INDIR(2) System Calls Manual INDIR(2)
indir - indirect system call
(indir = 0.)
sys indir; call
The system call at the location call is executed. Execution resumes
after the indir call.
The main purpose of indir is to allow a program to store arguments in
system calls and execute them out of line in the data segment. This
preserves the purity of the text segment.
If indir is executed indirectly, it is a no-op. If the instruction at
the indirect location is not a system call, indir returns error code
EINVAL; see intro(2).