arch/s390/include/asm/alternative.h

   1 #ifndef _ASM_S390_ALTERNATIVE_H
   2 #define _ASM_S390_ALTERNATIVE_H
   3
   4 #ifndef __ASSEMBLY__
   5
   6 #include <linux/types.h>
   7 #include <linux/stddef.h>
   8 #include <linux/stringify.h>
   9
  10 struct alt_instr {
  11         s32 instr_offset;       /* original instruction */
  12         s32 repl_offset;        /* offset to replacement instruction */
  13         u16 facility;           /* facility bit set for replacement */
  14         u8  instrlen;           /* length of original instruction */
  15         u8  replacementlen;     /* length of new instruction */
  16 } __packed;
  17
  18 #ifdef CONFIG_ALTERNATIVES
  19 extern void apply_alternative_instructions(void);
  20 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  21 #else
  22 static inline void apply_alternative_instructions(void) {};
  23 static inline void apply_alternatives(struct alt_instr *start,
  24                                       struct alt_instr *end) {};
  25 #endif
  26 /*
  27  * |661:       |662:      |6620      |663:
  28  * +-----------+---------------------+
  29  * | oldinstr  | oldinstr_padding    |
  30  * |           +----------+----------+
  31  * |           |          |          |
  32  * |           | >6 bytes |6/4/2 nops|
  33  * |           |6 bytes jg----------->
  34  * +-----------+---------------------+
  35  *               ^^ static padding ^^
  36  *
  37  * .altinstr_replacement section
  38  * +---------------------+-----------+
  39  * |6641:                            |6651:
  40  * | alternative instr 1             |
  41  * +-----------+---------+- - - - - -+
  42  * |6642:                |6652:      |
  43  * | alternative instr 2 | padding
  44  * +---------------------+- - - - - -+
  45  *                        ^ runtime ^
  46  *
  47  * .altinstructions section
  48  * +---------------------------------+
  49  * | alt_instr entries for each      |
  50  * | alternative instr               |
  51  * +---------------------------------+
  52  */
  53
  54 #define b_altinstr(num) "664"#num
  55 #define e_altinstr(num) "665"#num
  56
  57 #define e_oldinstr_pad_end      "663"
  58 #define oldinstr_len            "662b-661b"
  59 #define oldinstr_total_len      e_oldinstr_pad_end"b-661b"
  60 #define altinstr_len(num)       e_altinstr(num)"b-"b_altinstr(num)"b"
  61 #define oldinstr_pad_len(num) \
  62         "-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
  63         "((" altinstr_len(num) ")-(" oldinstr_len "))"
  64
  65 #define INSTR_LEN_SANITY_CHECK(len)                                     \
  66         ".if " len " > 254\n"                                           \
  67         "\t.error \"cpu alternatives does not support instructions "    \
  68                 "blocks > 254 bytes\"\n"                                \
  69         ".endif\n"                                                      \
  70         ".if (" len ") %% 2\n"                                          \
  71         "\t.error \"cpu alternatives instructions length is odd\"\n"    \
  72         ".endif\n"
  73
  74 #define OLDINSTR_PADDING(oldinstr, num)                                 \
  75         ".if " oldinstr_pad_len(num) " > 6\n"                           \
  76         "\tjg " e_oldinstr_pad_end "f\n"                                \
  77         "6620:\n"                                                       \
  78         "\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
  79         ".else\n"                                                       \
  80         "\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n"        \
  81         "\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n"   \
  82         "\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n"  \
  83         ".endif\n"
  84
  85 #define OLDINSTR(oldinstr, num)                                         \
  86         "661:\n\t" oldinstr "\n662:\n"                                  \
  87         OLDINSTR_PADDING(oldinstr, num)                                 \
  88         e_oldinstr_pad_end ":\n"                                        \
  89         INSTR_LEN_SANITY_CHECK(oldinstr_len)
  90
  91 #define OLDINSTR_2(oldinstr, num1, num2)                                \
  92         "661:\n\t" oldinstr "\n662:\n"                                  \
  93         ".if " altinstr_len(num1) " < " altinstr_len(num2) "\n"         \
  94         OLDINSTR_PADDING(oldinstr, num2)                                \
  95         ".else\n"                                                       \
  96         OLDINSTR_PADDING(oldinstr, num1)                                \
  97         ".endif\n"                                                      \
  98         e_oldinstr_pad_end ":\n"                                        \
  99         INSTR_LEN_SANITY_CHECK(oldinstr_len)
 100
 101 #define ALTINSTR_ENTRY(facility, num)                                   \
 102         "\t.long 661b - .\n"                    /* old instruction */   \
 103         "\t.long " b_altinstr(num)"b - .\n"     /* alt instruction */   \
 104         "\t.word " __stringify(facility) "\n"   /* facility bit    */   \
 105         "\t.byte " oldinstr_total_len "\n"      /* source len      */   \
 106         "\t.byte " altinstr_len(num) "\n"       /* alt instruction len */
 107
 108 #define ALTINSTR_REPLACEMENT(altinstr, num)     /* replacement */       \
 109         b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"      \
 110         INSTR_LEN_SANITY_CHECK(altinstr_len(num))
 111
 112 #ifdef CONFIG_ALTERNATIVES
 113 /* alternative assembly primitive: */
 114 #define ALTERNATIVE(oldinstr, altinstr, facility) \
 115         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 116         ALTINSTR_REPLACEMENT(altinstr, 1)                               \
 117         ".popsection\n"                                                 \
 118         OLDINSTR(oldinstr, 1)                                           \
 119         ".pushsection .altinstructions,\"a\"\n"                         \
 120         ALTINSTR_ENTRY(facility, 1)                                     \
 121         ".popsection\n"
 122
 123 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
 124         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 125         ALTINSTR_REPLACEMENT(altinstr1, 1)                              \
 126         ALTINSTR_REPLACEMENT(altinstr2, 2)                              \
 127         ".popsection\n"                                                 \
 128         OLDINSTR_2(oldinstr, 1, 2)                                      \
 129         ".pushsection .altinstructions,\"a\"\n"                         \
 130         ALTINSTR_ENTRY(facility1, 1)                                    \
 131         ALTINSTR_ENTRY(facility2, 2)                                    \
 132         ".popsection\n"
 133 #else
 134 /* Alternative instructions are disabled, let's put just oldinstr in */
 135 #define ALTERNATIVE(oldinstr, altinstr, facility) \
 136         oldinstr "\n"
 137
 138 #define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
 139         oldinstr "\n"
 140 #endif
 141
 142 /*
 143  * Alternative instructions for different CPU types or capabilities.
 144  *
 145  * This allows to use optimized instructions even on generic binary
 146  * kernels.
 147  *
 148  * oldinstr is padded with jump and nops at compile time if altinstr is
 149  * longer. altinstr is padded with jump and nops at run-time during patching.
 150  *
 151  * For non barrier like inlines please define new variants
 152  * without volatile and memory clobber.
 153  */
 154 #define alternative(oldinstr, altinstr, facility)                       \
 155         asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
 156
 157 #define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
 158         asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,          \
 159                                    altinstr2, facility2) ::: "memory")
 160
 161 #endif /* __ASSEMBLY__ */
 162
 163 #endif /* _ASM_S390_ALTERNATIVE_H */