#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <asm/uaccess.h>

#define CREATE_TRACE_POINTS
#include <trace/events/kmem.h>

/**
 * 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);

/**
 * 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);

/**
 * __krealloc - like krealloc() but don't free @p.
 * @p: object to reallocate memory for.
 * @new_size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * This function is like krealloc() except it never frees the originally
 * allocated buffer. Use this if you don't want to free the buffer immediately
 * like, for example, with RCU.
 */
void *__krealloc(const void *p, size_t new_size, gfp_t flags)
{
        void *ret;
        size_t ks = 0;

        if (unlikely(!new_size))
                return ZERO_SIZE_PTR;

        if (p)
                ks = ksize(p);

        if (ks >= new_size)
                return (void *)p;

        ret = kmalloc_track_caller(new_size, flags);
        if (ret && p)
                memcpy(ret, p, ks);

        return ret;
}
EXPORT_SYMBOL(__krealloc);

/**
 * krealloc - reallocate memory. The contents will remain unchanged.
 * @p: object to reallocate memory for.
 * @new_size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * The contents of the object pointed to are preserved up to the
 * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 * %NULL pointer, the object pointed to is freed.
 */
void *krealloc(const void *p, size_t new_size, gfp_t flags)
{
        void *ret;

        if (unlikely(!new_size)) {
                kfree(p);
                return ZERO_SIZE_PTR;
        }

        ret = __krealloc(p, new_size, flags);
        if (ret && p != ret)
                kfree(p);

        return ret;
}
EXPORT_SYMBOL(krealloc);

/**
 * kzfree - like kfree but zero memory
 * @p: object to free memory of
 *
 * The memory of the object @p points to is zeroed before freed.
 * If @p is %NULL, kzfree() does nothing.
 *
 * Note: this function zeroes the whole allocated buffer which can be a good
 * deal bigger than the requested buffer size passed to kmalloc(). So be
 * careful when using this function in performance sensitive code.
 */
void kzfree(const void *p)
{
        size_t ks;
        void *mem = (void *)p;

        if (unlikely(ZERO_OR_NULL_PTR(mem)))
                return;
        ks = ksize(mem);
        memset(mem, 0, ks);
        kfree(mem);
}
EXPORT_SYMBOL(kzfree);

/*
 * 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);

#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;
        mm->unmap_area = arch_unmap_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 __attribute__((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 __attribute__((weak)) get_user_pages_fast(unsigned long start,
                                int nr_pages, int write, struct page **pages)
{
        struct mm_struct *mm = current->mm;
        int ret;

        down_read(&mm->mmap_sem);
        ret = get_user_pages(current, mm, start, nr_pages,
                                        write, 0, pages, NULL);
        up_read(&mm->mmap_sem);

        return ret;
}
EXPORT_SYMBOL_GPL(get_user_pages_fast);

/* Tracepoints definitions. */
EXPORT_TRACEPOINT_SYMBOL(kmalloc);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
EXPORT_TRACEPOINT_SYMBOL(kfree);
EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);