]>
Commit | Line | Data |
---|---|---|
bbc69863 RM |
1 | #include <linux/ptrace.h> |
2 | #include <linux/sched.h> | |
68db0cf1 | 3 | #include <linux/sched/task_stack.h> |
8bc3bcc9 | 4 | #include <linux/export.h> |
bbc69863 RM |
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 | { | |
aa1f1a63 AL |
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); | |
bbc69863 | 22 | return -EAGAIN; |
aa1f1a63 | 23 | } |
bbc69863 RM |
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 | ||
aa1f1a63 | 32 | put_task_stack(target); |
bbc69863 RM |
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 | } |