blob: a72cd0996230b152acf33e4767059cfc3e77742f [file] [log] [blame]
Roland McGrathbbc69862008-07-25 19:45:59 -07001#include <linux/ptrace.h>
2#include <linux/sched.h>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -05003#include <linux/export.h>
Roland McGrathbbc69862008-07-25 19:45:59 -07004#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{
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070010 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. */
Kees Cook673dfb62017-03-23 15:46:16 -070014 *sp = *pc = 0;
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070015 *callno = -1;
16 return 0;
17 }
18
19 regs = task_pt_regs(target);
20 if (unlikely(!regs)) {
21 put_task_stack(target);
Roland McGrathbbc69862008-07-25 19:45:59 -070022 return -EAGAIN;
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070023 }
Roland McGrathbbc69862008-07-25 19:45:59 -070024
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
Andy Lutomirskiaa1f1a62016-09-15 22:45:47 -070032 put_task_stack(target);
Roland McGrathbbc69862008-07-25 19:45:59 -070033 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}