syscall.c 2.7 KB

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  1. // SPDX-License-Identifier: GPL-2.0
  2. #include <linux/ptrace.h>
  3. #include <linux/sched.h>
  4. #include <linux/sched/task_stack.h>
  5. #include <linux/export.h>
  6. #include <asm/syscall.h>
  7. static int collect_syscall(struct task_struct *target, struct syscall_info *info)
  8. {
  9. unsigned long args[6] = { };
  10. struct pt_regs *regs;
  11. if (!try_get_task_stack(target)) {
  12. /* Task has no stack, so the task isn't in a syscall. */
  13. memset(info, 0, sizeof(*info));
  14. info->data.nr = -1;
  15. return 0;
  16. }
  17. regs = task_pt_regs(target);
  18. if (unlikely(!regs)) {
  19. put_task_stack(target);
  20. return -EAGAIN;
  21. }
  22. info->sp = user_stack_pointer(regs);
  23. info->data.instruction_pointer = instruction_pointer(regs);
  24. info->data.nr = syscall_get_nr(target, regs);
  25. if (info->data.nr != -1L)
  26. syscall_get_arguments(target, regs, args);
  27. info->data.args[0] = args[0];
  28. info->data.args[1] = args[1];
  29. info->data.args[2] = args[2];
  30. info->data.args[3] = args[3];
  31. info->data.args[4] = args[4];
  32. info->data.args[5] = args[5];
  33. put_task_stack(target);
  34. return 0;
  35. }
  36. /**
  37. * task_current_syscall - Discover what a blocked task is doing.
  38. * @target: thread to examine
  39. * @info: structure with the following fields:
  40. * .sp - filled with user stack pointer
  41. * .data.nr - filled with system call number or -1
  42. * .data.args - filled with @maxargs system call arguments
  43. * .data.instruction_pointer - filled with user PC
  44. *
  45. * If @target is blocked in a system call, returns zero with @info.data.nr
  46. * set to the call's number and @info.data.args filled in with its
  47. * arguments. Registers not used for system call arguments may not be available
  48. * and it is not kosher to use &struct user_regset calls while the system
  49. * call is still in progress. Note we may get this result if @target
  50. * has finished its system call but not yet returned to user mode, such
  51. * as when it's stopped for signal handling or syscall exit tracing.
  52. *
  53. * If @target is blocked in the kernel during a fault or exception,
  54. * returns zero with *@info.data.nr set to -1 and does not fill in
  55. * @info.data.args. If so, it's now safe to examine @target using
  56. * &struct user_regset get() calls as long as we're sure @target won't return
  57. * to user mode.
  58. *
  59. * Returns -%EAGAIN if @target does not remain blocked.
  60. */
  61. int task_current_syscall(struct task_struct *target, struct syscall_info *info)
  62. {
  63. long state;
  64. unsigned long ncsw;
  65. if (target == current)
  66. return collect_syscall(target, info);
  67. state = target->state;
  68. if (unlikely(!state))
  69. return -EAGAIN;
  70. ncsw = wait_task_inactive(target, state);
  71. if (unlikely(!ncsw) ||
  72. unlikely(collect_syscall(target, info)) ||
  73. unlikely(wait_task_inactive(target, state) != ncsw))
  74. return -EAGAIN;
  75. return 0;
  76. }