syscall_get_return_value(9) [suse man page]

SYSCALL_GET_RETURN_V(9) 					   Machine State					   SYSCALL_GET_RETURN_V(9)

NAME

       syscall_get_return_value - get the return value of a traced system call

SYNOPSIS

       long syscall_get_return_value(struct task_struct * task, struct pt_regs * regs);

ARGUMENTS

       task
	   task of interest, must be blocked

       regs

	   task_pt_regs of task

DESCRIPTION

       Returns the return value of the successful system call. This value is meaningless if syscall_get_error returned nonzero.

       It's only valid to call this when task is stopped for tracing on exit from a system call, due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT.

Kernel Hackers Manual 2.6.					     July 2010						   SYSCALL_GET_RETURN_V(9)

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)