The quilt patch titled
Subject: mul_u64_u64_div_u64: basic sanity test
has been removed from the -mm tree. Its filename was
mul_u64_u64_div_u64-basic-sanity-test.patch
This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Nicolas Pitre <npitre@xxxxxxxxxxxx>
Subject: mul_u64_u64_div_u64: basic sanity test
Date: Sun, 7 Jul 2024 15:05:20 -0400
Verify that edge cases produce proper results, and some more.
[npitre@xxxxxxxxxxxx: avoid undefined shift value]
Link: https://lkml.kernel.org/r/7rrs9pn1-n266-3013-9q6n-1osp8r8s0rrn@xxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240707190648.1982714-3-nico@xxxxxxxxxxx
Signed-off-by: Nicolas Pitre <npitre@xxxxxxxxxxxx>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
Cc: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/Kconfig.debug | 10 ++
lib/math/Makefile | 1
lib/math/div64.c | 9 ++
lib/math/test_mul_u64_u64_div_u64.c | 99 ++++++++++++++++++++++++++
4 files changed, 118 insertions(+), 1 deletion(-)
--- a/lib/Kconfig.debug~mul_u64_u64_div_u64-basic-sanity-test
+++ a/lib/Kconfig.debug
@@ -2280,6 +2280,16 @@ config TEST_DIV64
If unsure, say N.
+config TEST_MULDIV64
+ tristate "mul_u64_u64_div_u64() test"
+ depends on DEBUG_KERNEL || m
+ help
+ Enable this to turn on 'mul_u64_u64_div_u64()' function test.
+ This test is executed only once during system boot (so affects
+ only boot time), or at module load time.
+
+ If unsure, say N.
+
config TEST_IOV_ITER
tristate "Test iov_iter operation" if !KUNIT_ALL_TESTS
depends on KUNIT
--- a/lib/math/div64.c~mul_u64_u64_div_u64-basic-sanity-test
+++ a/lib/math/div64.c
@@ -212,11 +212,18 @@ u64 mul_u64_u64_div_u64(u64 a, u64 b, u6
#endif
+ /* make sure c is not zero, trigger exception otherwise */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdiv-by-zero"
+ if (unlikely(c == 0))
+ return 1/0;
+#pragma GCC diagnostic pop
+
int shift = __builtin_ctzll(c);
/* try reducing the fraction in case the dividend becomes <= 64 bits */
if ((n_hi >> shift) == 0) {
- u64 n = (n_lo >> shift) | (n_hi << (64 - shift));
+ u64 n = shift ? (n_lo >> shift) | (n_hi << (64 - shift)) : n_lo;
return div64_u64(n, c >> shift);
/*
--- a/lib/math/Makefile~mul_u64_u64_div_u64-basic-sanity-test
+++ a/lib/math/Makefile
@@ -6,4 +6,5 @@ obj-$(CONFIG_PRIME_NUMBERS) += prime_num
obj-$(CONFIG_RATIONAL) += rational.o
obj-$(CONFIG_TEST_DIV64) += test_div64.o
+obj-$(CONFIG_TEST_MULDIV64) += test_mul_u64_u64_div_u64.o
obj-$(CONFIG_RATIONAL_KUNIT_TEST) += rational-test.o
diff --git a/lib/math/test_mul_u64_u64_div_u64.c a/lib/math/test_mul_u64_u64_div_u64.c
new file mode 100664
--- /dev/null
+++ a/lib/math/test_mul_u64_u64_div_u64.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 BayLibre SAS
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/math64.h>
+
+typedef struct { u64 a; u64 b; u64 c; u64 result; } test_params;
+
+static test_params test_values[] = {
+/* this contains many edge values followed by a couple random values */
+{ 0xb, 0x7, 0x3, 0x19 },
+{ 0xffff0000, 0xffff0000, 0xf, 0x1110eeef00000000 },
+{ 0xffffffff, 0xffffffff, 0x1, 0xfffffffe00000001 },
+{ 0xffffffff, 0xffffffff, 0x2, 0x7fffffff00000000 },
+{ 0x1ffffffff, 0xffffffff, 0x2, 0xfffffffe80000000 },
+{ 0x1ffffffff, 0xffffffff, 0x3, 0xaaaaaaa9aaaaaaab },
+{ 0x1ffffffff, 0x1ffffffff, 0x4, 0xffffffff00000000 },
+{ 0xffff000000000000, 0xffff000000000000, 0xffff000000000001, 0xfffeffffffffffff },
+{ 0x3333333333333333, 0x3333333333333333, 0x5555555555555555, 0x1eb851eb851eb851 },
+{ 0x7fffffffffffffff, 0x2, 0x3, 0x5555555555555554 },
+{ 0xffffffffffffffff, 0x2, 0x8000000000000000, 0x3 },
+{ 0xffffffffffffffff, 0x2, 0xc000000000000000, 0x2 },
+{ 0xffffffffffffffff, 0x4000000000000004, 0x8000000000000000, 0x8000000000000007 },
+{ 0xffffffffffffffff, 0x4000000000000001, 0x8000000000000000, 0x8000000000000001 },
+{ 0xffffffffffffffff, 0x8000000000000001, 0xffffffffffffffff, 0x8000000000000001 },
+{ 0xfffffffffffffffe, 0x8000000000000001, 0xffffffffffffffff, 0x8000000000000000 },
+{ 0xffffffffffffffff, 0x8000000000000001, 0xfffffffffffffffe, 0x8000000000000001 },
+{ 0xffffffffffffffff, 0x8000000000000001, 0xfffffffffffffffd, 0x8000000000000002 },
+{ 0x7fffffffffffffff, 0xffffffffffffffff, 0xc000000000000000, 0xaaaaaaaaaaaaaaa8 },
+{ 0xffffffffffffffff, 0x7fffffffffffffff, 0xa000000000000000, 0xccccccccccccccca },
+{ 0xffffffffffffffff, 0x7fffffffffffffff, 0x9000000000000000, 0xe38e38e38e38e38b },
+{ 0x7fffffffffffffff, 0x7fffffffffffffff, 0x5000000000000000, 0xccccccccccccccc9 },
+{ 0xffffffffffffffff, 0xfffffffffffffffe, 0xffffffffffffffff, 0xfffffffffffffffe },
+{ 0xe6102d256d7ea3ae, 0x70a77d0be4c31201, 0xd63ec35ab3220357, 0x78f8bf8cc86c6e18 },
+{ 0xf53bae05cb86c6e1, 0x3847b32d2f8d32e0, 0xcfd4f55a647f403c, 0x42687f79d8998d35 },
+{ 0x9951c5498f941092, 0x1f8c8bfdf287a251, 0xa3c8dc5f81ea3fe2, 0x1d887cb25900091f },
+{ 0x374fee9daa1bb2bb, 0x0d0bfbff7b8ae3ef, 0xc169337bd42d5179, 0x03bb2dbaffcbb961 },
+{ 0xeac0d03ac10eeaf0, 0x89be05dfa162ed9b, 0x92bb1679a41f0e4b, 0xdc5f5cc9e270d216 },
+};
+
+/*
+ * The above table can be verified with the following shell script:
+ *
+ * #!/bin/sh
+ * sed -ne 's/^{ \+\(.*\), \+\(.*\), \+\(.*\), \+\(.*\) },$/\1 \2 \3 \4/p' \
+ * lib/math/test_mul_u64_u64_div_u64.c |
+ * while read a b c r; do
+ * expected=$( printf "obase=16; ibase=16; %X * %X / %X\n" $a $b $c | bc )
+ * given=$( printf "%X\n" $r )
+ * if [ "$expected" = "$given" ]; then
+ * echo "$a * $b / $c = $r OK"
+ * else
+ * echo "$a * $b / $c = $r is wrong" >&2
+ * echo "should be equivalent to 0x$expected" >&2
+ * exit 1
+ * fi
+ * done
+ */
+
+static int __init test_init(void)
+{
+ int i;
+
+ 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;
+ u64 result = mul_u64_u64_div_u64(a, b, c);
+
+ 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);
+ }
+ }
+
+ pr_info("Completed mul_u64_u64_div_u64() test\n");
+ return 0;
+}
+
+static void __exit test_exit(void)
+{
+}
+
+module_init(test_init);
+module_exit(test_exit);
+
+MODULE_AUTHOR("Nicolas Pitre");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("mul_u64_u64_div_u64() test module");
_
Patches currently in -mm which might be from npitre@xxxxxxxxxxxx are
