LXR linux/arch/arm/include/asm/fncpy.h

   1/*
   2 * arch/arm/include/asm/fncpy.h - helper macros for function body copying
   3 *
   4 * Copyright (C) 2011 Linaro Limited
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful,
  11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 * GNU General Public License for more details.
  14 *
  15 * You should have received a copy of the GNU General Public License
  16 * along with this program; if not, write to the Free Software
  17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  18 */
  19
  20/*
  21 * These macros are intended for use when there is a need to copy a low-level
  22 * function body into special memory.
  23 *
  24 * For example, when reconfiguring the SDRAM controller, the code doing the
  25 * reconfiguration may need to run from SRAM.
  26 *
  27 * NOTE: that the copied function body must be entirely self-contained and
  28 * position-independent in order for this to work properly.
  29 *
  30 * NOTE: in order for embedded literals and data to get referenced correctly,
  31 * the alignment of functions must be preserved when copying.  To ensure this,
  32 * the source and destination addresses for fncpy() must be aligned to a
  33 * multiple of 8 bytes: you will be get a BUG() if this condition is not met.
  34 * You will typically need a ".align 3" directive in the assembler where the
  35 * function to be copied is defined, and ensure that your allocator for the
  36 * destination buffer returns 8-byte-aligned pointers.
  37 *
  38 * Typical usage example:
  39 *
  40 * extern int f(args);
  41 * extern uint32_t size_of_f;
  42 * int (*copied_f)(args);
  43 * void *sram_buffer;
  44 *
  45 * copied_f = fncpy(sram_buffer, &f, size_of_f);
  46 *
  47 * ... later, call the function: ...
  48 *
  49 * copied_f(args);
  50 *
  51 * The size of the function to be copied can't be determined from C:
  52 * this must be determined by other means, such as adding assmbler directives
  53 * in the file where f is defined.
  54 */
  55
  56#ifndef __ASM_FNCPY_H
  57#define __ASM_FNCPY_H
  58
  59#include <linux/types.h>
  60#include <linux/string.h>
  61
  62#include <asm/bug.h>
  63#include <asm/cacheflush.h>
  64
  65/*
  66 * Minimum alignment requirement for the source and destination addresses
  67 * for function copying.
  68 */
  69#define FNCPY_ALIGN 8
  70
  71#define fncpy(dest_buf, funcp, size) ({                                 \
  72        uintptr_t __funcp_address;                                      \
  73        typeof(funcp) __result;                                         \
  74                                                                        \
  75        asm("" : "=r" (__funcp_address) : "0" (funcp));                 \
  76                                                                        \
  77        /*                                                              \
  78         * Ensure alignment of source and destination addresses,        \
  79         * disregarding the function's Thumb bit:                       \
  80         */                                                             \
  81        BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) ||             \
  82                (__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1))); \
  83                                                                        \
  84        memcpy(dest_buf, (void const *)(__funcp_address & ~1), size);   \
  85        flush_icache_range((unsigned long)(dest_buf),                   \
  86                (unsigned long)(dest_buf) + (size));                    \
  87                                                                        \
  88        asm("" : "=r" (__result)                                        \
  89                : "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1))); \
  90                                                                        \
  91        __result;                                                       \
  92})
  93
  94#endif /* !__ASM_FNCPY_H */
  95