Date: Mon, 31 May 1999 16:33:15 -0700 (PDT) From: aron@cs.rice.edu To: freebsd-gnats-submit@freebsd.org Subject: kern/11968: kldload should call module entry point before initializing kernel data structures Message-ID: <19990531233315.BE40E14CE6@hub.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 11968 >Category: kern >Synopsis: kldload should call module entry point before initializing kernel data structures >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Mon May 31 16:40:01 PDT 1999 >Closed-Date: >Last-Modified: >Originator: Mohit Aron >Release: FreeBSD-3.2-RELEASE >Organization: Rice University >Environment: FreeBSD luzern.cs.rice.edu 3.2-RELEASE FreeBSD 3.2-RELEASE #2: Fri May 28 15:22:48 CDT 1999 aron@luzern.cs.rice.edu:/usr/src/sys/compile/LUZERN i386 >Description: It seems that kldload calls the entry point in the module only after the kernel data structures pertaining to the module have been initialized. For example, if the module defines a new system call, the entry point is called only after the name of the system call and its arguments have been definined in the kernel. This deviates from modload which used to call the entry point before doing such initializations. With the lkm interface, I used to have a boilerplate code for the module that used to call module specific initialization function to get the number of arguments for the syscall. Currently there's no way to do this with the kld interface and the arguments and name of the syscall has to be defined statically using the SYSCALL_MODULE(). Changing these later in the code for the module entry point has no effect. If the kld interface were to initialze the kernel structures after calling the module entry point, it'll become possible for dynamically specifying the number of arguments and name of the system call. The above is more a matter of good taste in software engineering and so I'm putting the problem under the non-critical category with low priority. >How-To-Repeat: Try increasing the number of arguments to the syscall defined in /usr/share/examples/kld/syscall/module/syscall.c in the module entry point function - load(). This can be done by setting hello_sysent.sy_narg to an appropriate value. Within the actual system call, try printing the arguments. When you load this module and the user application makes the system call with some arguments, all that the actual system call code gets is junk. This is because the kernel already thinks that the system call needs no arguments (because the number of arguments were 0 when SYSCALL_MODULE() was defined). >Fix: The module entry point should be called before the kernel data structures are initialized to reflect the name and number of arguments of the system call being defined. >Release-Note: >Audit-Trail: >Unformatted: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19990531233315.BE40E14CE6>