1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * arch/arm/include/asm/fncpy.h - helper macros for function body copying 4 * 5 * Copyright (C) 2011 Linaro Limited 6 */ 7 8 /* 9 * These macros are intended for use when there is a need to copy a low-level 10 * function body into special memory. 11 * 12 * For example, when reconfiguring the SDRAM controller, the code doing the 13 * reconfiguration may need to run from SRAM. 14 * 15 * NOTE: that the copied function body must be entirely self-contained and 16 * position-independent in order for this to work properly. 17 * 18 * NOTE: in order for embedded literals and data to get referenced correctly, 19 * the alignment of functions must be preserved when copying. To ensure this, 20 * the source and destination addresses for fncpy() must be aligned to a 21 * multiple of 8 bytes: you will be get a BUG() if this condition is not met. 22 * You will typically need a ".align 3" directive in the assembler where the 23 * function to be copied is defined, and ensure that your allocator for the 24 * destination buffer returns 8-byte-aligned pointers. 25 * 26 * Typical usage example: 27 * 28 * extern int f(args); 29 * extern uint32_t size_of_f; 30 * int (*copied_f)(args); 31 * void *sram_buffer; 32 * 33 * copied_f = fncpy(sram_buffer, &f, size_of_f); 34 * 35 * ... later, call the function: ... 36 * 37 * copied_f(args); 38 * 39 * The size of the function to be copied can't be determined from C: 40 * this must be determined by other means, such as adding assmbler directives 41 * in the file where f is defined. 42 */ 43 44 #ifndef __ASM_FNCPY_H 45 #define __ASM_FNCPY_H 46 47 #include <linux/types.h> 48 #include <linux/string.h> 49 50 #include <asm/bug.h> 51 #include <asm/cacheflush.h> 52 53 /* 54 * Minimum alignment requirement for the source and destination addresses 55 * for function copying. 56 */ 57 #define FNCPY_ALIGN 8 58 59 #define fncpy(dest_buf, funcp, size) ({ \ 60 uintptr_t __funcp_address; \ 61 typeof(funcp) __result; \ 62 \ 63 asm("" : "=r" (__funcp_address) : "0" (funcp)); \ 64 \ 65 /* \ 66 * Ensure alignment of source and destination addresses, \ 67 * disregarding the function's Thumb bit: \ 68 */ \ 69 BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) || \ 70 (__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1))); \ 71 \ 72 memcpy(dest_buf, (void const *)(__funcp_address & ~1), size); \ 73 flush_icache_range((unsigned long)(dest_buf), \ 74 (unsigned long)(dest_buf) + (size)); \ 75 \ 76 asm("" : "=r" (__result) \ 77 : "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1))); \ 78 \ 79 __result; \ 80 }) 81 82 #endif /* !__ASM_FNCPY_H */ 83