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 *callno = -1; 16 return 0; 17 } 18 19 regs = task_pt_regs(target); 20 if (unlikely(!regs)) { 21 put_task_stack(target); 22 return -EAGAIN; 23 } 24 25 *sp = user_stack_pointer(regs); 26 *pc = instruction_pointer(regs); 27 28 *callno = syscall_get_nr(target, regs); 29 if (*callno != -1L && maxargs > 0) 30 syscall_get_arguments(target, regs, 0, maxargs, args); 31 32 put_task_stack(target); 33 return 0; 34 } 35 36 /** 37 * task_current_syscall - Discover what a blocked task is doing. 38 * @target: thread to examine 39 * @callno: filled with system call number or -1 40 * @args: filled with @maxargs system call arguments 41 * @maxargs: number of elements in @args to fill 42 * @sp: filled with user stack pointer 43 * @pc: filled with user PC 44 * 45 * If @target is blocked in a system call, returns zero with *@callno 46 * set to the the call's number and @args filled in with its arguments. 47 * Registers not used for system call arguments may not be available and 48 * it is not kosher to use &struct user_regset calls while the system 49 * call is still in progress. Note we may get this result if @target 50 * has finished its system call but not yet returned to user mode, such 51 * as when it's stopped for signal handling or syscall exit tracing. 52 * 53 * If @target is blocked in the kernel during a fault or exception, 54 * returns zero with *@callno set to -1 and does not fill in @args. 55 * If so, it's now safe to examine @target using &struct user_regset 56 * get() calls as long as we're sure @target won't return to user mode. 57 * 58 * Returns -%EAGAIN if @target does not remain blocked. 59 * 60 * Returns -%EINVAL if @maxargs is too large (maximum is six). 61 */ 62 int task_current_syscall(struct task_struct *target, long *callno, 63 unsigned long args[6], unsigned int maxargs, 64 unsigned long *sp, unsigned long *pc) 65 { 66 long state; 67 unsigned long ncsw; 68 69 if (unlikely(maxargs > 6)) 70 return -EINVAL; 71 72 if (target == current) 73 return collect_syscall(target, callno, args, maxargs, sp, pc); 74 75 state = target->state; 76 if (unlikely(!state)) 77 return -EAGAIN; 78 79 ncsw = wait_task_inactive(target, state); 80 if (unlikely(!ncsw) || 81 unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) || 82 unlikely(wait_task_inactive(target, state) != ncsw)) 83 return -EAGAIN; 84 85 return 0; 86 } 87