1 #include <linux/ptrace.h> 2 #include <linux/sched.h> 3 #include <linux/module.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); 76