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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* arch/arm/include/asm/fncpy.h - helper macros for function body copying
*
* Copyright (C) 2011 Linaro Limited
*/
/*
* These macros are intended for use when there is a need to copy a low-level
* function body into special memory.
*
* For example, when reconfiguring the SDRAM controller, the code doing the
* reconfiguration may need to run from SRAM.
*
* NOTE: that the copied function body must be entirely self-contained and
* position-independent in order for this to work properly.
*
* NOTE: in order for embedded literals and data to get referenced correctly,
* the alignment of functions must be preserved when copying. To ensure this,
* the source and destination addresses for fncpy() must be aligned to a
* multiple of 8 bytes: you will be get a BUG() if this condition is not met.
* You will typically need a ".align 3" directive in the assembler where the
* function to be copied is defined, and ensure that your allocator for the
* destination buffer returns 8-byte-aligned pointers.
*
* Typical usage example:
*
* extern int f(args);
* extern uint32_t size_of_f;
* int (*copied_f)(args);
* void *sram_buffer;
*
* copied_f = fncpy(sram_buffer, &f, size_of_f);
*
* ... later, call the function: ...
*
* copied_f(args);
*
* The size of the function to be copied can't be determined from C:
* this must be determined by other means, such as adding assmbler directives
* in the file where f is defined.
*/
#ifndef __ASM_FNCPY_H
#define __ASM_FNCPY_H
#include <linux/types.h>
#include <linux/string.h>
/*
* Minimum alignment requirement for the source and destination addresses
* for function copying.
*/
#define FNCPY_ALIGN 8
#define fncpy(dest_buf, funcp, size) ({ \
uintptr_t __funcp_address; \
typeof(funcp) __result; \
\
asm("" : "=r" (__funcp_address) : "0" (funcp)); \
\
memcpy(dest_buf, (void const *)(__funcp_address & ~1), size); \
\
asm("" : "=r" (__result) \
: "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1))); \
\
__result; \
})
#endif /* !__ASM_FNCPY_H */
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