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