From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-x336.google.com (mail-ot1-x336.google.com [IPv6:2607:f8b0:4864:20::336]) by sourceware.org (Postfix) with ESMTPS id 396303858D38 for ; Mon, 10 Apr 2023 21:33:16 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 396303858D38 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-ot1-x336.google.com with SMTP id ca22-20020a056830611600b006a3c1e2b6d2so5367917otb.13 for ; Mon, 10 Apr 2023 14:33:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1681162395; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=yVnZmIPgjh7v7cnS3oPNX9SlSZRii+8OiJ4EOZT3T0g=; b=WQcrhFdEpiAUz+nUnAf6eCZqch9t3MAHy2AeMwchCjyO/OIHoj1ICVxdNlthSMJg4Q R7aT6TWYx9pfBE6qTLIXYVfX/AEIvJuLPlMCs9PrEmXXcwsGDtMjm+SeT9Fb/kMd2t61 xep3IzFc5XJLbIvvXLZHjrGz0w634CUm2grz/PKWNqgzDj1Gn+T2bXCKGQ0aL463Xsdz HjKcC7EJoggecICfrcDZaw1bGkRrDQh/hAiurHm9KsmfkQRVeZcOL/RAweM9by1aRoD4 OFqjXJDpzTPwhURcyF+xB0zAbXRKVNrbre3vpGZgJgMHR8ghJRd3SRL7u90z3i8rSbo8 kmDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1681162395; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=yVnZmIPgjh7v7cnS3oPNX9SlSZRii+8OiJ4EOZT3T0g=; b=QO0B2gz6Qd4IfBPY8zeQFJ9Iq4lgmJ+drMpNy54/brNpbypW1iLZPtJTRu/h1ELWJF idmGQqqaBsx4aqMz3qsB190hnPreuQQ227mR3risJuAHN6Og2iWNgNSLAP7Y6rrQIBVv 5zpvKpG7mvFw/Gf+UOu3n6tL9XUE+KMYkSYdbUDGSUOP+++fwpOkrE5gSsRcfk+kp+cm qUZuwNcOOaOQdK/1gt6FDeQNVYcRSicx7egqt5y79CLWzIazaLRCcxuzVUrRVza/S7/M 5hWuQ9DG4h9olyOvxVqJeSauGYOHGfyNA9sh5y6N+IZcd9jyPDon3443othxMQPcBH6f 89lA== X-Gm-Message-State: AAQBX9dky8E+DNdeuCh6MvdWLxw+cXpdANsB7g1Wkv6fr7MOeJuOCmwz AU1c8aRtaNv08jEQuCHGeBYcdFj9vT+88qXQ+rUFPT1hCgp9Lw== X-Google-Smtp-Source: AKy350YR42gniTpz10j5CjxgvB656jiZxpKAuuCcIwavJZZRqEtosMDIcFIzVvYhmVejSi4p9n0fwQ8Oo/6b+Stsl1o= X-Received: by 2002:a05:6830:1d55:b0:699:7883:940d with SMTP id p21-20020a0568301d5500b006997883940dmr2285823oth.7.1681162395561; Mon, 10 Apr 2023 14:33:15 -0700 (PDT) MIME-Version: 1.0 References: <20230319151017.531737-19-bugaevc@gmail.com> <20230403115621.258636-1-bugaevc@gmail.com> <20230403115621.258636-3-bugaevc@gmail.com> <20230410190431.epkqgn3groggrcr3@begin> In-Reply-To: <20230410190431.epkqgn3groggrcr3@begin> From: Sergey Bugaev Date: Tue, 11 Apr 2023 00:33:04 +0300 Message-ID: Subject: Re: [PATCH v2 18.2/34] hurd: Port trampoline.c to x86_64 To: Samuel Thibault Cc: bug-hurd@gnu.org, libc-alpha@sourceware.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,KAM_NUMSUBJECT,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Mon, Apr 10, 2023 at 10:04=E2=80=AFPM Samuel Thibault wrote: > Sergey Bugaev, le lun. 03 avril 2023 14:56:21 +0300, a ecrit: > > @@ -110,6 +132,10 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, = const struct sigaction *action > > ucontext_t *uctxp; /* Points to uctx, below. */ > > } posix; > > }; > > + > > +#ifdef __x86_64__ > > + void *_pad; > > +#endif > > Please mention what that is for. This is to make sigreturn_addr 16-byte aligned (and this is verified by the static assert below). Our %rsp points right here at &sigreturn_addr when we call the user's signal handler (and then sigreturn, except we ret to it instead of call'ing it, but either way it's pushing or popping 8 bytes), and it needs to be 16-byte aligned before a function call per the x86_64 ABI. You're right that another comment next to _pad itself wouldn't hurt. Sergey