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, long *callno,
 9			   unsigned long args[6], unsigned int maxargs,
10			   unsigned long *sp, unsigned long *pc)
11{
12	struct pt_regs *regs;
13
14	if (!try_get_task_stack(target)) {
15		/* Task has no stack, so the task isn't in a syscall. */
16		*sp = *pc = 0;
17		*callno = -1;
18		return 0;
19	}
20
21	regs = task_pt_regs(target);
22	if (unlikely(!regs)) {
23		put_task_stack(target);
24		return -EAGAIN;
25	}
26
27	*sp = user_stack_pointer(regs);
28	*pc = instruction_pointer(regs);
29
30	*callno = syscall_get_nr(target, regs);
31	if (*callno != -1L && maxargs > 0)
32		syscall_get_arguments(target, regs, 0, maxargs, args);
33
34	put_task_stack(target);
35	return 0;
36}
37
38/**
39 * task_current_syscall - Discover what a blocked task is doing.
40 * @target:		thread to examine
41 * @callno:		filled with system call number or -1
42 * @args:		filled with @maxargs system call arguments
43 * @maxargs:		number of elements in @args to fill
44 * @sp:			filled with user stack pointer
45 * @pc:			filled with user PC
46 *
47 * If @target is blocked in a system call, returns zero with *@callno
48 * set to the the call's number and @args filled in with its arguments.
49 * Registers not used for system call arguments may not be available and
50 * it is not kosher to use &struct user_regset calls while the system
51 * call is still in progress.  Note we may get this result if @target
52 * has finished its system call but not yet returned to user mode, such
53 * as when it's stopped for signal handling or syscall exit tracing.
54 *
55 * If @target is blocked in the kernel during a fault or exception,
56 * returns zero with *@callno set to -1 and does not fill in @args.
57 * If so, it's now safe to examine @target using &struct user_regset
58 * get() calls as long as we're sure @target won't return to user mode.
59 *
60 * Returns -%EAGAIN if @target does not remain blocked.
61 *
62 * Returns -%EINVAL if @maxargs is too large (maximum is six).
63 */
64int task_current_syscall(struct task_struct *target, long *callno,
65			 unsigned long args[6], unsigned int maxargs,
66			 unsigned long *sp, unsigned long *pc)
67{
68	long state;
69	unsigned long ncsw;
70
71	if (unlikely(maxargs > 6))
72		return -EINVAL;
73
74	if (target == current)
75		return collect_syscall(target, callno, args, maxargs, sp, pc);
76
77	state = target->state;
78	if (unlikely(!state))
79		return -EAGAIN;
80
81	ncsw = wait_task_inactive(target, state);
82	if (unlikely(!ncsw) ||
83	    unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
84	    unlikely(wait_task_inactive(target, state) != ncsw))
85		return -EAGAIN;
86
87	return 0;
88}