blob: a72cd0996230b152acf33e4767059cfc3e77742f
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 | *sp = *pc = 0; |
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 |