ARM: 6640/1: Thumb-2: Symbol manipulation macros for function body copying

/*

 * arch/arm/include/asm/fncpy.h - helper macros for function body copying

 *

 * Copyright (C) 2011 Linaro Limited

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

 */

/*

 * 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>

#include <asm/bug.h>

#include <asm/cacheflush.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));			\

									\

	/*								\

	 * Ensure alignment of source and destination addresses,	\

	 * disregarding the function's Thumb bit:			\

	 */								\

	BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) ||		\

		(__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1)));	\

									\

	memcpy(dest_buf, (void const *)(__funcp_address & ~1), size);	\

	flush_icache_range((unsigned long)(dest_buf),			\

		(unsigned long)(dest_buf) + (size));			\

									\

	asm("" : "=r" (__result)					\

		: "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1)));	\

									\

	__result;							\

})

#endif /* !__ASM_FNCPY_H */