suse man page for syscall_get_return_value

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)