v4.19.13 snapshot.
diff --git a/mm/util.c b/mm/util.c
new file mode 100644
index 0000000..9e3ebd2
--- /dev/null
+++ b/mm/util.c
@@ -0,0 +1,790 @@
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/compiler.h>
+#include <linux/export.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/task_stack.h>
+#include <linux/security.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/mman.h>
+#include <linux/hugetlb.h>
+#include <linux/vmalloc.h>
+#include <linux/userfaultfd_k.h>
+
+#include <asm/sections.h>
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+static inline int is_kernel_rodata(unsigned long addr)
+{
+ return addr >= (unsigned long)__start_rodata &&
+ addr < (unsigned long)__end_rodata;
+}
+
+/**
+ * kfree_const - conditionally free memory
+ * @x: pointer to the memory
+ *
+ * Function calls kfree only if @x is not in .rodata section.
+ */
+void kfree_const(const void *x)
+{
+ if (!is_kernel_rodata((unsigned long)x))
+ kfree(x);
+}
+EXPORT_SYMBOL(kfree_const);
+
+/**
+ * kstrdup - allocate space for and copy an existing string
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ */
+char *kstrdup(const char *s, gfp_t gfp)
+{
+ size_t len;
+ char *buf;
+
+ if (!s)
+ return NULL;
+
+ len = strlen(s) + 1;
+ buf = kmalloc_track_caller(len, gfp);
+ if (buf)
+ memcpy(buf, s, len);
+ return buf;
+}
+EXPORT_SYMBOL(kstrdup);
+
+/**
+ * kstrdup_const - conditionally duplicate an existing const string
+ * @s: the string to duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Function returns source string if it is in .rodata section otherwise it
+ * fallbacks to kstrdup.
+ * Strings allocated by kstrdup_const should be freed by kfree_const.
+ */
+const char *kstrdup_const(const char *s, gfp_t gfp)
+{
+ if (is_kernel_rodata((unsigned long)s))
+ return s;
+
+ return kstrdup(s, gfp);
+}
+EXPORT_SYMBOL(kstrdup_const);
+
+/**
+ * kstrndup - allocate space for and copy an existing string
+ * @s: the string to duplicate
+ * @max: read at most @max chars from @s
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Note: Use kmemdup_nul() instead if the size is known exactly.
+ */
+char *kstrndup(const char *s, size_t max, gfp_t gfp)
+{
+ size_t len;
+ char *buf;
+
+ if (!s)
+ return NULL;
+
+ len = strnlen(s, max);
+ buf = kmalloc_track_caller(len+1, gfp);
+ if (buf) {
+ memcpy(buf, s, len);
+ buf[len] = '\0';
+ }
+ return buf;
+}
+EXPORT_SYMBOL(kstrndup);
+
+/**
+ * kmemdup - duplicate region of memory
+ *
+ * @src: memory region to duplicate
+ * @len: memory region length
+ * @gfp: GFP mask to use
+ */
+void *kmemdup(const void *src, size_t len, gfp_t gfp)
+{
+ void *p;
+
+ p = kmalloc_track_caller(len, gfp);
+ if (p)
+ memcpy(p, src, len);
+ return p;
+}
+EXPORT_SYMBOL(kmemdup);
+
+/**
+ * kmemdup_nul - Create a NUL-terminated string from unterminated data
+ * @s: The data to stringify
+ * @len: The size of the data
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ */
+char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
+{
+ char *buf;
+
+ if (!s)
+ return NULL;
+
+ buf = kmalloc_track_caller(len + 1, gfp);
+ if (buf) {
+ memcpy(buf, s, len);
+ buf[len] = '\0';
+ }
+ return buf;
+}
+EXPORT_SYMBOL(kmemdup_nul);
+
+/**
+ * memdup_user - duplicate memory region from user space
+ *
+ * @src: source address in user space
+ * @len: number of bytes to copy
+ *
+ * Returns an ERR_PTR() on failure. Result is physically
+ * contiguous, to be freed by kfree().
+ */
+void *memdup_user(const void __user *src, size_t len)
+{
+ void *p;
+
+ p = kmalloc_track_caller(len, GFP_USER);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ if (copy_from_user(p, src, len)) {
+ kfree(p);
+ return ERR_PTR(-EFAULT);
+ }
+
+ return p;
+}
+EXPORT_SYMBOL(memdup_user);
+
+/**
+ * vmemdup_user - duplicate memory region from user space
+ *
+ * @src: source address in user space
+ * @len: number of bytes to copy
+ *
+ * Returns an ERR_PTR() on failure. Result may be not
+ * physically contiguous. Use kvfree() to free.
+ */
+void *vmemdup_user(const void __user *src, size_t len)
+{
+ void *p;
+
+ p = kvmalloc(len, GFP_USER);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ if (copy_from_user(p, src, len)) {
+ kvfree(p);
+ return ERR_PTR(-EFAULT);
+ }
+
+ return p;
+}
+EXPORT_SYMBOL(vmemdup_user);
+
+/**
+ * strndup_user - duplicate an existing string from user space
+ * @s: The string to duplicate
+ * @n: Maximum number of bytes to copy, including the trailing NUL.
+ */
+char *strndup_user(const char __user *s, long n)
+{
+ char *p;
+ long length;
+
+ length = strnlen_user(s, n);
+
+ if (!length)
+ return ERR_PTR(-EFAULT);
+
+ if (length > n)
+ return ERR_PTR(-EINVAL);
+
+ p = memdup_user(s, length);
+
+ if (IS_ERR(p))
+ return p;
+
+ p[length - 1] = '\0';
+
+ return p;
+}
+EXPORT_SYMBOL(strndup_user);
+
+/**
+ * memdup_user_nul - duplicate memory region from user space and NUL-terminate
+ *
+ * @src: source address in user space
+ * @len: number of bytes to copy
+ *
+ * Returns an ERR_PTR() on failure.
+ */
+void *memdup_user_nul(const void __user *src, size_t len)
+{
+ char *p;
+
+ /*
+ * Always use GFP_KERNEL, since copy_from_user() can sleep and
+ * cause pagefault, which makes it pointless to use GFP_NOFS
+ * or GFP_ATOMIC.
+ */
+ p = kmalloc_track_caller(len + 1, GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ if (copy_from_user(p, src, len)) {
+ kfree(p);
+ return ERR_PTR(-EFAULT);
+ }
+ p[len] = '\0';
+
+ return p;
+}
+EXPORT_SYMBOL(memdup_user_nul);
+
+void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
+ struct vm_area_struct *prev, struct rb_node *rb_parent)
+{
+ struct vm_area_struct *next;
+
+ vma->vm_prev = prev;
+ if (prev) {
+ next = prev->vm_next;
+ prev->vm_next = vma;
+ } else {
+ mm->mmap = vma;
+ if (rb_parent)
+ next = rb_entry(rb_parent,
+ struct vm_area_struct, vm_rb);
+ else
+ next = NULL;
+ }
+ vma->vm_next = next;
+ if (next)
+ next->vm_prev = vma;
+}
+
+/* Check if the vma is being used as a stack by this task */
+int vma_is_stack_for_current(struct vm_area_struct *vma)
+{
+ struct task_struct * __maybe_unused t = current;
+
+ return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
+}
+
+#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+{
+ mm->mmap_base = TASK_UNMAPPED_BASE;
+ mm->get_unmapped_area = arch_get_unmapped_area;
+}
+#endif
+
+/*
+ * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
+ * back to the regular GUP.
+ * Note a difference with get_user_pages_fast: this always returns the
+ * number of pages pinned, 0 if no pages were pinned.
+ * If the architecture does not support this function, simply return with no
+ * pages pinned.
+ */
+int __weak __get_user_pages_fast(unsigned long start,
+ int nr_pages, int write, struct page **pages)
+{
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__get_user_pages_fast);
+
+/**
+ * get_user_pages_fast() - pin user pages in memory
+ * @start: starting user address
+ * @nr_pages: number of pages from start to pin
+ * @write: whether pages will be written to
+ * @pages: array that receives pointers to the pages pinned.
+ * Should be at least nr_pages long.
+ *
+ * Returns number of pages pinned. This may be fewer than the number
+ * requested. If nr_pages is 0 or negative, returns 0. If no pages
+ * were pinned, returns -errno.
+ *
+ * get_user_pages_fast provides equivalent functionality to get_user_pages,
+ * operating on current and current->mm, with force=0 and vma=NULL. However
+ * unlike get_user_pages, it must be called without mmap_sem held.
+ *
+ * get_user_pages_fast may take mmap_sem and page table locks, so no
+ * assumptions can be made about lack of locking. get_user_pages_fast is to be
+ * implemented in a way that is advantageous (vs get_user_pages()) when the
+ * user memory area is already faulted in and present in ptes. However if the
+ * pages have to be faulted in, it may turn out to be slightly slower so
+ * callers need to carefully consider what to use. On many architectures,
+ * get_user_pages_fast simply falls back to get_user_pages.
+ */
+int __weak get_user_pages_fast(unsigned long start,
+ int nr_pages, int write, struct page **pages)
+{
+ return get_user_pages_unlocked(start, nr_pages, pages,
+ write ? FOLL_WRITE : 0);
+}
+EXPORT_SYMBOL_GPL(get_user_pages_fast);
+
+unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
+ unsigned long len, unsigned long prot,
+ unsigned long flag, unsigned long pgoff)
+{
+ unsigned long ret;
+ struct mm_struct *mm = current->mm;
+ unsigned long populate;
+ LIST_HEAD(uf);
+
+ ret = security_mmap_file(file, prot, flag);
+ if (!ret) {
+ if (down_write_killable(&mm->mmap_sem))
+ return -EINTR;
+ ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
+ &populate, &uf);
+ up_write(&mm->mmap_sem);
+ userfaultfd_unmap_complete(mm, &uf);
+ if (populate)
+ mm_populate(ret, populate);
+ }
+ return ret;
+}
+
+unsigned long vm_mmap(struct file *file, unsigned long addr,
+ unsigned long len, unsigned long prot,
+ unsigned long flag, unsigned long offset)
+{
+ if (unlikely(offset + PAGE_ALIGN(len) < offset))
+ return -EINVAL;
+ if (unlikely(offset_in_page(offset)))
+ return -EINVAL;
+
+ return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
+}
+EXPORT_SYMBOL(vm_mmap);
+
+/**
+ * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
+ * failure, fall back to non-contiguous (vmalloc) allocation.
+ * @size: size of the request.
+ * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
+ * @node: numa node to allocate from
+ *
+ * Uses kmalloc to get the memory but if the allocation fails then falls back
+ * to the vmalloc allocator. Use kvfree for freeing the memory.
+ *
+ * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
+ * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
+ * preferable to the vmalloc fallback, due to visible performance drawbacks.
+ *
+ * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
+ * fall back to vmalloc.
+ */
+void *kvmalloc_node(size_t size, gfp_t flags, int node)
+{
+ gfp_t kmalloc_flags = flags;
+ void *ret;
+
+ /*
+ * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
+ * so the given set of flags has to be compatible.
+ */
+ if ((flags & GFP_KERNEL) != GFP_KERNEL)
+ return kmalloc_node(size, flags, node);
+
+ /*
+ * We want to attempt a large physically contiguous block first because
+ * it is less likely to fragment multiple larger blocks and therefore
+ * contribute to a long term fragmentation less than vmalloc fallback.
+ * However make sure that larger requests are not too disruptive - no
+ * OOM killer and no allocation failure warnings as we have a fallback.
+ */
+ if (size > PAGE_SIZE) {
+ kmalloc_flags |= __GFP_NOWARN;
+
+ if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
+ kmalloc_flags |= __GFP_NORETRY;
+ }
+
+ ret = kmalloc_node(size, kmalloc_flags, node);
+
+ /*
+ * It doesn't really make sense to fallback to vmalloc for sub page
+ * requests
+ */
+ if (ret || size <= PAGE_SIZE)
+ return ret;
+
+ return __vmalloc_node_flags_caller(size, node, flags,
+ __builtin_return_address(0));
+}
+EXPORT_SYMBOL(kvmalloc_node);
+
+/**
+ * kvfree() - Free memory.
+ * @addr: Pointer to allocated memory.
+ *
+ * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
+ * It is slightly more efficient to use kfree() or vfree() if you are certain
+ * that you know which one to use.
+ *
+ * Context: Any context except NMI.
+ */
+void kvfree(const void *addr)
+{
+ if (is_vmalloc_addr(addr))
+ vfree(addr);
+ else
+ kfree(addr);
+}
+EXPORT_SYMBOL(kvfree);
+
+static inline void *__page_rmapping(struct page *page)
+{
+ unsigned long mapping;
+
+ mapping = (unsigned long)page->mapping;
+ mapping &= ~PAGE_MAPPING_FLAGS;
+
+ return (void *)mapping;
+}
+
+/* Neutral page->mapping pointer to address_space or anon_vma or other */
+void *page_rmapping(struct page *page)
+{
+ page = compound_head(page);
+ return __page_rmapping(page);
+}
+
+/*
+ * Return true if this page is mapped into pagetables.
+ * For compound page it returns true if any subpage of compound page is mapped.
+ */
+bool page_mapped(struct page *page)
+{
+ int i;
+
+ if (likely(!PageCompound(page)))
+ return atomic_read(&page->_mapcount) >= 0;
+ page = compound_head(page);
+ if (atomic_read(compound_mapcount_ptr(page)) >= 0)
+ return true;
+ if (PageHuge(page))
+ return false;
+ for (i = 0; i < hpage_nr_pages(page); i++) {
+ if (atomic_read(&page[i]._mapcount) >= 0)
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL(page_mapped);
+
+struct anon_vma *page_anon_vma(struct page *page)
+{
+ unsigned long mapping;
+
+ page = compound_head(page);
+ mapping = (unsigned long)page->mapping;
+ if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+ return NULL;
+ return __page_rmapping(page);
+}
+
+struct address_space *page_mapping(struct page *page)
+{
+ struct address_space *mapping;
+
+ page = compound_head(page);
+
+ /* This happens if someone calls flush_dcache_page on slab page */
+ if (unlikely(PageSlab(page)))
+ return NULL;
+
+ if (unlikely(PageSwapCache(page))) {
+ swp_entry_t entry;
+
+ entry.val = page_private(page);
+ return swap_address_space(entry);
+ }
+
+ mapping = page->mapping;
+ if ((unsigned long)mapping & PAGE_MAPPING_ANON)
+ return NULL;
+
+ return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
+}
+EXPORT_SYMBOL(page_mapping);
+
+/*
+ * For file cache pages, return the address_space, otherwise return NULL
+ */
+struct address_space *page_mapping_file(struct page *page)
+{
+ if (unlikely(PageSwapCache(page)))
+ return NULL;
+ return page_mapping(page);
+}
+
+/* Slow path of page_mapcount() for compound pages */
+int __page_mapcount(struct page *page)
+{
+ int ret;
+
+ ret = atomic_read(&page->_mapcount) + 1;
+ /*
+ * For file THP page->_mapcount contains total number of mapping
+ * of the page: no need to look into compound_mapcount.
+ */
+ if (!PageAnon(page) && !PageHuge(page))
+ return ret;
+ page = compound_head(page);
+ ret += atomic_read(compound_mapcount_ptr(page)) + 1;
+ if (PageDoubleMap(page))
+ ret--;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__page_mapcount);
+
+int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
+int sysctl_overcommit_ratio __read_mostly = 50;
+unsigned long sysctl_overcommit_kbytes __read_mostly;
+int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
+unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
+unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
+
+int overcommit_ratio_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ sysctl_overcommit_kbytes = 0;
+ return ret;
+}
+
+int overcommit_kbytes_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret == 0 && write)
+ sysctl_overcommit_ratio = 0;
+ return ret;
+}
+
+/*
+ * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
+ */
+unsigned long vm_commit_limit(void)
+{
+ unsigned long allowed;
+
+ if (sysctl_overcommit_kbytes)
+ allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
+ else
+ allowed = ((totalram_pages - hugetlb_total_pages())
+ * sysctl_overcommit_ratio / 100);
+ allowed += total_swap_pages;
+
+ return allowed;
+}
+
+/*
+ * Make sure vm_committed_as in one cacheline and not cacheline shared with
+ * other variables. It can be updated by several CPUs frequently.
+ */
+struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
+
+/*
+ * The global memory commitment made in the system can be a metric
+ * that can be used to drive ballooning decisions when Linux is hosted
+ * as a guest. On Hyper-V, the host implements a policy engine for dynamically
+ * balancing memory across competing virtual machines that are hosted.
+ * Several metrics drive this policy engine including the guest reported
+ * memory commitment.
+ */
+unsigned long vm_memory_committed(void)
+{
+ return percpu_counter_read_positive(&vm_committed_as);
+}
+EXPORT_SYMBOL_GPL(vm_memory_committed);
+
+/*
+ * Check that a process has enough memory to allocate a new virtual
+ * mapping. 0 means there is enough memory for the allocation to
+ * succeed and -ENOMEM implies there is not.
+ *
+ * We currently support three overcommit policies, which are set via the
+ * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting.rst
+ *
+ * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
+ * Additional code 2002 Jul 20 by Robert Love.
+ *
+ * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
+ *
+ * Note this is a helper function intended to be used by LSMs which
+ * wish to use this logic.
+ */
+int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
+{
+ long free, allowed, reserve;
+
+ VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
+ -(s64)vm_committed_as_batch * num_online_cpus(),
+ "memory commitment underflow");
+
+ vm_acct_memory(pages);
+
+ /*
+ * Sometimes we want to use more memory than we have
+ */
+ if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
+ return 0;
+
+ if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
+ free = global_zone_page_state(NR_FREE_PAGES);
+ free += global_node_page_state(NR_FILE_PAGES);
+
+ /*
+ * shmem pages shouldn't be counted as free in this
+ * case, they can't be purged, only swapped out, and
+ * that won't affect the overall amount of available
+ * memory in the system.
+ */
+ free -= global_node_page_state(NR_SHMEM);
+
+ free += get_nr_swap_pages();
+
+ /*
+ * Any slabs which are created with the
+ * SLAB_RECLAIM_ACCOUNT flag claim to have contents
+ * which are reclaimable, under pressure. The dentry
+ * cache and most inode caches should fall into this
+ */
+ free += global_node_page_state(NR_SLAB_RECLAIMABLE);
+
+ /*
+ * Part of the kernel memory, which can be released
+ * under memory pressure.
+ */
+ free += global_node_page_state(
+ NR_INDIRECTLY_RECLAIMABLE_BYTES) >> PAGE_SHIFT;
+
+ /*
+ * Leave reserved pages. The pages are not for anonymous pages.
+ */
+ if (free <= totalreserve_pages)
+ goto error;
+ else
+ free -= totalreserve_pages;
+
+ /*
+ * Reserve some for root
+ */
+ if (!cap_sys_admin)
+ free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
+
+ if (free > pages)
+ return 0;
+
+ goto error;
+ }
+
+ allowed = vm_commit_limit();
+ /*
+ * Reserve some for root
+ */
+ if (!cap_sys_admin)
+ allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
+
+ /*
+ * Don't let a single process grow so big a user can't recover
+ */
+ if (mm) {
+ reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
+ allowed -= min_t(long, mm->total_vm / 32, reserve);
+ }
+
+ if (percpu_counter_read_positive(&vm_committed_as) < allowed)
+ return 0;
+error:
+ vm_unacct_memory(pages);
+
+ return -ENOMEM;
+}
+
+/**
+ * get_cmdline() - copy the cmdline value to a buffer.
+ * @task: the task whose cmdline value to copy.
+ * @buffer: the buffer to copy to.
+ * @buflen: the length of the buffer. Larger cmdline values are truncated
+ * to this length.
+ * Returns the size of the cmdline field copied. Note that the copy does
+ * not guarantee an ending NULL byte.
+ */
+int get_cmdline(struct task_struct *task, char *buffer, int buflen)
+{
+ int res = 0;
+ unsigned int len;
+ struct mm_struct *mm = get_task_mm(task);
+ unsigned long arg_start, arg_end, env_start, env_end;
+ if (!mm)
+ goto out;
+ if (!mm->arg_end)
+ goto out_mm; /* Shh! No looking before we're done */
+
+ down_read(&mm->mmap_sem);
+ arg_start = mm->arg_start;
+ arg_end = mm->arg_end;
+ env_start = mm->env_start;
+ env_end = mm->env_end;
+ up_read(&mm->mmap_sem);
+
+ len = arg_end - arg_start;
+
+ if (len > buflen)
+ len = buflen;
+
+ res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
+
+ /*
+ * If the nul at the end of args has been overwritten, then
+ * assume application is using setproctitle(3).
+ */
+ if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
+ len = strnlen(buffer, res);
+ if (len < res) {
+ res = len;
+ } else {
+ len = env_end - env_start;
+ if (len > buflen - res)
+ len = buflen - res;
+ res += access_process_vm(task, env_start,
+ buffer+res, len,
+ FOLL_FORCE);
+ res = strnlen(buffer, res);
+ }
+ }
+out_mm:
+ mmput(mm);
+out:
+ return res;
+}