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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
bbc69863 RM |
2 | #include <linux/ptrace.h> |
3 | #include <linux/sched.h> | |
68db0cf1 | 4 | #include <linux/sched/task_stack.h> |
8bc3bcc9 | 5 | #include <linux/export.h> |
bbc69863 RM |
6 | #include <asm/syscall.h> |
7 | ||
631b7aba | 8 | static int collect_syscall(struct task_struct *target, struct syscall_info *info) |
bbc69863 | 9 | { |
aa1f1a63 AL |
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. */ | |
631b7aba SRRH |
14 | memset(info, 0, sizeof(*info)); |
15 | info->data.nr = -1; | |
aa1f1a63 AL |
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 | 24 | |
631b7aba SRRH |
25 | info->sp = user_stack_pointer(regs); |
26 | info->data.instruction_pointer = instruction_pointer(regs); | |
bbc69863 | 27 | |
631b7aba SRRH |
28 | info->data.nr = syscall_get_nr(target, regs); |
29 | if (info->data.nr != -1L) | |
b35f549d | 30 | syscall_get_arguments(target, regs, |
631b7aba | 31 | (unsigned long *)&info->data.args[0]); |
bbc69863 | 32 | |
aa1f1a63 | 33 | put_task_stack(target); |
bbc69863 RM |
34 | return 0; |
35 | } | |
36 | ||
37 | /** | |
38 | * task_current_syscall - Discover what a blocked task is doing. | |
39 | * @target: thread to examine | |
631b7aba SRRH |
40 | * @info: structure with the following fields: |
41 | * .sp - filled with user stack pointer | |
42 | * .data.nr - filled with system call number or -1 | |
43 | * .data.args - filled with @maxargs system call arguments | |
44 | * .data.instruction_pointer - filled with user PC | |
bbc69863 | 45 | * |
631b7aba SRRH |
46 | * If @target is blocked in a system call, returns zero with @info.data.nr |
47 | * set to the the call's number and @info.data.args filled in with its | |
48 | * arguments. Registers not used for system call arguments may not be available | |
49 | * and it is not kosher to use &struct user_regset calls while the system | |
bbc69863 RM |
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, | |
631b7aba SRRH |
55 | * returns zero with *@info.data.nr set to -1 and does not fill in |
56 | * @info.data.args. If so, it's now safe to examine @target using | |
57 | * &struct user_regset get() calls as long as we're sure @target won't return | |
58 | * to user mode. | |
bbc69863 RM |
59 | * |
60 | * Returns -%EAGAIN if @target does not remain blocked. | |
bbc69863 | 61 | */ |
631b7aba | 62 | int task_current_syscall(struct task_struct *target, struct syscall_info *info) |
bbc69863 RM |
63 | { |
64 | long state; | |
65 | unsigned long ncsw; | |
66 | ||
bbc69863 | 67 | if (target == current) |
631b7aba | 68 | return collect_syscall(target, info); |
bbc69863 RM |
69 | |
70 | state = target->state; | |
71 | if (unlikely(!state)) | |
72 | return -EAGAIN; | |
73 | ||
74 | ncsw = wait_task_inactive(target, state); | |
75 | if (unlikely(!ncsw) || | |
631b7aba | 76 | unlikely(collect_syscall(target, info)) || |
bbc69863 RM |
77 | unlikely(wait_task_inactive(target, state) != ncsw)) |
78 | return -EAGAIN; | |
79 | ||
80 | return 0; | |
81 | } |