special_insns.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2#ifndef _TOOLS_ASM_X86_SPECIAL_INSNS_H
 3#define _TOOLS_ASM_X86_SPECIAL_INSNS_H
 4
 5/* The dst parameter must be 64-bytes aligned */
 6static inline void movdir64b(void *dst, const void *src)
 7{
 8	const struct { char _[64]; } *__src = src;
 9	struct { char _[64]; } *__dst = dst;
10
11	/*
12	 * MOVDIR64B %(rdx), rax.
13	 *
14	 * Both __src and __dst must be memory constraints in order to tell the
15	 * compiler that no other memory accesses should be reordered around
16	 * this one.
17	 *
18	 * Also, both must be supplied as lvalues because this tells
19	 * the compiler what the object is (its size) the instruction accesses.
20	 * I.e., not the pointers but what they point to, thus the deref'ing '*'.
21	 */
22	asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
23		     : "+m" (*__dst)
24		     :  "m" (*__src), "a" (__dst), "d" (__src));
25}
26
27#endif /* _TOOLS_ASM_X86_SPECIAL_INSNS_H */