[PATCH] kunit: memcpy: Split slow memcpy tests into MEMCPY_SLOW_KUNIT_TEST

[Kees Cook <keescook@chromium.org>]

Since the long memcpy tests may stall a system for tens of seconds
in virtualized architecture environments, split those tests off under
CONFIG_MEMCPY_SLOW_KUNIT_TEST so they can be separately disabled.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/lkml/20221226195206.GA2626419@roeck-us.net
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-and-tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: David Gow <davidgow@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v2: fix tristate to bool
v1: https://lore.kernel.org/lkml/20230107040203.never.112-kees@kernel.org
---
 lib/Kconfig.debug  |  9 +++++++++
 lib/memcpy_kunit.c | 15 ++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c2c78d0e761c..f90637171453 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2621,6 +2621,15 @@ config MEMCPY_KUNIT_TEST
 
 	  If unsure, say N.
 
+config MEMCPY_SLOW_KUNIT_TEST
+	bool "Include exhaustive memcpy tests" if !KUNIT_ALL_TESTS
+	depends on MEMCPY_KUNIT_TEST
+	default KUNIT_ALL_TESTS
+	help
+	  Some memcpy tests are quite exhaustive in checking for overlaps
+	  and bit ranges. These can be very slow, so they are split out
+	  as a separate config.
+
 config IS_SIGNED_TYPE_KUNIT_TEST
 	tristate "Test is_signed_type() macro" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c
index 89128551448d..5a545e1b5dbb 100644
--- a/lib/memcpy_kunit.c
+++ b/lib/memcpy_kunit.c
@@ -307,8 +307,12 @@ static void set_random_nonzero(struct kunit *test, u8 *byte)
 	}
 }
 
-static void init_large(struct kunit *test)
+static int init_large(struct kunit *test)
 {
+	if (!IS_ENABLED(CONFIG_MEMCPY_SLOW_KUNIT_TEST)) {
+		kunit_skip(test, "Slow test skipped. Enable with CONFIG_MEMCPY_SLOW_KUNIT_TEST=y");
+		return -EBUSY;
+	}
 
 	/* Get many bit patterns. */
 	get_random_bytes(large_src, ARRAY_SIZE(large_src));
@@ -319,6 +323,8 @@ static void init_large(struct kunit *test)
 
 	/* Explicitly zero the entire destination. */
 	memset(large_dst, 0, ARRAY_SIZE(large_dst));
+
+	return 0;
 }
 
 /*
@@ -327,7 +333,9 @@ static void init_large(struct kunit *test)
  */
 static void copy_large_test(struct kunit *test, bool use_memmove)
 {
-	init_large(test);
+
+	if (init_large(test))
+		return;
 
 	/* Copy a growing number of non-overlapping bytes ... */
 	for (int bytes = 1; bytes <= ARRAY_SIZE(large_src); bytes++) {
@@ -472,7 +480,8 @@ static void memmove_overlap_test(struct kunit *test)
 	static const int bytes_start = 1;
 	static const int bytes_end = ARRAY_SIZE(large_src) + 1;
 
-	init_large(test);
+	if (init_large(test))
+		return;
 
 	/* Copy a growing number of overlapping bytes ... */
 	for (int bytes = bytes_start; bytes < bytes_end;
-- 
2.34.1