Branch data     Line data    Source code

       1                 :            : #include <linux/ptrace.h>
       2                 :            : #include <linux/sched.h>
       3                 :            : #include <linux/export.h>
       4                 :            : #include <asm/syscall.h>
       5                 :            : 
       6                 :          0 : static int collect_syscall(struct task_struct *target, long *callno,
       7                 :            :                            unsigned long args[6], unsigned int maxargs,
       8                 :            :                            unsigned long *sp, unsigned long *pc)
       9                 :            : {
      10                 :         12 :         struct pt_regs *regs = task_pt_regs(target);
      11         [ +  - ]:          6 :         if (unlikely(!regs))
      12                 :            :                 return -EAGAIN;
      13                 :            : 
      14                 :          6 :         *sp = user_stack_pointer(regs);
      15                 :          6 :         *pc = instruction_pointer(regs);
      16                 :            : 
      17                 :          6 :         *callno = syscall_get_nr(target, regs);
      18 [ +  - ][ +  - ]:          6 :         if (*callno != -1L && maxargs > 0)
      19                 :            :                 syscall_get_arguments(target, regs, 0, maxargs, args);
      20                 :            : 
      21                 :            :         return 0;
      22                 :            : }
      23                 :            : 
      24                 :            : /**
      25                 :            :  * task_current_syscall - Discover what a blocked task is doing.
      26                 :            :  * @target:             thread to examine
      27                 :            :  * @callno:             filled with system call number or -1
      28                 :            :  * @args:               filled with @maxargs system call arguments
      29                 :            :  * @maxargs:            number of elements in @args to fill
      30                 :            :  * @sp:                 filled with user stack pointer
      31                 :            :  * @pc:                 filled with user PC
      32                 :            :  *
      33                 :            :  * If @target is blocked in a system call, returns zero with *@callno
      34                 :            :  * set to the the call's number and @args filled in with its arguments.
      35                 :            :  * Registers not used for system call arguments may not be available and
      36                 :            :  * it is not kosher to use &struct user_regset calls while the system
      37                 :            :  * call is still in progress.  Note we may get this result if @target
      38                 :            :  * has finished its system call but not yet returned to user mode, such
      39                 :            :  * as when it's stopped for signal handling or syscall exit tracing.
      40                 :            :  *
      41                 :            :  * If @target is blocked in the kernel during a fault or exception,
      42                 :            :  * returns zero with *@callno set to -1 and does not fill in @args.
      43                 :            :  * If so, it's now safe to examine @target using &struct user_regset
      44                 :            :  * get() calls as long as we're sure @target won't return to user mode.
      45                 :            :  *
      46                 :            :  * Returns -%EAGAIN if @target does not remain blocked.
      47                 :            :  *
      48                 :            :  * Returns -%EINVAL if @maxargs is too large (maximum is six).
      49                 :            :  */
      50                 :          0 : int task_current_syscall(struct task_struct *target, long *callno,
      51                 :            :                          unsigned long args[6], unsigned int maxargs,
      52                 :            :                          unsigned long *sp, unsigned long *pc)
      53                 :            : {
      54                 :            :         long state;
      55                 :            :         unsigned long ncsw;
      56                 :            : 
      57         [ +  - ]:          6 :         if (unlikely(maxargs > 6))
      58                 :            :                 return -EINVAL;
      59                 :            : 
      60         [ +  - ]:          6 :         if (target == current)
      61                 :          6 :                 return collect_syscall(target, callno, args, maxargs, sp, pc);
      62                 :            : 
      63                 :          0 :         state = target->state;
      64         [ #  # ]:          0 :         if (unlikely(!state))
      65                 :            :                 return -EAGAIN;
      66                 :            : 
      67                 :          0 :         ncsw = wait_task_inactive(target, state);
      68   [ #  #  #  # ]:          0 :         if (unlikely(!ncsw) ||
      69         [ #  # ]:          0 :             unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
      70                 :          0 :             unlikely(wait_task_inactive(target, state) != ncsw))
      71                 :            :                 return -EAGAIN;
      72                 :            : 
      73                 :            :         return 0;
      74                 :            : }
      75                 :            : EXPORT_SYMBOL_GPL(task_current_syscall);