diff options
| -rw-r--r-- | lib/Kconfig.debug | 10 | ||||
| -rw-r--r-- | lib/math/Makefile | 1 | ||||
| -rw-r--r-- | lib/math/div64.c | 9 | ||||
| -rw-r--r-- | lib/math/test_mul_u64_u64_div_u64.c | 99 |
4 files changed, 118 insertions, 1 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index a30c03a66172..bf0995d328b3 100644 --- a/lib/Kconfig.debug +++ b/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 diff --git a/lib/math/Makefile b/lib/math/Makefile index 91fcdb0c9efe..981a26127e08 100644 --- a/lib/math/Makefile +++ b/lib/math/Makefile @@ -6,4 +6,5 @@ obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o obj-$(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/div64.c b/lib/math/div64.c index b7fc75246399..5faa29208bdb 100644 --- a/lib/math/div64.c +++ b/lib/math/div64.c @@ -212,11 +212,18 @@ u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c) #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); /* diff --git a/lib/math/test_mul_u64_u64_div_u64.c b/lib/math/test_mul_u64_u64_div_u64.c new file mode 100644 index 000000000000..58d058de4e73 --- /dev/null +++ b/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"); |