arch/arm/kernel/insn.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/bug.h>
   3 #include <linux/kernel.h>
   4 #include <asm/opcodes.h>
   5
   6 static unsigned long __arm_gen_branch_thumb2(unsigned long pc,
   7                                              unsigned long addr, bool link,
   8                                              bool warn)
   9 {
  10         unsigned long s, j1, j2, i1, i2, imm10, imm11;
  11         unsigned long first, second;
  12         long offset;
  13
  14         offset = (long)addr - (long)(pc + 4);
  15         if (offset < -16777216 || offset > 16777214) {
  16                 WARN_ON_ONCE(warn);
  17                 return 0;
  18         }
  19
  20         s       = (offset >> 24) & 0x1;
  21         i1      = (offset >> 23) & 0x1;
  22         i2      = (offset >> 22) & 0x1;
  23         imm10   = (offset >> 12) & 0x3ff;
  24         imm11   = (offset >>  1) & 0x7ff;
  25
  26         j1 = (!i1) ^ s;
  27         j2 = (!i2) ^ s;
  28
  29         first = 0xf000 | (s << 10) | imm10;
  30         second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11;
  31         if (link)
  32                 second |= 1 << 14;
  33
  34         return __opcode_thumb32_compose(first, second);
  35 }
  36
  37 static unsigned long __arm_gen_branch_arm(unsigned long pc, unsigned long addr,
  38                                           bool link, bool warn)
  39 {
  40         unsigned long opcode = 0xea000000;
  41         long offset;
  42
  43         if (link)
  44                 opcode |= 1 << 24;
  45
  46         offset = (long)addr - (long)(pc + 8);
  47         if (unlikely(offset < -33554432 || offset > 33554428)) {
  48                 WARN_ON_ONCE(warn);
  49                 return 0;
  50         }
  51
  52         offset = (offset >> 2) & 0x00ffffff;
  53
  54         return opcode | offset;
  55 }
  56
  57 unsigned long
  58 __arm_gen_branch(unsigned long pc, unsigned long addr, bool link, bool warn)
  59 {
  60         if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
  61                 return __arm_gen_branch_thumb2(pc, addr, link, warn);
  62         else
  63                 return __arm_gen_branch_arm(pc, addr, link, warn);
  64 }