Re: [PATCH v1] x86: Remove wcsnlen-sse4_1 from wcslen ifunc-impl-list [BZ #28064]

["H.J. Lu" <hjl.tools@gmail.com>]

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On Thu, Jul 8, 2021 at 5:21 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Jul 8, 2021 at 1:22 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > The following commit
> >
> > commit 6f573a27b6c8b4236445810a44660612323f5a73
> > Author: Noah Goldstein <goldstein.w.n@gmail.com>
> > Date:   Wed Jun 23 01:19:34 2021 -0400
> >
> >     x86-64: Add wcslen optimize for sse4.1
> >
> > Added wcsnlen-sse4.1 to the wcslen ifunc implementation list and did
> > not add wcslen-sse4.1 to wcslen ifunc implementation list. This commit
> > fixes that by removing wcsnlen-sse4.1 from the wcslen ifunc
> > implementation list and adding wcslen-sse4.1 to the ifunc
> > implementation list.
> >
> > Testing:
> > test-wcslen.c is passing as well as all other tests in wcsmbs and
> > string.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> > I was unable to actually reproduce the bug on my machine, even after
> > reordering ifunc-wcslen.h to prefer the sse4.1
> > implementation. Although this most definetly is a bug.
> >
> >
> > I ran the following command. Is there an issue with the command? Or
> > does rdx happen to always have a len >= actual length of the string?
>
> That must be the case.   We can do something similar to
>
> sysdeps/x86_64/x32/tst-size_t-strnlen.c
>
> to write a testcase.

Here is the patch with a testcase.   Please include it in your fix and
mention BZ #28064 in your commit log.

> > $> rm -rf build; mkdir -p build/glibc; (cd build/glibc/; unset LD_LIBRARY_PATH; /absolute/path/to/src/glibc/configure --prefix=/usr; make --silent; make xcheck; make -r -C /absolute/path/to/src/glibc/string/ objdir=`pwd` check; make -r -C /absolute/path/to/src/glibc/wcsmbs/ objdir=`pwd` check);
> >
> >
> >
> >  sysdeps/x86_64/multiarch/ifunc-impl-list.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > index dbd1ebf298..39ab10613b 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > @@ -684,9 +684,9 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wcslen_evex)
> > -             IFUNC_IMPL_ADD (array, i, wcsnlen,
> > +             IFUNC_IMPL_ADD (array, i, wcslen,
> >                               CPU_FEATURE_USABLE (SSE4_1),
> > -                             __wcsnlen_sse4_1)
> > +                             __wcslen_sse4_1)
> >               IFUNC_IMPL_ADD (array, i, wcslen, 1, __wcslen_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/wcsnlen.c.  */
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> --
> H.J.



-- 
H.J.

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From fa568b344d2d4a8c3130c2e49f2f8dcee62e24da Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 8 Jul 2021 06:50:37 -0700
Subject: [PATCH] x86-64: Test strlen and wcslen with 0 in the RSI register

commit 6f573a27b6c8b4236445810a44660612323f5a73
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Wed Jun 23 01:19:34 2021 -0400

    x86-64: Add wcslen optimize for sse4.1

added wcsnlen-sse4.1 to the wcslen ifunc implementation list.  Since the
random value in the the RSI register is larger than the wide-character
string length in the existing wcslen test, it didn't trigger the wcslen
test failure.  Add a test to force 0 into the RSI register before calling
wcslen.
---
 sysdeps/x86_64/Makefile         |  7 +++
 sysdeps/x86_64/tst-rsi-strlen.c | 81 +++++++++++++++++++++++++++++++++
 sysdeps/x86_64/tst-rsi-wcslen.c | 20 ++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 sysdeps/x86_64/tst-rsi-strlen.c
 create mode 100644 sysdeps/x86_64/tst-rsi-wcslen.c

diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index 06a444b6af..3fc03f4a19 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -20,6 +20,8 @@ endif
 ifeq ($(subdir),string)
 sysdep_routines += strcasecmp_l-nonascii strncase_l-nonascii
 gen-as-const-headers += locale-defines.sym
+tests += \
+  tst-rsi-strlen
 endif
 
 ifeq ($(subdir),elf)
@@ -191,6 +193,11 @@ ifeq ($(subdir),csu)
 gen-as-const-headers += tlsdesc.sym rtld-offsets.sym
 endif
 
+ifeq ($(subdir),wcsmbs)
+tests += \
+  tst-rsi-wcslen
+endif
+
 $(objpfx)x86_64/tst-x86_64mod-1.os: $(objpfx)tst-x86_64mod-1.os
 	$(make-target-directory)
 	rm -f $@
diff --git a/sysdeps/x86_64/tst-rsi-strlen.c b/sysdeps/x86_64/tst-rsi-strlen.c
new file mode 100644
index 0000000000..0d3cc431a6
--- /dev/null
+++ b/sysdeps/x86_64/tst-rsi-strlen.c
@@ -0,0 +1,81 @@
+/* Test strlen with 0 in the RSI register.
+   Copyright (C) 2021 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/>.  */
+
+#ifdef WIDE
+# define TEST_NAME "wcslen"
+#else
+# define TEST_NAME "strlen"
+#endif /* WIDE */
+
+#define TEST_MAIN
+#include <string/test-string.h>
+
+#ifdef WIDE
+# include <wchar.h>
+# define STRLEN wcslen
+# define CHAR wchar_t
+#else
+# define STRLEN strlen
+# define CHAR char
+#endif /* WIDE */
+
+IMPL (STRLEN, 1)
+
+typedef size_t (*proto_t) (const CHAR *);
+
+typedef struct
+{
+  void (*fn) (void);
+} parameter_t;
+
+size_t
+__attribute__ ((weak, noinline, noclone))
+do_strlen (parameter_t a, int zero, const CHAR *str)
+{
+  return CALL (&a, str);
+}
+
+static int
+test_main (void)
+{
+  test_init ();
+
+  size_t size = page_size / sizeof (CHAR) - 1;
+  CHAR *buf = (CHAR *) buf2;
+  buf[size] = 0;
+
+  parameter_t a;
+
+  int ret = 0;
+  FOR_EACH_IMPL (impl, 0)
+    {
+      a.fn = impl->fn;
+      /* NB: Pass 0 in RSI.  */
+      size_t res = do_strlen (a, 0, buf);
+      if (res != size)
+	{
+	  error (0, 0, "Wrong result in function %s: %zu != %zu",
+		 impl->name, res, size);
+	  ret = 1;
+	}
+    }
+
+  return ret ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/x86_64/tst-rsi-wcslen.c b/sysdeps/x86_64/tst-rsi-wcslen.c
new file mode 100644
index 0000000000..f45a7dfb51
--- /dev/null
+++ b/sysdeps/x86_64/tst-rsi-wcslen.c
@@ -0,0 +1,20 @@
+/* Test wcslen with 0 in the RSI register.
+   Copyright (C) 2021 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/>.  */
+
+#define WIDE 1
+#include "tst-rsi-strlen.c"
-- 
2.31.1