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| 2 | |
| 3 | * arch/arm/include/asm/fncpy.h - helper macros for function body copying
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| 4 | *
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| 5 | * Copyright (C) 2011 Linaro Limited
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| 6 |
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| 7 |
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| 8 | |
| 9 | * These macros are intended for use when there is a need to copy a low-level
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| 10 | * function body into special memory.
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| 11 | *
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| 12 | * For example, when reconfiguring the SDRAM controller, the code doing the
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| 13 | * reconfiguration may need to run from SRAM.
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| 14 | *
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| 15 | * NOTE: that the copied function body must be entirely self-contained and
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| 16 | * position-independent in order for this to work properly.
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| 17 | *
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| 18 | * NOTE: in order for embedded literals and data to get referenced correctly,
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| 19 | * the alignment of functions must be preserved when copying. To ensure this,
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| 20 | * the source and destination addresses for fncpy() must be aligned to a
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| 21 | * multiple of 8 bytes: you will be get a BUG() if this condition is not met.
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| 22 | * You will typically need a ".align 3" directive in the assembler where the
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| 23 | * function to be copied is defined, and ensure that your allocator for the
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| 24 | * destination buffer returns 8-byte-aligned pointers.
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| 25 | *
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| 26 | * Typical usage example:
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| 27 | *
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| 28 | * extern int f(args);
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| 29 | * extern uint32_t size_of_f;
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| 30 | * int (*copied_f)(args);
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| 31 | * void *sram_buffer;
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| 32 | *
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| 33 | * copied_f = fncpy(sram_buffer, &f, size_of_f);
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| 34 | *
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| 35 | * ... later, call the function: ...
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| 36 | *
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| 37 | * copied_f(args);
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| 38 | *
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| 39 | * The size of the function to be copied can't be determined from C:
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| 40 | * this must be determined by other means, such as adding assmbler directives
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| 41 | * in the file where f is defined.
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| 42 |
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| 43 |
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| 44 | #ifndef __ASM_FNCPY_H
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| 45 | #define __ASM_FNCPY_H
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| 46 |
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| 47 | #include <linux/types.h>
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| 48 | #include <linux/string.h>
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| 49 |
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| 50 | #include <asm/bug.h>
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| 51 | #include <asm/cacheflush.h>
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| 52 |
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| 53 | |
| 54 | * Minimum alignment requirement for the source and destination addresses
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| 55 | * for function copying.
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| 56 |
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| 57 | #define FNCPY_ALIGN 8
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| 58 |
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| 59 | #define fncpy(dest_buf, funcp, size) ({ \
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| 60 | uintptr_t __funcp_address; \
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| 61 | typeof(funcp) __result; \
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| 62 | \
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| 63 | asm("" : "=r" (__funcp_address) : "0" (funcp)); \
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| 64 | \
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| 65 | |
| 66 | * Ensure alignment of source and destination addresses, \
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| 67 | * disregarding the function's Thumb bit: \
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| 68 | \
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| 69 | BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) || \
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| 70 | (__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1))); \
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| 71 | \
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| 72 | memcpy(dest_buf, (void const *)(__funcp_address & ~1), size); \
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| 73 | flush_icache_range((unsigned long)(dest_buf), \
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| 74 | (unsigned long)(dest_buf) + (size)); \
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| 75 | \
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| 76 | asm("" : "=r" (__result) \
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| 77 | : "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1))); \
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| 78 | \
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| 79 | __result; \
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| 80 | })
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| 81 |
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| 82 | #endif
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