LXR linux/arch/parisc/kernel/jump

   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
  13static 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
  21void 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
  46void 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}
  56