linux-kernel - [PATCH] kunit: Fix kunit_kstrdup

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Message-ID: <20240806020136.3481593-1-davidgow@google.com>
Date: Tue,  6 Aug 2024 10:01:34 +0800
From: David Gow <davidgow@...gle.com>
To: Brendan Higgins <brendan.higgins@...ux.dev>, Rae Moar <rmoar@...gle.com>, 
	Shuah Khan <skhan@...uxfoundation.org>, Kees Cook <kees@...nel.org>, 
	Maxime Ripard <mripard@...nel.org>, Nico Pache <npache@...hat.com>
Cc: David Gow <davidgow@...gle.com>, Stephen Rothwell <sfr@...b.auug.org.au>, 
	kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] kunit: Fix kunit_kstrdup_const() with modules

In commit 7d3c33b290b1 ("kunit: Device wrappers should also manage driver name"),
the kunit_kstrdup_const() and kunit_kfree_const() were introduced as an
optimisation of kunit_kstrdup(), which only copy/free strings from the
kernel rodata.

However, these are inline functions, and is_kernel_rodata() only works
for built-in code. This causes problems in two cases:
- If kunit is built as a module, __{start,end}_rodata is not defined.
- If a kunit test using these functions is built as a module, it will
  suffer the same fate.

Restrict the is_kernel_rodata() case to when KUnit is built as a module,
which fixes the first case, at the cost of losing the optimisation.

Also, make kunit_{kstrdup,kfree}_const non-inline, so that other modules
using them will not accidentally depend on is_kernel_rodata(). If KUnit
is built-in, they'll benefit from the optimisation, if KUnit is not,
they won't, but the string will be properly duplicated.

(And fix a couple of typos in the doc comment, too.)

Reported-by: Nico Pache <npache@...hat.com>
Closes: https://lore.kernel.org/all/CAA1CXcDKht4vOL-acxrARbm6JhGna8_k8wjYJ-vHONink8aZ=w@mail.gmail.com/
Fixes: 7d3c33b290b1 ("kunit: Device wrappers should also manage driver name")
Signed-off-by: David Gow <davidgow@...gle.com>
---
 include/kunit/test.h | 16 +++-------------
 lib/kunit/test.c     | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h
index da9e84de14c0..5ac237c949a0 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -489,11 +489,7 @@ static inline void *kunit_kcalloc(struct kunit *test, size_t n, size_t size, gfp
  * Calls kunit_kfree() only if @x is not in .rodata section.
  * See kunit_kstrdup_const() for more information.
  */
-static inline void kunit_kfree_const(struct kunit *test, const void *x)
-{
-	if (!is_kernel_rodata((unsigned long)x))
-		kunit_kfree(test, x);
-}
+void kunit_kfree_const(struct kunit *test, const void *x);
 
 /**
  * kunit_kstrdup() - Duplicates a string into a test managed allocation.
@@ -527,16 +523,10 @@ static inline char *kunit_kstrdup(struct kunit *test, const char *str, gfp_t gfp
  * @gfp: flags passed to underlying kmalloc().
  *
  * Calls kunit_kstrdup() only if @str is not in the rodata section. Must be freed with
- * kunit_free_const() -- not kunit_free().
+ * kunit_kfree_const() -- not kunit_kfree().
  * See kstrdup_const() and kunit_kmalloc_array() for more information.
  */
-static inline const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp)
-{
-	if (is_kernel_rodata((unsigned long)str))
-		return str;
-
-	return kunit_kstrdup(test, str, gfp);
-}
+const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp);
 
 /**
  * kunit_vm_mmap() - Allocate KUnit-tracked vm_mmap() area
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index e8b1b52a19ab..089c832e3cdb 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -874,6 +874,25 @@ void kunit_kfree(struct kunit *test, const void *ptr)
 }
 EXPORT_SYMBOL_GPL(kunit_kfree);
 
+void kunit_kfree_const(struct kunit *test, const void *x)
+{
+#if !IS_MODULE(CONFIG_KUNIT)
+	if (!is_kernel_rodata((unsigned long)x))
+#endif
+		kunit_kfree(test, x);
+}
+EXPORT_SYMBOL_GPL(kunit_kfree_const);
+
+const char *kunit_kstrdup_const(struct kunit *test, const char *str, gfp_t gfp)
+{
+#if !IS_MODULE(CONFIG_KUNIT)
+	if (is_kernel_rodata((unsigned long)str))
+		return str;
+#endif
+	return kunit_kstrdup(test, str, gfp);
+}
+EXPORT_SYMBOL_GPL(kunit_kstrdup_const);
+
 void kunit_cleanup(struct kunit *test)
 {
 	struct kunit_resource *res;
-- 
2.46.0.rc2.264.g509ed76dc8-goog