From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id E7DF43858D1E for ; Wed, 17 May 2023 09:29:21 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org E7DF43858D1E Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684315761; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type; bh=2eSQBQvN7PV+8l59AcE5p/KCZQQGuwvQaV5mE7wlVp8=; b=FTJNXz0Jc9KrLfnft/E4ryCp5z3406eKY8tH29cOQwnFlw1JBVz1FTkCiBwvN1YoXBWoJP S51x9Avou1s8ZVzNfS0KHtfPVGW1dHw4B0tAzB7N7jxJNg/18U0W4EMyzSaNk3cwmz3eZD JXluKi/0AZJwJ+j3uVMhju3K9nUmZCg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-594-yJkW1-LnO72TmWdYB1R2uA-1; Wed, 17 May 2023 05:29:20 -0400 X-MC-Unique: yJkW1-LnO72TmWdYB1R2uA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5C60C1C04B53 for ; Wed, 17 May 2023 09:29:20 +0000 (UTC) Received: from oldenburg3.str.redhat.com (unknown [10.39.195.46]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B735F63F5B for ; Wed, 17 May 2023 09:29:19 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: Making a syscall before ld.so self-relocation on MIPS Date: Wed, 17 May 2023 11:29:18 +0200 Message-ID: <87wn17jogh.fsf@oldenburg3.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: I'm reviewing HIDDEN_VAR_NEEDS_DYNAMIC_RELOC if they support inline system calls (without function calls), so that I can make a system call (mmap actually) before initial self-relocation of the dynamic loader. So far, it looks good in theory, except on MIPS. First there is MIPS16: /* There's no MIPS16 syscall instruction, so we go through out-of-line standard MIPS wrappers. These do use inline snippets below though, through INTERNAL_SYSCALL_MIPS16. Spilling the syscall number to memory gives the best code in that case, avoiding the need to save and restore a static register. */ Is MIPS16 the default in GCC? We don't build for explicitly in scripts/build-many-glibcs.py. Without MIPS16, many arguments use out-of-line function calls. But it seems that the effective relative address range for branches is fairly large. Maybe we can call a hidden function in ld.so without a relocation dependency after all? Thanks, Florian