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