From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) by sourceware.org (Postfix) with ESMTPS id 88FE2385DC22 for ; Mon, 7 Jun 2021 18:29:53 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 88FE2385DC22 Received: by mail-qk1-x736.google.com with SMTP id c18so2575932qkc.11 for ; Mon, 07 Jun 2021 11:29:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=L0ua484rCSj55FnA/aSNzwrk1t5T1xuxCrxYNhXtexk=; b=BgxsPgbpMh/SpDfW77GgyBqIOk+1xFsIPJrt8dVsaPX9G9ay1QpD2mtebaHvUA/bLi TI3h+Zi5Hsh0H4WBxCRtKZd6JXuzmbY2baYzvZggHdWSZ7BaKzYmyN4cS1ft4Yy+9C7r /AS04+Lc9KjDbqYO5Qiwhy0gcPVPzI+RUv9MLJcmshM5uFDdnnJXBuFbP0EHx37mssGh cafCNkF4xvr2WKIiunr0JQNN57YMup5scuiMhu8KdiV1IbVwkDVCRvdicledxK1hO7Rm fAhlX+xsOvS26kyZXU8sk3EGvEiqSb/+9dBrixsxDZSGlMHv6aTJ4Kt5lswxxskfM7Le fhpw== X-Gm-Message-State: AOAM531Gv8O7zLZDiXWY4K76AUtTJWnylYFw33SFWgW82rS+U3GaHAgw 42zBDjHLof4DWjfVvSUgqe6YOw== X-Google-Smtp-Source: ABdhPJylOkX95MwoWVkQ2e2eO9vboLdA6mL5FW/r6KRI3hsOxpRaQ+P8iM7MSG9JalqdOq+EqnJAyw== X-Received: by 2002:a05:620a:1267:: with SMTP id b7mr3091486qkl.385.1623090592978; Mon, 07 Jun 2021 11:29:52 -0700 (PDT) Received: from [192.168.1.4] ([177.194.59.218]) by smtp.gmail.com with ESMTPSA id a21sm9580574qtm.54.2021.06.07.11.29.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Jun 2021 11:29:52 -0700 (PDT) Subject: Re: [PATCH v2 14/25] y2038: Use a common definition for msqid_ds To: Carlos O'Donell , libc-alpha@sourceware.org References: <20210518205613.1487824-1-adhemerval.zanella@linaro.org> <20210518205613.1487824-15-adhemerval.zanella@linaro.org> From: Adhemerval Zanella Message-ID: Date: Mon, 7 Jun 2021 15:29:49 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, NICE_REPLY_A, 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: Mon, 07 Jun 2021 18:29:55 -0000 On 04/06/2021 16:38, Carlos O'Donell wrote: > On 5/18/21 4:56 PM, Adhemerval Zanella wrote: >> From: Lukasz Majewski >> >> Instead of replicate the same definitions from struct_msqid64_ds.h >> on the multiple struct_msqid_ds.h, use a common header which is included >> when required (struct_msqid64_ds_helper.h). >> >> The __USE_TIME_BITS64 is not defined internally yet, although the >> internal header is used when building the 64-bit stat implementations. > > Requesting a v3 please. > > Please add the __glibc_reserved* members to the structures to preserve > maximum compatibility with the kernel structure. > > What I would like to see is that __glibc_reserved4 and __glibc_reserved5 > are *preserved* for both ABIs in the dual-time case. The kernel for msqid > still has the following: > > 26 struct msqid64_ds { > 27 struct ipc64_perm msg_perm; > 28 #if __BITS_PER_LONG == 64 > 29 long msg_stime; /* last msgsnd time */ > 30 long msg_rtime; /* last msgrcv time */ > 31 long msg_ctime; /* last change time */ > 32 #else > 33 unsigned long msg_stime; /* last msgsnd time */ > 34 unsigned long msg_stime_high; > 35 unsigned long msg_rtime; /* last msgrcv time */ > 36 unsigned long msg_rtime_high; > 37 unsigned long msg_ctime; /* last change time */ > 38 unsigned long msg_ctime_high; > 39 #endif > 40 unsigned long msg_cbytes; /* current number of bytes on queue */ > 41 unsigned long msg_qnum; /* number of messages in queue */ > 42 unsigned long msg_qbytes; /* max number of bytes on queue */ > 43 __kernel_pid_t msg_lspid; /* pid of last msgsnd */ > 44 __kernel_pid_t msg_lrpid; /* last receive pid */ > 45 unsigned long __unused4; > 46 unsigned long __unused5; > 47 }; > > For maximum compatibility with future kernel changes we should keep > the unused fields in the glibc equivalent structure. If the values are > ever used then they would already be allocated as part of the size of > the structure without the need for an ABI change. Given that these are > somewhat legacy APIs we should be aiming for preserving existing behaviour > rather than aiming for the smallest possible size structure. > > On i686 the new 64-bit time_t struct is only 80 bytes, while the original > struct size is 88 bytes. Adding the reserved entries brings this back to > 88 bytes in the new ABI. We can add static asserts if we think we need to > check exactly for alignment of 64-bit time_t, but since we copy from a > kernel structure I'm largely worried about the ABI being too small to cary > the information that we might need to copy from the matching kernel struct. > Alright, I already sent my findings that it would increase the msqid_ds size for _TIME_BITS=64 on some legacy ABIs (arm, mips, s390) but as we discussed on weekly call it should be fine. I don't think we need a static assert to check for alignment here (since glibc export struct for _TIME_BITS might not be potentially equal to kernel expected one and we already do the heavy lifting in msgctl to copy and adjust the fields). > > This is a spurious cleanup from the last patch IMO. If possible please move it > into the previous commit. > > s/defitions/definitions/g > >> Copyright (C) 2021 Free Software Foundation, Inc. >> This file is part of the GNU C Library. >> Ack, I just removed this change. >> diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds.h b/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds.h >> index 43e8cd7cfc..992734914a 100644 >> --- a/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds.h >> +++ b/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds.h >> @@ -25,14 +25,6 @@ >> #else >> struct __msqid64_ds >> { >> - struct ipc_perm msg_perm; /* structure describing operation permission */ >> - __time64_t msg_stime; /* time of last msgsnd command */ >> - __time64_t msg_rtime; /* time of last msgsnd command */ >> - __time64_t msg_ctime; /* time of last change */ >> - __syscall_ulong_t __msg_cbytes; /* current number of bytes on queue */ >> - msgqnum_t msg_qnum; /* number of messages currently on queue */ >> - msglen_t msg_qbytes; /* max number of bytes allowed on queue */ >> - __pid_t msg_lspid; /* pid of last msgsnd() */ >> - __pid_t msg_lrpid; /* pid of last msgrcv() */ >> +# include > > OK. Used unconditionally since this is 64-bit time_t. > >> }; >> #endif >> diff --git a/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds_helper.h b/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds_helper.h >> new file mode 100644 >> index 0000000000..02dfddaa2b >> --- /dev/null >> +++ b/sysdeps/unix/sysv/linux/bits/types/struct_msqid64_ds_helper.h >> @@ -0,0 +1,28 @@ >> +/* Common defintions for struct msqid_ds with 64 bit time. > > s/defintions/definitions/g Ack. > >> + 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 >> + . */ >> + > > Reviewing... > >> + /* Content of internal __msqid64_ds. */ >> + struct ipc_perm msg_perm; /* structure describing operation permission */ > > OK. > >> + __time64_t msg_stime; /* time of last msgsnd command */ >> + __time64_t msg_rtime; /* time of last msgsnd command */ >> + __time64_t msg_ctime; /* time of last change */ > > OK. Usually a tuple of * and *_high (endian swapping for order applied). > >> + __syscall_ulong_t __msg_cbytes; /* current number of bytes on queue */ > > OK. > >> + msgqnum_t msg_qnum; /* number of messages currently on queue */ > > OK. > >> + msglen_t msg_qbytes; /* max number of bytes allowed on queue */ > > OK. > >> + __pid_t msg_lspid; /* pid of last msgsnd() */ >> + __pid_t msg_lrpid; /* pid of last msgrcv() */ > > OK. > > Add __glibc_reserved4/5 entries here. > Ack.