// SPDX-License-Identifier: GPL-2.0-only
/* binder_alloc.c
 *
 * Android IPC Subsystem
 *
 * Copyright (C) 2007-2017 Google, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/list.h>
#include <linux/sched/mm.h>
#include <linux/module.h>
#include <linux/rtmutex.h>
#include <linux/rbtree.h>
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/list_lru.h>
#include <linux/ratelimit.h>
#include <asm/cacheflush.h>
#include <linux/uaccess.h>
#include <linux/highmem.h>
#include <linux/sizes.h>
#include "binder_alloc.h"
#include "binder_trace.h"

struct list_lru binder_alloc_lru;

static DEFINE_MUTEX(binder_alloc_mmap_lock);

enum {
        BINDER_DEBUG_USER_ERROR             = 1U << 0,
        BINDER_DEBUG_OPEN_CLOSE             = 1U << 1,
        BINDER_DEBUG_BUFFER_ALLOC           = 1U << 2,
        BINDER_DEBUG_BUFFER_ALLOC_ASYNC     = 1U << 3,
};
static uint32_t binder_alloc_debug_mask = BINDER_DEBUG_USER_ERROR;

module_param_named(debug_mask, binder_alloc_debug_mask,
                   uint, 0644);

#define binder_alloc_debug(mask, x...) \
        do { \
                if (binder_alloc_debug_mask & mask) \
                        pr_info_ratelimited(x); \
        } while (0)

static struct binder_buffer *binder_buffer_next(struct binder_buffer *buffer)
{
        return list_entry(buffer->entry.next, struct binder_buffer, entry);
}

static struct binder_buffer *binder_buffer_prev(struct binder_buffer *buffer)
{
        return list_entry(buffer->entry.prev, struct binder_buffer, entry);
}

static size_t binder_alloc_buffer_size(struct binder_alloc *alloc,
                                       struct binder_buffer *buffer)
{
        if (list_is_last(&buffer->entry, &alloc->buffers))
                return alloc->buffer + alloc->buffer_size - buffer->user_data;
        return binder_buffer_next(buffer)->user_data - buffer->user_data;
}

static void binder_insert_free_buffer(struct binder_alloc *alloc,
                                      struct binder_buffer *new_buffer)
{
        struct rb_node **p = &alloc->free_buffers.rb_node;
        struct rb_node *parent = NULL;
        struct binder_buffer *buffer;
        size_t buffer_size;
        size_t new_buffer_size;

        BUG_ON(!new_buffer->free);

        new_buffer_size = binder_alloc_buffer_size(alloc, new_buffer);

        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                     "%d: add free buffer, size %zd, at %pK\n",
                      alloc->pid, new_buffer_size, new_buffer);

        while (*p) {
                parent = *p;
                buffer = rb_entry(parent, struct binder_buffer, rb_node);
                BUG_ON(!buffer->free);

                buffer_size = binder_alloc_buffer_size(alloc, buffer);

                if (new_buffer_size < buffer_size)
                        p = &parent->rb_left;
                else
                        p = &parent->rb_right;
        }
        rb_link_node(&new_buffer->rb_node, parent, p);
        rb_insert_color(&new_buffer->rb_node, &alloc->free_buffers);
}

static void binder_insert_allocated_buffer_locked(
                struct binder_alloc *alloc, struct binder_buffer *new_buffer)
{
        struct rb_node **p = &alloc->allocated_buffers.rb_node;
        struct rb_node *parent = NULL;
        struct binder_buffer *buffer;

        BUG_ON(new_buffer->free);

        while (*p) {
                parent = *p;
                buffer = rb_entry(parent, struct binder_buffer, rb_node);
                BUG_ON(buffer->free);

                if (new_buffer->user_data < buffer->user_data)
                        p = &parent->rb_left;
                else if (new_buffer->user_data > buffer->user_data)
                        p = &parent->rb_right;
                else
                        BUG();
        }
        rb_link_node(&new_buffer->rb_node, parent, p);
        rb_insert_color(&new_buffer->rb_node, &alloc->allocated_buffers);
}

static struct binder_buffer *binder_alloc_prepare_to_free_locked(
                struct binder_alloc *alloc,
                uintptr_t user_ptr)
{
        struct rb_node *n = alloc->allocated_buffers.rb_node;
        struct binder_buffer *buffer;
        void __user *uptr;

        uptr = (void __user *)user_ptr;

        while (n) {
                buffer = rb_entry(n, struct binder_buffer, rb_node);
                BUG_ON(buffer->free);

                if (uptr < buffer->user_data)
                        n = n->rb_left;
                else if (uptr > buffer->user_data)
                        n = n->rb_right;
                else {
                        /*
                         * Guard against user threads attempting to
                         * free the buffer when in use by kernel or
                         * after it's already been freed.
                         */
                        if (!buffer->allow_user_free)
                                return ERR_PTR(-EPERM);
                        buffer->allow_user_free = 0;
                        return buffer;
                }
        }
        return NULL;
}

/**
 * binder_alloc_prepare_to_free() - get buffer given user ptr
 * @alloc:      binder_alloc for this proc
 * @user_ptr:   User pointer to buffer data
 *
 * Validate userspace pointer to buffer data and return buffer corresponding to
 * that user pointer. Search the rb tree for buffer that matches user data
 * pointer.
 *
 * Return:      Pointer to buffer or NULL
 */
struct binder_buffer *binder_alloc_prepare_to_free(struct binder_alloc *alloc,
                                                   uintptr_t user_ptr)
{
        struct binder_buffer *buffer;

        mutex_lock(&alloc->mutex);
        buffer = binder_alloc_prepare_to_free_locked(alloc, user_ptr);
        mutex_unlock(&alloc->mutex);
        return buffer;
}

static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
                                    void __user *start, void __user *end)
{
        void __user *page_addr;
        unsigned long user_page_addr;
        struct binder_lru_page *page;
        struct vm_area_struct *vma = NULL;
        struct mm_struct *mm = NULL;
        bool need_mm = false;

        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                     "%d: %s pages %pK-%pK\n", alloc->pid,
                     allocate ? "allocate" : "free", start, end);

        if (end <= start)
                return 0;

        trace_binder_update_page_range(alloc, allocate, start, end);

        if (allocate == 0)
                goto free_range;

        for (page_addr = start; page_addr < end; page_addr += PAGE_SIZE) {
                page = &alloc->pages[(page_addr - alloc->buffer) / PAGE_SIZE];
                if (!page->page_ptr) {
                        need_mm = true;
                        break;
                }
        }

        if (need_mm && mmget_not_zero(alloc->vma_vm_mm))
                mm = alloc->vma_vm_mm;

        if (mm) {
                mmap_read_lock(mm);
                vma = alloc->vma;
        }

        if (!vma && need_mm) {
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "%d: binder_alloc_buf failed to map pages in userspace, no vma\n",
                                   alloc->pid);
                goto err_no_vma;
        }

        for (page_addr = start; page_addr < end; page_addr += PAGE_SIZE) {
                int ret;
                bool on_lru;
                size_t index;

                index = (page_addr - alloc->buffer) / PAGE_SIZE;
                page = &alloc->pages[index];

                if (page->page_ptr) {
                        trace_binder_alloc_lru_start(alloc, index);

                        on_lru = list_lru_del(&binder_alloc_lru, &page->lru);
                        WARN_ON(!on_lru);

                        trace_binder_alloc_lru_end(alloc, index);
                        continue;
                }

                if (WARN_ON(!vma))
                        goto err_page_ptr_cleared;

                trace_binder_alloc_page_start(alloc, index);
                page->page_ptr = alloc_page(GFP_KERNEL |
                                            __GFP_HIGHMEM |
                                            __GFP_ZERO);
                if (!page->page_ptr) {
                        pr_err("%d: binder_alloc_buf failed for page at %pK\n",
                                alloc->pid, page_addr);
                        goto err_alloc_page_failed;
                }
                page->alloc = alloc;
                INIT_LIST_HEAD(&page->lru);

                user_page_addr = (uintptr_t)page_addr;
                ret = vm_insert_page(vma, user_page_addr, page[0].page_ptr);
                if (ret) {
                        pr_err("%d: binder_alloc_buf failed to map page at %lx in userspace\n",
                               alloc->pid, user_page_addr);
                        goto err_vm_insert_page_failed;
                }

                if (index + 1 > alloc->pages_high)
                        alloc->pages_high = index + 1;

                trace_binder_alloc_page_end(alloc, index);
        }
        if (mm) {
                mmap_read_unlock(mm);
                mmput(mm);
        }
        return 0;

free_range:
        for (page_addr = end - PAGE_SIZE; 1; page_addr -= PAGE_SIZE) {
                bool ret;
                size_t index;

                index = (page_addr - alloc->buffer) / PAGE_SIZE;
                page = &alloc->pages[index];

                trace_binder_free_lru_start(alloc, index);

                ret = list_lru_add(&binder_alloc_lru, &page->lru);
                WARN_ON(!ret);

                trace_binder_free_lru_end(alloc, index);
                if (page_addr == start)
                        break;
                continue;

err_vm_insert_page_failed:
                __free_page(page->page_ptr);
                page->page_ptr = NULL;
err_alloc_page_failed:
err_page_ptr_cleared:
                if (page_addr == start)
                        break;
        }
err_no_vma:
        if (mm) {
                mmap_read_unlock(mm);
                mmput(mm);
        }
        return vma ? -ENOMEM : -ESRCH;
}


static inline void binder_alloc_set_vma(struct binder_alloc *alloc,
                struct vm_area_struct *vma)
{
        if (vma)
                alloc->vma_vm_mm = vma->vm_mm;
        /*
         * If we see alloc->vma is not NULL, buffer data structures set up
         * completely. Look at smp_rmb side binder_alloc_get_vma.
         * We also want to guarantee new alloc->vma_vm_mm is always visible
         * if alloc->vma is set.
         */
        smp_wmb();
        alloc->vma = vma;
}

static inline struct vm_area_struct *binder_alloc_get_vma(
                struct binder_alloc *alloc)
{
        struct vm_area_struct *vma = NULL;

        if (alloc->vma) {
                /* Look at description in binder_alloc_set_vma */
                smp_rmb();
                vma = alloc->vma;
        }
        return vma;
}

static bool debug_low_async_space_locked(struct binder_alloc *alloc, int pid)
{
        /*
         * Find the amount and size of buffers allocated by the current caller;
         * The idea is that once we cross the threshold, whoever is responsible
         * for the low async space is likely to try to send another async txn,
         * and at some point we'll catch them in the act. This is more efficient
         * than keeping a map per pid.
         */
        struct rb_node *n;
        struct binder_buffer *buffer;
        size_t total_alloc_size = 0;
        size_t num_buffers = 0;

        for (n = rb_first(&alloc->allocated_buffers); n != NULL;
                 n = rb_next(n)) {
                buffer = rb_entry(n, struct binder_buffer, rb_node);
                if (buffer->pid != pid)
                        continue;
                if (!buffer->async_transaction)
                        continue;
                total_alloc_size += binder_alloc_buffer_size(alloc, buffer)
                        + sizeof(struct binder_buffer);
                num_buffers++;
        }

        /*
         * Warn if this pid has more than 50 transactions, or more than 50% of
         * async space (which is 25% of total buffer size). Oneway spam is only
         * detected when the threshold is exceeded.
         */
        if (num_buffers > 50 || total_alloc_size > alloc->buffer_size / 4) {
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                             "%d: pid %d spamming oneway? %zd buffers allocated for a total size of %zd\n",
                              alloc->pid, pid, num_buffers, total_alloc_size);
                if (!alloc->oneway_spam_detected) {
                        alloc->oneway_spam_detected = true;
                        return true;
                }
        }
        return false;
}

static struct binder_buffer *binder_alloc_new_buf_locked(
                                struct binder_alloc *alloc,
                                size_t data_size,
                                size_t offsets_size,
                                size_t extra_buffers_size,
                                int is_async,
                                int pid)
{
        struct rb_node *n = alloc->free_buffers.rb_node;
        struct binder_buffer *buffer;
        size_t buffer_size;
        struct rb_node *best_fit = NULL;
        void __user *has_page_addr;
        void __user *end_page_addr;
        size_t size, data_offsets_size;
        int ret;

        if (!binder_alloc_get_vma(alloc)) {
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "%d: binder_alloc_buf, no vma\n",
                                   alloc->pid);
                return ERR_PTR(-ESRCH);
        }

        data_offsets_size = ALIGN(data_size, sizeof(void *)) +
                ALIGN(offsets_size, sizeof(void *));

        if (data_offsets_size < data_size || data_offsets_size < offsets_size) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                "%d: got transaction with invalid size %zd-%zd\n",
                                alloc->pid, data_size, offsets_size);
                return ERR_PTR(-EINVAL);
        }
        size = data_offsets_size + ALIGN(extra_buffers_size, sizeof(void *));
        if (size < data_offsets_size || size < extra_buffers_size) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                "%d: got transaction with invalid extra_buffers_size %zd\n",
                                alloc->pid, extra_buffers_size);
                return ERR_PTR(-EINVAL);
        }
        if (is_async &&
            alloc->free_async_space < size + sizeof(struct binder_buffer)) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                             "%d: binder_alloc_buf size %zd failed, no async space left\n",
                              alloc->pid, size);
                return ERR_PTR(-ENOSPC);
        }

        /* Pad 0-size buffers so they get assigned unique addresses */
        size = max(size, sizeof(void *));

        while (n) {
                buffer = rb_entry(n, struct binder_buffer, rb_node);
                BUG_ON(!buffer->free);
                buffer_size = binder_alloc_buffer_size(alloc, buffer);

                if (size < buffer_size) {
                        best_fit = n;
                        n = n->rb_left;
                } else if (size > buffer_size)
                        n = n->rb_right;
                else {
                        best_fit = n;
                        break;
                }
        }
        if (best_fit == NULL) {
                size_t allocated_buffers = 0;
                size_t largest_alloc_size = 0;
                size_t total_alloc_size = 0;
                size_t free_buffers = 0;
                size_t largest_free_size = 0;
                size_t total_free_size = 0;

                for (n = rb_first(&alloc->allocated_buffers); n != NULL;
                     n = rb_next(n)) {
                        buffer = rb_entry(n, struct binder_buffer, rb_node);
                        buffer_size = binder_alloc_buffer_size(alloc, buffer);
                        allocated_buffers++;
                        total_alloc_size += buffer_size;
                        if (buffer_size > largest_alloc_size)
                                largest_alloc_size = buffer_size;
                }
                for (n = rb_first(&alloc->free_buffers); n != NULL;
                     n = rb_next(n)) {
                        buffer = rb_entry(n, struct binder_buffer, rb_node);
                        buffer_size = binder_alloc_buffer_size(alloc, buffer);
                        free_buffers++;
                        total_free_size += buffer_size;
                        if (buffer_size > largest_free_size)
                                largest_free_size = buffer_size;
                }
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "%d: binder_alloc_buf size %zd failed, no address space\n",
                                   alloc->pid, size);
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "allocated: %zd (num: %zd largest: %zd), free: %zd (num: %zd largest: %zd)\n",
                                   total_alloc_size, allocated_buffers,
                                   largest_alloc_size, total_free_size,
                                   free_buffers, largest_free_size);
                return ERR_PTR(-ENOSPC);
        }
        if (n == NULL) {
                buffer = rb_entry(best_fit, struct binder_buffer, rb_node);
                buffer_size = binder_alloc_buffer_size(alloc, buffer);
        }

        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                     "%d: binder_alloc_buf size %zd got buffer %pK size %zd\n",
                      alloc->pid, size, buffer, buffer_size);

        has_page_addr = (void __user *)
                (((uintptr_t)buffer->user_data + buffer_size) & PAGE_MASK);
        WARN_ON(n && buffer_size != size);
        end_page_addr =
                (void __user *)PAGE_ALIGN((uintptr_t)buffer->user_data + size);
        if (end_page_addr > has_page_addr)
                end_page_addr = has_page_addr;
        ret = binder_update_page_range(alloc, 1, (void __user *)
                PAGE_ALIGN((uintptr_t)buffer->user_data), end_page_addr);
        if (ret)
                return ERR_PTR(ret);

        if (buffer_size != size) {
                struct binder_buffer *new_buffer;

                new_buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
                if (!new_buffer) {
                        pr_err("%s: %d failed to alloc new buffer struct\n",
                               __func__, alloc->pid);
                        goto err_alloc_buf_struct_failed;
                }
                new_buffer->user_data = (u8 __user *)buffer->user_data + size;
                list_add(&new_buffer->entry, &buffer->entry);
                new_buffer->free = 1;
                binder_insert_free_buffer(alloc, new_buffer);
        }

        rb_erase(best_fit, &alloc->free_buffers);
        buffer->free = 0;
        buffer->allow_user_free = 0;
        binder_insert_allocated_buffer_locked(alloc, buffer);
        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                     "%d: binder_alloc_buf size %zd got %pK\n",
                      alloc->pid, size, buffer);
        buffer->data_size = data_size;
        buffer->offsets_size = offsets_size;
        buffer->async_transaction = is_async;
        buffer->extra_buffers_size = extra_buffers_size;
        buffer->pid = pid;
        buffer->oneway_spam_suspect = false;
        if (is_async) {
                alloc->free_async_space -= size + sizeof(struct binder_buffer);
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC_ASYNC,
                             "%d: binder_alloc_buf size %zd async free %zd\n",
                              alloc->pid, size, alloc->free_async_space);
                if (alloc->free_async_space < alloc->buffer_size / 10) {
                        /*
                         * Start detecting spammers once we have less than 20%
                         * of async space left (which is less than 10% of total
                         * buffer size).
                         */
                        buffer->oneway_spam_suspect = debug_low_async_space_locked(alloc, pid);
                } else {
                        alloc->oneway_spam_detected = false;
                }
        }
        return buffer;

err_alloc_buf_struct_failed:
        binder_update_page_range(alloc, 0, (void __user *)
                                 PAGE_ALIGN((uintptr_t)buffer->user_data),
                                 end_page_addr);
        return ERR_PTR(-ENOMEM);
}

/**
 * binder_alloc_new_buf() - Allocate a new binder buffer
 * @alloc:              binder_alloc for this proc
 * @data_size:          size of user data buffer
 * @offsets_size:       user specified buffer offset
 * @extra_buffers_size: size of extra space for meta-data (eg, security context)
 * @is_async:           buffer for async transaction
 * @pid:                                pid to attribute allocation to (used for debugging)
 *
 * Allocate a new buffer given the requested sizes. Returns
 * the kernel version of the buffer pointer. The size allocated
 * is the sum of the three given sizes (each rounded up to
 * pointer-sized boundary)
 *
 * Return:      The allocated buffer or %NULL if error
 */
struct binder_buffer *binder_alloc_new_buf(struct binder_alloc *alloc,
                                           size_t data_size,
                                           size_t offsets_size,
                                           size_t extra_buffers_size,
                                           int is_async,
                                           int pid)
{
        struct binder_buffer *buffer;

        mutex_lock(&alloc->mutex);
        buffer = binder_alloc_new_buf_locked(alloc, data_size, offsets_size,
                                             extra_buffers_size, is_async, pid);
        mutex_unlock(&alloc->mutex);
        return buffer;
}

static void __user *buffer_start_page(struct binder_buffer *buffer)
{
        return (void __user *)((uintptr_t)buffer->user_data & PAGE_MASK);
}

static void __user *prev_buffer_end_page(struct binder_buffer *buffer)
{
        return (void __user *)
                (((uintptr_t)(buffer->user_data) - 1) & PAGE_MASK);
}

static void binder_delete_free_buffer(struct binder_alloc *alloc,
                                      struct binder_buffer *buffer)
{
        struct binder_buffer *prev, *next = NULL;
        bool to_free = true;

        BUG_ON(alloc->buffers.next == &buffer->entry);
        prev = binder_buffer_prev(buffer);
        BUG_ON(!prev->free);
        if (prev_buffer_end_page(prev) == buffer_start_page(buffer)) {
                to_free = false;
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                   "%d: merge free, buffer %pK share page with %pK\n",
                                   alloc->pid, buffer->user_data,
                                   prev->user_data);
        }

        if (!list_is_last(&buffer->entry, &alloc->buffers)) {
                next = binder_buffer_next(buffer);
                if (buffer_start_page(next) == buffer_start_page(buffer)) {
                        to_free = false;
                        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                           "%d: merge free, buffer %pK share page with %pK\n",
                                           alloc->pid,
                                           buffer->user_data,
                                           next->user_data);
                }
        }

        if (PAGE_ALIGNED(buffer->user_data)) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                   "%d: merge free, buffer start %pK is page aligned\n",
                                   alloc->pid, buffer->user_data);
                to_free = false;
        }

        if (to_free) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                   "%d: merge free, buffer %pK do not share page with %pK or %pK\n",
                                   alloc->pid, buffer->user_data,
                                   prev->user_data,
                                   next ? next->user_data : NULL);
                binder_update_page_range(alloc, 0, buffer_start_page(buffer),
                                         buffer_start_page(buffer) + PAGE_SIZE);
        }
        list_del(&buffer->entry);
        kfree(buffer);
}

static void binder_free_buf_locked(struct binder_alloc *alloc,
                                   struct binder_buffer *buffer)
{
        size_t size, buffer_size;

        buffer_size = binder_alloc_buffer_size(alloc, buffer);

        size = ALIGN(buffer->data_size, sizeof(void *)) +
                ALIGN(buffer->offsets_size, sizeof(void *)) +
                ALIGN(buffer->extra_buffers_size, sizeof(void *));

        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                     "%d: binder_free_buf %pK size %zd buffer_size %zd\n",
                      alloc->pid, buffer, size, buffer_size);

        BUG_ON(buffer->free);
        BUG_ON(size > buffer_size);
        BUG_ON(buffer->transaction != NULL);
        BUG_ON(buffer->user_data < alloc->buffer);
        BUG_ON(buffer->user_data > alloc->buffer + alloc->buffer_size);

        if (buffer->async_transaction) {
                alloc->free_async_space += size + sizeof(struct binder_buffer);

                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC_ASYNC,
                             "%d: binder_free_buf size %zd async free %zd\n",
                              alloc->pid, size, alloc->free_async_space);
        }

        binder_update_page_range(alloc, 0,
                (void __user *)PAGE_ALIGN((uintptr_t)buffer->user_data),
                (void __user *)(((uintptr_t)
                          buffer->user_data + buffer_size) & PAGE_MASK));

        rb_erase(&buffer->rb_node, &alloc->allocated_buffers);
        buffer->free = 1;
        if (!list_is_last(&buffer->entry, &alloc->buffers)) {
                struct binder_buffer *next = binder_buffer_next(buffer);

                if (next->free) {
                        rb_erase(&next->rb_node, &alloc->free_buffers);
                        binder_delete_free_buffer(alloc, next);
                }
        }
        if (alloc->buffers.next != &buffer->entry) {
                struct binder_buffer *prev = binder_buffer_prev(buffer);

                if (prev->free) {
                        binder_delete_free_buffer(alloc, buffer);
                        rb_erase(&prev->rb_node, &alloc->free_buffers);
                        buffer = prev;
                }
        }
        binder_insert_free_buffer(alloc, buffer);
}

static void binder_alloc_clear_buf(struct binder_alloc *alloc,
                                   struct binder_buffer *buffer);
/**
 * binder_alloc_free_buf() - free a binder buffer
 * @alloc:      binder_alloc for this proc
 * @buffer:     kernel pointer to buffer
 *
 * Free the buffer allocated via binder_alloc_new_buf()
 */
void binder_alloc_free_buf(struct binder_alloc *alloc,
                            struct binder_buffer *buffer)
{
        /*
         * We could eliminate the call to binder_alloc_clear_buf()
         * from binder_alloc_deferred_release() by moving this to
         * binder_alloc_free_buf_locked(). However, that could
         * increase contention for the alloc mutex if clear_on_free
         * is used frequently for large buffers. The mutex is not
         * needed for correctness here.
         */
        if (buffer->clear_on_free) {
                binder_alloc_clear_buf(alloc, buffer);
                buffer->clear_on_free = false;
        }
        mutex_lock(&alloc->mutex);
        binder_free_buf_locked(alloc, buffer);
        mutex_unlock(&alloc->mutex);
}

/**
 * binder_alloc_mmap_handler() - map virtual address space for proc
 * @alloc:      alloc structure for this proc
 * @vma:        vma passed to mmap()
 *
 * Called by binder_mmap() to initialize the space specified in
 * vma for allocating binder buffers
 *
 * Return:
 *      0 = success
 *      -EBUSY = address space already mapped
 *      -ENOMEM = failed to map memory to given address space
 */
int binder_alloc_mmap_handler(struct binder_alloc *alloc,
                              struct vm_area_struct *vma)
{
        int ret;
        const char *failure_string;
        struct binder_buffer *buffer;

        mutex_lock(&binder_alloc_mmap_lock);
        if (alloc->buffer_size) {
                ret = -EBUSY;
                failure_string = "already mapped";
                goto err_already_mapped;
        }
        alloc->buffer_size = min_t(unsigned long, vma->vm_end - vma->vm_start,
                                   SZ_4M);
        mutex_unlock(&binder_alloc_mmap_lock);

        alloc->buffer = (void __user *)vma->vm_start;

        alloc->pages = kcalloc(alloc->buffer_size / PAGE_SIZE,
                               sizeof(alloc->pages[0]),
                               GFP_KERNEL);
        if (alloc->pages == NULL) {
                ret = -ENOMEM;
                failure_string = "alloc page array";
                goto err_alloc_pages_failed;
        }

        buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
        if (!buffer) {
                ret = -ENOMEM;
                failure_string = "alloc buffer struct";
                goto err_alloc_buf_struct_failed;
        }

        buffer->user_data = alloc->buffer;
        list_add(&buffer->entry, &alloc->buffers);
        buffer->free = 1;
        binder_insert_free_buffer(alloc, buffer);
        alloc->free_async_space = alloc->buffer_size / 2;
        binder_alloc_set_vma(alloc, vma);
        mmgrab(alloc->vma_vm_mm);

        return 0;

err_alloc_buf_struct_failed:
        kfree(alloc->pages);
        alloc->pages = NULL;
err_alloc_pages_failed:
        alloc->buffer = NULL;
        mutex_lock(&binder_alloc_mmap_lock);
        alloc->buffer_size = 0;
err_already_mapped:
        mutex_unlock(&binder_alloc_mmap_lock);
        binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                           "%s: %d %lx-%lx %s failed %d\n", __func__,
                           alloc->pid, vma->vm_start, vma->vm_end,
                           failure_string, ret);
        return ret;
}


void binder_alloc_deferred_release(struct binder_alloc *alloc)
{
        struct rb_node *n;
        int buffers, page_count;
        struct binder_buffer *buffer;

        buffers = 0;
        mutex_lock(&alloc->mutex);
        BUG_ON(alloc->vma);

        while ((n = rb_first(&alloc->allocated_buffers))) {
                buffer = rb_entry(n, struct binder_buffer, rb_node);

                /* Transaction should already have been freed */
                BUG_ON(buffer->transaction);

                if (buffer->clear_on_free) {
                        binder_alloc_clear_buf(alloc, buffer);
                        buffer->clear_on_free = false;
                }
                binder_free_buf_locked(alloc, buffer);
                buffers++;
        }

        while (!list_empty(&alloc->buffers)) {
                buffer = list_first_entry(&alloc->buffers,
                                          struct binder_buffer, entry);
                WARN_ON(!buffer->free);

                list_del(&buffer->entry);
                WARN_ON_ONCE(!list_empty(&alloc->buffers));
                kfree(buffer);
        }

        page_count = 0;
        if (alloc->pages) {
                int i;

                for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
                        void __user *page_addr;
                        bool on_lru;

                        if (!alloc->pages[i].page_ptr)
                                continue;

                        on_lru = list_lru_del(&binder_alloc_lru,
                                              &alloc->pages[i].lru);
                        page_addr = alloc->buffer + i * PAGE_SIZE;
                        binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
                                     "%s: %d: page %d at %pK %s\n",
                                     __func__, alloc->pid, i, page_addr,
                                     on_lru ? "on lru" : "active");
                        __free_page(alloc->pages[i].page_ptr);
                        page_count++;
                }
                kfree(alloc->pages);
        }
        mutex_unlock(&alloc->mutex);
        if (alloc->vma_vm_mm)
                mmdrop(alloc->vma_vm_mm);

        binder_alloc_debug(BINDER_DEBUG_OPEN_CLOSE,
                     "%s: %d buffers %d, pages %d\n",
                     __func__, alloc->pid, buffers, page_count);
}

static void print_binder_buffer(struct seq_file *m, const char *prefix,
                                struct binder_buffer *buffer)
{
        seq_printf(m, "%s %d: %pK size %zd:%zd:%zd %s\n",
                   prefix, buffer->debug_id, buffer->user_data,
                   buffer->data_size, buffer->offsets_size,
                   buffer->extra_buffers_size,
                   buffer->transaction ? "active" : "delivered");
}

/**
 * binder_alloc_print_allocated() - print buffer info
 * @m:     seq_file for output via seq_printf()
 * @alloc: binder_alloc for this proc
 *
 * Prints information about every buffer associated with
 * the binder_alloc state to the given seq_file
 */
void binder_alloc_print_allocated(struct seq_file *m,
                                  struct binder_alloc *alloc)
{
        struct rb_node *n;

        mutex_lock(&alloc->mutex);
        for (n = rb_first(&alloc->allocated_buffers); n != NULL; n = rb_next(n))
                print_binder_buffer(m, "  buffer",
                                    rb_entry(n, struct binder_buffer, rb_node));
        mutex_unlock(&alloc->mutex);
}

/**
 * binder_alloc_print_pages() - print page usage
 * @m:     seq_file for output via seq_printf()
 * @alloc: binder_alloc for this proc
 */
void binder_alloc_print_pages(struct seq_file *m,
                              struct binder_alloc *alloc)
{
        struct binder_lru_page *page;
        int i;
        int active = 0;
        int lru = 0;
        int free = 0;

        mutex_lock(&alloc->mutex);
        /*
         * Make sure the binder_alloc is fully initialized, otherwise we might
         * read inconsistent state.
         */
        if (binder_alloc_get_vma(alloc) != NULL) {
                for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
                        page = &alloc->pages[i];
                        if (!page->page_ptr)
                                free++;
                        else if (list_empty(&page->lru))
                                active++;
                        else
                                lru++;
                }
        }
        mutex_unlock(&alloc->mutex);
        seq_printf(m, "  pages: %d:%d:%d\n", active, lru, free);
        seq_printf(m, "  pages high watermark: %zu\n", alloc->pages_high);
}

/**
 * binder_alloc_get_allocated_count() - return count of buffers
 * @alloc: binder_alloc for this proc
 *
 * Return: count of allocated buffers
 */
int binder_alloc_get_allocated_count(struct binder_alloc *alloc)
{
        struct rb_node *n;
        int count = 0;

        mutex_lock(&alloc->mutex);
        for (n = rb_first(&alloc->allocated_buffers); n != NULL; n = rb_next(n))
                count++;
        mutex_unlock(&alloc->mutex);
        return count;
}


/**
 * binder_alloc_vma_close() - invalidate address space
 * @alloc: binder_alloc for this proc
 *
 * Called from binder_vma_close() when releasing address space.
 * Clears alloc->vma to prevent new incoming transactions from
 * allocating more buffers.
 */
void binder_alloc_vma_close(struct binder_alloc *alloc)
{
        binder_alloc_set_vma(alloc, NULL);
}

/**
 * binder_alloc_free_page() - shrinker callback to free pages
 * @item:   item to free
 * @lock:   lock protecting the item
 * @cb_arg: callback argument
 *
 * Called from list_lru_walk() in binder_shrink_scan() to free
 * up pages when the system is under memory pressure.
 */
enum lru_status binder_alloc_free_page(struct list_head *item,
                                       struct list_lru_one *lru,
                                       spinlock_t *lock,
                                       void *cb_arg)
        __must_hold(lock)
{
        struct mm_struct *mm = NULL;
        struct binder_lru_page *page = container_of(item,
                                                    struct binder_lru_page,
                                                    lru);
        struct binder_alloc *alloc;
        uintptr_t page_addr;
        size_t index;
        struct vm_area_struct *vma;

        alloc = page->alloc;
        if (!mutex_trylock(&alloc->mutex))

                goto err_get_alloc_mutex_failed;

        if (!page->page_ptr)
                goto err_page_already_freed;

        index = page - alloc->pages;
        page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;

        mm = alloc->vma_vm_mm;
        if (!mmget_not_zero(mm))
                goto err_mmget;
        if (!mmap_read_trylock(mm))
                goto err_mmap_read_lock_failed;
        vma = binder_alloc_get_vma(alloc);

        list_lru_isolate(lru, item);
        spin_unlock(lock);

        if (vma) {
                trace_binder_unmap_user_start(alloc, index);

                zap_page_range(vma, page_addr, PAGE_SIZE);

                trace_binder_unmap_user_end(alloc, index);
        }
        mmap_read_unlock(mm);
        mmput_async(mm);

        trace_binder_unmap_kernel_start(alloc, index);

        __free_page(page->page_ptr);
        page->page_ptr = NULL;

        trace_binder_unmap_kernel_end(alloc, index);

        spin_lock(lock);
        mutex_unlock(&alloc->mutex);
        return LRU_REMOVED_RETRY;

err_mmap_read_lock_failed:
        mmput_async(mm);
err_mmget:
err_page_already_freed:
        mutex_unlock(&alloc->mutex);
err_get_alloc_mutex_failed:
        return LRU_SKIP;
}

static unsigned long
binder_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
        unsigned long ret = list_lru_count(&binder_alloc_lru);
        return ret;
}

static unsigned long
binder_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
        unsigned long ret;

        ret = list_lru_walk(&binder_alloc_lru, binder_alloc_free_page,
                            NULL, sc->nr_to_scan);
        return ret;
}

static struct shrinker binder_shrinker = {
        .count_objects = binder_shrink_count,
        .scan_objects = binder_shrink_scan,
        .seeks = DEFAULT_SEEKS,
};

/**
 * binder_alloc_init() - called by binder_open() for per-proc initialization
 * @alloc: binder_alloc for this proc
 *
 * Called from binder_open() to initialize binder_alloc fields for
 * new binder proc
 */
void binder_alloc_init(struct binder_alloc *alloc)
{
        alloc->pid = current->group_leader->pid;
        mutex_init(&alloc->mutex);
        INIT_LIST_HEAD(&alloc->buffers);
}

int binder_alloc_shrinker_init(void)
{
        int ret = list_lru_init(&binder_alloc_lru);

        if (ret == 0) {
                ret = register_shrinker(&binder_shrinker);
                if (ret)
                        list_lru_destroy(&binder_alloc_lru);
        }
        return ret;
}

/**
 * check_buffer() - verify that buffer/offset is safe to access
 * @alloc: binder_alloc for this proc
 * @buffer: binder buffer to be accessed
 * @offset: offset into @buffer data
 * @bytes: bytes to access from offset
 *
 * Check that the @offset/@bytes are within the size of the given
 * @buffer and that the buffer is currently active and not freeable.
 * Offsets must also be multiples of sizeof(u32). The kernel is
 * allowed to touch the buffer in two cases:
 *
 * 1) when the buffer is being created:
 *     (buffer->free == 0 && buffer->allow_user_free == 0)
 * 2) when the buffer is being torn down:
 *     (buffer->free == 0 && buffer->transaction == NULL).
 *
 * Return: true if the buffer is safe to access
 */
static inline bool check_buffer(struct binder_alloc *alloc,
                                struct binder_buffer *buffer,
                                binder_size_t offset, size_t bytes)
{
        size_t buffer_size = binder_alloc_buffer_size(alloc, buffer);

        return buffer_size >= bytes &&
                offset <= buffer_size - bytes &&
                IS_ALIGNED(offset, sizeof(u32)) &&
                !buffer->free &&
                (!buffer->allow_user_free || !buffer->transaction);
}

/**
 * binder_alloc_get_page() - get kernel pointer for given buffer offset
 * @alloc: binder_alloc for this proc
 * @buffer: binder buffer to be accessed
 * @buffer_offset: offset into @buffer data
 * @pgoffp: address to copy final page offset to
 *
 * Lookup the struct page corresponding to the address
 * at @buffer_offset into @buffer->user_data. If @pgoffp is not
 * NULL, the byte-offset into the page is written there.
 *
 * The caller is responsible to ensure that the offset points
 * to a valid address within the @buffer and that @buffer is
 * not freeable by the user. Since it can't be freed, we are
 * guaranteed that the corresponding elements of @alloc->pages[]
 * cannot change.
 *
 * Return: struct page
 */
static struct page *binder_alloc_get_page(struct binder_alloc *alloc,
                                          struct binder_buffer *buffer,
                                          binder_size_t buffer_offset,
                                          pgoff_t *pgoffp)
{
        binder_size_t buffer_space_offset = buffer_offset +
                (buffer->user_data - alloc->buffer);
        pgoff_t pgoff = buffer_space_offset & ~PAGE_MASK;
        size_t index = buffer_space_offset >> PAGE_SHIFT;
        struct binder_lru_page *lru_page;

        lru_page = &alloc->pages[index];
        *pgoffp = pgoff;
        return lru_page->page_ptr;
}

/**
 * binder_alloc_clear_buf() - zero out buffer
 * @alloc: binder_alloc for this proc
 * @buffer: binder buffer to be cleared
 *
 * memset the given buffer to 0
 */
static void binder_alloc_clear_buf(struct binder_alloc *alloc,
                                   struct binder_buffer *buffer)
{
        size_t bytes = binder_alloc_buffer_size(alloc, buffer);
        binder_size_t buffer_offset = 0;

        while (bytes) {
                unsigned long size;
                struct page *page;
                pgoff_t pgoff;
                void *kptr;

                page = binder_alloc_get_page(alloc, buffer,
                                             buffer_offset, &pgoff);
                size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
                kptr = kmap(page) + pgoff;
                memset(kptr, 0, size);
                kunmap(page);
                bytes -= size;
                buffer_offset += size;
        }
}

/**
 * binder_alloc_copy_user_to_buffer() - copy src user to tgt user
 * @alloc: binder_alloc for this proc
 * @buffer: binder buffer to be accessed
 * @buffer_offset: offset into @buffer data
 * @from: userspace pointer to source buffer
 * @bytes: bytes to copy
 *
 * Copy bytes from source userspace to target buffer.
 *
 * Return: bytes remaining to be copied
 */
unsigned long
binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
                                 struct binder_buffer *buffer,
                                 binder_size_t buffer_offset,
                                 const void __user *from,
                                 size_t bytes)
{
        if (!check_buffer(alloc, buffer, buffer_offset, bytes))
                return bytes;

        while (bytes) {
                unsigned long size;
                unsigned long ret;
                struct page *page;
                pgoff_t pgoff;
                void *kptr;

                page = binder_alloc_get_page(alloc, buffer,
                                             buffer_offset, &pgoff);
                size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
                kptr = kmap(page) + pgoff;
                ret = copy_from_user(kptr, from, size);
                kunmap(page);
                if (ret)
                        return bytes - size + ret;
                bytes -= size;
                from += size;
                buffer_offset += size;
        }
        return 0;
}

static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
                                       bool to_buffer,
                                       struct binder_buffer *buffer,
                                       binder_size_t buffer_offset,
                                       void *ptr,
                                       size_t bytes)
{
        /* All copies must be 32-bit aligned and 32-bit size */
        if (!check_buffer(alloc, buffer, buffer_offset, bytes))
                return -EINVAL;

        while (bytes) {
                unsigned long size;
                struct page *page;
                pgoff_t pgoff;
                void *tmpptr;
                void *base_ptr;

                page = binder_alloc_get_page(alloc, buffer,
                                             buffer_offset, &pgoff);
                size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
                base_ptr = kmap_atomic(page);
                tmpptr = base_ptr + pgoff;
                if (to_buffer)
                        memcpy(tmpptr, ptr, size);
                else
                        memcpy(ptr, tmpptr, size);
                /*
                 * kunmap_atomic() takes care of flushing the cache
                 * if this device has VIVT cache arch
                 */
                kunmap_atomic(base_ptr);
                bytes -= size;
                pgoff = 0;
                ptr = ptr + size;
                buffer_offset += size;
        }
        return 0;
}

int binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
                                struct binder_buffer *buffer,
                                binder_size_t buffer_offset,
                                void *src,
                                size_t bytes)
{
        return binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
                                           src, bytes);
}

int binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
                                  void *dest,
                                  struct binder_buffer *buffer,
                                  binder_size_t buffer_offset,
                                  size_t bytes)
{
        return binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
                                           dest, bytes);
}