Branch data     Line data    Source code

       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                 :            : 
       8                 :          0 : static int collect_syscall(struct task_struct *target, struct syscall_info *info)
       9                 :            : {
      10                 :            :         struct pt_regs *regs;
      11                 :            : 
      12                 :          0 :         if (!try_get_task_stack(target)) {
      13                 :            :                 /* Task has no stack, so the task isn't in a syscall. */
      14                 :          0 :                 memset(info, 0, sizeof(*info));
      15                 :          0 :                 info->data.nr = -1;
      16                 :          0 :                 return 0;
      17                 :            :         }
      18                 :            : 
      19                 :          0 :         regs = task_pt_regs(target);
      20                 :          0 :         if (unlikely(!regs)) {
      21                 :            :                 put_task_stack(target);
      22                 :            :                 return -EAGAIN;
      23                 :            :         }
      24                 :            : 
      25                 :          0 :         info->sp = user_stack_pointer(regs);
      26                 :          0 :         info->data.instruction_pointer = instruction_pointer(regs);
      27                 :            : 
      28                 :          0 :         info->data.nr = syscall_get_nr(target, regs);
      29                 :          0 :         if (info->data.nr != -1L)
      30                 :            :                 syscall_get_arguments(target, regs,
      31                 :            :                                       (unsigned long *)&info->data.args[0]);
      32                 :            : 
      33                 :            :         put_task_stack(target);
      34                 :            :         return 0;
      35                 :            : }
      36                 :            : 
      37                 :            : /**
      38                 :            :  * task_current_syscall - Discover what a blocked task is doing.
      39                 :            :  * @target:             thread to examine
      40                 :            :  * @info:               structure with the following fields:
      41                 :            :  *                       .sp        - filled with user stack pointer
      42                 :            :  *                       .data.nr   - filled with system call number or -1
      43                 :            :  *                       .data.args - filled with @maxargs system call arguments
      44                 :            :  *                       .data.instruction_pointer - filled with user PC
      45                 :            :  *
      46                 :            :  * If @target is blocked in a system call, returns zero with @info.data.nr
      47                 :            :  * set to the the call's number and @info.data.args filled in with its
      48                 :            :  * arguments. Registers not used for system call arguments may not be available
      49                 :            :  * and it is not kosher to use &struct user_regset calls while the system
      50                 :            :  * call is still in progress.  Note we may get this result if @target
      51                 :            :  * has finished its system call but not yet returned to user mode, such
      52                 :            :  * as when it's stopped for signal handling or syscall exit tracing.
      53                 :            :  *
      54                 :            :  * If @target is blocked in the kernel during a fault or exception,
      55                 :            :  * returns zero with *@info.data.nr set to -1 and does not fill in
      56                 :            :  * @info.data.args. If so, it's now safe to examine @target using
      57                 :            :  * &struct user_regset get() calls as long as we're sure @target won't return
      58                 :            :  * to user mode.
      59                 :            :  *
      60                 :            :  * Returns -%EAGAIN if @target does not remain blocked.
      61                 :            :  */
      62                 :          0 : int task_current_syscall(struct task_struct *target, struct syscall_info *info)
      63                 :            : {
      64                 :            :         long state;
      65                 :            :         unsigned long ncsw;
      66                 :            : 
      67                 :          0 :         if (target == current)
      68                 :          0 :                 return collect_syscall(target, info);
      69                 :            : 
      70                 :          0 :         state = target->state;
      71                 :          0 :         if (unlikely(!state))
      72                 :            :                 return -EAGAIN;
      73                 :            : 
      74                 :          0 :         ncsw = wait_task_inactive(target, state);
      75                 :          0 :         if (unlikely(!ncsw) ||
      76                 :          0 :             unlikely(collect_syscall(target, info)) ||
      77                 :          0 :             unlikely(wait_task_inactive(target, state) != ncsw))
      78                 :            :                 return -EAGAIN;
      79                 :            : 
      80                 :            :         return 0;
      81                 :            : }