alternative.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _ASM_S390_ALTERNATIVE_H
  3#define _ASM_S390_ALTERNATIVE_H
  4
  5/*
  6 * Each alternative comes with a 32 bit feature field:
  7 *	union {
  8 *		u32 feature;
  9 *		struct {
 10 *			u32 ctx	 : 4;
 11 *			u32 type : 8;
 12 *			u32 data : 20;
 13 *		};
 14 *	}
 15 *
 16 * @ctx is a bitfield, where only one bit must be set. Each bit defines
 17 * in which context an alternative is supposed to be applied to the
 18 * kernel image:
 19 *
 20 * - from the decompressor before the kernel itself is executed
 21 * - from early kernel code from within the kernel
 22 *
 23 * @type is a number which defines the type and with that the type
 24 * specific alternative patching.
 25 *
 26 * @data is additional type specific information which defines if an
 27 * alternative should be applied.
 28 */
 29
 30#define ALT_CTX_EARLY		1
 31#define ALT_CTX_LATE		2
 32#define ALT_CTX_ALL		(ALT_CTX_EARLY | ALT_CTX_LATE)
 33
 34#define ALT_TYPE_FACILITY	0
 35#define ALT_TYPE_FEATURE	1
 36#define ALT_TYPE_SPEC		2
 37
 38#define ALT_DATA_SHIFT		0
 39#define ALT_TYPE_SHIFT		20
 40#define ALT_CTX_SHIFT		28
 41
 42#define ALT_FACILITY(facility)		(ALT_CTX_EARLY << ALT_CTX_SHIFT		| \
 43					 ALT_TYPE_FACILITY << ALT_TYPE_SHIFT	| \
 44					 (facility) << ALT_DATA_SHIFT)
 45
 46#define ALT_FEATURE(feature)		(ALT_CTX_EARLY << ALT_CTX_SHIFT		| \
 47					 ALT_TYPE_FEATURE << ALT_TYPE_SHIFT	| \
 48					 (feature) << ALT_DATA_SHIFT)
 49
 50#define ALT_SPEC(facility)		(ALT_CTX_LATE << ALT_CTX_SHIFT		| \
 51					 ALT_TYPE_SPEC << ALT_TYPE_SHIFT	| \
 52					 (facility) << ALT_DATA_SHIFT)
 53
 54#ifndef __ASSEMBLER__
 55
 56#include <linux/types.h>
 57#include <linux/stddef.h>
 58#include <linux/stringify.h>
 59
 60struct alt_instr {
 61	s32 instr_offset;	/* original instruction */
 62	s32 repl_offset;	/* offset to replacement instruction */
 63	union {
 64		u32 feature;	/* feature required for replacement */
 65		struct {
 66			u32 ctx	 : 4;  /* context */
 67			u32 type : 8;  /* type of alternative */
 68			u32 data : 20; /* patching information */
 69		};
 70	};
 71	u8  instrlen;		/* length of original instruction */
 72} __packed;
 73
 74extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
 75
 76void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx);
 77
 78static inline void apply_alternative_instructions(void)
 79{
 80	__apply_alternatives(__alt_instructions, __alt_instructions_end, ALT_CTX_LATE);
 81}
 82
 83static inline void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
 84{
 85	__apply_alternatives(start, end, ALT_CTX_ALL);
 86}
 87
 88/*
 89 * +---------------------------------+
 90 * |661:			     |662:
 91 * | oldinstr			     |
 92 * +---------------------------------+
 93 *
 94 * .altinstr_replacement section
 95 * +---------------------------------+
 96 * |6641:			     |6651:
 97 * | alternative instr 1	     |
 98 * +---------------------------------+
 99 * |6642:			     |6652:
100 * | alternative instr 2	     |
101 * +---------------------------------+
102 *
103 * .altinstructions section
104 * +---------------------------------+
105 * | alt_instr entries for each      |
106 * | alternative instr		     |
107 * +---------------------------------+
108 */
109
110#define b_altinstr(num)		"664"#num
111#define e_altinstr(num)		"665"#num
112#define oldinstr_len		"662b-661b"
113#define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
114
115#define OLDINSTR(oldinstr) \
116	"661:\n\t" oldinstr "\n662:\n"
117
118#define ALTINSTR_ENTRY(feature, num)					\
119	"\t.long 661b - .\n"			/* old instruction */	\
120	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
121	"\t.long " __stringify(feature) "\n"	/* feature	   */	\
122	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
123	"\t.org . - (" oldinstr_len ") & 1\n"				\
124	"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"	\
125	"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
126
127#define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
128	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
129
130/* alternative assembly primitive: */
131#define ALTERNATIVE(oldinstr, altinstr, feature) \
132	".pushsection .altinstr_replacement, \"ax\"\n"			\
133	ALTINSTR_REPLACEMENT(altinstr, 1)				\
134	".popsection\n"							\
135	OLDINSTR(oldinstr)						\
136	".pushsection .altinstructions,\"a\"\n"				\
137	ALTINSTR_ENTRY(feature, 1)					\
138	".popsection\n"
139
140#define ALTERNATIVE_2(oldinstr, altinstr1, feature1, altinstr2, feature2)\
141	".pushsection .altinstr_replacement, \"ax\"\n"			\
142	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
143	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
144	".popsection\n"							\
145	OLDINSTR(oldinstr)						\
146	".pushsection .altinstructions,\"a\"\n"				\
147	ALTINSTR_ENTRY(feature1, 1)					\
148	ALTINSTR_ENTRY(feature2, 2)					\
149	".popsection\n"
150
151/*
152 * Alternative instructions for different CPU types or capabilities.
153 *
154 * This allows to use optimized instructions even on generic binary
155 * kernels.
156 *
157 * oldinstr is padded with jump and nops at compile time if altinstr is
158 * longer. altinstr is padded with jump and nops at run-time during patching.
159 *
160 * For non barrier like inlines please define new variants
161 * without volatile and memory clobber.
162 */
163#define alternative(oldinstr, altinstr, feature)			\
164	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature) : : : "memory")
165
166#define alternative_2(oldinstr, altinstr1, feature1, altinstr2, feature2) \
167	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, feature1,   \
168				   altinstr2, feature2) ::: "memory")
169
170/* Alternative inline assembly with input. */
171#define alternative_input(oldinstr, newinstr, feature, input...)	\
172	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
173		: : input)
174
175/* Like alternative_input, but with a single output argument */
176#define alternative_io(oldinstr, altinstr, feature, output, input...)	\
177	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature)	\
178		: output : input)
179
180/* Use this macro if more than one output parameter is needed. */
181#define ASM_OUTPUT2(a...) a
182
183/* Use this macro if clobbers are needed without inputs. */
184#define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
185
186#else  /* __ASSEMBLER__ */
187
188/*
189 * Issue one struct alt_instr descriptor entry (need to put it into
190 * the section .altinstructions, see below). This entry contains
191 * enough information for the alternatives patching code to patch an
192 * instruction. See apply_alternatives().
193 */
194.macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
195	.long	\orig_start - .
196	.long	\alt_start - .
197	.long	\feature
198	.byte	\orig_end - \orig_start
199	.org	. - ( \orig_end - \orig_start ) & 1
200	.org	. - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
201	.org	. - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
202.endm
203
204/*
205 * Define an alternative between two instructions. If @feature is
206 * present, early code in apply_alternatives() replaces @oldinstr with
207 * @newinstr.
208 */
209.macro ALTERNATIVE oldinstr, newinstr, feature
210	.pushsection .altinstr_replacement,"ax"
211770:	\newinstr
212771:	.popsection
213772:	\oldinstr
214773:	.pushsection .altinstructions,"a"
215	alt_entry 772b, 773b, 770b, 771b, \feature
216	.popsection
217.endm
218
219/*
220 * Define an alternative between two instructions. If @feature is
221 * present, early code in apply_alternatives() replaces @oldinstr with
222 * @newinstr.
223 */
224.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
225	.pushsection .altinstr_replacement,"ax"
226770:	\newinstr1
227771:	\newinstr2
228772:	.popsection
229773:	\oldinstr
230774:	.pushsection .altinstructions,"a"
231	alt_entry 773b, 774b, 770b, 771b,\feature1
232	alt_entry 773b, 774b, 771b, 772b,\feature2
233	.popsection
234.endm
235
236#endif /* __ASSEMBLER__ */
237
238#endif /* _ASM_S390_ALTERNATIVE_H */