perf_regs.c 2.3 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081
  1. // SPDX-License-Identifier: GPL-2.0
  2. #include <linux/compat.h>
  3. #include <linux/errno.h>
  4. #include <linux/kernel.h>
  5. #include <linux/perf_event.h>
  6. #include <linux/bug.h>
  7. #include <linux/sched/task_stack.h>
  8. #include <asm/perf_regs.h>
  9. #include <asm/ptrace.h>
  10. u64 perf_reg_value(struct pt_regs *regs, int idx)
  11. {
  12. if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_MAX))
  13. return 0;
  14. /*
  15. * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
  16. * we're stuck with it for ABI compatability reasons.
  17. *
  18. * For a 32-bit consumer inspecting a 32-bit task, then it will look at
  19. * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
  20. * These correspond directly to a prefix of the registers saved in our
  21. * 'struct pt_regs', with the exception of the PC, so we copy that down
  22. * (x15 corresponds to SP_hyp in the architecture).
  23. *
  24. * So far, so good.
  25. *
  26. * The oddity arises when a 64-bit consumer looks at a 32-bit task and
  27. * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
  28. * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
  29. * PC registers would normally live. The initial idea was to allow a
  30. * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
  31. * how well that works in practice, somebody might be relying on it.
  32. *
  33. * At the time we make a sample, we don't know whether the consumer is
  34. * 32-bit or 64-bit, so we have to cater for both possibilities.
  35. */
  36. if (compat_user_mode(regs)) {
  37. if ((u32)idx == PERF_REG_ARM64_SP)
  38. return regs->compat_sp;
  39. if ((u32)idx == PERF_REG_ARM64_LR)
  40. return regs->compat_lr;
  41. if (idx == 15)
  42. return regs->pc;
  43. }
  44. if ((u32)idx == PERF_REG_ARM64_SP)
  45. return regs->sp;
  46. if ((u32)idx == PERF_REG_ARM64_PC)
  47. return regs->pc;
  48. return regs->regs[idx];
  49. }
  50. #define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))
  51. int perf_reg_validate(u64 mask)
  52. {
  53. if (!mask || mask & REG_RESERVED)
  54. return -EINVAL;
  55. return 0;
  56. }
  57. u64 perf_reg_abi(struct task_struct *task)
  58. {
  59. if (is_compat_thread(task_thread_info(task)))
  60. return PERF_SAMPLE_REGS_ABI_32;
  61. else
  62. return PERF_SAMPLE_REGS_ABI_64;
  63. }
  64. void perf_get_regs_user(struct perf_regs *regs_user,
  65. struct pt_regs *regs,
  66. struct pt_regs *regs_user_copy)
  67. {
  68. regs_user->regs = task_pt_regs(current);
  69. regs_user->abi = perf_reg_abi(current);
  70. }