linux-kernel - [PATCH v2 02/20] test-dyndbg: show that DEBUG enables prdbgs at compiletime

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Message-Id: <20230113193016.749791-3-jim.cromie@gmail.com>
Date:   Fri, 13 Jan 2023 12:29:58 -0700
From:   Jim Cromie <jim.cromie@...il.com>
To:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org
Cc:     jani.nikula@...el.com, ville.syrjala@...ux.intel.com,
        daniel.vetter@...ll.ch, seanpaul@...omium.org, robdclark@...il.com,
        jbaron@...mai.com, gregkh@...uxfoundation.org,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v2 02/20] test-dyndbg: show that DEBUG enables prdbgs at compiletime

Dyndbg is required to enable prdbgs at compile-time if DEBUG is
defined.  Show this works; add the defn to test_dynamic_debug.c,
and manually inspect/verify its effect at module load:

[   15.292810] dyndbg: module:test_dynamic_debug attached 4 classes
[   15.293189] dyndbg:  32 debug prints in module test_dynamic_debug
[   15.293715] test_dd: init start
[   15.293716] test_dd: doing categories
[   15.293716] test_dd: LOW msg
...
[   15.293733] test_dd: L6 msg
[   15.293733] test_dd: L7 msg
[   15.293733] test_dd: init done

NOTES:

As is observable above, define DEBUG enables all prdbgs, including
those in mod_init-fn, and more notably, the class'd ones (callsites
with non-default class_ids).

This differs from the >control interface, which in order to properly
protect a client's class'd prdbgs, requires a "class FOO" in queries
to change them.  If this sounds wrong, note that the DEBUG is in the
module source file, and is thus privileged.

This yields an occaisional surprise; the following disables all the
compile-time enabled plain prdbgs, but leaves the class'd ones
enabled.

 :#> modprobe test_dynamic_debug dyndbg==_

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 lib/test_dynamic_debug.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index a01f0193a419..89dd7f285e31 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -8,6 +8,8 @@

 #define pr_fmt(fmt) "test_dd: " fmt

+#define DEBUG /* enable all prdbgs (plain & class'd) at compiletime */
+
 #include <linux/module.h>

 /* run tests by reading or writing sysfs node: do_prints */
-- 
2.39.0