/arch/ppc64/lib/sstep.c

https://bitbucket.org/evzijst/gittest · C · 141 lines · 105 code · 6 blank · 30 comment · 35 complexity · 639df0b67f846c43feb94ff7cbe06560 MD5 · raw file

  1. /*
  2. * Single-step support.
  3. *
  4. * Copyright (C) 2004 Paul Mackerras <paulus@au.ibm.com>, IBM
  5. *
  6. * This program is free software; you can redistribute it and/or
  7. * modify it under the terms of the GNU General Public License
  8. * as published by the Free Software Foundation; either version
  9. * 2 of the License, or (at your option) any later version.
  10. */
  11. #include <linux/kernel.h>
  12. #include <linux/ptrace.h>
  13. #include <asm/sstep.h>
  14. #include <asm/processor.h>
  15. extern char system_call_common[];
  16. /* Bits in SRR1 that are copied from MSR */
  17. #define MSR_MASK 0xffffffff87c0ffff
  18. /*
  19. * Determine whether a conditional branch instruction would branch.
  20. */
  21. static int branch_taken(unsigned int instr, struct pt_regs *regs)
  22. {
  23. unsigned int bo = (instr >> 21) & 0x1f;
  24. unsigned int bi;
  25. if ((bo & 4) == 0) {
  26. /* decrement counter */
  27. --regs->ctr;
  28. if (((bo >> 1) & 1) ^ (regs->ctr == 0))
  29. return 0;
  30. }
  31. if ((bo & 0x10) == 0) {
  32. /* check bit from CR */
  33. bi = (instr >> 16) & 0x1f;
  34. if (((regs->ccr >> (31 - bi)) & 1) != ((bo >> 3) & 1))
  35. return 0;
  36. }
  37. return 1;
  38. }
  39. /*
  40. * Emulate instructions that cause a transfer of control.
  41. * Returns 1 if the step was emulated, 0 if not,
  42. * or -1 if the instruction is one that should not be stepped,
  43. * such as an rfid, or a mtmsrd that would clear MSR_RI.
  44. */
  45. int emulate_step(struct pt_regs *regs, unsigned int instr)
  46. {
  47. unsigned int opcode, rd;
  48. unsigned long int imm;
  49. opcode = instr >> 26;
  50. switch (opcode) {
  51. case 16: /* bc */
  52. imm = (signed short)(instr & 0xfffc);
  53. if ((instr & 2) == 0)
  54. imm += regs->nip;
  55. regs->nip += 4;
  56. if ((regs->msr & MSR_SF) == 0)
  57. regs->nip &= 0xffffffffUL;
  58. if (instr & 1)
  59. regs->link = regs->nip;
  60. if (branch_taken(instr, regs))
  61. regs->nip = imm;
  62. return 1;
  63. case 17: /* sc */
  64. /*
  65. * N.B. this uses knowledge about how the syscall
  66. * entry code works. If that is changed, this will
  67. * need to be changed also.
  68. */
  69. regs->gpr[9] = regs->gpr[13];
  70. regs->gpr[11] = regs->nip + 4;
  71. regs->gpr[12] = regs->msr & MSR_MASK;
  72. regs->gpr[13] = (unsigned long) get_paca();
  73. regs->nip = (unsigned long) &system_call_common;
  74. regs->msr = MSR_KERNEL;
  75. return 1;
  76. case 18: /* b */
  77. imm = instr & 0x03fffffc;
  78. if (imm & 0x02000000)
  79. imm -= 0x04000000;
  80. if ((instr & 2) == 0)
  81. imm += regs->nip;
  82. if (instr & 1) {
  83. regs->link = regs->nip + 4;
  84. if ((regs->msr & MSR_SF) == 0)
  85. regs->link &= 0xffffffffUL;
  86. }
  87. if ((regs->msr & MSR_SF) == 0)
  88. imm &= 0xffffffffUL;
  89. regs->nip = imm;
  90. return 1;
  91. case 19:
  92. switch (instr & 0x7fe) {
  93. case 0x20: /* bclr */
  94. case 0x420: /* bcctr */
  95. imm = (instr & 0x400)? regs->ctr: regs->link;
  96. regs->nip += 4;
  97. if ((regs->msr & MSR_SF) == 0) {
  98. regs->nip &= 0xffffffffUL;
  99. imm &= 0xffffffffUL;
  100. }
  101. if (instr & 1)
  102. regs->link = regs->nip;
  103. if (branch_taken(instr, regs))
  104. regs->nip = imm;
  105. return 1;
  106. case 0x24: /* rfid, scary */
  107. return -1;
  108. }
  109. case 31:
  110. rd = (instr >> 21) & 0x1f;
  111. switch (instr & 0x7fe) {
  112. case 0xa6: /* mfmsr */
  113. regs->gpr[rd] = regs->msr & MSR_MASK;
  114. regs->nip += 4;
  115. if ((regs->msr & MSR_SF) == 0)
  116. regs->nip &= 0xffffffffUL;
  117. return 1;
  118. case 0x164: /* mtmsrd */
  119. /* only MSR_EE and MSR_RI get changed if bit 15 set */
  120. /* mtmsrd doesn't change MSR_HV and MSR_ME */
  121. imm = (instr & 0x10000)? 0x8002: 0xefffffffffffefffUL;
  122. imm = (regs->msr & MSR_MASK & ~imm)
  123. | (regs->gpr[rd] & imm);
  124. if ((imm & MSR_RI) == 0)
  125. /* can't step mtmsrd that would clear MSR_RI */
  126. return -1;
  127. regs->msr = imm;
  128. regs->nip += 4;
  129. if ((imm & MSR_SF) == 0)
  130. regs->nip &= 0xffffffffUL;
  131. return 1;
  132. }
  133. }
  134. return 0;
  135. }