From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by sourceware.org (Postfix) with ESMTPS id 750583850438 for ; Tue, 22 Jun 2021 23:29:15 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 750583850438 Received: by mail-pg1-x532.google.com with SMTP id v7so126131pgl.2 for ; Tue, 22 Jun 2021 16:29:15 -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=IYDvTBF4TqkC51GS2IbzdO7lLPJ3wgCuTFgMlh94x8I=; b=VtN6AACSKlAc15ew2rCJ+xid3M5E6DWpL2OJR8DSU8pI31z5F/S/a3EPHdfwTfzbWS 7gL83wFlbJd5yYCyTQohdu7deZHsKGS0nFTUliBXVz0tqBtzQlnsc2IwyYZkvZWGCn2b pC8g+0GVPlBQovQtm0QBkdSb9gjHE32xUBUUYz/7+NkuHmPCx57gIe1jol9Ez4nhj3sl BYzdC+//biyaiV0asIZuLY7GjeEqE/O+iCZeCbytKBWGumAqWMYKKWFbuERFjd9Nwseh wdKR3vE/AUr3nUoWnC4I3DdIvGWNQ1tYI4ENTrAgBQZopNhlyRLGLjVkyKGuXatOSAyC TsaQ== X-Gm-Message-State: AOAM533Acb4bNrnfic5ED+aITTCFsgg+4aZUpbt/gPmkBJaGHamTqSHW wqvdtKWNzOtoTPoYzxxUzp3kUyRauyz6U64uvF8= X-Google-Smtp-Source: ABdhPJyO5VH20S4/P5z0MrdF1kuQ/pwsO1NRnGlnkTIqRn1jPMfnox6bkiO+dhGTq/9BPnpaZ1TrvTFnJ03QgcU6FLU= X-Received: by 2002:a62:1657:0:b029:301:af69:5ae3 with SMTP id 84-20020a6216570000b0290301af695ae3mr5897333pfw.57.1624404554256; Tue, 22 Jun 2021 16:29:14 -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: "H.J. Lu" Date: Tue, 22 Jun 2021 16:28:38 -0700 Message-ID: Subject: Re: [PATCH v2 3/3] x86: Fix overflow bug in wcsnlen-sse4_1 and wcsnlen-avx2 [BZ #27974] To: Noah Goldstein Cc: GNU C Library , "Carlos O'Donell" Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3032.5 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, 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 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: Tue, 22 Jun 2021 23:29:18 -0000 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 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. > 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.