/* binder_alloc_selftest.c
 *
 * Android IPC Subsystem
 *
 * Copyright (C) 2017 Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mm_types.h>
#include <linux/err.h>
#include "binder_alloc.h"

#define BUFFER_NUM 5
#define BUFFER_MIN_SIZE (PAGE_SIZE / 8)

static bool binder_selftest_run = true;
static int binder_selftest_failures;
static DEFINE_MUTEX(binder_selftest_lock);

/**
 * enum buf_end_align_type - Page alignment of a buffer
 * end with regard to the end of the previous buffer.
 *
 * In the pictures below, buf2 refers to the buffer we
 * are aligning. buf1 refers to previous buffer by addr.
 * Symbol [ means the start of a buffer, ] means the end
 * of a buffer, and | means page boundaries.
 */
enum buf_end_align_type {
        /**
         * @SAME_PAGE_UNALIGNED: The end of this buffer is on
         * the same page as the end of the previous buffer and
         * is not page aligned. Examples:
         * buf1 ][ buf2 ][ ...
         * buf1 ]|[ buf2 ][ ...
         */
        SAME_PAGE_UNALIGNED = 0,
        /**
         * @SAME_PAGE_ALIGNED: When the end of the previous buffer
         * is not page aligned, the end of this buffer is on the
         * same page as the end of the previous buffer and is page
         * aligned. When the previous buffer is page aligned, the
         * end of this buffer is aligned to the next page boundary.
         * Examples:
         * buf1 ][ buf2 ]| ...
         * buf1 ]|[ buf2 ]| ...
         */
        SAME_PAGE_ALIGNED,
        /**
         * @NEXT_PAGE_UNALIGNED: The end of this buffer is on
         * the page next to the end of the previous buffer and
         * is not page aligned. Examples:
         * buf1 ][ buf2 | buf2 ][ ...
         * buf1 ]|[ buf2 | buf2 ][ ...
         */
        NEXT_PAGE_UNALIGNED,
        /**
         * @NEXT_PAGE_ALIGNED: The end of this buffer is on
         * the page next to the end of the previous buffer and
         * is page aligned. Examples:
         * buf1 ][ buf2 | buf2 ]| ...
         * buf1 ]|[ buf2 | buf2 ]| ...
         */
        NEXT_PAGE_ALIGNED,
        /**
         * @NEXT_NEXT_UNALIGNED: The end of this buffer is on
         * the page that follows the page after the end of the
         * previous buffer and is not page aligned. Examples:
         * buf1 ][ buf2 | buf2 | buf2 ][ ...
         * buf1 ]|[ buf2 | buf2 | buf2 ][ ...
         */
        NEXT_NEXT_UNALIGNED,
        LOOP_END,
};

static void pr_err_size_seq(size_t *sizes, int *seq)
{
        int i;

        pr_err("alloc sizes: ");
        for (i = 0; i < BUFFER_NUM; i++)
                pr_cont("[%zu]", sizes[i]);
        pr_cont("\n");
        pr_err("free seq: ");
        for (i = 0; i < BUFFER_NUM; i++)
                pr_cont("[%d]", seq[i]);
        pr_cont("\n");
}

static bool check_buffer_pages_allocated(struct binder_alloc *alloc,
                                         struct binder_buffer *buffer,
                                         size_t size)
{
        void *page_addr, *end;
        int page_index;

        end = (void *)PAGE_ALIGN((uintptr_t)buffer->data + size);
        page_addr = buffer->data;
        for (; page_addr < end; page_addr += PAGE_SIZE) {
                page_index = (page_addr - alloc->buffer) / PAGE_SIZE;
                if (!alloc->pages[page_index].page_ptr ||
                    !list_empty(&alloc->pages[page_index].lru)) {
                        pr_err("expect alloc but is %s at page index %d\n",
                               alloc->pages[page_index].page_ptr ?
                               "lru" : "free", page_index);
                        return false;
                }
        }
        return true;
}

static void binder_selftest_alloc_buf(struct binder_alloc *alloc,
                                      struct binder_buffer *buffers[],
                                      size_t *sizes, int *seq)
{
        int i;

        for (i = 0; i < BUFFER_NUM; i++) {
                buffers[i] = binder_alloc_new_buf(alloc, sizes[i], 0, 0, 0);
                if (IS_ERR(buffers[i]) ||
                    !check_buffer_pages_allocated(alloc, buffers[i],
                                                  sizes[i])) {
                        pr_err_size_seq(sizes, seq);
                        binder_selftest_failures++;
                }
        }
}

static void binder_selftest_free_buf(struct binder_alloc *alloc,
                                     struct binder_buffer *buffers[],
                                     size_t *sizes, int *seq, size_t end)
{
        int i;

        for (i = 0; i < BUFFER_NUM; i++)
                binder_alloc_free_buf(alloc, buffers[seq[i]]);

        for (i = 0; i < end / PAGE_SIZE; i++) {
                /**
                 * Error message on a free page can be false positive
                 * if binder shrinker ran during binder_alloc_free_buf
                 * calls above.
                 */
                if (list_empty(&alloc->pages[i].lru)) {
                        pr_err_size_seq(sizes, seq);
                        pr_err("expect lru but is %s at page index %d\n",
                               alloc->pages[i].page_ptr ? "alloc" : "free", i);
                        binder_selftest_failures++;
                }
        }
}

static void binder_selftest_free_page(struct binder_alloc *alloc)
{
        int i;
        unsigned long count;

        while ((count = list_lru_count(&binder_alloc_lru))) {
                list_lru_walk(&binder_alloc_lru, binder_alloc_free_page,
                              NULL, count);
        }

        for (i = 0; i < (alloc->buffer_size / PAGE_SIZE); i++) {
                if (alloc->pages[i].page_ptr) {
                        pr_err("expect free but is %s at page index %d\n",
                               list_empty(&alloc->pages[i].lru) ?
                               "alloc" : "lru", i);
                        binder_selftest_failures++;
                }
        }
}

static void binder_selftest_alloc_free(struct binder_alloc *alloc,
                                       size_t *sizes, int *seq, size_t end)
{
        struct binder_buffer *buffers[BUFFER_NUM];

        binder_selftest_alloc_buf(alloc, buffers, sizes, seq);
        binder_selftest_free_buf(alloc, buffers, sizes, seq, end);

        /* Allocate from lru. */
        binder_selftest_alloc_buf(alloc, buffers, sizes, seq);
        if (list_lru_count(&binder_alloc_lru))
                pr_err("lru list should be empty but is not\n");

        binder_selftest_free_buf(alloc, buffers, sizes, seq, end);
        binder_selftest_free_page(alloc);
}

static bool is_dup(int *seq, int index, int val)
{
        int i;

        for (i = 0; i < index; i++) {
                if (seq[i] == val)
                        return true;
        }
        return false;
}

/* Generate BUFFER_NUM factorial free orders. */
static void binder_selftest_free_seq(struct binder_alloc *alloc,
                                     size_t *sizes, int *seq,
                                     int index, size_t end)
{
        int i;

        if (index == BUFFER_NUM) {
                binder_selftest_alloc_free(alloc, sizes, seq, end);
                return;
        }
        for (i = 0; i < BUFFER_NUM; i++) {
                if (is_dup(seq, index, i))
                        continue;
                seq[index] = i;
                binder_selftest_free_seq(alloc, sizes, seq, index + 1, end);
        }
}

static void binder_selftest_alloc_size(struct binder_alloc *alloc,
                                       size_t *end_offset)
{
        int i;
        int seq[BUFFER_NUM] = {0};
        size_t front_sizes[BUFFER_NUM];
        size_t back_sizes[BUFFER_NUM];
        size_t last_offset, offset = 0;

        for (i = 0; i < BUFFER_NUM; i++) {
                last_offset = offset;
                offset = end_offset[i];
                front_sizes[i] = offset - last_offset;
                back_sizes[BUFFER_NUM - i - 1] = front_sizes[i];
        }
        /*
         * Buffers share the first or last few pages.
         * Only BUFFER_NUM - 1 buffer sizes are adjustable since
         * we need one giant buffer before getting to the last page.
         */
        back_sizes[0] += alloc->buffer_size - end_offset[BUFFER_NUM - 1];
        binder_selftest_free_seq(alloc, front_sizes, seq, 0,
                                 end_offset[BUFFER_NUM - 1]);
        binder_selftest_free_seq(alloc, back_sizes, seq, 0, alloc->buffer_size);
}

static void binder_selftest_alloc_offset(struct binder_alloc *alloc,
                                         size_t *end_offset, int index)
{
        int align;
        size_t end, prev;

        if (index == BUFFER_NUM) {
                binder_selftest_alloc_size(alloc, end_offset);
                return;
        }
        prev = index == 0 ? 0 : end_offset[index - 1];
        end = prev;

        BUILD_BUG_ON(BUFFER_MIN_SIZE * BUFFER_NUM >= PAGE_SIZE);

        for (align = SAME_PAGE_UNALIGNED; align < LOOP_END; align++) {
                if (align % 2)
                        end = ALIGN(end, PAGE_SIZE);
                else
                        end += BUFFER_MIN_SIZE;
                end_offset[index] = end;
                binder_selftest_alloc_offset(alloc, end_offset, index + 1);
        }
}

/**
 * binder_selftest_alloc() - Test alloc and free of buffer pages.
 * @alloc: Pointer to alloc struct.
 *
 * Allocate BUFFER_NUM buffers to cover all page alignment cases,
 * then free them in all orders possible. Check that pages are
 * correctly allocated, put onto lru when buffers are freed, and
 * are freed when binder_alloc_free_page is called.
 */
void binder_selftest_alloc(struct binder_alloc *alloc)
{
        size_t end_offset[BUFFER_NUM];

        if (!binder_selftest_run)
                return;
        mutex_lock(&binder_selftest_lock);
        if (!binder_selftest_run || !alloc->vma)
                goto done;
        pr_info("STARTED\n");
        binder_selftest_alloc_offset(alloc, end_offset, 0);
        binder_selftest_run = false;
        if (binder_selftest_failures > 0)
                pr_info("%d tests FAILED\n", binder_selftest_failures);
        else
                pr_info("PASSED\n");

done:
        mutex_unlock(&binder_selftest_lock);
}