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 */