syscall.c

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    1 #include <linux/ptrace.h>
    2 #include <linux/sched.h>
    3 #include <linux/export.h>
    4 #include <asm/syscall.h>
    5 
    6 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         struct pt_regs *regs = task_pt_regs(target);
   11         if (unlikely(!regs))
   12                 return -EAGAIN;
   13 
   14         *sp = user_stack_pointer(regs);
   15         *pc = instruction_pointer(regs);
   16 
   17         *callno = syscall_get_nr(target, regs);
   18         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 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         if (unlikely(maxargs > 6))
   58                 return -EINVAL;
   59 
   60         if (target == current)
   61                 return collect_syscall(target, callno, args, maxargs, sp, pc);
   62 
   63         state = target->state;
   64         if (unlikely(!state))
   65                 return -EAGAIN;
   66 
   67         ncsw = wait_task_inactive(target, state);
   68         if (unlikely(!ncsw) ||
   69             unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
   70             unlikely(wait_task_inactive(target, state) != ncsw))
   71                 return -EAGAIN;
   72 
   73         return 0;
   74 }
   75 EXPORT_SYMBOL_GPL(task_current_syscall);

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FreeBSD/Linux Kernel Cross Reference sys/lib/syscall.c

FreeBSD/Linux Kernel Cross Reference
sys/lib/syscall.c