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kunit/fortify: Expand testing of __compiletime_strlen()

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It seems that Clang thinks __builtin_constant_p() of undefined variables
should return true[1]. This is being fixed separately[2], but in the
meantime, expand the fortify tests to help track this kind of thing down
faster in the future.

Link: https://github.com/ClangBuiltLinux/linux/issues/2073 [1]
Link: https://github.com/llvm/llvm-project/pull/130713 [2]
Link: https://lore.kernel.org/r/20250312000349.work.786-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Kees Cook 2025-03-11 17:03:56 -07:00
parent d985e4399a
commit 416cf1f4d9
1 changed files with 17 additions and 0 deletions
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17
lib/tests/fortify_kunit.c
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@ -60,6 +60,7 @@ static int fortify_write_overflows;
static const char array_of_10[] = "this is 10";
static const char *ptr_of_11 = "this is 11!";
static const char * const unchanging_12 = "this is 12!!";
static char array_unknown[] = "compiler thinks I might change";
void fortify_add_kunit_error(int write)
@ -83,12 +84,28 @@ void fortify_add_kunit_error(int write)
static void fortify_test_known_sizes(struct kunit *test)
{
char stack[80] = "Test!";
KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(stack)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(stack), 5);
KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen("88888888")));
KUNIT_EXPECT_EQ(test, __compiletime_strlen("88888888"), 8);
KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen(array_of_10)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_of_10), 10);
KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(ptr_of_11)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(ptr_of_11), 11);
KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen(unchanging_12)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(unchanging_12), 12);
KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(array_unknown)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_unknown), SIZE_MAX);
/* Externally defined and dynamically sized string pointer: */
KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(test->name)));
KUNIT_EXPECT_EQ(test, __compiletime_strlen(test->name), SIZE_MAX);
}