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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 */ |