lib/random32: convert selftest to KUnit

Convert the existing prandom selftest (lib/random32.c) to use the KUnit
framework (lib/tests/random32_kunit.c).  Unlike typical KUnit tests, this
file is directly #included into lib/random32.c.

The new test:
- Removes the legacy CONFIG_RANDOM32_SELFTEST from lib/random32.c.
- Adds CONFIG_PRANDOM_KUNIT_TEST (defaulting to KUNIT_ALL_TESTS).
- Moves the test logic to lib/tests/random32_kunit.c.

This commit is verified by `./tools/testing/kunit/kunit.py run`
with the .kunit/.kunitconfig:

CONFIG_KUNIT=y
CONFIG_PRANDOM_KUNIT_TEST=y

Link: https://lore.kernel.org/20260630030447.77522-1-note351@hotmail.com
Signed-off-by: Kir Chou <note351@hotmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 10 insertions, 174 deletions

diff --git a/lib/random32.c b/lib/random32.c
index 24e7acd9343f..dad90219c351 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -41,6 +41,7 @@
 #include <linux/bitops.h>
 #include <linux/slab.h>
 #include <linux/unaligned.h>
+#include <kunit/visibility.h>
 
 /**
  *	prandom_u32_state - seeded pseudo-random number generator.
@@ -92,7 +93,14 @@ void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
 }
 EXPORT_SYMBOL(prandom_bytes_state);
 
-static void prandom_warmup(struct rnd_state *state)
+/*
+ * Only declared here so that it has a prototype when made
+ * non-static for KUnit testing (avoids -Wmissing-prototypes).
+ */
+#if IS_ENABLED(CONFIG_KUNIT)
+void prandom_warmup(struct rnd_state *state);
+#endif
+VISIBLE_IF_KUNIT void prandom_warmup(struct rnd_state *state)
 {
 	/* Calling RNG ten times to satisfy recurrence condition */
 	prandom_u32_state(state);
@@ -106,6 +114,7 @@ static void prandom_warmup(struct rnd_state *state)
 	prandom_u32_state(state);
 	prandom_u32_state(state);
 }
+EXPORT_SYMBOL_IF_KUNIT(prandom_warmup);
 
 void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
 {
@@ -125,176 +134,3 @@ void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
 	}
 }
 EXPORT_SYMBOL(prandom_seed_full_state);
-
-#ifdef CONFIG_RANDOM32_SELFTEST
-static struct prandom_test1 {
-	u32 seed;
-	u32 result;
-} test1[] = {
-	{ 1U, 3484351685U },
-	{ 2U, 2623130059U },
-	{ 3U, 3125133893U },
-	{ 4U,  984847254U },
-};
-
-static struct prandom_test2 {
-	u32 seed;
-	u32 iteration;
-	u32 result;
-} test2[] = {
-	/* Test cases against taus113 from GSL library. */
-	{  931557656U, 959U, 2975593782U },
-	{ 1339693295U, 876U, 3887776532U },
-	{ 1545556285U, 961U, 1615538833U },
-	{  601730776U, 723U, 1776162651U },
-	{ 1027516047U, 687U,  511983079U },
-	{  416526298U, 700U,  916156552U },
-	{ 1395522032U, 652U, 2222063676U },
-	{  366221443U, 617U, 2992857763U },
-	{ 1539836965U, 714U, 3783265725U },
-	{  556206671U, 994U,  799626459U },
-	{  684907218U, 799U,  367789491U },
-	{ 2121230701U, 931U, 2115467001U },
-	{ 1668516451U, 644U, 3620590685U },
-	{  768046066U, 883U, 2034077390U },
-	{ 1989159136U, 833U, 1195767305U },
-	{  536585145U, 996U, 3577259204U },
-	{ 1008129373U, 642U, 1478080776U },
-	{ 1740775604U, 939U, 1264980372U },
-	{ 1967883163U, 508U,   10734624U },
-	{ 1923019697U, 730U, 3821419629U },
-	{  442079932U, 560U, 3440032343U },
-	{ 1961302714U, 845U,  841962572U },
-	{ 2030205964U, 962U, 1325144227U },
-	{ 1160407529U, 507U,  240940858U },
-	{  635482502U, 779U, 4200489746U },
-	{ 1252788931U, 699U,  867195434U },
-	{ 1961817131U, 719U,  668237657U },
-	{ 1071468216U, 983U,  917876630U },
-	{ 1281848367U, 932U, 1003100039U },
-	{  582537119U, 780U, 1127273778U },
-	{ 1973672777U, 853U, 1071368872U },
-	{ 1896756996U, 762U, 1127851055U },
-	{  847917054U, 500U, 1717499075U },
-	{ 1240520510U, 951U, 2849576657U },
-	{ 1685071682U, 567U, 1961810396U },
-	{ 1516232129U, 557U,    3173877U },
-	{ 1208118903U, 612U, 1613145022U },
-	{ 1817269927U, 693U, 4279122573U },
-	{ 1510091701U, 717U,  638191229U },
-	{  365916850U, 807U,  600424314U },
-	{  399324359U, 702U, 1803598116U },
-	{ 1318480274U, 779U, 2074237022U },
-	{  697758115U, 840U, 1483639402U },
-	{ 1696507773U, 840U,  577415447U },
-	{ 2081979121U, 981U, 3041486449U },
-	{  955646687U, 742U, 3846494357U },
-	{ 1250683506U, 749U,  836419859U },
-	{  595003102U, 534U,  366794109U },
-	{   47485338U, 558U, 3521120834U },
-	{  619433479U, 610U, 3991783875U },
-	{  704096520U, 518U, 4139493852U },
-	{ 1712224984U, 606U, 2393312003U },
-	{ 1318233152U, 922U, 3880361134U },
-	{  855572992U, 761U, 1472974787U },
-	{   64721421U, 703U,  683860550U },
-	{  678931758U, 840U,  380616043U },
-	{  692711973U, 778U, 1382361947U },
-	{  677703619U, 530U, 2826914161U },
-	{   92393223U, 586U, 1522128471U },
-	{ 1222592920U, 743U, 3466726667U },
-	{  358288986U, 695U, 1091956998U },
-	{ 1935056945U, 958U,  514864477U },
-	{  735675993U, 990U, 1294239989U },
-	{ 1560089402U, 897U, 2238551287U },
-	{   70616361U, 829U,   22483098U },
-	{  368234700U, 731U, 2913875084U },
-	{   20221190U, 879U, 1564152970U },
-	{  539444654U, 682U, 1835141259U },
-	{ 1314987297U, 840U, 1801114136U },
-	{ 2019295544U, 645U, 3286438930U },
-	{  469023838U, 716U, 1637918202U },
-	{ 1843754496U, 653U, 2562092152U },
-	{  400672036U, 809U, 4264212785U },
-	{  404722249U, 965U, 2704116999U },
-	{  600702209U, 758U,  584979986U },
-	{  519953954U, 667U, 2574436237U },
-	{ 1658071126U, 694U, 2214569490U },
-	{  420480037U, 749U, 3430010866U },
-	{  690103647U, 969U, 3700758083U },
-	{ 1029424799U, 937U, 3787746841U },
-	{ 2012608669U, 506U, 3362628973U },
-	{ 1535432887U, 998U,   42610943U },
-	{ 1330635533U, 857U, 3040806504U },
-	{ 1223800550U, 539U, 3954229517U },
-	{ 1322411537U, 680U, 3223250324U },
-	{ 1877847898U, 945U, 2915147143U },
-	{ 1646356099U, 874U,  965988280U },
-	{  805687536U, 744U, 4032277920U },
-	{ 1948093210U, 633U, 1346597684U },
-	{  392609744U, 783U, 1636083295U },
-	{  690241304U, 770U, 1201031298U },
-	{ 1360302965U, 696U, 1665394461U },
-	{ 1220090946U, 780U, 1316922812U },
-	{  447092251U, 500U, 3438743375U },
-	{ 1613868791U, 592U,  828546883U },
-	{  523430951U, 548U, 2552392304U },
-	{  726692899U, 810U, 1656872867U },
-	{ 1364340021U, 836U, 3710513486U },
-	{ 1986257729U, 931U,  935013962U },
-	{  407983964U, 921U,  728767059U },
-};
-
-static void prandom_state_selftest_seed(struct rnd_state *state, u32 seed)
-{
-#define LCG(x)	 ((x) * 69069U)	/* super-duper LCG */
-	state->s1 = __seed(LCG(seed),        2U);
-	state->s2 = __seed(LCG(state->s1),   8U);
-	state->s3 = __seed(LCG(state->s2),  16U);
-	state->s4 = __seed(LCG(state->s3), 128U);
-}
-
-static int __init prandom_state_selftest(void)
-{
-	int i, j, errors = 0, runs = 0;
-	bool error = false;
-
-	for (i = 0; i < ARRAY_SIZE(test1); i++) {
-		struct rnd_state state;
-
-		prandom_state_selftest_seed(&state, test1[i].seed);
-		prandom_warmup(&state);
-
-		if (test1[i].result != prandom_u32_state(&state))
-			error = true;
-	}
-
-	if (error)
-		pr_warn("prandom: seed boundary self test failed\n");
-	else
-		pr_info("prandom: seed boundary self test passed\n");
-
-	for (i = 0; i < ARRAY_SIZE(test2); i++) {
-		struct rnd_state state;
-
-		prandom_state_selftest_seed(&state, test2[i].seed);
-		prandom_warmup(&state);
-
-		for (j = 0; j < test2[i].iteration - 1; j++)
-			prandom_u32_state(&state);
-
-		if (test2[i].result != prandom_u32_state(&state))
-			errors++;
-
-		runs++;
-		cond_resched();
-	}
-
-	if (errors)
-		pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
-	else
-		pr_info("prandom: %d self tests passed\n", runs);
-	return 0;
-}
-core_initcall(prandom_state_selftest);
-#endif