LXR linux/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
   6static 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
  37static 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
  57unsigned 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}
  65