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Date: Fri, 16 Feb 2024 10:01:05 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Charlie Jenkins <charlie@...osinc.com>, David Laight <David.Laight@...lab.com>,
Palmer Dabbelt <palmer@...belt.com>, Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v6 0/2] lib: checksum: Fix issues with checksum tests
Hi Günter,
On Mon, Feb 12, 2024 at 6:13 PM Guenter Roeck <linux@...ck-us.net> wrote:
> On Mon, Feb 12, 2024 at 12:26:08AM -0500, Charlie Jenkins wrote:
> > On Sun, Feb 11, 2024 at 11:18:36AM -0800, Guenter Roeck wrote:
> > > On 2/7/24 16:22, Charlie Jenkins wrote:
> > > > The ip_fast_csum and csum_ipv6_magic tests did not have the data
> > > > types properly casted, and improperly misaligned data.
> > > >
> > > > Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> > >
> > > I sorted out most of the problems with this version, but I still get:
> > >
> > > # test_csum_ipv6_magic: ASSERTION FAILED at lib/checksum_kunit.c:513
> > > Expected ( u64)csum_result == ( u64)expected, but
> > > ( u64)csum_result == 16630 (0x40f6)
> > > ( u64)expected == 65535 (0xffff)
> > > not ok 5 test_csum_ipv6_magic
> > >
> > > on m68k:q800. This is suspicious because there is no 0xffff in
> > > expected_csum_ipv6_magic[]. With some debugging information:
> > >
> > > ####### num_tests=86 i=84 expect array size=84
> > > ####### MAX_LEN=512 WORD_ALIGNMENT=4 magic data size=42
> > >
> > > That means the loop
> > >
> > > for (int i = 0; i < num_tests; i++) {
> > > ...
> > > expected = (__force __sum16)expected_csum_ipv6_magic[i];
> > > ...
> > > }
> > >
> > > will access data beyond the end of the expected_csum_ipv6_magic[] array,
> > > possibly because m68k doesn't pad struct csum_ipv6_magic_data to 44 bytes.
> >
> > Okay I will check that out.
> >
> > >
> > > In this context, is the comment about proto having to be 0 really true ?
> > > It seems to me that the calculated checksum must be identical on both
> > > little and big endian systems. After all, they need to be able to talk
> > > to each other.
> >
> > I agree, but I couldn't find a solution other than setting it to zero.
> > Maybe I am missing something simple...
> >
>
> Try the patch below on top of yours. It should work on both big and little
> endian systems.
>
> Key changes:
> - use random_buf directly instead of copying anything
> - no need to convert source / destination addresses
> - csum in the buffer is in network byte order and needs
> to stay that way
> - len in the buffer is in network byte order and needs to be
> converted to host byte order since that is expected by
> csum_ipv6_magic()
> - the expected value is in host byte order and needs to be
> converted to network byte order for comparison
> - protocol is just fine and converted by csum_ipv6_magic()
> as needed
Thanks for your patch!
> --- a/lib/checksum_kunit.c
> +++ b/lib/checksum_kunit.c
> @@ -465,44 +468,36 @@ static void test_ip_fast_csum(struct kunit *test)
> }
> }
>
> +#define IPV6_NUM_TESTS ((MAX_LEN - sizeof(struct in6_addr) * 2 - sizeof(int) * 3) / WORD_ALIGNMENT)
> +
> static void test_csum_ipv6_magic(struct kunit *test)
> {
> #if defined(CONFIG_NET)
> + const struct in6_addr *saddr;
> + const struct in6_addr *daddr;
> + unsigned int len;
> __sum16 csum_result, expected;
> - struct csum_ipv6_magic_data {
> - const struct in6_addr saddr;
> - const struct in6_addr daddr;
> - unsigned int len;
> - __wsum csum;
> - unsigned char proto;
> - } data, *data_ptr;
> - int num_tests = MAX_LEN / WORD_ALIGNMENT - sizeof(struct csum_ipv6_magic_data);
> + unsigned char proto;
> + unsigned int csum;
>
> - for (int i = 0; i < num_tests; i++) {
> - data_ptr = (struct csum_ipv6_magic_data *)(random_buf + (i * WORD_ALIGNMENT));
> + const int daddr_offset = sizeof(struct in6_addr);
> + const int len_offset = sizeof(struct in6_addr) + sizeof(struct in6_addr);
> + const int csum_offset = sizeof(struct in6_addr) + sizeof(struct in6_addr) +
> + sizeof(int);
> + const int proto_offset = sizeof(struct in6_addr) + sizeof(struct in6_addr) +
> + sizeof(int) * 2;
Please no manual offset calculations.
Please fix the csum_ipv6_magic_data structure definition instead.
>
> - cpu_to_be32_array((__be32 *)&data.saddr, (const u32 *)&data_ptr->saddr,
> - sizeof_field(struct csum_ipv6_magic_data, saddr) / 4);
> - cpu_to_be32_array((__be32 *)&data.daddr, (const u32 *)&data_ptr->daddr,
> - sizeof_field(struct csum_ipv6_magic_data, daddr) / 4);
> - data.len = data_ptr->len;
> - data.csum = (__force __wsum)htonl((__force u32)data_ptr->csum);
> - /*
> - * proto must be zero to be compatible between big-endian and
> - * little-endian CPUs. On little-endian CPUs, proto is
> - * converted to a big-endian 32-bit value before the checksum
> - * operation. This causes proto to be in the most significant
> - * 8 bits on a little-endian CPU. On big-endian CPUs proto will
> - * remain in the least significant 8 bits. There does not exist
> - * a transformation to an arbitrary proto that will allow
> - * csum_ipv6_magic to return the same value on a big-endian and
> - * little-endian CPUs.
> - */
> - data.proto = 0;
> - csum_result = csum_ipv6_magic(&data.saddr, &data.daddr,
> - data.len, data.proto,
> - data.csum);
> - expected = (__force __sum16)expected_csum_ipv6_magic[i];
> + for (int i = 0; i < IPV6_NUM_TESTS; i++) {
> + int index = i * WORD_ALIGNMENT;
> +
> + saddr = (const struct in6_addr *)(random_buf + index);
> + daddr = (const struct in6_addr *)(random_buf + index + daddr_offset);
> + len = ntohl(*(unsigned int *)(random_buf + index + len_offset));
> + csum = *(unsigned int *)(random_buf + index + csum_offset);
> + proto = *(random_buf + index + proto_offset);
> +
> + csum_result = csum_ipv6_magic(saddr, daddr, len, proto, csum);
> + expected = (__force __sum16)htons(expected_csum_ipv6_magic[i]);
> CHECK_EQ(csum_result, expected);
> }
> #endif /* !CONFIG_NET */
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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