Linux Kernel  3.7.1
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insn.c
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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);
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 }