arch/parisc/kernel/jump_label.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2019 Helge Deller <deller@gmx.de>
   4  *
   5  * Based on arch/arm64/kernel/jump_label.c
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/jump_label.h>
   9 #include <linux/bug.h>
  10 #include <asm/alternative.h>
  11 #include <asm/patch.h>
  12
  13 static inline int reassemble_17(int as17)
  14 {
  15         return (((as17 & 0x10000) >> 16) |
  16                 ((as17 & 0x0f800) << 5) |
  17                 ((as17 & 0x00400) >> 8) |
  18                 ((as17 & 0x003ff) << 3));
  19 }
  20
  21 void arch_jump_label_transform(struct jump_entry *entry,
  22                                enum jump_label_type type)
  23 {
  24         void *addr = (void *)jump_entry_code(entry);
  25         u32 insn;
  26
  27         if (type == JUMP_LABEL_JMP) {
  28                 void *target = (void *)jump_entry_target(entry);
  29                 int distance = target - addr;
  30                 /*
  31                  * Encode the PA1.1 "b,n" instruction with a 17-bit
  32                  * displacement.  In case we hit the BUG(), we could use
  33                  * another branch instruction with a 22-bit displacement on
  34                  * 64-bit CPUs instead. But this seems sufficient for now.
  35                  */
  36                 distance -= 8;
  37                 BUG_ON(distance > 262143 || distance < -262144);
  38                 insn = 0xe8000002 | reassemble_17(distance >> 2);
  39         } else {
  40                 insn = INSN_NOP;
  41         }
  42
  43         patch_text(addr, insn);
  44 }
  45
  46 void arch_jump_label_transform_static(struct jump_entry *entry,
  47                                       enum jump_label_type type)
  48 {
  49         /*
  50          * We use the architected NOP in arch_static_branch, so there's no
  51          * need to patch an identical NOP over the top of it here. The core
  52          * will call arch_jump_label_transform from a module notifier if the
  53          * NOP needs to be replaced by a branch.
  54          */
  55 }