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Message-Id: <20250405204530.186242-4-david.laight.linux@gmail.com>
Date: Sat, 5 Apr 2025 21:45:30 +0100
From: David Laight <david.laight.linux@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Cc: David Laight <david.laight.linux@...il.com>,
Uwe Kleine-König <u.kleine-koenig@...libre.com>,
Nicolas Pitre <npitre@...libre.com>,
Oleg Nesterov <oleg@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Biju Das <biju.das.jz@...renesas.com>
Subject: [PATCH 3/3] lib: Update the muldiv64 tests to verify the C on x86-64
div64.c contains a 128 by 64 division algorithm which x86-64 overrides
it with an asm implementation.
So running the muldiv64 tests only verifies the asm code.
Since x86-64 is the most likely test system compile the default
code into an x86-64 kernel (under a different name) when the tests
are being built.
Verify that both the asm and C functions generate the correct results.
Signed-off-by: David Laight <david.laight.linux@...il.com>
---
lib/math/div64.c | 18 ++++++++++++++++--
lib/math/test_mul_u64_u64_div_u64.c | 26 ++++++++++++++++++++------
2 files changed, 36 insertions(+), 8 deletions(-)
diff --git a/lib/math/div64.c b/lib/math/div64.c
index 50e025174495..38ee5c01c288 100644
--- a/lib/math/div64.c
+++ b/lib/math/div64.c
@@ -25,6 +25,8 @@
#include <linux/minmax.h>
#include <linux/log2.h>
+#include <generated/autoconf.h>
+
/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32
@@ -183,10 +185,22 @@ u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
}
EXPORT_SYMBOL(iter_div_u64_rem);
-#if !defined(mul_u64_add_u64_div_u64)
+/*
+ * If the architecture overrides the implementation below and the test module
+ * is being built then compile the default implementation with a different name
+ * so that it can be tested.
+ */
+#if defined(mul_u64_add_u64_div_u64) && (defined(CONFIG_TEST_MULDIV64) || defined(CONFIG_TEST_MULDIV64_MODULE))
+#define TEST_MULDIV64
+#undef mul_u64_add_u64_div_u64
+#define mul_u64_add_u64_div_u64 mul_u64_add_u64_div_u64_test
+u64 mul_u64_add_u64_div_u64_test(u64 a, u64 b, u64 c, u64 d);
+#endif
+
+#if !defined( mul_u64_add_u64_div_u64) || defined(TEST_MULDIV64)
u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d)
{
-#if defined(__SIZEOF_INT128__)
+#if defined(__SIZEOF_INT128__) && !defined(TEST_MULDIV64)
/* native 64x64=128 bits multiplication */
u128 prod = (u128)a * b + c;
diff --git a/lib/math/test_mul_u64_u64_div_u64.c b/lib/math/test_mul_u64_u64_div_u64.c
index 9548eb7458c7..e2289b412601 100644
--- a/lib/math/test_mul_u64_u64_div_u64.c
+++ b/lib/math/test_mul_u64_u64_div_u64.c
@@ -73,6 +73,10 @@ done
*/
+#ifdef mul_u64_add_u64_div_u64
+u64 mul_u64_add_u64_div_u64_test(u64 a, u64 b, u64 add, u64 c);
+#endif
+
static int __init test_init(void)
{
int errors = 0;
@@ -80,21 +84,31 @@ static int __init test_init(void)
pr_info("Starting mul_u64_u64_div_u64() test\n");
- for (i = 0; i < ARRAY_SIZE(test_values); i++) {
- u64 a = test_values[i].a;
- u64 b = test_values[i].b;
- u64 c = test_values[i].c;
- u64 expected_result = test_values[i].result;
+ for (i = 0; i < ARRAY_SIZE(test_values) * 2; i++) {
+ u64 a = test_values[i / 2].a;
+ u64 b = test_values[i / 2].b;
+ u64 c = test_values[i / 2].c;
+ u64 expected_result = test_values[i / 2].result;
u64 result = mul_u64_u64_div_u64(a, b, c);
u64 result_up = mul_u64_u64_div_u64_roundup(a, b, c);
+#ifdef mul_u64_add_u64_div_u64
+ if (i & 1) {
+ /* Verify the generic C version */
+ result = mul_u64_add_u64_div_u64_test(a, b, 0, c);
+ result_up = mul_u64_add_u64_div_u64_test(a, b, c - 1, c);
+ }
+#else
+ i++;
+#endif
+
if (result != expected_result) {
pr_err("ERROR: 0x%016llx * 0x%016llx / 0x%016llx\n", a, b, c);
pr_err("ERROR: expected result: %016llx\n", expected_result);
pr_err("ERROR: obtained result: %016llx\n", result);
errors++;
}
- expected_result += test_values[i].round_up;
+ expected_result += test_values[i / 2].round_up;
if (result_up != expected_result) {
pr_err("ERROR: 0x%016llx * 0x%016llx +/ 0x%016llx\n", a, b, c);
pr_err("ERROR: expected result: %016llx\n", expected_result);
--
2.39.5
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