[Bug libc/25824] New: Abnormal function of strnlen in aarch64

[Bug libc/25824] New: Abnormal function of strnlen in aarch64

[zhuyan34 at huawei dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

            Bug ID: 25824
           Summary: Abnormal function of strnlen in aarch64
           Product: glibc
           Version: 2.31
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: zhuyan34 at huawei dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

In aarch64, the strnlen interface has a problem when the string length is more
than 9

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

--- Comment #1 from Andreas Schwab <schwab@linux-m68k.org> ---
*** Bug 25825 has been marked as a duplicate of this bug. ***

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[zhuyan34 at huawei dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

--- Comment #2 from Yan Zhu <zhuyan34 at huawei dot com> ---
There is a testcase.

#include <stdio.h>
#include <string.h>

void init_base(char *base, int len)
{
        int i;
        for (i = 0; i < len; i++) {
                base[i] = 'x';
        }
        base[len] = '\0';
}

int main(int argc, char *argv[])
{
        int i;
        char base[1000];
        char buff[1000];
        size_t n;

        for (i = 1; i < 1000; i++) {
                memset(buff, 0, 1000);
                init_base(base, i);             
                n = strnlen(base, 1000);      
                if ( i == n )
                        printf("size=%d is equel\n", i);
                else
                        printf("size=%d is not equel%s\n", i);
        }

    return 0;
}


The execution log is as follows：

arm64be /tmp # ./arm64be-test_strnlen
size=1 is equel
size=2 is equel
size=3 is equel
size=4 is equel
size=5 is equel
size=6 is equel
size=7 is equel
size=8 is equel
size=9 is not equel
size=10 is not equel
size=11 is not equel
size=12 is not equel
size=13 is not equel

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[zhuyan34 at huawei dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

--- Comment #3 from Yan Zhu <zhuyan34 at huawei dot com> ---
There is a testcase.

#include <stdio.h>
#include <string.h>

void init_base(char *base, int len)
{
        int i;
        for (i = 0; i < len; i++) {
                base[i] = 'x';
        }
        base[len] = '\0';
}

int main(int argc, char *argv[])
{
        int i;
        char base[1000];
        char buff[1000];
        size_t n;

        for (i = 1; i < 1000; i++) {
                memset(buff, 0, 1000);
                init_base(base, i);             
                n = strnlen(base, 1000);      
                if ( i == n )
                        printf("size=%d is equel\n", i);
                else
                        printf("size=%d is not equel%s\n", i);
        }

    return 0;
}


The execution log is as follows：

arm64be /tmp # ./arm64be-test_strnlen
size=1 is equel
size=2 is equel
size=3 is equel
size=4 is equel
size=5 is equel
size=6 is equel
size=7 is equel
size=8 is equel
size=9 is not equel
size=10 is not equel
size=11 is not equel
size=12 is not equel
size=13 is not equel

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
               Host|                            |aarch64_be-*-*

--- Comment #4 from Andreas Schwab <schwab@linux-m68k.org> ---
This does not fail on little-endian aarch64.

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[wdijkstr at arm dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

Wilco <wdijkstr at arm dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wdijkstr at arm dot com

--- Comment #5 from Wilco <wdijkstr at arm dot com> ---
(In reply to Yan Zhu from comment #0)
> In aarch64, the strnlen interface has a problem when the string length is
> more than 9

In big-endian? Yes that rev64 only swaps bytes in each 64-bit word, so you
still need to swap the index in mov data1, datav2.d[0].

This sequence comes from strlen_asimd.S originally. And now strcpy.S has it
too.

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[wdijkstr at arm dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

--- Comment #6 from Wilco <wdijkstr at arm dot com> ---
(In reply to Wilco from comment #5)
> (In reply to Yan Zhu from comment #0)
> > In aarch64, the strnlen interface has a problem when the string length is
> > more than 9
> 
> In big-endian? Yes that rev64 only swaps bytes in each 64-bit word, so you
> still need to swap the index in mov data1, datav2.d[0].
> 
> This sequence comes from strlen_asimd.S originally. And now strcpy.S has it
> too.

Btw I have a faster strnlen I'll post soon that will fix one of the 3 cases.

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[nsz at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

Szabolcs Nagy <nsz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |nsz at gcc dot gnu.org
   Target Milestone|---                         |2.32
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-05-15

--- Comment #7 from Szabolcs Nagy <nsz at gcc dot gnu.org> ---
bigendian strnlen, strcpy (and stpcpy) are fixed for glibc 2.32 in

commit 59b64f9cbbf1e98c6d187873de6c363994aee19d
Author:     Lexi Shao <shaolexi@huawei.com>
AuthorDate: 2020-05-15 18:48:59 +0800

    aarch64: fix strcpy and strnlen for big-endian [BZ #25824]

falkor and kunpeng920 specific strlen_asimd still needs to be fixed.

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

--- Comment #8 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Wilco Dijkstra <wilco@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f46ef33ad134bec7ac992f28ee4b8b0614590e3e

commit f46ef33ad134bec7ac992f28ee4b8b0614590e3e
Author: Wilco Dijkstra <wdijkstr@arm.com>
Date:   Fri Jul 17 14:09:36 2020 +0100

    AArch64: Improve strlen_asimd performance (bug 25824)

    Optimize strlen using a mix of scalar and SIMD code.  On modern micro
    architectures large strings are 2.6 times faster than existing
    strlen_asimd and 35% faster than the new MTE version of strlen.

    On a random strlen benchmark using small sizes the speedup is 7% vs
    strlen_asimd and 40% vs the MTE strlen.  This fixes the main strlen
    regressions on Cortex-A53 and other cores with a simple Neon unit.

    Rename __strlen_generic to __strlen_mte, and select strlen_asimd when
    MTE is not enabled (this is waiting on support for a HWCAP_MTE bit).

    This fixes big-endian bug 25824. Passes GLIBC regression tests.

    Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

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[Bug libc/25824] Abnormal function of strnlen in aarch64

[nsz at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=25824

Szabolcs Nagy <nsz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #9 from Szabolcs Nagy <nsz at gcc dot gnu.org> ---
fixed for 2.32

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