linux-kernel - WIP generic module->debug_flags and dynamic

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Date:   Wed, 10 Jun 2020 12:32:42 -0600
From:   jim.cromie@...il.com
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Joe Perches <joe@...ches.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Baron <jbaron@...mai.com>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: WIP generic module->debug_flags and dynamic_debug

so Ive got a WIP / broken / partial approach to giving all modules a
u32 flagset,
and enabling pr_debug based upon it.  I leave out the "pr_debug_typed(
bitpos )" for now.  For Stanimir, bits 1,2,3 could be high, middle,
low.

ATM its broken on my lack of container_of() skills.

Im trying to use it to get a struct module* using its name value thats
been copied
into a ddebug_table member.

Im relying on
cdf6d006968  dynamic_debug: don't duplicate modname in ddebug_add_module
to have the same value in both structs

but Im clearly missing a few things
besides the likely future trouble with .rodata builtin modules
(after compile prob solved)

It seems container_of wants me to use struct ddebug_table instead,
but I dont want a *ddebug_table.
Ive blindly guessed at adding & and * to 1st param, w/o understanding.

can anyone diagnose my problem ?


[jimc@...do build-virtme]$ git diff
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index a5d76f8f6b40..2bfd1aa083b3 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -20,6 +20,7 @@ struct _ddebug {
        const char *function;
        const char *filename;
        const char *format;
+       u32 reqd_flags; /*misleading name todo, probly should hold
just a single type-bit */
        unsigned int lineno:18;
        /*
         * The flags field controls the behaviour at the callsite.
diff --git a/include/linux/module.h b/include/linux/module.h
index 1ad393e62bef..06eeef438fd3 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -429,6 +429,7 @@ struct module {
        struct mod_arch_specific arch;

        unsigned long taints;   /* same bits as kernel:taint_flags */
+       u32 debugflags;

 #ifdef CONFIG_GENERIC_BUG
        /* Support for BUG */
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 63ae6f77a0e4..965ee96630b5 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -202,6 +202,20 @@ static int ddebug_change(const struct ddebug_query *query,
                        if ((~dp->flags & filter->mask) != filter->mask)
                                continue;

+                       /* screen on module->debugflags */
+                       if (query->module) {
+                               /* dt->modname is known == module->name */
+                               struct module *m =
+                                       container_of((&(dt->mod_name)),
+                                                    struct module, name);
+                               if (m->debugflags &&
+                                   ((m->debugflags & dp->reqd_flags)
+                                    != dp->reqd_flags))
+                                       continue;
+                               vpr_info("%s module-debugflags: 0x%x\n",
+                                        dt->mod_name, dp->reqd_flags);
+                       }
+
                        nfound++;

                        newflags = (dp->flags & mods->mask) | mods->flags;
(END)