1#include <linux/ptrace.h>
 2#include <linux/sched.h>
 
 3#include <linux/export.h>
 4#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{
10	struct pt_regs *regs = task_pt_regs(target);
11	if (unlikely(!regs))
 
 
 
 
 
 
 
 
 
 
12		return -EAGAIN;
 
13
14	*sp = user_stack_pointer(regs);
15	*pc = instruction_pointer(regs);
16
17	*callno = syscall_get_nr(target, regs);
18	if (*callno != -1L && maxargs > 0)
19		syscall_get_arguments(target, regs, 0, maxargs, args);
 
20
 
21	return 0;
22}
23
24/**
25 * task_current_syscall - Discover what a blocked task is doing.
26 * @target:		thread to examine
27 * @callno:		filled with system call number or -1
28 * @args:		filled with @maxargs system call arguments
29 * @maxargs:		number of elements in @args to fill
30 * @sp:			filled with user stack pointer
31 * @pc:			filled with user PC
32 *
33 * If @target is blocked in a system call, returns zero with *@callno
34 * set to the the call's number and @args filled in with its arguments.
35 * Registers not used for system call arguments may not be available and
36 * it is not kosher to use &struct user_regset calls while the system
37 * call is still in progress.  Note we may get this result if @target
38 * has finished its system call but not yet returned to user mode, such
39 * as when it's stopped for signal handling or syscall exit tracing.
40 *
41 * If @target is blocked in the kernel during a fault or exception,
42 * returns zero with *@callno set to -1 and does not fill in @args.
43 * If so, it's now safe to examine @target using &struct user_regset
44 * get() calls as long as we're sure @target won't return to user mode.
 
45 *
46 * Returns -%EAGAIN if @target does not remain blocked.
47 *
48 * Returns -%EINVAL if @maxargs is too large (maximum is six).
49 */
50int task_current_syscall(struct task_struct *target, long *callno,
51			 unsigned long args[6], unsigned int maxargs,
52			 unsigned long *sp, unsigned long *pc)
53{
54	long state;
55	unsigned long ncsw;
56
57	if (unlikely(maxargs > 6))
58		return -EINVAL;
59
60	if (target == current)
61		return collect_syscall(target, callno, args, maxargs, sp, pc);
62
63	state = target->state;
64	if (unlikely(!state))
65		return -EAGAIN;
66
67	ncsw = wait_task_inactive(target, state);
68	if (unlikely(!ncsw) ||
69	    unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
70	    unlikely(wait_task_inactive(target, state) != ncsw))
71		return -EAGAIN;
72
73	return 0;
74}

 1// SPDX-License-Identifier: GPL-2.0
 2#include <linux/ptrace.h>
 3#include <linux/sched.h>
 4#include <linux/sched/task_stack.h>
 5#include <linux/export.h>
 6#include <asm/syscall.h>
 7
 8static int collect_syscall(struct task_struct *target, struct syscall_info *info)
 
 
 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		memset(info, 0, sizeof(*info));
15		info->data.nr = -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	info->sp = user_stack_pointer(regs);
26	info->data.instruction_pointer = instruction_pointer(regs);
27
28	info->data.nr = syscall_get_nr(target, regs);
29	if (info->data.nr != -1L)
30		syscall_get_arguments(target, regs,
31				      (unsigned long *)&info->data.args[0]);
32
33	put_task_stack(target);
34	return 0;
35}
36
37/**
38 * task_current_syscall - Discover what a blocked task is doing.
39 * @target:		thread to examine
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
45 *
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
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,
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.
59 *
60 * Returns -%EAGAIN if @target does not remain blocked.
 
 
61 */
62int task_current_syscall(struct task_struct *target, struct syscall_info *info)
 
 
63{
64	long state;
65	unsigned long ncsw;
66
 
 
 
67	if (target == current)
68		return collect_syscall(target, info);
69
70	state = target->state;
71	if (unlikely(!state))
72		return -EAGAIN;
73
74	ncsw = wait_task_inactive(target, state);
75	if (unlikely(!ncsw) ||
76	    unlikely(collect_syscall(target, info)) ||
77	    unlikely(wait_task_inactive(target, state) != ncsw))
78		return -EAGAIN;
79
80	return 0;
81}