From nobody Wed Sep 10 06:37:15 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 923A6EB64DD for ; Thu, 27 Jul 2023 22:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230308AbjG0WrS (ORCPT ); Thu, 27 Jul 2023 18:47:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229804AbjG0WrP (ORCPT ); Thu, 27 Jul 2023 18:47:15 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 911DF1BC1 for ; Thu, 27 Jul 2023 15:47:14 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-583f048985bso15006157b3.2 for ; Thu, 27 Jul 2023 15:47:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1690498034; x=1691102834; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=h8M17W+SY6LNnIrBQCPmXoDqQ4N8XZNCU3T7YHTRw88=; b=qKt37uGq/wscmlYr8MsZg//pXb6RySyaO4y6NJeuPda08KKiBjtJBS67P14T6qV1M0 LL9mjLjQYaJiLnSUF4EWtgT2q06OnX5y+YpaxLHO6f+6a3EIbFNrTc+7RB4U+ZiuyvVa wVuGmAuWeRbHjs/5JgVP2QOlnsY5lyobE6B9bss/BiV7uNJCKRAb8KCsQodxtcNumAeV tfOwogzv3MOn84SrebCIma7DNohFZJb5l213YxgBfudwFCoGEAXHH/L6snpDUdyijney 6+Vc/w4tJvqI9+iRC6+Sw/3tZ8W5zMhUWDBE49fQTskT0ezoLHQgsg5p62+Ls2Lm9eBP fV9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690498034; x=1691102834; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=h8M17W+SY6LNnIrBQCPmXoDqQ4N8XZNCU3T7YHTRw88=; b=XtlUZ5LdxHjItjGAiEt+7IWwcfhmMR4lYDo3cYPcSGJ+N3ZAQOHwK+9Lr7MyyBzaxf kf0U/z3TTtCeXOXg8JkImgmcFfD7BMfnkpPvvhrumaBw++rmlSaM5yWvFdW+birmhBqz gSr7yAjdpzcNR+UgYZ8EsYis6Akkn4a4t/OygbaZCTNSLBQyh7zm490sk3QgPpjWXXts HFT+FG7HJM5VLh3RUWcM8PwPuRP4W+rMRNK/vyPw7/1BxaAZSGdNi9OfNTrZwRqamtZm 1cOZ9HnIQDWS8sjpTqNN4XwXlhQLos5Fvlk7NJeIQp+Be6uopuDcVw9oZC6FyCw7AYwC kCGQ== X-Gm-Message-State: ABy/qLYzZ/BTXWmkHw6LO9/wjV7f4IrYzfMVXF9+mAoO3LIfIfKNwnOc MMuoZSEc3xF2CVLOv9FqAZUVHY/nDgoctJH2z64= X-Google-Smtp-Source: APBJJlFGnVWRLJUkrTVrUmig5mpkfOptKBJYmMCfyEC709K8nbUaHxXMj+WKdKG5zBlRCFhHoXkA4S2rhsmnF/EMJIQ= X-Received: from ndesaulniers-desktop.svl.corp.google.com ([2620:15c:2d1:203:659f:4728:cfbb:8cc3]) (user=ndesaulniers job=sendgmr) by 2002:a05:690c:721:b0:573:8316:8d04 with SMTP id bt1-20020a05690c072100b0057383168d04mr212ywb.4.1690498033839; Thu, 27 Jul 2023 15:47:13 -0700 (PDT) Date: Thu, 27 Jul 2023 15:47:09 -0700 Mime-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAOzzwmQC/x2MQQqAIBAAvxJ7TjAlwr4SHdS2XCgLpQjEv7d0n GGYAhkTYYaxKZDwoUxnZOjaBnywcUNBCzMoqbQc1CDssWzXLYz2Enstlek74NjZjMIlG33gPN7 7zvJKuNL736e51g9FP1hgbQAAAA== X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=UIrHvErwpgNbhCkRZAYSX0CFd/XFEwqX3D0xqtqjNug= X-Developer-Signature: v=1; a=ed25519-sha256; t=1690498032; l=3429; i=ndesaulniers@google.com; s=20220923; h=from:subject:message-id; bh=h5xjymXwHB0lf01RIpHtYLR4vTj4v+sUfx87gYKkB7Y=; b=N2uJPCF50jFFN4PLKe1RA7MLTy5RlIkmUWI7lMBscLyrcTCLI3tbqj7jsQDczYGb8rXqmc7m4 fVVfKltnA+lByM/BerwonDXLZydewq7ck6QpVuol9QtpGTy2Znh+q3q X-Mailer: b4 0.12.2 Message-ID: <20230727-amdgpu-v1-1-a95690e75388@google.com> Subject: [PATCH] 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 --- include/drm/drm_exec.h | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h index 73205afec162..393ac022ed3a 100644 --- a/include/drm/drm_exec.h +++ b/include/drm/drm_exec.h @@ -70,18 +70,9 @@ 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); \ - });) + while(drm_exec_cleanup(exec)) =20 /** * drm_exec_retry_on_contention - restart the loop to grap all locks @@ -93,7 +84,7 @@ __drm_exec_retry: \ #define drm_exec_retry_on_contention(exec) \ do { \ if (unlikely(drm_exec_is_contended(exec))) \ - goto *__drm_exec_retry_ptr; \ + continue; \ } while (0) =20 /** --- base-commit: 451cc82bd11eb6a374f4dbcfc1cf007eafea91ab change-id: 20230727-amdgpu-93c0e5302951 Best regards, --=20 Nick Desaulniers