arch/loongarch/include/asm/alternative.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_ALTERNATIVE_H
   3 #define _ASM_ALTERNATIVE_H
   4
   5 #ifndef __ASSEMBLY__
   6
   7 #include <linux/types.h>
   8 #include <linux/stddef.h>
   9 #include <linux/stringify.h>
  10 #include <asm/asm.h>
  11
  12 struct alt_instr {
  13         s32 instr_offset;       /* offset to original instruction */
  14         s32 replace_offset;     /* offset to replacement instruction */
  15         u16 feature;            /* feature bit set for replacement */
  16         u8  instrlen;           /* length of original instruction */
  17         u8  replacementlen;     /* length of new instruction */
  18 } __packed;
  19
  20 /*
  21  * Debug flag that can be tested to see whether alternative
  22  * instructions were patched in already:
  23  */
  24 extern int alternatives_patched;
  25 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
  26
  27 extern void alternative_instructions(void);
  28 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  29
  30 #define b_replacement(num)      "664"#num
  31 #define e_replacement(num)      "665"#num
  32
  33 #define alt_end_marker          "663"
  34 #define alt_slen                "662b-661b"
  35 #define alt_total_slen          alt_end_marker"b-661b"
  36 #define alt_rlen(num)           e_replacement(num)"f-"b_replacement(num)"f"
  37
  38 #define __OLDINSTR(oldinstr, num)                                       \
  39         "661:\n\t" oldinstr "\n662:\n"                                  \
  40         ".fill -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "          \
  41                 "((" alt_rlen(num) ")-(" alt_slen ")) / 4, 4, 0x03400000\n"
  42
  43 #define OLDINSTR(oldinstr, num)                                         \
  44         __OLDINSTR(oldinstr, num)                                       \
  45         alt_end_marker ":\n"
  46
  47 #define alt_max_short(a, b)     "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
  48
  49 /*
  50  * Pad the second replacement alternative with additional NOPs if it is
  51  * additionally longer than the first replacement alternative.
  52  */
  53 #define OLDINSTR_2(oldinstr, num1, num2) \
  54         "661:\n\t" oldinstr "\n662:\n"                                                          \
  55         ".fill -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "  \
  56                 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) / 4, "    \
  57                 "4, 0x03400000\n"       \
  58         alt_end_marker ":\n"
  59
  60 #define ALTINSTR_ENTRY(feature, num)                                          \
  61         " .long 661b - .\n"                             /* label           */ \
  62         " .long " b_replacement(num)"f - .\n"           /* new instruction */ \
  63         " .short " __stringify(feature) "\n"            /* feature bit     */ \
  64         " .byte " alt_total_slen "\n"                   /* source len      */ \
  65         " .byte " alt_rlen(num) "\n"                    /* replacement len */
  66
  67 #define ALTINSTR_REPLACEMENT(newinstr, feature, num)    /* replacement */     \
  68         b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
  69
  70 /* alternative assembly primitive: */
  71 #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  72         OLDINSTR(oldinstr, 1)                                           \
  73         ".pushsection .altinstructions,\"a\"\n"                         \
  74         ALTINSTR_ENTRY(feature, 1)                                      \
  75         ".popsection\n"                                                 \
  76         ".subsection 1\n" \
  77         ALTINSTR_REPLACEMENT(newinstr, feature, 1)                      \
  78         ".previous\n"
  79
  80 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
  81         OLDINSTR_2(oldinstr, 1, 2)                                      \
  82         ".pushsection .altinstructions,\"a\"\n"                         \
  83         ALTINSTR_ENTRY(feature1, 1)                                     \
  84         ALTINSTR_ENTRY(feature2, 2)                                     \
  85         ".popsection\n"                                                 \
  86         ".subsection 1\n" \
  87         ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)                    \
  88         ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)                    \
  89         ".previous\n"
  90
  91 /*
  92  * Alternative instructions for different CPU types or capabilities.
  93  *
  94  * This allows to use optimized instructions even on generic binary
  95  * kernels.
  96  *
  97  * length of oldinstr must be longer or equal the length of newinstr
  98  * It can be padded with nops as needed.
  99  *
 100  * For non barrier like inlines please define new variants
 101  * without volatile and memory clobber.
 102  */
 103 #define alternative(oldinstr, newinstr, feature)                        \
 104         (asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory"))
 105
 106 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
 107         (asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory"))
 108
 109 #endif /* __ASSEMBLY__ */
 110
 111 #endif /* _ASM_ALTERNATIVE_H */