// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Cryptographic API.
 *
 * Cipher operations.
 *
 * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
 *               2002 Adam J. Richter <adam@yggdrasil.com>
 *               2004 Jean-Luc Cooke <jlcooke@certainkey.com>
 */

#include <crypto/scatterwalk.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/scatterlist.h>

void scatterwalk_skip(struct scatter_walk *walk, unsigned int nbytes)
{
        struct scatterlist *sg = walk->sg;

        nbytes += walk->offset - sg->offset;

        while (nbytes > sg->length) {
                nbytes -= sg->length;
                sg = sg_next(sg);
        }
        walk->sg = sg;
        walk->offset = sg->offset + nbytes;
}
EXPORT_SYMBOL_GPL(scatterwalk_skip);

inline void memcpy_from_scatterwalk(void *buf, struct scatter_walk *walk,
                                    unsigned int nbytes)
{
        do {
                unsigned int to_copy;

                to_copy = scatterwalk_next(walk, nbytes);
                memcpy(buf, walk->addr, to_copy);
                scatterwalk_done_src(walk, to_copy);
                buf += to_copy;
                nbytes -= to_copy;
        } while (nbytes);
}
EXPORT_SYMBOL_GPL(memcpy_from_scatterwalk);

inline void memcpy_to_scatterwalk(struct scatter_walk *walk, const void *buf,
                                  unsigned int nbytes)
{
        do {
                unsigned int to_copy;

                to_copy = scatterwalk_next(walk, nbytes);
                memcpy(walk->addr, buf, to_copy);
                scatterwalk_done_dst(walk, to_copy);
                buf += to_copy;
                nbytes -= to_copy;
        } while (nbytes);
}
EXPORT_SYMBOL_GPL(memcpy_to_scatterwalk);

void memcpy_from_sglist(void *buf, struct scatterlist *sg,
                        unsigned int start, unsigned int nbytes)
{
        struct scatter_walk walk;

        if (unlikely(nbytes == 0)) /* in case sg == NULL */
                return;

        scatterwalk_start_at_pos(&walk, sg, start);
        memcpy_from_scatterwalk(buf, &walk, nbytes);
}
EXPORT_SYMBOL_GPL(memcpy_from_sglist);

void memcpy_to_sglist(struct scatterlist *sg, unsigned int start,
                      const void *buf, unsigned int nbytes)
{
        struct scatter_walk walk;

        if (unlikely(nbytes == 0)) /* in case sg == NULL */
                return;

        scatterwalk_start_at_pos(&walk, sg, start);
        memcpy_to_scatterwalk(&walk, buf, nbytes);
}
EXPORT_SYMBOL_GPL(memcpy_to_sglist);

/**
 * memcpy_sglist() - Copy data from one scatterlist to another
 * @dst: The destination scatterlist.  Can be NULL if @nbytes == 0.
 * @src: The source scatterlist.  Can be NULL if @nbytes == 0.
 * @nbytes: Number of bytes to copy
 *
 * The scatterlists can describe exactly the same memory, in which case this
 * function is a no-op.  No other overlaps are supported.
 *
 * Context: Any context
 */
void memcpy_sglist(struct scatterlist *dst, struct scatterlist *src,
                   unsigned int nbytes)
{
        unsigned int src_offset, dst_offset;

        if (unlikely(nbytes == 0)) /* in case src and/or dst is NULL */
                return;

        src_offset = src->offset;
        dst_offset = dst->offset;
        for (;;) {
                /* Compute the length to copy this step. */
                unsigned int len = min3(src->offset + src->length - src_offset,
                                        dst->offset + dst->length - dst_offset,
                                        nbytes);
                struct page *src_page = sg_page(src);
                struct page *dst_page = sg_page(dst);
                const void *src_virt;
                void *dst_virt;

                if (IS_ENABLED(CONFIG_HIGHMEM)) {
                        /* HIGHMEM: we may have to actually map the pages. */
                        const unsigned int src_oip = offset_in_page(src_offset);
                        const unsigned int dst_oip = offset_in_page(dst_offset);
                        const unsigned int limit = PAGE_SIZE;

                        /* Further limit len to not cross a page boundary. */
                        len = min3(len, limit - src_oip, limit - dst_oip);

                        /* Compute the source and destination pages. */
                        src_page += src_offset / PAGE_SIZE;
                        dst_page += dst_offset / PAGE_SIZE;

                        if (src_page != dst_page) {
                                /* Copy between different pages. */
                                memcpy_page(dst_page, dst_oip,
                                            src_page, src_oip, len);
                                flush_dcache_page(dst_page);
                        } else if (src_oip != dst_oip) {
                                /* Copy between different parts of same page. */
                                dst_virt = kmap_local_page(dst_page);
                                memcpy(dst_virt + dst_oip, dst_virt + src_oip,
                                       len);
                                kunmap_local(dst_virt);
                                flush_dcache_page(dst_page);
                        } /* Else, it's the same memory.  No action needed. */
                } else {
                        /*
                         * !HIGHMEM: no mapping needed.  Just work in the linear
                         * buffer of each sg entry.  Note that we can cross page
                         * boundaries, as they are not significant in this case.
                         */
                        src_virt = page_address(src_page) + src_offset;
                        dst_virt = page_address(dst_page) + dst_offset;
                        if (src_virt != dst_virt) {
                                memcpy(dst_virt, src_virt, len);
                                if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE)
                                        __scatterwalk_flush_dcache_pages(
                                                dst_page, dst_offset, len);
                        } /* Else, it's the same memory.  No action needed. */
                }
                nbytes -= len;
                if (nbytes == 0) /* No more to copy? */
                        break;

                /*
                 * There's more to copy.  Advance the offsets by the length
                 * copied this step, and advance the sg entries as needed.
                 */
                src_offset += len;
                if (src_offset >= src->offset + src->length) {
                        src = sg_next(src);
                        src_offset = src->offset;
                }
                dst_offset += len;
                if (dst_offset >= dst->offset + dst->length) {
                        dst = sg_next(dst);
                        dst_offset = dst->offset;
                }
        }
}
EXPORT_SYMBOL_GPL(memcpy_sglist);

struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
                                     struct scatterlist *src,
                                     unsigned int len)
{
        for (;;) {
                if (!len)
                        return src;

                if (src->length > len)
                        break;

                len -= src->length;
                src = sg_next(src);
        }

        sg_init_table(dst, 2);
        sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
        scatterwalk_crypto_chain(dst, sg_next(src), 2);

        return dst;
}
EXPORT_SYMBOL_GPL(scatterwalk_ffwd);