#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/security.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/mman.h>
#include <linux/hugetlb.h>
#include <linux/vmalloc.h>

#include <asm/sections.h>
#include <asm/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
 */
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);

/**
 * 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.
 */
void *memdup_user(const void __user *src, size_t len)
{
        void *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, GFP_KERNEL);
        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);

/*
 * 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);

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 */
static int vm_is_stack_for_task(struct task_struct *t,
                                struct vm_area_struct *vma)
{
        return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}

/*
 * Check if the vma is being used as a stack.
 * If is_group is non-zero, check in the entire thread group or else
 * just check in the current task. Returns the task_struct of the task
 * that the vma is stack for. Must be called under rcu_read_lock().
 */
struct task_struct *task_of_stack(struct task_struct *task,
                                struct vm_area_struct *vma, bool in_group)
{
        if (vm_is_stack_for_task(task, vma))
                return task;

        if (in_group) {
                struct task_struct *t;

                for_each_thread(task, t) {
                        if (vm_is_stack_for_task(t, vma))
                                return t;
                }
        }

        return NULL;
}

#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm)
{
        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.
 * If the architecture not support this function, simply return with no
 * page 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)
{
        struct mm_struct *mm = current->mm;
        return get_user_pages_unlocked(current, mm, start, nr_pages,
                                       write, 0, pages);
}
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;

        ret = security_mmap_file(file, prot, flag);
        if (!ret) {
                down_write(&mm->mmap_sem);
                ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
                                    &populate);
                up_write(&mm->mmap_sem);
                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 & ~PAGE_MASK))
                return -EINVAL;

        return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
}
EXPORT_SYMBOL(vm_mmap);

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);
}

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)
{
        unsigned long mapping;

        /* 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 = (unsigned long)page->mapping;
        if (mapping & PAGE_MAPPING_FLAGS)
                return NULL;
        return page->mapping;
}

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;
}

/**
 * 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);
        if (!mm)
                goto out;
        if (!mm->arg_end)
                goto out_mm;    /* Shh! No looking before we're done */

        len = mm->arg_end - mm->arg_start;

        if (len > buflen)
                len = buflen;

        res = access_process_vm(task, mm->arg_start, buffer, len, 0);

        /*
         * 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 = mm->env_end - mm->env_start;
                        if (len > buflen - res)
                                len = buflen - res;
                        res += access_process_vm(task, mm->env_start,
                                                 buffer+res, len, 0);
                        res = strnlen(buffer, res);
                }
        }
out_mm:
        mmput(mm);
out:
        return res;
}