[PATCH v3 20/54] dyndbg: check DYNAMIC_DEBUG_CLASSMAP_DEFINE args at compile-time

[jim.cromie at gmail.com]

On Tue, Apr 15, 2025 at 4:04 AM Louis Chauvet <louis.chauvet at bootlin.com> wrote:
>
>
>
> Le 02/04/2025 à 19:41, Jim Cromie a écrit :
> > Add __DYNAMIC_DEBUG_CLASSMAP_CHECK to implement the following
> > arg-checks at compile-time:
> >
> >       0 <= _base < 63
> >       class_names is not empty
> >       class_names[0] is a string
>
> I don't see where this is checked, did I miss something?

kinda/sorta ?   theres no explicit check for "string".
BUT
this would fail, cuz 1 doesnt fit into a char* arr[0]
> > +DYNDBG_CLASSMAP_DEFINE(fail_str_type, 0, 0, 1 /* not a string */);

Im perhaps over-simplifying the description

>
> >       (class_names.length + _base) < 63
> >
> > These compile-time checks will prevent several misuses; 4 such
> > examples are added to test_dynamic_debug_submod.ko, and will fail
> > compilation if -DDD_MACRO_ARGCHECK is added to cflags.  This wouldn't
> > be a useful CONFIG_ item, since it breaks the build.
> >
> > Signed-off-by: Jim Cromie <jim.cromie at gmail.com>
> > ---
> > v3- $macro_name =~ s/DYNDBG/DYNAMIC_DEBUG/
> >
> > prev-
> > - split static-asserts to __DYNDBG_CLASSMAP_CHECK
> > - move __DYNDBG_CLASSMAP_CHECK above kdoc for DYNDBG_CLASSMAP_DEFINE
> >    silences kernel-doc warnings
> > ---
> >   include/linux/dynamic_debug.h |  9 +++++++++
> >   lib/test_dynamic_debug.c      | 11 +++++++++++
> >   2 files changed, 20 insertions(+)
> >
> > diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> > index 9af825c84e70..4941ef2adb46 100644
> > --- a/include/linux/dynamic_debug.h
> > +++ b/include/linux/dynamic_debug.h
> > @@ -99,6 +99,14 @@ struct _ddebug_class_map {
> >       enum ddebug_class_map_type map_type;
> >   };
> >
> > +#define __DYNAMIC_DEBUG_CLASSMAP_CHECK(_clnames, _base)                      \
> > +     static_assert(((_base) >= 0 && (_base) < _DPRINTK_CLASS_DFLT),  \
> > +                   "_base must be in 0..62");                        \
> > +     static_assert(ARRAY_SIZE(_clnames) > 0,                         \
> > +                   "classnames array size must be > 0");             \
> > +     static_assert((ARRAY_SIZE(_clnames) + (_base)) < _DPRINTK_CLASS_DFLT, \
> > +                   "_base + classnames.length exceeds range")
> > +
> >   /**
> >    * DYNAMIC_DEBUG_CLASSMAP_DEFINE - define debug classes used by a module.
> >    * @_var:   name of the classmap, exported for other modules coordinated use.
> > @@ -112,6 +120,7 @@ struct _ddebug_class_map {
> >    */
> >   #define DYNAMIC_DEBUG_CLASSMAP_DEFINE(_var, _mapty, _base, ...)             \
> >       static const char *_var##_classnames[] = { __VA_ARGS__ };       \
>
> Or maybe it was already enforced by this, but in this case the commit
> message contains too much checks.
>
> > +     __DYNAMIC_DEBUG_CLASSMAP_CHECK(_var##_classnames, (_base));     \
> >       extern struct _ddebug_class_map _var;                           \
> >       struct _ddebug_class_map __aligned(8) __used                    \
> >               __section("__dyndbg_class_maps") _var = {               \
> > diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
> > index e42916b08fd4..9f9e3fddd7e6 100644
> > --- a/lib/test_dynamic_debug.c
> > +++ b/lib/test_dynamic_debug.c
> > @@ -146,8 +146,19 @@ DYNDBG_CLASSMAP_DEFINE(classid_range_conflict, 0, D2_CORE + 1, "D3_CORE");
> >   DYNAMIC_DEBUG_CLASSMAP_USE(map_disjoint_bits);
> >   DYNAMIC_DEBUG_CLASSMAP_USE(map_level_num);
> >
> > +#if defined(DD_MACRO_ARGCHECK)
> > +/*
> > + * Exersize compile-time arg-checks in DYNDBG_CLASSMAP_DEFINE.
> > + * These will break compilation.
> > + */
> > +DYNDBG_CLASSMAP_DEFINE(fail_base_neg, 0, -1, "NEGATIVE_BASE_ARG");
> > +DYNDBG_CLASSMAP_DEFINE(fail_base_big, 0, 100, "TOOBIG_BASE_ARG");
> > +DYNDBG_CLASSMAP_DEFINE(fail_str_type, 0, 0, 1 /* not a string */);
> > +DYNDBG_CLASSMAP_DEFINE(fail_emptyclass, 0, 0 /* ,empty */);
> >   #endif
> >
> > +#endif /* TEST_DYNAMIC_DEBUG_SUBMOD */
> > +
> >   /* stand-in for all pr_debug etc */
> >   #define prdbg(SYM) __pr_debug_cls(SYM, #SYM " msg\n")
> >
>
> --
> Louis Chauvet, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>
>