1 #include <linux/ptrace.h> 2 #include <linux/sched.h> 3 #include <linux/sched/task_stack.h> 4 #include <linux/export.h> 5 #include <asm/syscall.h> 6 7 static int collect_syscall(struct task_struct *target, long *callno, 8 unsigned long args[6], unsigned int maxargs, 9 unsigned long *sp, unsigned long *pc) 10 { 11 struct pt_regs *regs; 12 13 if (!try_get_task_stack(target)) { 14 /* Task has no stack, so the task isn't in a syscall. */ 15 *sp = *pc = 0; 16 *callno = -1; 17 return 0; 18 } 19 20 regs = task_pt_regs(target); 21 if (unlikely(!regs)) { 22 put_task_stack(target); 23 return -EAGAIN; 24 } 25 26 *sp = user_stack_pointer(regs); 27 *pc = instruction_pointer(regs); 28 29 *callno = syscall_get_nr(target, regs); 30 if (*callno != -1L && maxargs > 0) 31 syscall_get_arguments(target, regs, 0, maxargs, args); 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 * @callno: filled with system call number or -1 41 * @args: filled with @maxargs system call arguments 42 * @maxargs: number of elements in @args to fill 43 * @sp: filled with user stack pointer 44 * @pc: filled with user PC 45 * 46 * If @target is blocked in a system call, returns zero with *@callno 47 * set to the the call's number and @args filled in with its arguments. 48 * Registers not used for system call arguments may not be available and 49 * 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 *@callno set to -1 and does not fill in @args. 56 * If so, it's now safe to examine @target using &struct user_regset 57 * get() calls as long as we're sure @target won't return to user mode. 58 * 59 * Returns -%EAGAIN if @target does not remain blocked. 60 * 61 * Returns -%EINVAL if @maxargs is too large (maximum is six). 62 */ 63 int task_current_syscall(struct task_struct *target, long *callno, 64 unsigned long args[6], unsigned int maxargs, 65 unsigned long *sp, unsigned long *pc) 66 { 67 long state; 68 unsigned long ncsw; 69 70 if (unlikely(maxargs > 6)) 71 return -EINVAL; 72 73 if (target == current) 74 return collect_syscall(target, callno, args, maxargs, sp, pc); 75 76 state = target->state; 77 if (unlikely(!state)) 78 return -EAGAIN; 79 80 ncsw = wait_task_inactive(target, state); 81 if (unlikely(!ncsw) || 82 unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) || 83 unlikely(wait_task_inactive(target, state) != ncsw)) 84 return -EAGAIN; 85 86 return 0; 87 } 88