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;
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 */
62int 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}

 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}