task_current_syscall(9) [suse man page]

TASK_CURRENT_SYSCALL(9) 					   Machine State					   TASK_CURRENT_SYSCALL(9)

NAME

       task_current_syscall - Discover what a blocked task is doing.

SYNOPSIS

       int task_current_syscall(struct task_struct * target, long * callno, unsigned long args[6], unsigned int maxargs, unsigned long * sp,
				unsigned long * pc);

ARGUMENTS

       target
	   thread to examine

       callno
	   filled with system call number or -1

       args[6]
	   filled with maxargs system call arguments

       maxargs
	   number of elements in args to fill

       sp
	   filled with user stack pointer

       pc
	   filled with user PC

DESCRIPTION

       If target is blocked in a system call, returns zero with *callno set to the the call's number and args filled in with its arguments.
       Registers not used for system call arguments may not be available and it is not kosher to use struct user_regset calls while the system
       call is still in progress. Note we may get this result if target has finished its system call but not yet returned to user mode, such as
       when it's stopped for signal handling or syscall exit tracing.

       If target is blocked in the kernel during a fault or exception, returns zero with *callno set to -1 and does not fill in args. If so, it's
       now safe to examine target using struct user_regset get calls as long as we're sure target won't return to user mode.

       Returns -EAGAIN if target does not remain blocked.

       Returns -EINVAL if maxargs is too large (maximum is six).

Kernel Hackers Manual 2.6.					     July 2010						   TASK_CURRENT_SYSCALL(9)

UTRACE_PREPARE_EXAMI(9) 					  utrace core API					   UTRACE_PREPARE_EXAMI(9)

NAME

       utrace_prepare_examine - prepare to examine thread state

SYNOPSIS

       int utrace_prepare_examine(struct task_struct * target, struct utrace_engine * engine, struct utrace_examiner * exam);

ARGUMENTS

       target
	   thread of interest, a struct task_struct pointer

       engine
	   engine pointer returned by utrace_attach_task

       exam
	   temporary state, a struct utrace_examiner pointer

DESCRIPTION

       This call prepares to safely examine the thread target using struct user_regset calls, or direct access to thread-synchronous fields.

       When target is current, this call is superfluous. When target is another thread, it must held stopped via UTRACE_STOP by engine.

       This call may block the caller until target stays stopped, so it must be called only after the caller is sure target is about to
       unschedule. This means a zero return from a utrace_control call on engine giving UTRACE_STOP, or a report_quiesce or report_signal callback
       to engine that used UTRACE_STOP in its return value.

       Returns -ESRCH if target is dead or -EINVAL if UTRACE_STOP was not used. If target has started running again despite UTRACE_STOP (for
       SIGKILL or a spurious wakeup), this call returns -EAGAIN.

       When this call returns zero, it's safe to use struct user_regset calls and task_user_regset_view on target and to examine some of its
       fields directly. When the examination is complete, a utrace_finish_examine call must follow to check whether it was completed safely.

Kernel Hackers Manual 2.6.					     July 2010						   UTRACE_PREPARE_EXAMI(9)