From: Noah Goldstein <goldstein.w.n@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v5] x86: Add a testcase for BZ #29863
Date: Mon, 19 Dec 2022 06:38:55 -0800 [thread overview]
Message-ID: <CAFUsyfKRv7C2Pg_veP4kf4SD1RSz+2K25zfQBqz_sf+WZyfzQw@mail.gmail.com> (raw)
In-Reply-To: <20221214213053.4174989-1-hjl.tools@gmail.com>
On Wed, Dec 14, 2022 at 1:30 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> When a thread is updating the memory area of memcmp and another thread
> is doing memcmp, the memcmp return value is undefined. Add a testcase
> to verify that memcmp won't segfault in this case.
> ---
> sysdeps/x86/Makefile | 8 +++
> sysdeps/x86/tst-memcmp-race.c | 106 ++++++++++++++++++++++++++++++++++
> 2 files changed, 114 insertions(+)
> create mode 100644 sysdeps/x86/tst-memcmp-race.c
>
> diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
> index 56fd5fc805..c3f05a06ab 100644
> --- a/sysdeps/x86/Makefile
> +++ b/sysdeps/x86/Makefile
> @@ -257,3 +257,11 @@ tests += \
> tests-static += \
> tst-sysconf-cache-linesize-static
> endif
> +
> +ifeq ($(subdir),nptl)
> +tests += \
> + tst-memcmp-race \
> +# tests
> +
> +CFLAGS-tst-memcmp-race.c += -O0
> +endif
> diff --git a/sysdeps/x86/tst-memcmp-race.c b/sysdeps/x86/tst-memcmp-race.c
> new file mode 100644
> index 0000000000..eefa9e43c4
> --- /dev/null
> +++ b/sysdeps/x86/tst-memcmp-race.c
> @@ -0,0 +1,106 @@
> +/* Test case for memcmp with race condition.
> + Copyright (C) 2022 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +/* Verify that there is no segfault when one thread is updating the
> + memory block of memcmp and the other thread is doing memcmp. */
> +
> +#define TEST_MAIN
> +#define TEST_NAME "memcmp"
> +
> +#include <stdio.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <string/test-string.h>
> +#include <support/xthread.h>
> +
> +#define NUM_THREADS 2
> +#define LOOP1 10000
> +#define LOOP2 1000000
> +
> +typedef int (*proto_t) (const void *, const void *, size_t);
> +
> +IMPL (memcmp, 1)
> +
> +struct arg
> +{
> + proto_t func;
> + size_t len;
> + int i;
> +};
> +
> +static void *
> +childThread (void *tArgs)
> +{
> + struct arg *a = (struct arg *) tArgs;
> + int i;
> +
> + if (0 == a->i % 2)
> + {
> + for (i = 0; i < LOOP1; i++)
> + {
> + int result = a->func (buf1, buf2, a->len);
So the test can catch more subtle errors can we test
with memcmp args at begining and end of a page.
i.e buf1/buf2 and (buf1 + page_size - a->len)/(buf2 + page_size - a->len).
> + printf ("i = %d : result = %d\n", i, result);
> + }
> + }
> + else
> + {
> + size_t offset = a->len > 16 ? a->len - 16 : 1;
> + for (i = 0; i < LOOP2; i++)
> + buf1[offset] = i & 1;
> + }
> +
> + return NULL;
> +}
> +
> +static void
> +do_one_test (proto_t func, size_t len)
> +{
> + int i;
> + pthread_t threads[NUM_THREADS];
> + struct arg a[NUM_THREADS];
> +
> + for (i = 0; i < NUM_THREADS; ++i)
> + {
> + a[i].func = func;
> + a[i].len = len;
> + a[i].i = i;
> + threads[i] = xpthread_create (NULL, childThread, (void *)&a[i]);
> + }
> +
> + for (i = 0; i < NUM_THREADS; ++i)
> + xpthread_join (threads[i]);
> +}
> +
> +int
> +test_main (void)
> +{
> + test_init ();
> +
> + memset (buf1, 1, page_size);
> + memset (buf2, 1, page_size);
> +
> + for (size_t i = 0; i <= 11; i++)
> + {
> + FOR_EACH_IMPL (impl, 0)
> + do_one_test ((proto_t) impl->fn, (1 << i) + 1);
can you also test 2^i - 1.
> + }
> +
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
> --
> 2.38.1
>
Can you move this to the string directory (so we run this on all
arch) and add corresponding tests for memcmpeq/wmemcmp.
next prev parent reply other threads:[~2022-12-19 14:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-14 21:30 H.J. Lu
2022-12-19 14:38 ` Noah Goldstein [this message]
2022-12-19 16:55 ` H.J. Lu
2022-12-19 17:50 ` Noah Goldstein
2022-12-19 18:04 ` H.J. Lu
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