From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x52c.google.com (mail-pg1-x52c.google.com [IPv6:2607:f8b0:4864:20::52c]) by sourceware.org (Postfix) with ESMTPS id 3663F396E844 for ; Wed, 23 Jun 2021 03:11:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 3663F396E844 Received: by mail-pg1-x52c.google.com with SMTP id n12so532570pgs.13 for ; Tue, 22 Jun 2021 20:11:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=K49nwOjAg1FSt915T0VklUY/+pWkvAWxrjcKV5Hz2bQ=; b=Qo4Gb9FK4+r62V50WD3eOODbXLQPuStjx2kyz8EK9faT64ZHTMJ8u4EHbd7GIwq6Tx wHck7x63yIfrkFRKYDzdcJz5gCWyDRyrJLAvN9q6TjCxrD9HpLMWgevXucg36rh6qm9n vxafma/yoha/VRxM15U8KlFflTisSlV/Pakl8YZ+HEyU06CG++dl3raEyuSRFwHrtl0c Ll2YQOnMnwWHp5heIiliS6Sln6K0BZp99ON7YktdlglVu2/2uK/FGww7ZuOEHyPUL0hF D62vbX/Mt58xytu0ifa6RCyPCfqqpsBu5zEJOXjdQOjsP2DPCMMeKQehLXV5B+fvCeid m3Jw== X-Gm-Message-State: AOAM53013gL5dStaVNjmR5LEcO7r8AHJURSwknaqoJp+8FcWCS7s/Brp 7pP9rm94c4y8BeJwaRauLpmCrTMcblpUfxsVygA= X-Google-Smtp-Source: ABdhPJwn33Ihypt2I6D6aC3rTzGjXAaulL1AZlPG13+3JH2oE8tgVE6Ulu+6rG0mO0fWHoNPXnakwkUv8iJ9PA2btWA= X-Received: by 2002:a62:53c1:0:b029:2ef:25e8:d9e5 with SMTP id h184-20020a6253c10000b02902ef25e8d9e5mr6725356pfb.74.1624417881329; Tue, 22 Jun 2021 20:11:21 -0700 (PDT) MIME-Version: 1.0 References: <20210609205257.123944-1-goldstein.w.n@gmail.com> <20210622181111.185897-3-goldstein.w.n@gmail.com> In-Reply-To: From: Noah Goldstein Date: Tue, 22 Jun 2021 23:11:10 -0400 Message-ID: Subject: Re: [PATCH v2 3/3] x86: Fix overflow bug in wcsnlen-sse4_1 and wcsnlen-avx2 [BZ #27974] To: "H.J. Lu" Cc: GNU C Library , "Carlos O'Donell" X-Spam-Status: No, score=-9.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, HTML_MESSAGE, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Jun 2021 03:11:26 -0000 On Tue, Jun 22, 2021 at 7:29 PM H.J. Lu wrote: > On Tue, Jun 22, 2021 at 4:16 PM Noah Goldstein > wrote: > > > > > > > > On Tue, Jun 22, 2021 at 5:34 PM H.J. Lu wrote: > >> > >> On Tue, Jun 22, 2021 at 11:20 AM Noah Goldstein < > goldstein.w.n@gmail.com> wrote: > >> > > >> > This commit fixes the bug mentioned in the previous commit. > >> > > >> > The previous implementations of wmemchr in these files relied > >> > on maxlen * sizeof(wchar_t) which was not guranteed by the standard. > >> > > >> > The new overflow tests added in the previous commit now > >> > pass (As well as all the other tests). > >> > > >> > Signed-off-by: Noah Goldstein > >> > --- > >> > sysdeps/x86_64/multiarch/strlen-avx2.S | 130 > ++++++++++++++++++------- > >> > sysdeps/x86_64/strlen.S | 14 ++- > >> > 2 files changed, 106 insertions(+), 38 deletions(-) > >> > > >> > diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S > b/sysdeps/x86_64/multiarch/strlen-avx2.S > >> > index bd2e6ee44a..b282a75613 100644 > >> > --- a/sysdeps/x86_64/multiarch/strlen-avx2.S > >> > +++ b/sysdeps/x86_64/multiarch/strlen-avx2.S > >> > @@ -44,21 +44,21 @@ > >> > > >> > # define VEC_SIZE 32 > >> > # define PAGE_SIZE 4096 > >> > +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE) > >> > > >> > .section SECTION(.text),"ax",@progbits > >> > ENTRY (STRLEN) > >> > # ifdef USE_AS_STRNLEN > >> > /* Check zero length. */ > >> > +# ifdef __ILP32__ > >> > + /* Clear upper bits. */ > >> > + and %RSI_LP, %RSI_LP > >> > +# else > >> > test %RSI_LP, %RSI_LP > >> > +# endif > >> > jz L(zero) > >> > /* Store max len in R8_LP before adjusting if using WCSLEN. > */ > >> > mov %RSI_LP, %R8_LP > >> > -# ifdef USE_AS_WCSLEN > >> > - shl $2, %RSI_LP > >> > -# elif defined __ILP32__ > >> > - /* Clear the upper 32 bits. */ > >> > - movl %esi, %esi > >> > -# endif > >> > # endif > >> > movl %edi, %eax > >> > movq %rdi, %rdx > >> > @@ -72,10 +72,10 @@ ENTRY (STRLEN) > >> > > >> > /* Check the first VEC_SIZE bytes. */ > >> > VPCMPEQ (%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > # ifdef USE_AS_STRNLEN > >> > /* If length < VEC_SIZE handle special. */ > >> > - cmpq $VEC_SIZE, %rsi > >> > + cmpq $CHAR_PER_VEC, %rsi > >> > jbe L(first_vec_x0) > >> > # endif > >> > /* If empty continue to aligned_more. Otherwise return bit > >> > @@ -84,6 +84,7 @@ ENTRY (STRLEN) > >> > jz L(aligned_more) > >> > tzcntl %eax, %eax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -97,9 +98,14 @@ L(zero): > >> > L(first_vec_x0): > >> > /* Set bit for max len so that tzcnt will return min of max > len > >> > and position of first match. */ > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Multiply length by 4 to get byte count. */ > >> > + sall $2, %esi > >> > +# endif > >> > btsq %rsi, %rax > >> > tzcntl %eax, %eax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -113,14 +119,19 @@ L(first_vec_x1): > >> > # ifdef USE_AS_STRNLEN > >> > /* Use ecx which was computed earlier to compute correct > value. > >> > */ > >> > +# ifdef USE_AS_WCSLEN > >> > + leal -(VEC_SIZE * 4 + 1)(%rax, %rcx, 4), %eax > >> > +# else > >> > subl $(VEC_SIZE * 4 + 1), %ecx > >> > addl %ecx, %eax > >> > +# endif > >> > # else > >> > subl %edx, %edi > >> > incl %edi > >> > addl %edi, %eax > >> > # endif > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -133,14 +144,19 @@ L(first_vec_x2): > >> > # ifdef USE_AS_STRNLEN > >> > /* Use ecx which was computed earlier to compute correct > value. > >> > */ > >> > +# ifdef USE_AS_WCSLEN > >> > + leal -(VEC_SIZE * 3 + 1)(%rax, %rcx, 4), %eax > >> > +# else > >> > subl $(VEC_SIZE * 3 + 1), %ecx > >> > addl %ecx, %eax > >> > +# endif > >> > # else > >> > subl %edx, %edi > >> > addl $(VEC_SIZE + 1), %edi > >> > addl %edi, %eax > >> > # endif > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -153,14 +169,19 @@ L(first_vec_x3): > >> > # ifdef USE_AS_STRNLEN > >> > /* Use ecx which was computed earlier to compute correct > value. > >> > */ > >> > +# ifdef USE_AS_WCSLEN > >> > + leal -(VEC_SIZE * 2 + 1)(%rax, %rcx, 4), %eax > >> > +# else > >> > subl $(VEC_SIZE * 2 + 1), %ecx > >> > addl %ecx, %eax > >> > +# endif > >> > # else > >> > subl %edx, %edi > >> > addl $(VEC_SIZE * 2 + 1), %edi > >> > addl %edi, %eax > >> > # endif > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -173,14 +194,19 @@ L(first_vec_x4): > >> > # ifdef USE_AS_STRNLEN > >> > /* Use ecx which was computed earlier to compute correct > value. > >> > */ > >> > +# ifdef USE_AS_WCSLEN > >> > + leal -(VEC_SIZE * 1 + 1)(%rax, %rcx, 4), %eax > >> > +# else > >> > subl $(VEC_SIZE + 1), %ecx > >> > addl %ecx, %eax > >> > +# endif > >> > # else > >> > subl %edx, %edi > >> > addl $(VEC_SIZE * 3 + 1), %edi > >> > addl %edi, %eax > >> > # endif > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -195,10 +221,14 @@ L(cross_page_continue): > >> > /* Check the first 4 * VEC_SIZE. Only one VEC_SIZE at a time > >> > since data is only aligned to VEC_SIZE. */ > >> > # ifdef USE_AS_STRNLEN > >> > - /* + 1 because rdi is aligned to VEC_SIZE - 1. + CHAR_SIZE > because > >> > - it simplies the logic in last_4x_vec_or_less. */ > >> > + /* + 1 because rdi is aligned to VEC_SIZE - 1. + CHAR_SIZE > >> > + because it simplies the logic in last_4x_vec_or_less. */ > >> > leaq (VEC_SIZE * 4 + CHAR_SIZE + 1)(%rdi), %rcx > >> > subq %rdx, %rcx > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get the wchar_t count. */ > >> > + sarl $2, %ecx > >> > +# endif > >> > # endif > >> > /* Load first VEC regardless. */ > >> > VPCMPEQ 1(%rdi), %ymm0, %ymm1 > >> > @@ -207,34 +237,38 @@ L(cross_page_continue): > >> > subq %rcx, %rsi > >> > jb L(last_4x_vec_or_less) > >> > # endif > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(first_vec_x1) > >> > > >> > VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(first_vec_x2) > >> > > >> > VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(first_vec_x3) > >> > > >> > VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(first_vec_x4) > >> > > >> > /* Align data to VEC_SIZE * 4 - 1. */ > >> > # ifdef USE_AS_STRNLEN > >> > /* Before adjusting length check if at last VEC_SIZE * 4. */ > >> > - cmpq $(VEC_SIZE * 4 - 1), %rsi > >> > + cmpq $(CHAR_PER_VEC * 4 - 1), %rsi > >> > jbe L(last_4x_vec_or_less_load) > >> > incq %rdi > >> > movl %edi, %ecx > >> > orq $(VEC_SIZE * 4 - 1), %rdi > >> > andl $(VEC_SIZE * 4 - 1), %ecx > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get the wchar_t count. */ > >> > + sarl $2, %ecx > >> > +# endif > >> > /* Readjust length. */ > >> > addq %rcx, %rsi > >> > # else > >> > @@ -246,13 +280,13 @@ L(cross_page_continue): > >> > L(loop_4x_vec): > >> > # ifdef USE_AS_STRNLEN > >> > /* Break if at end of length. */ > >> > - subq $(VEC_SIZE * 4), %rsi > >> > + subq $(CHAR_PER_VEC * 4), %rsi > >> > jb L(last_4x_vec_or_less_cmpeq) > >> > # endif > >> > - /* Save some code size by microfusing VPMINU with the load. > Since > >> > - the matches in ymm2/ymm4 can only be returned if there > where no > >> > - matches in ymm1/ymm3 respectively there is no issue with > overlap. > >> > - */ > >> > + /* Save some code size by microfusing VPMINU with the load. > >> > + Since the matches in ymm2/ymm4 can only be returned if > there > >> > + where no matches in ymm1/ymm3 respectively there is no > issue > >> > + with overlap. */ > >> > vmovdqa 1(%rdi), %ymm1 > >> > VPMINU (VEC_SIZE + 1)(%rdi), %ymm1, %ymm2 > >> > vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm3 > >> > @@ -260,7 +294,7 @@ L(loop_4x_vec): > >> > > >> > VPMINU %ymm2, %ymm4, %ymm5 > >> > VPCMPEQ %ymm5, %ymm0, %ymm5 > >> > - vpmovmskb %ymm5, %ecx > >> > + vpmovmskb %ymm5, %ecx > >> > > >> > subq $-(VEC_SIZE * 4), %rdi > >> > testl %ecx, %ecx > >> > @@ -268,27 +302,28 @@ L(loop_4x_vec): > >> > > >> > > >> > VPCMPEQ %ymm1, %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > subq %rdx, %rdi > >> > testl %eax, %eax > >> > jnz L(last_vec_return_x0) > >> > > >> > VPCMPEQ %ymm2, %ymm0, %ymm2 > >> > - vpmovmskb %ymm2, %eax > >> > + vpmovmskb %ymm2, %eax > >> > testl %eax, %eax > >> > jnz L(last_vec_return_x1) > >> > > >> > /* Combine last 2 VEC. */ > >> > VPCMPEQ %ymm3, %ymm0, %ymm3 > >> > - vpmovmskb %ymm3, %eax > >> > - /* rcx has combined result from all 4 VEC. It will only be > used if > >> > - the first 3 other VEC all did not contain a match. */ > >> > + vpmovmskb %ymm3, %eax > >> > + /* rcx has combined result from all 4 VEC. It will only be > used > >> > + if the first 3 other VEC all did not contain a match. */ > >> > salq $32, %rcx > >> > orq %rcx, %rax > >> > tzcntq %rax, %rax > >> > subq $(VEC_SIZE * 2 - 1), %rdi > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -297,15 +332,19 @@ L(loop_4x_vec): > >> > # ifdef USE_AS_STRNLEN > >> > .p2align 4 > >> > L(last_4x_vec_or_less_load): > >> > - /* Depending on entry adjust rdi / prepare first VEC in > ymm1. */ > >> > + /* Depending on entry adjust rdi / prepare first VEC in ymm1. > >> > + */ > >> > subq $-(VEC_SIZE * 4), %rdi > >> > L(last_4x_vec_or_less_cmpeq): > >> > VPCMPEQ 1(%rdi), %ymm0, %ymm1 > >> > L(last_4x_vec_or_less): > >> > - > >> > - vpmovmskb %ymm1, %eax > >> > - /* If remaining length > VEC_SIZE * 2. This works if esi is > off by > >> > - VEC_SIZE * 4. */ > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Multiply length by 4 to get byte count. */ > >> > + sall $2, %esi > >> > +# endif > >> > + vpmovmskb %ymm1, %eax > >> > + /* If remaining length > VEC_SIZE * 2. This works if esi is > off > >> > + by VEC_SIZE * 4. */ > >> > testl $(VEC_SIZE * 2), %esi > >> > jnz L(last_4x_vec) > >> > > >> > @@ -320,7 +359,7 @@ L(last_4x_vec_or_less): > >> > jb L(max) > >> > > >> > VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > tzcntl %eax, %eax > >> > /* Check the end of data. */ > >> > cmpl %eax, %esi > >> > @@ -329,6 +368,7 @@ L(last_4x_vec_or_less): > >> > addl $(VEC_SIZE + 1), %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -340,6 +380,7 @@ L(last_vec_return_x0): > >> > subq $(VEC_SIZE * 4 - 1), %rdi > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -350,6 +391,7 @@ L(last_vec_return_x1): > >> > subq $(VEC_SIZE * 3 - 1), %rdi > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -366,6 +408,7 @@ L(last_vec_x1_check): > >> > incl %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -381,14 +424,14 @@ L(last_4x_vec): > >> > jnz L(last_vec_x1) > >> > > >> > VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(last_vec_x2) > >> > > >> > /* Normalize length. */ > >> > andl $(VEC_SIZE * 4 - 1), %esi > >> > VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > testl %eax, %eax > >> > jnz L(last_vec_x3) > >> > > >> > @@ -396,7 +439,7 @@ L(last_4x_vec): > >> > jb L(max) > >> > > >> > VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > tzcntl %eax, %eax > >> > /* Check the end of data. */ > >> > cmpl %eax, %esi > >> > @@ -405,6 +448,7 @@ L(last_4x_vec): > >> > addl $(VEC_SIZE * 3 + 1), %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -419,6 +463,7 @@ L(last_vec_x1): > >> > incl %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -432,6 +477,7 @@ L(last_vec_x2): > >> > addl $(VEC_SIZE + 1), %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -447,6 +493,7 @@ L(last_vec_x3): > >> > addl $(VEC_SIZE * 2 + 1), %eax > >> > addq %rdi, %rax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > shrq $2, %rax > >> > # endif > >> > VZEROUPPER_RETURN > >> > @@ -455,13 +502,13 @@ L(max_end): > >> > VZEROUPPER_RETURN > >> > # endif > >> > > >> > - /* Cold case for crossing page with first load. */ > >> > + /* Cold case for crossing page with first load. */ > >> > .p2align 4 > >> > L(cross_page_boundary): > >> > /* Align data to VEC_SIZE - 1. */ > >> > orq $(VEC_SIZE - 1), %rdi > >> > VPCMPEQ -(VEC_SIZE - 1)(%rdi), %ymm0, %ymm1 > >> > - vpmovmskb %ymm1, %eax > >> > + vpmovmskb %ymm1, %eax > >> > /* Remove the leading bytes. sarxl only uses bits [5:0] of > COUNT > >> > so no need to manually mod rdx. */ > >> > sarxl %edx, %eax, %eax > >> > @@ -470,6 +517,10 @@ L(cross_page_boundary): > >> > jnz L(cross_page_less_vec) > >> > leaq 1(%rdi), %rcx > >> > subq %rdx, %rcx > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Divide bytes by 4 to get wchar_t count. */ > >> > + shrl $2, %ecx > >> > +# endif > >> > /* Check length. */ > >> > cmpq %rsi, %rcx > >> > jb L(cross_page_continue) > >> > @@ -479,6 +530,7 @@ L(cross_page_boundary): > >> > jz L(cross_page_continue) > >> > tzcntl %eax, %eax > >> > # ifdef USE_AS_WCSLEN > >> > + /* NB: Divide length by 4 to get wchar_t count. */ > >> > shrl $2, %eax > >> > # endif > >> > # endif > >> > @@ -489,6 +541,10 @@ L(return_vzeroupper): > >> > .p2align 4 > >> > L(cross_page_less_vec): > >> > tzcntl %eax, %eax > >> > +# ifdef USE_AS_WCSLEN > >> > + /* NB: Multiply length by 4 to get byte count. */ > >> > + sall $2, %esi > >> > +# endif > >> > cmpq %rax, %rsi > >> > cmovb %esi, %eax > >> > # ifdef USE_AS_WCSLEN > >> > diff --git a/sysdeps/x86_64/strlen.S b/sysdeps/x86_64/strlen.S > >> > index d223ea1700..3fc6734910 100644 > >> > --- a/sysdeps/x86_64/strlen.S > >> > +++ b/sysdeps/x86_64/strlen.S > >> > @@ -65,12 +65,24 @@ ENTRY(strlen) > >> > ret > >> > L(n_nonzero): > >> > # ifdef AS_WCSLEN > >> > - shl $2, %RSI_LP > >> > +/* Check for overflow from maxlen * sizeof(wchar_t). If it would > >> > + overflow the only way this program doesn't have undefined behavior > >> > + is if there is a null terminator in valid memory so strlen will > >> > + suffice. */ > >> > + mov %RSI_LP, %R10_LP > >> > + sar $62, %R10_LP > >> > + test %R10_LP, %R10_LP > >> > + jnz __wcslen_sse2 > >> > >> Branch to __wcslen_sse2 is wrong for 2 reasons: > >> > >> 1. __wcslen_sse2 is undefined with --disable-multi-arch. > > > > Won't __wcsnlen_sse2 be undefined with --disable-multi-arch as well? > > > >> > >> 2. You should skip ENDBR64 at function entry. > >> > >> Please create a new label and branch to it. > >> > > I am not quite sure how to do this. I am trying to use > > strstr-sse2-unaligned.S as a template: > > > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86_64/multiarch/strstr-sse2-unaligned.S;h=21e1a5f7cfde8ec07fcc4fc80d26984a58d651d7;hb=HEAD#l78 > > which appears to make a direct call to the global label of __strchr_sse2 > > without anything special in strchr-sse2.S or strstr-sse2-unaligned.S. > This is different since all files are in sysdeps/x86_64/multiarch. > I see. So it turns out we are missing wcslen_sse4_1 which strlen.S can also implement (it passes all tests). Would jumping to that be valid? Otherwise I think the best bet is to add a target for wcslen_sse4_1 and define it and wcsnlen_sse4_1 in the same file so the label is visible. The only issue is the #defines in strlen.S need to all be protected which is a bit messy. If we don't want to define wcslen_sse4_1 for whatever reason, I already have this approach working with defining wcsnlen_sse4_1 in the same file as wcslen-sse2.S and entering from a local label. But looking at the code it seems the strlen.S file is a bit better optimized. Thoughts? > > Is there an example in the code you know of I can follow? > > There are no exact same codes. > > memmove-vec-unaligned-erms.S has > > ENTRY (MEMMOVE_SYMBOL (__memmove, unaligned)) > movq %rdi, %rax > L(start): <<<<<<<<<<<<<< This is equivalent to __wcslen_sse2. > # ifdef __ILP32__ > /* Clear the upper 32 bits. */ > movl %edx, %edx > # endif > >> > >> > + sal $2, %RSI_LP > >> > # endif > >> > > >> > /* Initialize long lived registers. */ > >> > > >> > add %RDI_LP, %RSI_LP > >> > +# ifdef AS_WCSLEN > >> > +/* Check for overflow again from s + maxlen * sizeof(wchar_t). */ > >> > + jbe __wcslen_sse2 > >> > +# endif > >> > mov %RSI_LP, %R10_LP > >> > and $-64, %R10_LP > >> > mov %RSI_LP, %R11_LP > >> > -- > >> > 2.25.1 > >> > > >> > >> Thanks. > >> > >> > >> -- > >> H.J. > > > > -- > H.J. >