arch/s390/include/asm/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_SPEC           1
  36 #define ALT_TYPE_LOWCORE        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_SPEC(facility)              (ALT_CTX_LATE << ALT_CTX_SHIFT          | \
  47                                          ALT_TYPE_SPEC << ALT_TYPE_SHIFT        | \
  48                                          (facility) << ALT_DATA_SHIFT)
  49
  50 #define ALT_LOWCORE                     (ALT_CTX_EARLY << ALT_CTX_SHIFT         | \
  51                                          ALT_TYPE_LOWCORE << ALT_TYPE_SHIFT)
  52
  53 #ifndef __ASSEMBLY__
  54
  55 #include <linux/types.h>
  56 #include <linux/stddef.h>
  57 #include <linux/stringify.h>
  58
  59 struct alt_instr {
  60         s32 instr_offset;       /* original instruction */
  61         s32 repl_offset;        /* offset to replacement instruction */
  62         union {
  63                 u32 feature;    /* feature required for replacement */
  64                 struct {
  65                         u32 ctx  : 4;  /* context */
  66                         u32 type : 8;  /* type of alternative */
  67                         u32 data : 20; /* patching information */
  68                 };
  69         };
  70         u8  instrlen;           /* length of original instruction */
  71 } __packed;
  72
  73 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
  74
  75 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx);
  76
  77 static inline void apply_alternative_instructions(void)
  78 {
  79         __apply_alternatives(__alt_instructions, __alt_instructions_end, ALT_CTX_LATE);
  80 }
  81
  82 static inline void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
  83 {
  84         __apply_alternatives(start, end, ALT_CTX_ALL);
  85 }
  86
  87 /*
  88  * +---------------------------------+
  89  * |661:                             |662:
  90  * | oldinstr                        |
  91  * +---------------------------------+
  92  *
  93  * .altinstr_replacement section
  94  * +---------------------------------+
  95  * |6641:                            |6651:
  96  * | alternative instr 1             |
  97  * +---------------------------------+
  98  * |6642:                            |6652:
  99  * | alternative instr 2             |
 100  * +---------------------------------+
 101  *
 102  * .altinstructions section
 103  * +---------------------------------+
 104  * | alt_instr entries for each      |
 105  * | alternative instr               |
 106  * +---------------------------------+
 107  */
 108
 109 #define b_altinstr(num)         "664"#num
 110 #define e_altinstr(num)         "665"#num
 111 #define oldinstr_len            "662b-661b"
 112 #define altinstr_len(num)       e_altinstr(num)"b-"b_altinstr(num)"b"
 113
 114 #define OLDINSTR(oldinstr) \
 115         "661:\n\t" oldinstr "\n662:\n"
 116
 117 #define ALTINSTR_ENTRY(feature, num)                                    \
 118         "\t.long 661b - .\n"                    /* old instruction */   \
 119         "\t.long " b_altinstr(num)"b - .\n"     /* alt instruction */   \
 120         "\t.long " __stringify(feature) "\n"    /* feature         */   \
 121         "\t.byte " oldinstr_len "\n"            /* instruction len */   \
 122         "\t.org . - (" oldinstr_len ") & 1\n"                           \
 123         "\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"     \
 124         "\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
 125
 126 #define ALTINSTR_REPLACEMENT(altinstr, num)     /* replacement */       \
 127         b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
 128
 129 /* alternative assembly primitive: */
 130 #define ALTERNATIVE(oldinstr, altinstr, feature) \
 131         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 132         ALTINSTR_REPLACEMENT(altinstr, 1)                               \
 133         ".popsection\n"                                                 \
 134         OLDINSTR(oldinstr)                                              \
 135         ".pushsection .altinstructions,\"a\"\n"                         \
 136         ALTINSTR_ENTRY(feature, 1)                                      \
 137         ".popsection\n"
 138
 139 #define ALTERNATIVE_2(oldinstr, altinstr1, feature1, altinstr2, feature2)\
 140         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 141         ALTINSTR_REPLACEMENT(altinstr1, 1)                              \
 142         ALTINSTR_REPLACEMENT(altinstr2, 2)                              \
 143         ".popsection\n"                                                 \
 144         OLDINSTR(oldinstr)                                              \
 145         ".pushsection .altinstructions,\"a\"\n"                         \
 146         ALTINSTR_ENTRY(feature1, 1)                                     \
 147         ALTINSTR_ENTRY(feature2, 2)                                     \
 148         ".popsection\n"
 149
 150 /*
 151  * Alternative instructions for different CPU types or capabilities.
 152  *
 153  * This allows to use optimized instructions even on generic binary
 154  * kernels.
 155  *
 156  * oldinstr is padded with jump and nops at compile time if altinstr is
 157  * longer. altinstr is padded with jump and nops at run-time during patching.
 158  *
 159  * For non barrier like inlines please define new variants
 160  * without volatile and memory clobber.
 161  */
 162 #define alternative(oldinstr, altinstr, feature)                        \
 163         asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature) : : : "memory")
 164
 165 #define alternative_2(oldinstr, altinstr1, feature1, altinstr2, feature2) \
 166         asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, feature1,   \
 167                                    altinstr2, feature2) ::: "memory")
 168
 169 /* Alternative inline assembly with input. */
 170 #define alternative_input(oldinstr, newinstr, feature, input...)        \
 171         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)   \
 172                 : : input)
 173
 174 /* Like alternative_input, but with a single output argument */
 175 #define alternative_io(oldinstr, altinstr, feature, output, input...)   \
 176         asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, feature)    \
 177                 : output : input)
 178
 179 /* Use this macro if more than one output parameter is needed. */
 180 #define ASM_OUTPUT2(a...) a
 181
 182 /* Use this macro if clobbers are needed without inputs. */
 183 #define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
 184
 185 #else  /* __ASSEMBLY__ */
 186
 187 /*
 188  * Issue one struct alt_instr descriptor entry (need to put it into
 189  * the section .altinstructions, see below). This entry contains
 190  * enough information for the alternatives patching code to patch an
 191  * instruction. See apply_alternatives().
 192  */
 193 .macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
 194         .long   \orig_start - .
 195         .long   \alt_start - .
 196         .long   \feature
 197         .byte   \orig_end - \orig_start
 198         .org    . - ( \orig_end - \orig_start ) & 1
 199         .org    . - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
 200         .org    . - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
 201 .endm
 202
 203 /*
 204  * Define an alternative between two instructions. If @feature is
 205  * present, early code in apply_alternatives() replaces @oldinstr with
 206  * @newinstr.
 207  */
 208 .macro ALTERNATIVE oldinstr, newinstr, feature
 209         .pushsection .altinstr_replacement,"ax"
 210 770:    \newinstr
 211 771:    .popsection
 212 772:    \oldinstr
 213 773:    .pushsection .altinstructions,"a"
 214         alt_entry 772b, 773b, 770b, 771b, \feature
 215         .popsection
 216 .endm
 217
 218 /*
 219  * Define an alternative between two instructions. If @feature is
 220  * present, early code in apply_alternatives() replaces @oldinstr with
 221  * @newinstr.
 222  */
 223 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
 224         .pushsection .altinstr_replacement,"ax"
 225 770:    \newinstr1
 226 771:    \newinstr2
 227 772:    .popsection
 228 773:    \oldinstr
 229 774:    .pushsection .altinstructions,"a"
 230         alt_entry 773b, 774b, 770b, 771b,\feature1
 231         alt_entry 773b, 774b, 771b, 772b,\feature2
 232         .popsection
 233 .endm
 234
 235 #endif /* __ASSEMBLY__ */
 236
 237 #endif /* _ASM_S390_ALTERNATIVE_H */