Date: Wed, 24 Jan 2007 15:06:24 +0200 From: Danny Braniss <danny@cs.huji.ac.il> To: Luigi Rizzo <rizzo@icir.org> Cc: current@freebsd.org Subject: Re: visibility of symbols defined in a kld module ? Message-ID: <E1H9hpY-000NMl-Du@cs1.cs.huji.ac.il> In-Reply-To: <20070124031216.A54472@xorpc.icir.org> References: <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 ?
/* in linux_module_header.h */
#define LINUX_MODULE(name) \
static __inline usb_register(p)\
{\
extern void *module_##name##_info;\
module_##name##_info = p;\
}
#define LINUX_MODULE_DCL(name)\
LINUX_MODULE(name)\
void *module_##name##_info
/* in linux_driver_stub.c */
#include "linux_module_header.h"
LINUX_MODULE_DCL(pwc);
/* and in the rest of the code */
#include "linux_module_header.h"
LINUX_MODULE(pwc);
cheers,
danny
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