runtime-const.h

 1/* SPDX-License-Identifier: GPL-2.0 */
 2#ifndef _ASM_RUNTIME_CONST_H
 3#define _ASM_RUNTIME_CONST_H
 4
 5#ifdef MODULE
 6  #error "Cannot use runtime-const infrastructure from modules"
 7#endif
 8
 9#ifdef __ASSEMBLY__
10
11.macro RUNTIME_CONST_PTR sym reg
12	movq	$0x0123456789abcdef, %\reg
13	1:
14	.pushsection runtime_ptr_\sym, "a"
15	.long	1b - 8 - .
16	.popsection
17.endm
18
19#else /* __ASSEMBLY__ */
20
21#define runtime_const_ptr(sym) ({				\
22	typeof(sym) __ret;					\
23	asm_inline("mov %1,%0\n1:\n"				\
24		".pushsection runtime_ptr_" #sym ",\"a\"\n\t"	\
25		".long 1b - %c2 - .\n"				\
26		".popsection"					\
27		:"=r" (__ret)					\
28		:"i" ((unsigned long)0x0123456789abcdefull),	\
29		 "i" (sizeof(long)));				\
30	__ret; })
31
32// The 'typeof' will create at _least_ a 32-bit type, but
33// will happily also take a bigger type and the 'shrl' will
34// clear the upper bits
35#define runtime_const_shift_right_32(val, sym) ({		\
36	typeof(0u+(val)) __ret = (val);				\
37	asm_inline("shrl $12,%k0\n1:\n"				\
38		".pushsection runtime_shift_" #sym ",\"a\"\n\t"	\
39		".long 1b - 1 - .\n"				\
40		".popsection"					\
41		:"+r" (__ret));					\
42	__ret; })
43
44#define runtime_const_init(type, sym) do {		\
45	extern s32 __start_runtime_##type##_##sym[];	\
46	extern s32 __stop_runtime_##type##_##sym[];	\
47	runtime_const_fixup(__runtime_fixup_##type,	\
48		(unsigned long)(sym), 			\
49		__start_runtime_##type##_##sym,		\
50		__stop_runtime_##type##_##sym);		\
51} while (0)
52
53/*
54 * The text patching is trivial - you can only do this at init time,
55 * when the text section hasn't been marked RO, and before the text
56 * has ever been executed.
57 */
58static inline void __runtime_fixup_ptr(void *where, unsigned long val)
59{
60	*(unsigned long *)where = val;
61}
62
63static inline void __runtime_fixup_shift(void *where, unsigned long val)
64{
65	*(unsigned char *)where = val;
66}
67
68static inline void runtime_const_fixup(void (*fn)(void *, unsigned long),
69	unsigned long val, s32 *start, s32 *end)
70{
71	while (start < end) {
72		fn(*start + (void *)start, val);
73		start++;
74	}
75}
76
77#endif /* __ASSEMBLY__ */
78#endif