blob: 63239e097b13a847fee8b5067d693cbbbf80a691 [file] [log] [blame]
Roland McGrathbbc69862008-07-25 19:45:59 -07001#include <linux/ptrace.h>
2#include <linux/sched.h>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -05003#include <linux/export.h>
Roland McGrathbbc69862008-07-25 19:45:59 -07004#include <asm/syscall.h>
5
6static 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{
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070010 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);
Roland McGrathbbc69862008-07-25 19:45:59 -070021 return -EAGAIN;
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070022 }
Roland McGrathbbc69862008-07-25 19:45:59 -070023
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
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070031 put_task_stack(target);
Roland McGrathbbc69862008-07-25 19:45:59 -070032 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 */
61int 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}