Re: Modularizing net80211 (was: link_set info needed)

[Paul Goyette <paul%whooppee.com@localhost>]

On Fri, 27 Apr 2012, Joerg Sonnenberger wrote:

> On Fri, Apr 27, 2012 at 06:34:40AM -0700, Paul Goyette wrote:
> > On Fri, 27 Apr 2012, Joerg Sonnenberger wrote:
> >
> > > On Fri, Apr 27, 2012 at 05:51:30AM -0700, Paul Goyette wrote:
> > > > 3. Replacing the use of link_set with direct calls to all of the
> > > >   crypto/auth initializers.
> > >
> > > I believe this to a noticable regression due to bugs in the module
> > > framework. It should support either link sets or _init sections.
> > > If the latter is supposed to be the way forward, current linkset usage
> > > should be adjusted and an appropiate place in the kernel for calling all
> > > static initializers be found.
> >
> > Thanks for the feedback.  I am not familiar with the "_init
> > sections" stuff - can you provide a reference or example?
>
> That's effectively how __attribute__((constructor)) or the corrsponding
> C++ functionality is implemented. The necessary clue in userland is
> crt*.o, would wouldn't be that hard to adopt for kernel usage.

I took a look at this, at it seems to be fairly straight-forward to 
allow constructors/destructors in modules.  The attached patch will 
invoke a module's constructors immediately before the xxx_modcmd(INIT) 
call, and the destructors will be called immediately after the 
xxx_modcmd(FINI).

This mechanism only works for modules that are "separate" from the 
kernel (loaded via "boot" or from "filesys").  "builtin" modules still 
need to use the link_set mechanism.



-------------------------------------------------------------------------
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:       |
| Customer Service | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com    |
| Network Engineer | 0786 F758 55DE 53BA 7731 | pgoyette at juniper.net |
| Kernel Developer |                          | pgoyette at netbsd.org  |
-------------------------------------------------------------------------

Index: kern_module.c
===================================================================
RCS file: /cvsroot/src/sys/kern/kern_module.c,v
retrieving revision 1.86
diff -u -p -r1.86 kern_module.c
--- kern_module.c       4 Dec 2011 19:24:59 -0000       1.86
+++ kern_module.c       28 Apr 2012 14:20:56 -0000
@@ -98,6 +98,8 @@ static void   module_enqueue(module_t *);
 
 static bool    module_merge_dicts(prop_dictionary_t, const prop_dictionary_t);
 
+static void    module_do_tors(const char *, module_t *);
+
 static void    sysctl_module_setup(void);
 
 /*
@@ -1055,6 +1057,11 @@ module_do_load(const char *name, bool is
                        goto fail;
                }
        }
+       /*
+        * If module has constructors, call them now
+        */
+       module_do_tors(".ctors", mod);
+
        prev_active = module_active;
        module_active = mod;
        error = (*mi->mi_modcmd)(MODULE_CMD_INIT, filedict ? filedict : props);
@@ -1145,6 +1152,11 @@ module_do_unload(const char *name, bool 
                    error);
                return error;
        }
+       /*
+        * If module has destructors, call them
+        */
+       module_do_tors(".dtors", mod);
+
        module_count--;
        TAILQ_REMOVE(&module_list, mod, mod_chain);
        for (i = 0; i < mod->mod_nrequired; i++) {
@@ -1431,3 +1443,26 @@ out:
 
        return !error;
 }
+
+/*
+ * Call the list of contructors/destructors, if any
+ */
+
+typedef void (*tor_func_t)(void);
+
+static void
+module_do_tors(const char *section, module_t *mod)
+{
+       tor_func_t f, *s_addr;
+       size_t s_size;
+
+       if (kobj_find_section(mod->mod_kobj, section, (void **)&s_addr, &s_size)
+                   != 0)
+               return;
+       KASSERT(s_size % sizeof(f) == 0);
+       while (s_size > 0) {
+               f = *(s_addr++);
+               s_size -= sizeof(f);
+               (*f)();
+       }
+}