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#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}