From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 16CBECAC5A7 for ; Tue, 23 Sep 2025 11:18:17 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v110w-0003fK-GK; Tue, 23 Sep 2025 07:16:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v110s-0003eI-67 for qemu-devel@nongnu.org; Tue, 23 Sep 2025 07:16:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v110b-00049e-Kw for qemu-devel@nongnu.org; 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Tue, 23 Sep 2025 11:16:21 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.33]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F12701800452; Tue, 23 Sep 2025 11:16:20 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 454F021E6A27; Tue, 23 Sep 2025 13:16:18 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: qemu-devel@nongnu.org, richard.henderson@linaro.org, Pierrick Bouvier , odaki@rsg.ci.i.u-tokyo.ac.jp, marcandre.lureau@redhat.com, berrange@redhat.com, vsementsov@yandex-team.ru Subject: Re: [PATCH v3 02/13] tcg: Fix error reporting on mprotect() failure in tcg_region_init() In-Reply-To: <6ebc31f0-c6cf-4e14-a87d-5b59f6c6105f@linaro.org> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Tue, 23 Sep 2025 11:41:03 +0200") References: <20250923091000.3180122-1-armbru@redhat.com> <20250923091000.3180122-3-armbru@redhat.com> <6ebc31f0-c6cf-4e14-a87d-5b59f6c6105f@linaro.org> Date: Tue, 23 Sep 2025 13:16:18 +0200 Message-ID: <87h5wta071.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_PASS=-0.001, T_SPF_HELO_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Philippe Mathieu-Daud=C3=A9 writes: > On 23/9/25 11:09, Markus Armbruster wrote: >> tcg_region_init() calls one of qemu_mprotect_rwx(), >> qemu_mprotect_rw(), and mprotect(), then reports failure with >> error_setg_errno(&error_fatal, errno, ...). >> >> The use of &error_fatal is undesirable. qapi/error.h advises: >> >> * Please don't error_setg(&error_fatal, ...), use error_report() and >> * exit(), because that's more obvious. >> >> The use of errno is wrong. qemu_mprotect_rwx() and qemu_mprotect_rw() >> wrap around qemu_mprotect__osdep(). qemu_mprotect__osdep() calls >> mprotect() on POSIX, VirtualProtect() on Windows, and reports failure >> with error_report(). VirtualProtect() doesn't set errno. mprotect() >> does, but error_report() may clobber it. >> >> Fix tcg_region_init() to report errors only when it calls mprotect(), >> and rely on qemu_mprotect_rwx()'s and qemu_mprotect_rw()'s error >> reporting otherwise. Use error_report(), not error_setg(). >> >> Fixes: 22c6a9938f75 (tcg: Merge buffer protection and guard page protect= ion) >> Fixes: 6bc144237a85 (tcg: Use Error with alloc_code_gen_buffer) >> Cc: Richard Henderson >> Signed-off-by: Markus Armbruster >> Reviewed-by: Daniel P. Berrang=C3=A9 >> Reviewed-by: Richard Henderson >> --- >> tcg/region.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> diff --git a/tcg/region.c b/tcg/region.c >> index 7ea0b37a84..2181267e48 100644 >> --- a/tcg/region.c >> +++ b/tcg/region.c >> @@ -832,13 +832,16 @@ void tcg_region_init(size_t tb_size, int splitwx, = unsigned max_threads) >> } else { >> #ifdef CONFIG_POSIX >> rc =3D mprotect(start, end - start, need_prot); >> + if (rc) { >> + error_report("mprotect of jit buffer: %s", >> + strerror(errno)); > > I'm not keen on handling errors differently in the same function. > > qemu_mprotect_rwx() and qemu_mprotect_rw() already print the error. Yes: they call qemu_mprotect__osdep(), which uses error_report(). > Why not add qemu_mprotect() as a simple qemu_mprotect__osdep() alias, > then call it here, also covering the non-POSIX case? > (Question for Richard, after looking at commits 22c6a9938f7 and more > importantly 97a83753c9 -- wondering about WoA). There is no commit 97a83753c9. Do you mean a97a83753c9? I'd like to merge this commit as is. It's a minimal fix, and it's been reviewed. We can always improve on top. >> + } >> #else >> g_assert_not_reached(); >> #endif >> } >> if (rc) { >> - error_setg_errno(&error_fatal, errno, >> - "mprotect of jit buffer"); >> + exit(1); >> } >> } >> if (have_prot !=3D 0) {