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 #ifndef __ASSEMBLY__
   6
   7 #include <linux/types.h>
   8 #include <linux/stddef.h>
   9 #include <linux/stringify.h>
  10
  11 struct alt_instr {
  12         s32 instr_offset;       /* original instruction */
  13         s32 repl_offset;        /* offset to replacement instruction */
  14         u16 facility;           /* facility bit set for replacement */
  15         u8  instrlen;           /* length of original instruction */
  16         u8  replacementlen;     /* length of new instruction */
  17 } __packed;
  18
  19 void apply_alternative_instructions(void);
  20 void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  21
  22 /*
  23  * |661:       |662:      |6620      |663:
  24  * +-----------+---------------------+
  25  * | oldinstr  | oldinstr_padding    |
  26  * |           +----------+----------+
  27  * |           |          |          |
  28  * |           | >6 bytes |6/4/2 nops|
  29  * |           |6 bytes jg----------->
  30  * +-----------+---------------------+
  31  *               ^^ static padding ^^
  32  *
  33  * .altinstr_replacement section
  34  * +---------------------+-----------+
  35  * |6641:                            |6651:
  36  * | alternative instr 1             |
  37  * +-----------+---------+- - - - - -+
  38  * |6642:                |6652:      |
  39  * | alternative instr 2 | padding
  40  * +---------------------+- - - - - -+
  41  *                        ^ runtime ^
  42  *
  43  * .altinstructions section
  44  * +---------------------------------+
  45  * | alt_instr entries for each      |
  46  * | alternative instr               |
  47  * +---------------------------------+
  48  */
  49
  50 #define b_altinstr(num) "664"#num
  51 #define e_altinstr(num) "665"#num
  52
  53 #define e_oldinstr_pad_end      "663"
  54 #define oldinstr_len            "662b-661b"
  55 #define oldinstr_total_len      e_oldinstr_pad_end"b-661b"
  56 #define altinstr_len(num)       e_altinstr(num)"b-"b_altinstr(num)"b"
  57 #define oldinstr_pad_len(num) \
  58         "-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
  59         "((" altinstr_len(num) ")-(" oldinstr_len "))"
  60
  61 #define INSTR_LEN_SANITY_CHECK(len)                                     \
  62         ".if " len " > 254\n"                                           \
  63         "\t.error \"cpu alternatives does not support instructions "    \
  64                 "blocks > 254 bytes\"\n"                                \
  65         ".endif\n"                                                      \
  66         ".if (" len ") %% 2\n"                                          \
  67         "\t.error \"cpu alternatives instructions length is odd\"\n"    \
  68         ".endif\n"
  69
  70 #define OLDINSTR_PADDING(oldinstr, num)                                 \
  71         ".if " oldinstr_pad_len(num) " > 6\n"                           \
  72         "\tjg " e_oldinstr_pad_end "f\n"                                \
  73         "6620:\n"                                                       \
  74         "\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
  75         ".else\n"                                                       \
  76         "\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n"        \
  77         "\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n"   \
  78         "\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n"  \
  79         ".endif\n"
  80
  81 #define OLDINSTR(oldinstr, num)                                         \
  82         "661:\n\t" oldinstr "\n662:\n"                                  \
  83         OLDINSTR_PADDING(oldinstr, num)                                 \
  84         e_oldinstr_pad_end ":\n"                                        \
  85         INSTR_LEN_SANITY_CHECK(oldinstr_len)
  86
  87 #define OLDINSTR_2(oldinstr, num1, num2)                                \
  88         "661:\n\t" oldinstr "\n662:\n"                                  \
  89         ".if " altinstr_len(num1) " < " altinstr_len(num2) "\n"         \
  90         OLDINSTR_PADDING(oldinstr, num2)                                \
  91         ".else\n"                                                       \
  92         OLDINSTR_PADDING(oldinstr, num1)                                \
  93         ".endif\n"                                                      \
  94         e_oldinstr_pad_end ":\n"                                        \
  95         INSTR_LEN_SANITY_CHECK(oldinstr_len)
  96
  97 #define ALTINSTR_ENTRY(facility, num)                                   \
  98         "\t.long 661b - .\n"                    /* old instruction */   \
  99         "\t.long " b_altinstr(num)"b - .\n"     /* alt instruction */   \
 100         "\t.word " __stringify(facility) "\n"   /* facility bit    */   \
 101         "\t.byte " oldinstr_total_len "\n"      /* source len      */   \
 102         "\t.byte " altinstr_len(num) "\n"       /* alt instruction len */
 103
 104 #define ALTINSTR_REPLACEMENT(altinstr, num)     /* replacement */       \
 105         b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"      \
 106         INSTR_LEN_SANITY_CHECK(altinstr_len(num))
 107
 108 /* alternative assembly primitive: */
 109 #define ALTERNATIVE(oldinstr, altinstr, facility) \
 110         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 111         ALTINSTR_REPLACEMENT(altinstr, 1)                               \
 112         ".popsection\n"                                                 \
 113         OLDINSTR(oldinstr, 1)                                           \
 114         ".pushsection .altinstructions,\"a\"\n"                         \
 115         ALTINSTR_ENTRY(facility, 1)                                     \
 116         ".popsection\n"
 117
 118 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
 119         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 120         ALTINSTR_REPLACEMENT(altinstr1, 1)                              \
 121         ALTINSTR_REPLACEMENT(altinstr2, 2)                              \
 122         ".popsection\n"                                                 \
 123         OLDINSTR_2(oldinstr, 1, 2)                                      \
 124         ".pushsection .altinstructions,\"a\"\n"                         \
 125         ALTINSTR_ENTRY(facility1, 1)                                    \
 126         ALTINSTR_ENTRY(facility2, 2)                                    \
 127         ".popsection\n"
 128
 129 /*
 130  * Alternative instructions for different CPU types or capabilities.
 131  *
 132  * This allows to use optimized instructions even on generic binary
 133  * kernels.
 134  *
 135  * oldinstr is padded with jump and nops at compile time if altinstr is
 136  * longer. altinstr is padded with jump and nops at run-time during patching.
 137  *
 138  * For non barrier like inlines please define new variants
 139  * without volatile and memory clobber.
 140  */
 141 #define alternative(oldinstr, altinstr, facility)                       \
 142         asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
 143
 144 #define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
 145         asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,          \
 146                                    altinstr2, facility2) ::: "memory")
 147
 148 #endif /* __ASSEMBLY__ */
 149
 150 #endif /* _ASM_S390_ALTERNATIVE_H */