arch/riscv/kernel/jump_label.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2020 Emil Renner Berthing
   4  *
   5  * Based on arch/arm64/kernel/jump_label.c
   6  */
   7 #include <linux/jump_label.h>
   8 #include <linux/kernel.h>
   9 #include <linux/memory.h>
  10 #include <linux/mutex.h>
  11 #include <asm/bug.h>
  12 #include <asm/patch.h>
  13
  14 #define RISCV_INSN_NOP 0x00000013U
  15 #define RISCV_INSN_JAL 0x0000006fU
  16
  17 void arch_jump_label_transform(struct jump_entry *entry,
  18                                enum jump_label_type type)
  19 {
  20         void *addr = (void *)jump_entry_code(entry);
  21         u32 insn;
  22
  23         if (type == JUMP_LABEL_JMP) {
  24                 long offset = jump_entry_target(entry) - jump_entry_code(entry);
  25
  26                 if (WARN_ON(offset & 1 || offset < -524288 || offset >= 524288))
  27                         return;
  28
  29                 insn = RISCV_INSN_JAL |
  30                         (((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
  31                         (((u32)offset & GENMASK(11, 11)) << (20 - 11)) |
  32                         (((u32)offset & GENMASK(10,  1)) << (21 -  1)) |
  33                         (((u32)offset & GENMASK(20, 20)) << (31 - 20));
  34         } else {
  35                 insn = RISCV_INSN_NOP;
  36         }
  37
  38         mutex_lock(&text_mutex);
  39         patch_text_nosync(addr, &insn, sizeof(insn));
  40         mutex_unlock(&text_mutex);
  41 }
  42
  43 void arch_jump_label_transform_static(struct jump_entry *entry,
  44                                       enum jump_label_type type)
  45 {
  46         /*
  47          * We use the same instructions in the arch_static_branch and
  48          * arch_static_branch_jump inline functions, so there's no
  49          * need to patch them up here.
  50          * The core will call arch_jump_label_transform  when those
  51          * instructions need to be replaced.
  52          */
  53 }