SYSCALL_DEFINE1(uselib, const char __user *, library)

  {

  	struct linux_binfmt *fmt;

  	struct file *file;

  	struct filename *tmp = getname(library);

  	int error = PTR_ERR(tmp);

  	static const struct open_flags uselib_flags = {
  		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,

  		.acc_mode = MAY_READ | MAY_EXEC,

  		.intent = LOOKUP_OPEN,
  		.lookup_flags = LOOKUP_FOLLOW,

  	};

  	if (IS_ERR(tmp))
  		goto out;

  	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);

  	putname(tmp);
  	error = PTR_ERR(file);
  	if (IS_ERR(file))

  		goto out;
  
  	error = -EINVAL;

  	if (!S_ISREG(file_inode(file)->i_mode))

  		goto exit;

  	error = -EACCES;

  	if (path_noexec(&file->f_path))

  		goto exit;

  	fsnotify_open(file);

  	error = -ENOEXEC;

  	read_lock(&binfmt_lock);
  	list_for_each_entry(fmt, &formats, lh) {
  		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);

  exit:

  	fput(file);
  out:
    	return error;

  }

  #endif /* #ifdef CONFIG_USELIB */

  #ifdef CONFIG_MMU

  /*
   * The nascent bprm->mm is not visible until exec_mmap() but it can
   * use a lot of memory, account these pages in current->mm temporary
   * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
   * change the counter back via acct_arg_size(0).
   */

  static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)

  {
  	struct mm_struct *mm = current->mm;
  	long diff = (long)(pages - bprm->vma_pages);
  
  	if (!mm || !diff)
  		return;
  
  	bprm->vma_pages = pages;

  	add_mm_counter(mm, MM_ANONPAGES, diff);

  }

  static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,

  		int write)
  {
  	struct page *page;
  	int ret;

  	unsigned int gup_flags = FOLL_FORCE;

  
  #ifdef CONFIG_STACK_GROWSUP
  	if (write) {

  		ret = expand_downwards(bprm->vma, pos);

  		if (ret < 0)
  			return NULL;
  	}
  #endif

  
  	if (write)
  		gup_flags |= FOLL_WRITE;

  	/*
  	 * We are doing an exec().  'current' is the process
  	 * doing the exec and bprm->mm is the new process's mm.
  	 */

  	ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,

  			&page, NULL, NULL);

  	if (ret <= 0)
  		return NULL;
  
  	if (write) {

  		unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;

  		unsigned long ptr_size, limit;

  		/*
  		 * Since the stack will hold pointers to the strings, we
  		 * must account for them as well.
  		 *
  		 * The size calculation is the entire vma while each arg page is
  		 * built, so each time we get here it's calculating how far it
  		 * is currently (rather than each call being just the newly
  		 * added size from the arg page).  As a result, we need to
  		 * always add the entire size of the pointers, so that on the
  		 * last call to get_arg_page() we'll actually have the entire
  		 * correct size.
  		 */
  		ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
  		if (ptr_size > ULONG_MAX - size)
  			goto fail;
  		size += ptr_size;

  		acct_arg_size(bprm, size / PAGE_SIZE);

  		/*
  		 * We've historically supported up to 32 pages (ARG_MAX)
  		 * of argument strings even with small stacks
  		 */
  		if (size <= ARG_MAX)
  			return page;

  
  		/*

  		 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
  		 * (whichever is smaller) 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.
  		 */

  		limit = _STK_LIM / 4 * 3;
  		limit = min(limit, rlimit(RLIMIT_STACK) / 4);
  		if (size > limit)

  			goto fail;

  	}
  
  	return page;

  
  fail:
  	put_page(page);
  	return NULL;

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

  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;

  	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)

  		return -ENOMEM;

  	if (down_write_killable(&mm->mmap_sem)) {
  		err = -EINTR;
  		goto err_free;
  	}

  	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.
  	 */

  	BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);

  	vma->vm_end = STACK_TOP_MAX;
  	vma->vm_start = vma->vm_end - PAGE_SIZE;

  	vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;

  	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);

  	INIT_LIST_HEAD(&vma->anon_vma_chain);

  	err = insert_vm_struct(mm, vma);

  	if (err)

  		goto err;

  
  	mm->stack_vm = mm->total_vm = 1;

  	arch_bprm_mm_init(mm, vma);

  	up_write(&mm->mmap_sem);

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

  	return 0;

  err:

  	up_write(&mm->mmap_sem);

  err_free:

  	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 inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)

  {
  }

  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().
   */

  static 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 = __bprm_mm_init(bprm);
  	if (err)
  		goto err;
  
  	return 0;
  
  err:
  	if (mm) {
  		bprm->mm = NULL;
  		mmdrop(mm);
  	}
  
  	return err;
  }

  struct user_arg_ptr {

  #ifdef CONFIG_COMPAT
  	bool is_compat;
  #endif
  	union {
  		const char __user *const __user *native;
  #ifdef CONFIG_COMPAT

  		const compat_uptr_t __user *compat;

  #endif
  	} ptr;

  };
  
  static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)

  {

  	const char __user *native;
  
  #ifdef CONFIG_COMPAT
  	if (unlikely(argv.is_compat)) {
  		compat_uptr_t compat;
  
  		if (get_user(compat, argv.ptr.compat + nr))
  			return ERR_PTR(-EFAULT);

  		return compat_ptr(compat);
  	}
  #endif
  
  	if (get_user(native, argv.ptr.native + nr))

  		return ERR_PTR(-EFAULT);

  	return native;

  }

  /*
   * count() counts the number of strings in array ARGV.
   */

  static int count(struct user_arg_ptr argv, int max)

  {
  	int i = 0;

  	if (argv.ptr.native != NULL) {

  		for (;;) {

  			const char __user *p = get_user_arg_ptr(argv, i);

  			if (!p)
  				break;

  
  			if (IS_ERR(p))
  				return -EFAULT;

  			if (i >= max)

  				return -E2BIG;

  			++i;

  
  			if (fatal_signal_pending(current))
  				return -ERESTARTNOHAND;

  			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, struct user_arg_ptr argv,

  			struct linux_binprm *bprm)

  {
  	struct page *kmapped_page = NULL;
  	char *kaddr = NULL;

  	unsigned long kpos = 0;

  	int ret;
  
  	while (argc-- > 0) {

  		const char __user *str;

  		int len;
  		unsigned long pos;

  		ret = -EFAULT;
  		str = get_user_arg_ptr(argv, argc);
  		if (IS_ERR(str))

  			goto out;

  		len = strnlen_user(str, MAX_ARG_STRLEN);
  		if (!len)
  			goto out;
  
  		ret = -E2BIG;
  		if (!valid_arg_len(bprm, len))

  			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;

  			if (fatal_signal_pending(current)) {
  				ret = -ERESTARTNOHAND;
  				goto out;
  			}

  			cond_resched();

  			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, const char *const *__argv,

  			struct linux_binprm *bprm)

  {
  	int r;
  	mm_segment_t oldfs = get_fs();

  	struct user_arg_ptr argv = {

  		.ptr.native = (const char __user *const  __user *)__argv,

  	};

  	set_fs(KERNEL_DS);

  	r = copy_strings(argc, 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)
  	 */

  	if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
  		return -ENOMEM;

  
  	/*
  	 * 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, false))

  		return -ENOMEM;
  
  	lru_add_drain();

  	tlb_gather_mmu(&tlb, mm, old_start, old_end);

  	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 : USER_PGTABLES_CEILING);

  	} 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 : USER_PGTABLES_CEILING);

  	}

  	tlb_finish_mmu(&tlb, old_start, old_end);

  
  	/*

  	 * Shrink the vma to just the new range.  Always succeeds.

  	 */
  	vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
  
  	return 0;

  }

  /*
   * 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;

  	unsigned long stack_size;
  	unsigned long stack_expand;
  	unsigned long rlim_stack;

  
  #ifdef CONFIG_STACK_GROWSUP

  	/* Limit stack size */

  	stack_base = rlimit_max(RLIMIT_STACK);

  	if (stack_base > STACK_SIZE_MAX)
  		stack_base = STACK_SIZE_MAX;

  	/* Add space for stack randomization. */
  	stack_base += (STACK_RND_MASK << PAGE_SHIFT);

  	/* 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);

  
  	if (unlikely(stack_top < mmap_min_addr) ||
  	    unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
  		return -ENOMEM;

  	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;

  	if (down_write_killable(&mm->mmap_sem))
  		return -EINTR;

  	vm_flags = VM_STACK_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;

  	vm_flags |= VM_STACK_INCOMPLETE_SETUP;

  
  	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)
  			goto out_unlock;

  	}

  	/* mprotect_fixup is overkill to remove the temporary stack flags */
  	vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;

  	stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */

  	stack_size = vma->vm_end - vma->vm_start;
  	/*
  	 * Align this down to a page boundary as expand_stack
  	 * will align it up.
  	 */
  	rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;

  #ifdef CONFIG_STACK_GROWSUP

  	if (stack_size + stack_expand > rlim_stack)
  		stack_base = vma->vm_start + rlim_stack;
  	else
  		stack_base = vma->vm_end + stack_expand;

  #else

  	if (stack_size + stack_expand > rlim_stack)
  		stack_base = vma->vm_end - rlim_stack;
  	else
  		stack_base = vma->vm_start - stack_expand;

  #endif

  	current->mm->start_stack = bprm->p;

  	ret = expand_stack(vma, stack_base);
  	if (ret)
  		ret = -EFAULT;
  
  out_unlock:

  	up_write(&mm->mmap_sem);

  	return ret;

  }

  EXPORT_SYMBOL(setup_arg_pages);

  #else
  
  /*
   * Transfer the program arguments and environment from the holding pages
   * onto the stack. The provided stack pointer is adjusted accordingly.
   */
  int transfer_args_to_stack(struct linux_binprm *bprm,
  			   unsigned long *sp_location)
  {
  	unsigned long index, stop, sp;
  	int ret = 0;
  
  	stop = bprm->p >> PAGE_SHIFT;
  	sp = *sp_location;
  
  	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
  		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
  		char *src = kmap(bprm->page[index]) + offset;
  		sp -= PAGE_SIZE - offset;
  		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
  			ret = -EFAULT;
  		kunmap(bprm->page[index]);
  		if (ret)
  			goto out;
  	}
  
  	*sp_location = sp;
  
  out:
  	return ret;
  }
  EXPORT_SYMBOL(transfer_args_to_stack);

  #endif /* CONFIG_MMU */

  static struct file *do_open_execat(int fd, struct filename *name, int flags)

  {

  	struct file *file;

  	int err;

  	struct open_flags open_exec_flags = {

  		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,

  		.acc_mode = MAY_EXEC,

  		.intent = LOOKUP_OPEN,
  		.lookup_flags = LOOKUP_FOLLOW,

  	};

  	if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
  		return ERR_PTR(-EINVAL);
  	if (flags & AT_SYMLINK_NOFOLLOW)
  		open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
  	if (flags & AT_EMPTY_PATH)
  		open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
  
  	file = do_filp_open(fd, name, &open_exec_flags);

  	if (IS_ERR(file))

  		goto out;
  
  	err = -EACCES;

  	if (!S_ISREG(file_inode(file)->i_mode))

  		goto exit;

  	if (path_noexec(&file->f_path))

  		goto exit;

  
  	err = deny_write_access(file);

  	if (err)
  		goto exit;

  	if (name->name[0] != '\0')
  		fsnotify_open(file);

  out:

  	return file;

  exit:
  	fput(file);

  	return ERR_PTR(err);
  }

  
  struct file *open_exec(const char *name)
  {

  	struct filename *filename = getname_kernel(name);
  	struct file *f = ERR_CAST(filename);
  
  	if (!IS_ERR(filename)) {
  		f = do_open_execat(AT_FDCWD, filename, 0);
  		putname(filename);
  	}
  	return f;

  }

  EXPORT_SYMBOL(open_exec);

  int kernel_read_file(struct file *file, void **buf, loff_t *size,

  		     loff_t max_size, enum kernel_read_file_id id)

  {
  	loff_t i_size, pos;
  	ssize_t bytes = 0;
  	int ret;
  
  	if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
  		return -EINVAL;

  	ret = security_kernel_read_file(file, id);
  	if (ret)
  		return ret;

  	ret = deny_write_access(file);
  	if (ret)
  		return ret;

  	i_size = i_size_read(file_inode(file));

  	if (max_size > 0 && i_size > max_size) {
  		ret = -EFBIG;
  		goto out;
  	}
  	if (i_size <= 0) {
  		ret = -EINVAL;
  		goto out;
  	}

  	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
  		*buf = vmalloc(i_size);

  	if (!*buf) {
  		ret = -ENOMEM;
  		goto out;
  	}

  
  	pos = 0;
  	while (pos < i_size) {

  		bytes = kernel_read(file, *buf + pos, i_size - pos, &pos);

  		if (bytes < 0) {
  			ret = bytes;
  			goto out;
  		}
  
  		if (bytes == 0)
  			break;

  	}
  
  	if (pos != i_size) {
  		ret = -EIO;

  		goto out_free;

  	}

  	ret = security_kernel_post_read_file(file, *buf, i_size, id);

  	if (!ret)
  		*size = pos;

  out_free:

  	if (ret < 0) {

  		if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
  			vfree(*buf);
  			*buf = NULL;
  		}

  	}

  
  out:
  	allow_write_access(file);

  	return ret;
  }
  EXPORT_SYMBOL_GPL(kernel_read_file);

  int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,

  			       loff_t max_size, enum kernel_read_file_id id)
  {
  	struct file *file;
  	int ret;
  
  	if (!path || !*path)
  		return -EINVAL;
  
  	file = filp_open(path, O_RDONLY, 0);
  	if (IS_ERR(file))
  		return PTR_ERR(file);
  
  	ret = kernel_read_file(file, buf, size, max_size, id);
  	fput(file);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(kernel_read_file_from_path);

  int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
  			     enum kernel_read_file_id id)
  {
  	struct fd f = fdget(fd);
  	int ret = -EBADF;
  
  	if (!f.file)
  		goto out;
  
  	ret = kernel_read_file(f.file, buf, size, max_size, id);
  out:
  	fdput(f);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);

  ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
  {

  	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);

  	if (res > 0)
  		flush_icache_range(addr, addr + len);
  	return res;
  }
  EXPORT_SYMBOL(read_code);

  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) {

  		sync_mm_rss(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_state and changing tsk->mm.

  		 */
  		down_read(&old_mm->mmap_sem);

  		if (unlikely(old_mm->core_state)) {

  			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);

  	tsk->mm->vmacache_seqnum = 0;
  	vmacache_flush(tsk);

  	task_unlock(tsk);

  	if (old_mm) {
  		up_read(&old_mm->mmap_sem);

  		BUG_ON(active_mm != old_mm);

  		setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);

  		mm_update_next_owner(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 *oldsighand = tsk->sighand;

  	spinlock_t *lock = &oldsighand->siglock;

  	if (thread_group_empty(tsk))

  		goto no_thread_group;
  
  	/*
  	 * Kill all other threads in the thread group.

  	 */

  	spin_lock_irq(lock);

  	if (signal_group_exit(sig)) {

  		/*
  		 * Another group action in progress, just
  		 * return so that the signal is processed.
  		 */
  		spin_unlock_irq(lock);

  		return -EAGAIN;
  	}

  	sig->group_exit_task = tsk;

  	sig->notify_count = zap_other_threads(tsk);
  	if (!thread_group_leader(tsk))
  		sig->notify_count--;

  	while (sig->notify_count) {

  		__set_current_state(TASK_KILLABLE);

  		spin_unlock_irq(lock);
  		schedule();

  		if (unlikely(__fatal_signal_pending(tsk)))
  			goto killed;

  		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 (!thread_group_leader(tsk)) {

  		struct task_struct *leader = tsk->group_leader;

  		for (;;) {

  			cgroup_threadgroup_change_begin(tsk);

  			write_lock_irq(&tasklist_lock);

  			/*
  			 * Do this under tasklist_lock to ensure that
  			 * exit_notify() can't miss ->group_exit_task
  			 */
  			sig->notify_count = -1;

  			if (likely(leader->exit_state))
  				break;

  			__set_current_state(TASK_KILLABLE);

  			write_unlock_irq(&tasklist_lock);

  			cgroup_threadgroup_change_end(tsk);

  			schedule();

  			if (unlikely(__fatal_signal_pending(tsk)))
  				goto killed;

  		}

  		/*
  		 * 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;

  		tsk->real_start_time = leader->real_start_time;

  		BUG_ON(!same_thread_group(leader, tsk));
  		BUG_ON(has_group_leader_pid(tsk));

  		/*
  		 * 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.
  		 */

  		tsk->pid = leader->pid;

  		change_pid(tsk, PIDTYPE_PID, task_pid(leader));

  		transfer_pid(leader, tsk, PIDTYPE_PGID);
  		transfer_pid(leader, tsk, PIDTYPE_SID);

  		list_replace_rcu(&leader->tasks, &tsk->tasks);

  		list_replace_init(&leader->sibling, &tsk->sibling);

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

  		tsk->exit_signal = SIGCHLD;

  		leader->exit_signal = -1;

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

  
  		/*
  		 * We are going to release_task()->ptrace_unlink() silently,
  		 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
  		 * the tracer wont't block again waiting for this thread.
  		 */
  		if (unlikely(leader->ptrace))
  			__wake_up_parent(leader, leader->parent);

  		write_unlock_irq(&tasklist_lock);

  		cgroup_threadgroup_change_end(tsk);

  
  		release_task(leader);

  	}

  	sig->group_exit_task = NULL;
  	sig->notify_count = 0;

  
  no_thread_group:

  	/* we have changed execution domain */
  	tsk->exit_signal = SIGCHLD;

  #ifdef CONFIG_POSIX_TIMERS

  	exit_itimers(sig);

  	flush_itimer_signals();

  #endif

  	if (atomic_read(&oldsighand->count) != 1) {
  		struct sighand_struct *newsighand;

  		/*

  		 * This ->sighand is shared with the CLONE_SIGHAND
  		 * but not CLONE_THREAD task, switch to the new one.

  		 */

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

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

  		rcu_assign_pointer(tsk->sighand, newsighand);

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

  		__cleanup_sighand(oldsighand);

  	}

  	BUG_ON(!thread_group_leader(tsk));

  	return 0;

  
  killed:
  	/* protects against exit_notify() and __exit_signal() */
  	read_lock(&tasklist_lock);
  	sig->group_exit_task = NULL;
  	sig->notify_count = 0;
  	read_unlock(&tasklist_lock);
  	return -EAGAIN;

  }

  char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)

  {

  	task_lock(tsk);

  	strncpy(buf, tsk->comm, buf_size);

  	task_unlock(tsk);

  	return buf;

  }

  EXPORT_SYMBOL_GPL(__get_task_comm);

  /*
   * These functions flushes out all traces of the currently running executable
   * so that a new one can be started
   */

  void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)

  {
  	task_lock(tsk);

  	trace_task_rename(tsk, buf);

  	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
  	task_unlock(tsk);

  	perf_event_comm(tsk, exec);

  }

  /*
   * Calling this is the point of no return. None of the failures will be
   * seen by userspace since either the process is already taking a fatal
   * signal (via de_thread() or coredump), or will have SEGV raised
   * (after exec_mmap()) by search_binary_handlers (see below).
   */

  int flush_old_exec(struct linux_binprm * bprm)
  {

  	int retval;

  
  	/*
  	 * 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;

  	/*
  	 * Must be called _before_ exec_mmap() as bprm->mm is
  	 * not visibile until then. This also enables the update
  	 * to be lockless.
  	 */

  	set_mm_exe_file(bprm->mm, bprm->file);

  	/*

  	 * Release all of the old mmap stuff
  	 */

  	acct_arg_size(bprm, 0);

  	retval = exec_mmap(bprm->mm);
  	if (retval)

  		goto out;

  	/*
  	 * After clearing bprm->mm (to mark that current is using the
  	 * prepared mm now), we have nothing left of the original
  	 * process. If anything from here on returns an error, the check
  	 * in search_binary_handler() will SEGV current.
  	 */
  	bprm->mm = NULL;

  	set_fs(USER_DS);

  	current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
  					PF_NOFREEZE | PF_NO_SETAFFINITY);

  	flush_thread();
  	current->personality &= ~bprm->per_clear;

  	/*
  	 * We have to apply CLOEXEC before we change whether the process is
  	 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
  	 * trying to access the should-be-closed file descriptors of a process
  	 * undergoing exec(2).
  	 */
  	do_close_on_exec(current->files);

  	return 0;
  
  out:
  	return retval;
  }
  EXPORT_SYMBOL(flush_old_exec);

  void would_dump(struct linux_binprm *bprm, struct file *file)
  {

  	struct inode *inode = file_inode(file);
  	if (inode_permission(inode, MAY_READ) < 0) {
  		struct user_namespace *old, *user_ns;

  		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;

  
  		/* Ensure mm->user_ns contains the executable */
  		user_ns = old = bprm->mm->user_ns;
  		while ((user_ns != &init_user_ns) &&
  		       !privileged_wrt_inode_uidgid(user_ns, inode))
  			user_ns = user_ns->parent;
  
  		if (old != user_ns) {
  			bprm->mm->user_ns = get_user_ns(user_ns);
  			put_user_ns(old);
  		}
  	}

  }
  EXPORT_SYMBOL(would_dump);

  void setup_new_exec(struct linux_binprm * bprm)
  {

  	/*
  	 * Once here, prepare_binrpm() will not be called any more, so
  	 * the final state of setuid/setgid/fscaps can be merged into the
  	 * secureexec flag.
  	 */
  	bprm->secureexec |= bprm->cap_elevated;

  	if (bprm->secureexec) {

  		/* Make sure parent cannot signal privileged process. */
  		current->pdeath_signal = 0;

  		/*
  		 * For secureexec, reset the stack limit to sane default to
  		 * avoid bad behavior from the prior rlimits. This has to
  		 * happen before arch_pick_mmap_layout(), which examines
  		 * RLIMIT_STACK, but after the point of no return to avoid

  		 * needing to clean up the change on failure.

  		 */
  		if (current->signal->rlim[RLIMIT_STACK].rlim_cur > _STK_LIM)
  			current->signal->rlim[RLIMIT_STACK].rlim_cur = _STK_LIM;
  	}

  	arch_pick_mmap_layout(current->mm);

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

  	/*
  	 * Figure out dumpability. Note that this checking only of current
  	 * is wrong, but userspace depends on it. This should be testing
  	 * bprm->secureexec instead.
  	 */

  	if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||

  	    !(uid_eq(current_euid(), current_uid()) &&
  	      gid_eq(current_egid(), current_gid())))

  		set_dumpable(current->mm, suid_dumpable);

  	else
  		set_dumpable(current->mm, SUID_DUMP_USER);

  	arch_setup_new_exec();

  	perf_event_exec();

  	__set_task_comm(current, kbasename(bprm->filename), true);

  	/* 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;

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

  	current->self_exec_id++;

  	flush_signal_handlers(current, 0);

  }

  EXPORT_SYMBOL(setup_new_exec);

  /*

   * Prepare credentials and lock ->cred_guard_mutex.
   * install_exec_creds() commits the new creds and drops the lock.
   * Or, if exec fails before, free_bprm() should release ->cred and
   * and unlock.
   */
  int prepare_bprm_creds(struct linux_binprm *bprm)
  {

  	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))

  		return -ERESTARTNOINTR;
  
  	bprm->cred = prepare_exec_creds();
  	if (likely(bprm->cred))
  		return 0;

  	mutex_unlock(&current->signal->cred_guard_mutex);

  	return -ENOMEM;
  }

  static void free_bprm(struct linux_binprm *bprm)

  {
  	free_arg_pages(bprm);
  	if (bprm->cred) {

  		mutex_unlock(&current->signal->cred_guard_mutex);

  		abort_creds(bprm->cred);
  	}

  	if (bprm->file) {
  		allow_write_access(bprm->file);
  		fput(bprm->file);
  	}

  	/* If a binfmt changed the interp, free it. */
  	if (bprm->interp != bprm->filename)
  		kfree(bprm->interp);

  	kfree(bprm);
  }

  int bprm_change_interp(const char *interp, struct linux_binprm *bprm)

  {
  	/* If a binfmt changed the interp, free it first. */
  	if (bprm->interp != bprm->filename)
  		kfree(bprm->interp);
  	bprm->interp = kstrdup(interp, GFP_KERNEL);
  	if (!bprm->interp)
  		return -ENOMEM;
  	return 0;
  }
  EXPORT_SYMBOL(bprm_change_interp);

  /*

   * install the new credentials for this executable
   */
  void install_exec_creds(struct linux_binprm *bprm)
  {
  	security_bprm_committing_creds(bprm);
  
  	commit_creds(bprm->cred);
  	bprm->cred = NULL;

  
  	/*
  	 * Disable monitoring for regular users
  	 * when executing setuid binaries. Must
  	 * wait until new credentials are committed
  	 * by commit_creds() above
  	 */
  	if (get_dumpable(current->mm) != SUID_DUMP_USER)
  		perf_event_exit_task(current);

  	/*
  	 * cred_guard_mutex must be held at least to this point to prevent

  	 * ptrace_attach() from altering our determination of the task's

  	 * credentials; any time after this it may be unlocked.
  	 */

  	security_bprm_committed_creds(bprm);

  	mutex_unlock(&current->signal->cred_guard_mutex);

  }
  EXPORT_SYMBOL(install_exec_creds);
  
  /*
   * determine how safe it is to execute the proposed program

   * - the caller must hold ->cred_guard_mutex to protect against

   *   PTRACE_ATTACH or seccomp thread-sync

   */

  static void check_unsafe_exec(struct linux_binprm *bprm)

  {

  	struct task_struct *p = current, *t;

  	unsigned n_fs;

  	if (p->ptrace)
  		bprm->unsafe |= LSM_UNSAFE_PTRACE;

  	/*
  	 * This isn't strictly necessary, but it makes it harder for LSMs to
  	 * mess up.
  	 */

  	if (task_no_new_privs(current))

  		bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;

  	t = p;

  	n_fs = 1;

  	spin_lock(&p->fs->lock);

  	rcu_read_lock();

  	while_each_thread(p, t) {

  		if (t->fs == p->fs)
  			n_fs++;

  	}

  	rcu_read_unlock();

  	if (p->fs->users > n_fs)

  		bprm->unsafe |= LSM_UNSAFE_SHARE;

  	else
  		p->fs->in_exec = 1;

  	spin_unlock(&p->fs->lock);

  }

  static void bprm_fill_uid(struct linux_binprm *bprm)
  {
  	struct inode *inode;
  	unsigned int mode;
  	kuid_t uid;
  	kgid_t gid;

  	/*
  	 * Since this can be called multiple times (via prepare_binprm),
  	 * we must clear any previous work done when setting set[ug]id
  	 * bits from any earlier bprm->file uses (for example when run
  	 * first for a setuid script then again for its interpreter).
  	 */

  	bprm->cred->euid = current_euid();
  	bprm->cred->egid = current_egid();

  	if (!mnt_may_suid(bprm->file->f_path.mnt))

  		return;
  
  	if (task_no_new_privs(current))
  		return;

  	inode = bprm->file->f_path.dentry->d_inode;

  	mode = READ_ONCE(inode->i_mode);
  	if (!(mode & (S_ISUID|S_ISGID)))
  		return;
  
  	/* Be careful if suid/sgid is set */

  	inode_lock(inode);

  
  	/* reload atomically mode/uid/gid now that lock held */
  	mode = inode->i_mode;
  	uid = inode->i_uid;
  	gid = inode->i_gid;

  	inode_unlock(inode);

  
  	/* We ignore suid/sgid if there are no mappings for them in the ns */
  	if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
  		 !kgid_has_mapping(bprm->cred->user_ns, gid))
  		return;
  
  	if (mode & S_ISUID) {
  		bprm->per_clear |= PER_CLEAR_ON_SETID;
  		bprm->cred->euid = uid;
  	}
  
  	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
  		bprm->per_clear |= PER_CLEAR_ON_SETID;
  		bprm->cred->egid = gid;
  	}
  }

  /*
   * Fill the binprm structure from the inode.

   * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes

   *
   * This may be called multiple times for binary chains (scripts for example).

   */
  int prepare_binprm(struct linux_binprm *bprm)
  {

  	int retval;

  	loff_t pos = 0;

  	bprm_fill_uid(bprm);

  
  	/* fill in binprm security blob */

  	retval = security_bprm_set_creds(bprm);

  	if (retval)
  		return retval;

  	bprm->called_set_creds = 1;

  	memset(bprm->buf, 0, BINPRM_BUF_SIZE);

  	return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);

  }
  
  EXPORT_SYMBOL(prepare_binprm);

  /*
   * 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);

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

  		kunmap_atomic(kaddr);

  		put_arg_page(page);

  	} while (offset == PAGE_SIZE);

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

  out:
  	return ret;

  }

  EXPORT_SYMBOL(remove_arg_zero);

  #define printable(c) (((c)=='\t') || ((c)=='
  ') || (0x20<=(c) && (c)<=0x7e))

  /*
   * cycle the list of binary formats handler, until one recognizes the image
   */

  int search_binary_handler(struct linux_binprm *bprm)

  {

  	bool need_retry = IS_ENABLED(CONFIG_MODULES);

  	struct linux_binfmt *fmt;

  	int retval;

  	/* This allows 4 levels of binfmt rewrites before failing hard. */

  	if (bprm->recursion_depth > 5)