arch/xtensa/include/asm/jump_label.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Copyright (C) 2018 Cadence Design Systems Inc. */
   3
   4 #ifndef _ASM_XTENSA_JUMP_LABEL_H
   5 #define _ASM_XTENSA_JUMP_LABEL_H
   6
   7 #ifndef __ASSEMBLY__
   8
   9 #include <linux/types.h>
  10
  11 #define JUMP_LABEL_NOP_SIZE 3
  12
  13 static __always_inline bool arch_static_branch(struct static_key *key,
  14                                                bool branch)
  15 {
  16         asm_volatile_goto("1:\n\t"
  17                           "_nop\n\t"
  18                           ".pushsection __jump_table,  \"aw\"\n\t"
  19                           ".word 1b, %l[l_yes], %c0\n\t"
  20                           ".popsection\n\t"
  21                           : :  "i" (&((char *)key)[branch]) :  : l_yes);
  22
  23         return false;
  24 l_yes:
  25         return true;
  26 }
  27
  28 static __always_inline bool arch_static_branch_jump(struct static_key *key,
  29                                                     bool branch)
  30 {
  31         /*
  32          * Xtensa assembler will mark certain points in the code
  33          * as unreachable, so that later assembler or linker relaxation
  34          * passes could use them. A spot right after the J instruction
  35          * is one such point. Assembler and/or linker may insert padding
  36          * or literals here, breaking code flow in case the J instruction
  37          * is later replaced with NOP. Put a label right after the J to
  38          * make it reachable and wrap both into a no-transform block
  39          * to avoid any assembler interference with this.
  40          */
  41         asm_volatile_goto("1:\n\t"
  42                           ".begin no-transform\n\t"
  43                           "_j %l[l_yes]\n\t"
  44                           "2:\n\t"
  45                           ".end no-transform\n\t"
  46                           ".pushsection __jump_table,  \"aw\"\n\t"
  47                           ".word 1b, %l[l_yes], %c0\n\t"
  48                           ".popsection\n\t"
  49                           : :  "i" (&((char *)key)[branch]) :  : l_yes);
  50
  51         return false;
  52 l_yes:
  53         return true;
  54 }
  55
  56 typedef u32 jump_label_t;
  57
  58 struct jump_entry {
  59         jump_label_t code;
  60         jump_label_t target;
  61         jump_label_t key;
  62 };
  63
  64 #endif  /* __ASSEMBLY__ */
  65 #endif