root/arch/s390/include/asm/jump_label.h

INCLUDED FROM

DEFINITIONS

1. arch_static_branch
2. arch_static_branch_jump

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_S390_JUMP_LABEL_H
   3 #define _ASM_S390_JUMP_LABEL_H
   4 
   5 #ifndef __ASSEMBLY__
   6 
   7 #include <linux/types.h>
   8 #include <linux/stringify.h>
   9 
  10 #define JUMP_LABEL_NOP_SIZE 6
  11 #define JUMP_LABEL_NOP_OFFSET 2
  12 
  13 #if __GNUC__ < 9
  14 #define JUMP_LABEL_STATIC_KEY_CONSTRAINT "X"
  15 #else
  16 #define JUMP_LABEL_STATIC_KEY_CONSTRAINT "jdd"
  17 #endif
  18 
  19 /*
  20  * We use a brcl 0,2 instruction for jump labels at compile time so it
  21  * can be easily distinguished from a hotpatch generated instruction.
  22  */
  23 static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
  24 {
  25         asm_volatile_goto("0:   brcl    0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
  26                           ".pushsection __jump_table,\"aw\"\n"
  27                           ".balign      8\n"
  28                           ".long        0b-.,%l[label]-.\n"
  29                           ".quad        %0+%1-.\n"
  30                           ".popsection\n"
  31                           : : JUMP_LABEL_STATIC_KEY_CONSTRAINT (key), "i" (branch) : : label);
  32         return false;
  33 label:
  34         return true;
  35 }
  36 
  37 static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
  38 {
  39         asm_volatile_goto("0:   brcl 15,%l[label]\n"
  40                           ".pushsection __jump_table,\"aw\"\n"
  41                           ".balign      8\n"
  42                           ".long        0b-.,%l[label]-.\n"
  43                           ".quad        %0+%1-.\n"
  44                           ".popsection\n"
  45                           : : JUMP_LABEL_STATIC_KEY_CONSTRAINT (key), "i" (branch) : : label);
  46         return false;
  47 label:
  48         return true;
  49 }
  50 
  51 #endif  /* __ASSEMBLY__ */
  52 #endif