From nobody Wed Sep 10 06:49:07 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F5F8C001DC for ; Thu, 27 Jul 2023 22:51:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230361AbjG0Wv2 (ORCPT ); Thu, 27 Jul 2023 18:51:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229499AbjG0WvZ (ORCPT ); Thu, 27 Jul 2023 18:51:25 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D04B430D2 for ; Thu, 27 Jul 2023 15:51:01 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id 3f1490d57ef6-d052f49702dso1363092276.3 for ; Thu, 27 Jul 2023 15:51:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1690498261; x=1691103061; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=9gBFfLJA2QnUt2o02yj0CBzRwwnMTjBwRjYaFoYtp30=; b=tRjo0W7c5gh+Dl3UY4mPCGq5xDIupvaIqcoLAO+9A9kMjC1WtyedfU6hNp4MSytOPv +tlpG0WLRrdfIwlylaKATwQVYjuLN6/5nw+atV3kXwCugkKtuurz4KvMOG+WiX99AZKE JpuagiL99epKN2RpBFrz2XNkolkmASb84Mm39epg2pYFJ+aTGHvDFAR454touPNQrlxv 9PbUxILqC2VhCabFZuQA18iK20AVBdQIa0RykF6333oDvdoV2lUpoOUj7jbw0gwqtJ8B wccBZPAUPOHacmQ/pxoXlIGHNrW8HHMFWFHNOmkhzaIoPSyUgArPtv1HenJDOYcgiMC9 I6Yw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690498261; x=1691103061; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=9gBFfLJA2QnUt2o02yj0CBzRwwnMTjBwRjYaFoYtp30=; b=kdOoaQ1Nu9KrVMmFjw91T9at2eaFzlj679HkOK0C2tFDntO8b3/lEGkzuUtdVvSGLb zwkSSgC2lMXx9myy37/tpzS18OfFSHUsLXoYsBtbub6auy3EPe4/iIi+FYQO7j+qASNo KLWajeShaOh5Bu3MHyyRzl+MTLyyT5IUqhvFzKJUGTrVCkBFEumBSweDXFAy1kTHfcbK nI64iq3pORAIyOxC6Gmht6nSN9TpvrtiXqR+6+WXaqzG5W0m9w785vQzQ7x1lyUTx4Tw Z+mIcGeism95MgNQpPr7nCvkyWUoqXbyuU9/nFsFnjY3121FSzSNO/L0lEir0L9NBe5M Ax9w== X-Gm-Message-State: ABy/qLaLkQ2BAe5apdmWIHYL9DPPtx6tHZQuk4zlMnbGSDJvQ6QJJlMG 85MCVwK9Fz5Ec5HojtdmpSpctJtn10cx5clz86c= X-Google-Smtp-Source: APBJJlHs1u1Z2TVx58in2bo8paryCsP0hXDuuvI0B3YUjX8FowCyzCFy0y9JpwKV4OLjAO/T78ne7OXi3rwgeHRzdVE= X-Received: from ndesaulniers-desktop.svl.corp.google.com ([2620:15c:2d1:203:659f:4728:cfbb:8cc3]) (user=ndesaulniers job=sendgmr) by 2002:a25:d2c9:0:b0:d05:7ba4:67f9 with SMTP id j192-20020a25d2c9000000b00d057ba467f9mr144ybg.3.1690498261119; Thu, 27 Jul 2023 15:51:01 -0700 (PDT) Date: Thu, 27 Jul 2023 15:50:58 -0700 Mime-Version: 1.0 X-B4-Tracking: v=1; b=H4sIANH0wmQC/2WNyw6DIBQFf8XcdWl4hCJd+R+NC8RbIFEwUE0b4 7+Xuu1yJidzdiiYAxa4Nztk3EIJKVbglwasN9EhCWNl4JQLqrgiZh7dshItLEUpKNeSQR0PpiA ZsonW13lcp6nKJeMzvM/6o6/sQ3ml/DnPNvazf92NEUaMljdNUUnRtp1LyU14tWmG/jiOL3UgT tOyAAAA X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=UIrHvErwpgNbhCkRZAYSX0CFd/XFEwqX3D0xqtqjNug= X-Developer-Signature: v=1; a=ed25519-sha256; t=1690498259; l=3950; i=ndesaulniers@google.com; s=20220923; h=from:subject:message-id; bh=HmXOPSMRuaQICNAuT3z+gT3+4lGoIiU2zn92zax0abE=; b=C/jkLISLEg3RiEbGKI3rgPrsu0tsBb8GyyA/jdmvz1BRew0Z+NUTi11CP6+Z2T96EFYYXYUQh jtpaWUls+1bBQK1bfjI0vJFqRDFd85XQSGhQzFzs1b9y8kZQH7Qiop7 X-Mailer: b4 0.12.2 Message-ID: <20230727-amdgpu-v2-1-7fc66bc52bf6@google.com> Subject: [PATCH v2] drm: fix indirect goto into statement expression UB From: ndesaulniers@google.com To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Nathan Chancellor , Tom Rix Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Naresh Kamboju , Nick Desaulniers Content-Type: text/plain; charset="utf-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable A new diagnostic in clang-17 now produces the following build error: drivers/gpu/drm/tests/drm_exec_test.c:41:3: error: cannot jump from this indirect goto statement to one of its possible targets 41 | drm_exec_retry_on_contention(&exec); | ^ include/drm/drm_exec.h:96:4: note: expanded from macro 'drm_exec_retry_on_contention' 96 | goto *__drm_exec_retry_ptr; | ^ drivers/gpu/drm/tests/drm_exec_test.c:39:2: note: possible target of indirect goto statement 39 | drm_exec_until_all_locked(&exec) { | ^ include/drm/drm_exec.h:79:33: note: expanded from macro 'drm_exec_until_all_locked' 79 | __label__ __drm_exec_retry; drivers/gpu/drm/tests/drm_exec_test.c:39:2: note: jump enters a statement expression The GCC manually currently states that: >> Jumping into a statement expression with a computed goto (see Labels >> as Values) has undefined behavior. So the diagnostic appears correct, even if codegen happened to produce working code. Looking closer at this code, while the original combination of statement expression, local label, and computed/indirect goto GNU C expressions were clever, a simple while loop and continue block might have sufficed. This approach might not work as expected if drm_exec_until_all_locked "loops" can be nested, but that doesn't appear to be an existing use case in the codebase. Fixes: commit 09593216bff1 ("drm: execution context for GEM buffers v7") Link: https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html Link: https://github.com/ClangBuiltLinux/linux/issues/1890 Link: https://github.com/llvm/llvm-project/commit/20219106060208f0c2f5d096e= b3aed7b712f5067 Reported-by: Nathan Chancellor Reported-by: Naresh Kamboju Signed-off-by: Nick Desaulniers Tested-by: Nathan Chancellor # build --- Changes in v2: Fix the continue to be outside of the do while - Link to v1: https://lore.kernel.org/r/20230727-amdgpu-v1-1-a95690e75388@g= oogle.com --- include/drm/drm_exec.h | 21 +++++---------------- 1 file changed, 5 insertions(+), 16 deletions(-) diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h index 73205afec162..fa1cc5c3d021 100644 --- a/include/drm/drm_exec.h +++ b/include/drm/drm_exec.h @@ -70,18 +70,8 @@ struct drm_exec { * Core functionality of the drm_exec object. Loops until all GEM objects = are * locked and no more contention exists. At the beginning of the loop it is * guaranteed that no GEM object is locked. - * - * Since labels can't be defined local to the loops body we use a jump poi= nter - * to make sure that the retry is only used from within the loops body. */ -#define drm_exec_until_all_locked(exec) \ - for (void *__drm_exec_retry_ptr; ({ \ - __label__ __drm_exec_retry; \ -__drm_exec_retry: \ - __drm_exec_retry_ptr =3D &&__drm_exec_retry; \ - (void)__drm_exec_retry_ptr; \ - drm_exec_cleanup(exec); \ - });) +#define drm_exec_until_all_locked(exec) while(drm_exec_cleanup(exec)) =20 /** * drm_exec_retry_on_contention - restart the loop to grap all locks @@ -90,11 +80,10 @@ __drm_exec_retry: \ * Control flow helper to continue when a contention was detected and we n= eed to * clean up and re-start the loop to prepare all GEM objects. */ -#define drm_exec_retry_on_contention(exec) \ - do { \ - if (unlikely(drm_exec_is_contended(exec))) \ - goto *__drm_exec_retry_ptr; \ - } while (0) +#define drm_exec_retry_on_contention(exec) \ + if (unlikely(drm_exec_is_contended(exec))) \ + continue; \ + do {} while (0) =20 /** * drm_exec_is_contended - check for contention --- base-commit: 451cc82bd11eb6a374f4dbcfc1cf007eafea91ab change-id: 20230727-amdgpu-93c0e5302951 Best regards, --=20 Nick Desaulniers