/* binder_alloc.c
*
* Android IPC Subsystem
*
* Copyright (C) 2007-2017 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 <asm/cacheflush.h>
#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 "binder_alloc.h"
#include "binder_trace.h"
static DEFINE_MUTEX(binder_alloc_mmap_lock);
enum {
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;
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(x); \
} while (0)
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 - (void *)buffer->data;
return (size_t)list_entry(buffer->entry.next,
struct binder_buffer, entry) - (size_t)buffer->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 < buffer)
p = &parent->rb_left;
else if (new_buffer > buffer)
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_buffer_lookup_locked(
struct binder_alloc *alloc,
uintptr_t user_ptr)
{
struct rb_node *n = alloc->allocated_buffers.rb_node;
struct binder_buffer *buffer;
struct binder_buffer *kern_ptr;
kern_ptr = (struct binder_buffer *)(user_ptr - alloc->user_buffer_offset
- offsetof(struct binder_buffer, data));
while (n) {
buffer = rb_entry(n, struct binder_buffer, rb_node);
BUG_ON(buffer->free);
if (kern_ptr < buffer)
n = n->rb_left;
else if (kern_ptr > buffer)
n = n->rb_right;
else
return buffer;
}
return NULL;
}
/**
* binder_alloc_buffer_lookup() - 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_buffer_lookup(struct binder_alloc *alloc,
uintptr_t user_ptr)
{
struct binder_buffer *buffer;
mutex_lock(&alloc->mutex);
buffer = binder_alloc_buffer_lookup_locked(alloc, user_ptr);
mutex_unlock(&alloc->mutex);
return buffer;
}
static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
void *start, void *end,
struct vm_area_struct *vma)
{
void *page_addr;
unsigned long user_page_addr;
struct page **page;
struct mm_struct *mm;
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 (vma)
mm = NULL;
else
mm = get_task_mm(alloc->tsk);
if (mm) {
down_write(&mm->mmap_sem);
vma = alloc->vma;
if (vma && mm != alloc->vma_vm_mm) {
pr_err("%d: vma mm and task mm mismatch\n",
alloc->pid);
vma = NULL;
}
}
if (allocate == 0)
goto free_range;
if (vma == NULL) {
pr_err("%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;
page = &alloc->pages[(page_addr - alloc->buffer) / PAGE_SIZE];
BUG_ON(*page);
*page = alloc_page(GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
if (*page == NULL) {
pr_err("%d: binder_alloc_buf failed for page at %pK\n",
alloc->pid, page_addr);
goto err_alloc_page_failed;
}
ret = map_kernel_range_noflush((unsigned long)page_addr,
PAGE_SIZE, PAGE_KERNEL, page);
flush_cache_vmap((unsigned long)page_addr,
(unsigned long)page_addr + PAGE_SIZE);
if (ret != 1) {
pr_err("%d: binder_alloc_buf failed to map page at %pK in kernel\n",
alloc->pid, page_addr);
goto err_map_kernel_failed;
}
user_page_addr =
(uintptr_t)page_addr + alloc->user_buffer_offset;
ret = vm_insert_page(vma, user_page_addr, page[0]);
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;
}
/* vm_insert_page does not seem to increment the refcount */
}
if (mm) {
up_write(&mm->mmap_sem);
mmput(mm);
}
return 0;
free_range:
for (page_addr = end - PAGE_SIZE; page_addr >= start;
page_addr -= PAGE_SIZE) {
page = &alloc->pages[(page_addr - alloc->buffer) / PAGE_SIZE];
if (vma)
zap_page_range(vma, (uintptr_t)page_addr +
alloc->user_buffer_offset, PAGE_SIZE);
err_vm_insert_page_failed:
unmap_kernel_range((unsigned long)page_addr, PAGE_SIZE);
err_map_kernel_failed:
__free_page(*page);
*page = NULL;
err_alloc_page_failed:
;
}
err_no_vma:
if (mm) {
up_write(&mm->mmap_sem);
mmput(mm);
}
return -ENOMEM;
}
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)
{
struct rb_node *n = alloc->free_buffers.rb_node;
struct binder_buffer *buffer;
size_t buffer_size;
struct rb_node *best_fit = NULL;
void *has_page_addr;
void *end_page_addr;
size_t size, data_offsets_size;
if (alloc->vma == NULL) {
pr_err("%d: binder_alloc_buf, no vma\n",
alloc->pid);
return NULL;
}
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 NULL;
}
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 NULL;
}
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 NULL;
}
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) {
pr_err("%d: binder_alloc_buf size %zd failed, no address space\n",
alloc->pid, size);
return NULL;
}
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 *)(((uintptr_t)buffer->data + buffer_size) & PAGE_MASK);
if (n == NULL) {
if (size + sizeof(struct binder_buffer) + 4 >= buffer_size)
buffer_size = size; /* no room for other buffers */
else
buffer_size = size + sizeof(struct binder_buffer);
}
end_page_addr =
(void *)PAGE_ALIGN((uintptr_t)buffer->data + buffer_size);
if (end_page_addr > has_page_addr)
end_page_addr = has_page_addr;
if (binder_update_page_range(alloc, 1,
(void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr, NULL))
return NULL;
rb_erase(best_fit, &alloc->free_buffers);
buffer->free = 0;
binder_insert_allocated_buffer_locked(alloc, buffer);
if (buffer_size != size) {
struct binder_buffer *new_buffer = (void *)buffer->data + size;
list_add(&new_buffer->entry, &buffer->entry);
new_buffer->free = 1;
binder_insert_free_buffer(alloc, new_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;
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);
}
return buffer;
}
/**
* 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
*
* 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)
{
struct binder_buffer *buffer;
mutex_lock(&alloc->mutex);
buffer = binder_alloc_new_buf_locked(alloc, data_size, offsets_size,
extra_buffers_size, is_async);
mutex_unlock(&alloc->mutex);
return buffer;
}
static void *buffer_start_page(struct binder_buffer *buffer)
{
return (void *)((uintptr_t)buffer & PAGE_MASK);
}
static void *buffer_end_page(struct binder_buffer *buffer)
{
return (void *)(((uintptr_t)(buffer + 1) - 1) & PAGE_MASK);
}
static void binder_delete_free_buffer(struct binder_alloc *alloc,
struct binder_buffer *buffer)
{
struct binder_buffer *prev, *next = NULL;
int free_page_end = 1;
int free_page_start = 1;
BUG_ON(alloc->buffers.next == &buffer->entry);
prev = list_entry(buffer->entry.prev, struct binder_buffer, entry);
BUG_ON(!prev->free);
if (buffer_end_page(prev) == buffer_start_page(buffer)) {
free_page_start = 0;
if (buffer_end_page(prev) == buffer_end_page(buffer))
free_page_end = 0;
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: merge free, buffer %pK share page with %pK\n",
alloc->pid, buffer, prev);
}
if (!list_is_last(&buffer->entry, &alloc->buffers)) {
next = list_entry(buffer->entry.next,
struct binder_buffer, entry);
if (buffer_start_page(next) == buffer_end_page(buffer)) {
free_page_end = 0;
if (buffer_start_page(next) ==
buffer_start_page(buffer))
free_page_start = 0;
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: merge free, buffer %pK share page with %pK\n",
alloc->pid, buffer, prev);
}
}
list_del(&buffer->entry);
if (free_page_start || free_page_end) {
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: merge free, buffer %pK do not share page%s%s with %pK or %pK\n",
alloc->pid, buffer, free_page_start ? "" : " end",
free_page_end ? "" : " start", prev, next);
binder_update_page_range(alloc, 0, free_page_start ?
buffer_start_page(buffer) : buffer_end_page(buffer),
(free_page_end ? buffer_end_page(buffer) :
buffer_start_page(buffer)) + PAGE_SIZE, NULL);
}
}
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((void *)buffer < alloc->buffer);
BUG_ON((void *)buffer > 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 *)PAGE_ALIGN((uintptr_t)buffer->data),
(void *)(((uintptr_t)buffer->data + buffer_size) & PAGE_MASK),
NULL);
rb_erase(&buffer->rb_node, &alloc->allocated_buffers);
buffer->free = 1;
if (!list_is_last(&buffer->entry, &alloc->buffers)) {
struct binder_buffer *next = list_entry(buffer->entry.next,
struct binder_buffer, entry);
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 = list_entry(buffer->entry.prev,
struct binder_buffer, entry);
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);
}
/**
* 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_buffer()
*/
void binder_alloc_free_buf(struct binder_alloc *alloc,
struct binder_buffer *buffer)
{
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;
struct vm_struct *area;
const char *failure_string;
struct binder_buffer *buffer;
mutex_lock(&binder_alloc_mmap_lock);
if (alloc->buffer) {
ret = -EBUSY;
failure_string = "already mapped";
goto err_already_mapped;
}
area = get_vm_area(vma->vm_end - vma->vm_start, VM_IOREMAP);
if (area == NULL) {
ret = -ENOMEM;
failure_string = "get_vm_area";
goto err_get_vm_area_failed;
}
alloc->buffer = area->addr;
alloc->user_buffer_offset =
vma->vm_start - (uintptr_t)alloc->buffer;
mutex_unlock(&binder_alloc_mmap_lock);
#ifdef CONFIG_CPU_CACHE_VIPT
if (cache_is_vipt_aliasing()) {
while (CACHE_COLOUR(
(vma->vm_start ^ (uint32_t)alloc->buffer))) {
pr_info("%s: %d %lx-%lx maps %pK bad alignment\n",
__func__, alloc->pid, vma->vm_start,
vma->vm_end, alloc->buffer);
vma->vm_start += PAGE_SIZE;
}
}
#endif
alloc->pages = kzalloc(sizeof(alloc->pages[0]) *
((vma->vm_end - vma->vm_start) / PAGE_SIZE),
GFP_KERNEL);
if (alloc->pages == NULL) {
ret = -ENOMEM;
failure_string = "alloc page array";
goto err_alloc_pages_failed;
}
alloc->buffer_size = vma->vm_end - vma->vm_start;
if (binder_update_page_range(alloc, 1, alloc->buffer,
alloc->buffer + PAGE_SIZE, vma)) {
ret = -ENOMEM;
failure_string = "alloc small buf";
goto err_alloc_small_buf_failed;
}
buffer = alloc->buffer;
INIT_LIST_HEAD(&alloc->buffers);
list_add(&buffer->entry, &alloc->buffers);
buffer->free = 1;
binder_insert_free_buffer(alloc, buffer);
alloc->free_async_space = alloc->buffer_size / 2;
barrier();
alloc->vma = vma;
alloc->vma_vm_mm = vma->vm_mm;
return 0;
err_alloc_small_buf_failed:
kfree(alloc->pages);
alloc->pages = NULL;
err_alloc_pages_failed:
mutex_lock(&binder_alloc_mmap_lock);
vfree(alloc->buffer);
alloc->buffer = NULL;
err_get_vm_area_failed:
err_already_mapped:
mutex_unlock(&binder_alloc_mmap_lock);
pr_err("%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;
BUG_ON(alloc->vma);
buffers = 0;
mutex_lock(&alloc->mutex);
while ((n = rb_first(&alloc->allocated_buffers))) {
struct binder_buffer *buffer;
buffer = rb_entry(n, struct binder_buffer, rb_node);
/* Transaction should already have been freed */
BUG_ON(buffer->transaction);
binder_free_buf_locked(alloc, buffer);
buffers++;
}
page_count = 0;
if (alloc->pages) {
int i;
for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
void *page_addr;
if (!alloc->pages[i])
continue;
page_addr = alloc->buffer + i * PAGE_SIZE;
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%s: %d: page %d at %pK not freed\n",
__func__, alloc->pid, i, page_addr);
unmap_kernel_range((unsigned long)page_addr, PAGE_SIZE);
__free_page(alloc->pages[i]);
page_count++;
}
kfree(alloc->pages);
vfree(alloc->buffer);
}
mutex_unlock(&alloc->mutex);
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 %s\n",
prefix, buffer->debug_id, buffer->data,
buffer->data_size, buffer->offsets_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_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)
{
WRITE_ONCE(alloc->vma, NULL);
WRITE_ONCE(alloc->vma_vm_mm, NULL);
}
/**
* 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->tsk = current->group_leader;
alloc->pid = current->group_leader->pid;
mutex_init(&alloc->mutex);
}
