Re: Implementing hooks

morganat_private

Greg KH wrote:
> But your macro to pass arbitrary data across it will loose type
> safety.  How can you do:
>         SECURITY_HOOK_RETURN_ERROR(retval,basic_ops,ioperm,(foo, bar),"ioperm...")
> and keep the knowledge that the ioperm parameters foo and bar are of a
> specific type?  That's all I care about, type safety.

This is ok. The PAM code has

    D(("this %s that, whatever", "stuff")); 

all over. Where D(x) is conditionally compiled as

   printf x;

or a nop, depending on the #ifdef DEBUG condition.

> If you can, do this, then I totally agree with you.  My knowledge of the
> gcc preprocessor isn't sufficient to figure out how to do this.

In the case of the above macro, something like this (yes, I tested it!)
should be fine:

=========

#define SECURITY_HOOK_RETURN_ERROR(ret,major,minor,args,description) \
    do { \
       ret = security_module->major->minor args ; \
       if (ret) \
           return ret; \
    } while (0)

struct minor_sec_mod_s {
    int (*ioperm)(int INT, char *CONST_CHAR_P);
};

struct sec_mod_s {
    struct minor_sec_mod_s *basic_ops;
} *security_module;

main()
{
    int foo, retval;
    const char *bar;

    SECURITY_HOOK_RETURN_ERROR(retval,basic_ops,ioperm,(foo,
bar),"ioperm...");
}

=========

[Note, be happy that the clash of the 'const char *' and the 'char *'
shows up when you try to compile this - demonstrating that type checking
is alive and well. (No, don't try to run this at home ;) ]

Cheers

Andrew

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