arch/arm/kernel/insn.c

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