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; 11 12 if (!try_get_task_stack(target)) { 13 /* Task has no stack, so the task isn't in a syscall. */ 14 *callno = -1; 15 return 0; 16 } 17 18 regs = task_pt_regs(target); 19 if (unlikely(!regs)) { 20 put_task_stack(target); 21 return -EAGAIN; 22 } 23 24 *sp = user_stack_pointer(regs); 25 *pc = instruction_pointer(regs); 26 27 *callno = syscall_get_nr(target, regs); 28 if (*callno != -1L && maxargs > 0) 29 syscall_get_arguments(target, regs, 0, maxargs, args); 30 31 put_task_stack(target); 32 return 0; 33 } 34 35 /** 36 * task_current_syscall - Discover what a blocked task is doing. 37 * @target: thread to examine 38 * @callno: filled with system call number or -1 39 * @args: filled with @maxargs system call arguments 40 * @maxargs: number of elements in @args to fill 41 * @sp: filled with user stack pointer 42 * @pc: filled with user PC 43 * 44 * If @target is blocked in a system call, returns zero with *@callno 45 * set to the the call's number and @args filled in with its arguments. 46 * Registers not used for system call arguments may not be available and 47 * it is not kosher to use &struct user_regset calls while the system 48 * call is still in progress. Note we may get this result if @target 49 * has finished its system call but not yet returned to user mode, such 50 * as when it's stopped for signal handling or syscall exit tracing. 51 * 52 * If @target is blocked in the kernel during a fault or exception, 53 * returns zero with *@callno set to -1 and does not fill in @args. 54 * If so, it's now safe to examine @target using &struct user_regset 55 * get() calls as long as we're sure @target won't return to user mode. 56 * 57 * Returns -%EAGAIN if @target does not remain blocked. 58 * 59 * Returns -%EINVAL if @maxargs is too large (maximum is six). 60 */ 61 int task_current_syscall(struct task_struct *target, long *callno, 62 unsigned long args[6], unsigned int maxargs, 63 unsigned long *sp, unsigned long *pc) 64 { 65 long state; 66 unsigned long ncsw; 67 68 if (unlikely(maxargs > 6)) 69 return -EINVAL; 70 71 if (target == current) 72 return collect_syscall(target, callno, args, maxargs, sp, pc); 73 74 state = target->state; 75 if (unlikely(!state)) 76 return -EAGAIN; 77 78 ncsw = wait_task_inactive(target, state); 79 if (unlikely(!ncsw) || 80 unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) || 81 unlikely(wait_task_inactive(target, state) != ncsw)) 82 return -EAGAIN; 83 84 return 0; 85 } 86