mirror of
https://github.com/schoebel/mars
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d18c60f232
Very old idiotic bug. Under some circumstances, a byte beyond the end of a non-null-terminated string (such as produced by the VFS) might be read, potentially leading to a page fault just one byte after a page border.
235 lines
6.8 KiB
C
235 lines
6.8 KiB
C
/*
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* MARS Long Distance Replication Software
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*
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* This file is part of MARS project: http://schoebel.github.io/mars/
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*
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* Copyright (C) 2010-2014 Thomas Schoebel-Theuer
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* Copyright (C) 2011-2014 1&1 Internet AG
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef BRICK_MEM_H
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#define BRICK_MEM_H
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#include <linux/mm_types.h>
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#ifndef CONFIG_MARS_MODULE
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// when unsure, include faked config file
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#include "mars_config.h"
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#endif
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#define BRICK_DEBUG_MEM 4096
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#ifndef CONFIG_MARS_DEBUG_MEM
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#undef BRICK_DEBUG_MEM
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#endif
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#ifdef CONFIG_MARS_DEBUG_ORDER0
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#define BRICK_DEBUG_ORDER0
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#endif
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#define GFP_BRICK GFP_NOIO
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//#define GFP_BRICK GFP_KERNEL // can lead to deadlocks!
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extern long long brick_global_memavail;
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extern long long brick_global_memlimit;
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extern atomic64_t brick_global_block_used;
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/////////////////////////////////////////////////////////////////////////
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// compiler tweaking
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/* Some functions are known to return non-null pointer values,
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* at least under some Kconfig conditions.
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*
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* In code like...
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*
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* void *ptr = myfunction();
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* if (unlikely(!ptr)) {
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* printk("ERROR: this should not happen\n");
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* goto fail;
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* }
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*
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* ... the dead code elimination of gcc will not remove the if clause
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* because the function might return a NULL value, even if a human
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* would know that myfunction() does not return a NULL value.
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*
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* Unfortunately, the __attribute__((nonnull)) can only be applied
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* to input parameters, but not to the return value.
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*
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* More unfortunately, a small inline wrapper does not help,
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* because it seems that together with the elimination of the wrapper,
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* its nonnull attribute seems to be eliminated alltogether.
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* I don't know whether this is a bug or a feature (or just a weakness).
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*
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* Following is a small hack which solves the problem at least for gcc 4.7.
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*
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* In order to be useful, the -fdelete-null-pointer-checks must be set.
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* Since MARS is superuser-only anyway, enabling this for MARS should not
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* be a security risk
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* (c.f. upstream kernel commit a3ca86aea507904148870946d599e07a340b39bf)
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*/
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extern inline
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void *__mark_ptr_nonnull(void *_ptr)
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{
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char *ptr = _ptr;
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// fool gcc to believe that the pointer were dereferenced...
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asm("" : : "X" (*ptr));
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return ptr;
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}
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/* All the brick memory allocations are guaranteed to succeed when
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* CONFIG_MARS_MEM_RETRY is set. In case of low memory, they will just
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* retry (forever).
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*
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* Allow checking code to be written which works for both cases:
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* CONFIG_MARS_MEM_RETRY is selected, or not.
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*/
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#ifdef CONFIG_MARS_MEM_RETRY
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#define brick_mark_nonnull __mark_ptr_nonnull
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#else
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#define brick_mark_nonnull(p) (p)
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#endif
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/////////////////////////////////////////////////////////////////////////
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// small memory allocation (use this only for len < PAGE_SIZE)
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#define brick_mem_alloc(_len_) \
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({ \
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void *_res_ = _brick_mem_alloc(_len_, __LINE__); \
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brick_mark_nonnull(_res_); \
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})
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#define brick_zmem_alloc(_len_) \
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({ \
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void *_res_ = _brick_mem_alloc(_len_, __LINE__); \
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_res_ = brick_mark_nonnull(_res_); \
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if (_res_) { \
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memset(_res_, 0, _len_); \
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} \
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_res_; \
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})
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#define brick_mem_free(_data_) \
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do { \
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if (_data_) { \
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_brick_mem_free(_data_, __LINE__); \
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} \
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} while(0)
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// don't use the following directly
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extern void *_brick_mem_alloc(int len, int line) __attribute__((malloc)) __attribute__((alloc_size(1)));
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extern void _brick_mem_free(void *data, int line);
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/////////////////////////////////////////////////////////////////////////
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// string memory allocation
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#define BRICK_STRING_LEN 1024 /* default value when len == 0 */
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#define brick_string_alloc(_len_) \
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({ \
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char *_res_ = _brick_string_alloc((_len_), __LINE__); \
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(char*)brick_mark_nonnull(_res_); \
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})
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#define brick_strndup(_orig_,_len_) \
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({ \
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char *_res_ = _brick_string_alloc((_len_) + 1, __LINE__); \
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_res_ = brick_mark_nonnull(_res_); \
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if (_res_) { \
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strncpy(_res_, (_orig_), (_len_)); \
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/* always null-terminate for safety */ \
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_res_[_len_] = '\0'; \
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} \
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(char*)brick_mark_nonnull(_res_); \
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})
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#define brick_strdup(_orig_) \
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({ \
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int _len_ = strlen(_orig_); \
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char *_res_ = _brick_string_alloc((_len_) + 1, __LINE__); \
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_res_ = brick_mark_nonnull(_res_); \
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if (_res_) { \
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strncpy(_res_, (_orig_), (_len_) + 1); \
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} \
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(char*)brick_mark_nonnull(_res_); \
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})
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#define brick_string_free(_data_) \
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do { \
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if (_data_) { \
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_brick_string_free(_data_, __LINE__); \
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} \
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} while(0)
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// don't use the following directly
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extern char *_brick_string_alloc(int len, int line) __attribute__((malloc));
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extern void _brick_string_free(const char *data, int line);
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/////////////////////////////////////////////////////////////////////////
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// block memory allocation (for aligned multiples of 512 resp PAGE_SIZE)
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#define brick_block_alloc(_pos_,_len_) \
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({ \
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void *_res_ = _brick_block_alloc((_pos_), (_len_), __LINE__); \
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brick_mark_nonnull(_res_); \
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})
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#define brick_block_free(_data_,_len_)\
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do { \
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if (_data_) { \
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_brick_block_free((_data_), (_len_), __LINE__); \
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} \
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} while(0)
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extern struct page *brick_iomap(void *data, int *offset, int *len);
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// don't use the following directly
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extern void *_brick_block_alloc(loff_t pos, int len, int line) __attribute__((malloc)) __attribute__((alloc_size(2)));
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extern void _brick_block_free(void *data, int len, int cline);
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/////////////////////////////////////////////////////////////////////////
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// reservations / preallocation
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#define BRICK_MAX_ORDER 11
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#ifdef CONFIG_MARS_MEM_PREALLOC
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extern int brick_allow_freelist;
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extern int brick_pre_reserve[BRICK_MAX_ORDER+1];
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extern int brick_mem_freelist_max[BRICK_MAX_ORDER+1];
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extern int brick_mem_alloc_count[BRICK_MAX_ORDER+1];
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extern int brick_mem_alloc_max[BRICK_MAX_ORDER+1];
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extern int brick_mem_reserve(void);
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#endif
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extern void brick_mem_statistics(bool final);
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/////////////////////////////////////////////////////////////////////////
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// init
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extern int init_brick_mem(void);
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extern void exit_brick_mem(void);
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#endif
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