readme.alloc_syscall

来自「fsmlabs的real time linux的内核」· ALLOC_SYSCALL 代码 · 共 20 行

The concept shown here is what psc does to get a system call without needing
to patch the kernel source for psc - so this is simply all stolen from 
psc/psc.c .

This shows how to allocate a system call without requireing a patch to the 
kernel - and this should be more or less arch independant - what this does
is go down the syscall table from the top searching for a unused syscall 
number and then assigns the new syscall to that number - thats simply. The
problem is that the user-space app does not know that number and it would
not be too practical if we would need to recompile our apps all the time - so
we use a /proc file to pass the system call number we get to user-space apps
That is what syscall_check then does.

alloc_syscall.o: kernel module to allocate a free system call number int
                 the kernels system call table.

syscall_check: user-space application that grabs the syscall number from /proc
               and then invokes this system call.