Date: Wed, 24 Jan 2007 03:12:16 -0800 From: Luigi Rizzo <rizzo@icir.org> To: current@freebsd.org Subject: visibility of symbols defined in a kld module ? Message-ID: <20070124031216.A54472@xorpc.icir.org>
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I have the following problem while building a compat layer for compiling
linux drivers on FreeBSD:
a piece of code (let's restrict to a kld if it makes things simpler)
needs to register some information to the system calling a function:
usb_register(&some_data)
where some_data is a structure containing various info (callbacks etc)
for the code.
The problem is, i need to hook the argument of usb_register() to the kld.
If i write
/* in linux_module_header.h */
extern void *my_module_info;
#define usb_register(p) my_module_info = p
/* in linux_driver_stub.c, linked together with the rest of the code */
#include "linux_module_header.h"
void *my_module_info;
I get what i want, but then my_module_info is present in all modules
compiled with the same trick, so what happens when the modules are
kldloaded ? Does this symbol conflict (i.e. is this equivalent to RTLD_GLOBAL)
or each one sees its own symbols (i.e. like RTLD_LOCAL) ?
And besides, this would almost surely fail if i compile these things
not as modules but as part of the kernel.
The other trick i can think of is using some preprocessor-magic to
create unique names for the symbol, e.g. compile each kld with
-DDRIVER_NAME=pwc, -DDRIVER_NAME=gspca, -DDRIVER_NAME=dvb and then have
/* in linux_module_header.h */
#define MODINFO_NAME module_ ## DRIVER_NAME ## _info
extern void *MODINFO_NAME;
#define usb_register(p) MODINFO_NAME = p
/* in linux_driver_stub.c, linked together with the rest of the code */
#include "linux_module_header.h"
void *MODINFO_NAME;
This way each module has a different symbol and there are no conflict.
Other ideas ?
cheers
luigi
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