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