| Roland McGrath | bbc6986 | 2008-07-25 19:45:59 -0700 | [diff] [blame] | 1 | #include <linux/ptrace.h> |
| 2 | #include <linux/sched.h> |
| 3 | #include <linux/module.h> |
| 4 | #include <asm/syscall.h> |
| 5 | |
| 6 | static 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 | */ |
| 50 | int 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 | } |
| 75 | EXPORT_SYMBOL_GPL(task_current_syscall); |