[PATCH v13 27/36] dyndbg: check DYNAMIC_DEBUG_CLASSMAP_{DEFINE,USE_} args at compile-time

[Jim Cromie <jim.cromie@gmail.com>]

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
	(class_names.length + _base) < 63
	dd-map-type is known value

These compile-time checks will prevent several simple misuses, and
will issue obvious errors if violated.

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@gmail.com>
---
-v13

reword 2 failing tests (active only when -DDD_MACRO_ARGCHECK is
passed to cc) to better identify what error is being tested against

-v12

check map-type at compile-time

make base+len(classnames) check more explicit

dyndbg-test: add more tests of compile-time CHECKs

add 3 tests of static-asserts added to 2 macros:
DYNAMIC_DEBUG_CLASSMAP_{DEFINE,USE_}

_DEFINE():
1- validates maptype,
2- validate classmap.length + base-offset < 63
_USE_():
3- validate user-offset < 63

As before, these tests fail when activated:

make KCPPFLAGS="-DDD_MACRO_ARGCHECK" lib/test_dynamic_debug_submod.o

NOTE: _USE_() cannot test classmap.length, since its a property of
the referent, not the macro itself.

dyndbg-test: verify DYNAMIC_DEBUG_CLASSMAP_USE_() compile-time CHECK

Add another failing use-case, this time to verify that _USE properly
rejects an offset > 62.  This is an incomplete test; the proper test
is: classes.length + base + offset < 63, but the macro cannot test
classes.length at compile-time.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
 include/linux/dynamic_debug.h | 12 ++++++++++++
 lib/test_dynamic_debug.c      | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 71c91bc8d3a6..a1c75237abaa 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -181,6 +181,17 @@ struct _ddebug_class_param {
  * __pr_debug_cls(22, "no such class"); compiles but is not reachable
  */
 
+#define __DYNAMIC_DEBUG_CLASSMAP_CHECK(_clnames, _base, _mapty)		\
+	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 must be <= 62");	\
+	static_assert(((_mapty) >= DD_CLASS_TYPE_DISJOINT_BITS) &&	\
+		      ((_mapty) <= DD_CLASS_TYPE_LEVEL_NUM),		\
+		      "unknown class_map_type")
+
 /**
  * DYNAMIC_DEBUG_CLASSMAP_DEFINE - define debug classes used by a module.
  * @_var:   name of the classmap, exported for other modules coordinated use.
@@ -194,6 +205,7 @@ struct _ddebug_class_param {
  */
 #define DYNAMIC_DEBUG_CLASSMAP_DEFINE(_var, _mapty, _base, ...)		\
 	static const char *_var##_classnames[] = { __VA_ARGS__ };	\
+	__DYNAMIC_DEBUG_CLASSMAP_CHECK(_var##_classnames, (_base), (_mapty)); \
 	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 fc599bbe605e..2107d4821019 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -146,8 +146,23 @@ DYNAMIC_DEBUG_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 DYNAMIC_DEBUG_CLASSMAP_DEFINE.
+ * These will break compilation.
+ */
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_base_neg, 0, -1, "NEGATIVE_BASE_ARG");
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_base_big, 0, 100, "TOOBIG_BASE_ARG");
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_str_type, 0, 0, 1 /* not a string */);
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_emptyclass, 0, 0 /* ,empty */);
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_maptype, 3, 10, "no such type");
+DYNAMIC_DEBUG_CLASSMAP_DEFINE(fail_base_len, 0, 60,
+			      "base", "plus", "classes", "length", "too-big");
+DYNAMIC_DEBUG_CLASSMAP_USE_(fail_offset_big, 100);
 #endif
 
+#endif /* TEST_DYNAMIC_DEBUG_SUBMOD */
+
 /* stand-in for all pr_debug etc */
 #define prdbg(SYM) __pr_debug_cls(SYM, #SYM " msg\n")
 
-- 
2.53.0