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	unsigned long args[6] = { };
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		memset(info, 0, sizeof(*info));
16		info->data.nr = -1;
17		return 0;
18	}
19
20	regs = task_pt_regs(target);
21	if (unlikely(!regs)) {
22		put_task_stack(target);
23		return -EAGAIN;
24	}
25
26	info->sp = user_stack_pointer(regs);
27	info->data.instruction_pointer = instruction_pointer(regs);
28
29	info->data.nr = syscall_get_nr(target, regs);
30	if (info->data.nr != -1L)
31		syscall_get_arguments(target, regs, args);
32
33	info->data.args[0] = args[0];
34	info->data.args[1] = args[1];
35	info->data.args[2] = args[2];
36	info->data.args[3] = args[3];
37	info->data.args[4] = args[4];
38	info->data.args[5] = args[5];
39
40	put_task_stack(target);
41	return 0;
42}
43
44/**
45 * task_current_syscall - Discover what a blocked task is doing.
46 * @target:		thread to examine
47 * @info:		structure with the following fields:
48 *			 .sp        - filled with user stack pointer
49 *			 .data.nr   - filled with system call number or -1
50 *			 .data.args - filled with @maxargs system call arguments
51 *			 .data.instruction_pointer - filled with user PC
52 *
53 * If @target is blocked in a system call, returns zero with @info.data.nr
54 * set to the call's number and @info.data.args filled in with its
55 * arguments. Registers not used for system call arguments may not be available
56 * and it is not kosher to use &struct user_regset calls while the system
57 * call is still in progress.  Note we may get this result if @target
58 * has finished its system call but not yet returned to user mode, such
59 * as when it's stopped for signal handling or syscall exit tracing.
60 *
61 * If @target is blocked in the kernel during a fault or exception,
62 * returns zero with *@info.data.nr set to -1 and does not fill in
63 * @info.data.args. If so, it's now safe to examine @target using
64 * &struct user_regset get() calls as long as we're sure @target won't return
65 * to user mode.
66 *
67 * Returns -%EAGAIN if @target does not remain blocked.
 
 
68 */
69int task_current_syscall(struct task_struct *target, struct syscall_info *info)
 
 
70{
 
71	unsigned long ncsw;
72	unsigned int state;
 
 
73
74	if (target == current)
75		return collect_syscall(target, info);
76
77	state = READ_ONCE(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, info)) ||
84	    unlikely(wait_task_inactive(target, state) != ncsw))
85		return -EAGAIN;
86
87	return 0;
88}

 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}