From patchwork Fri Feb 16 20:23:34 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnd Bergmann X-Patchwork-Id: 13560524 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2EF67135A6F; Fri, 16 Feb 2024 20:23:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708115039; cv=none; b=W/ZyNW0UflRYyP/hmXQHFwKevKoSJQBFZd4dYHrOPJYjYpqymjw9GkZzgW6IUMle+qlvhjTNaHqbRtN4kRpq1z4ClT9eEZ9t2oJ08J6FrfRCMbztZ1QiLcwGuh6tMTj5HROpeBLEJtcNk08qnUcL/oJopeVfwM0H/ScVeLTwnMU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708115039; c=relaxed/simple; bh=Sq/Mpf4CU1DDxAJaU5smyIB6OI93uNYISckA1rqgEqc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=iB1ruXJJeSyQXtiVpWlmnoVzK6HCFHMjd4QBpMlOuamQeIvWRME/wgHBBDc17nUNExiTZ0Yc0DrdMtsoYC5p6HwA1LbeP6FVs4d0AQOhqcuH1j1CjmpdgCWEFJOYqNV9KcjGpEBgv/jAHRJ7/KC39Zx79RFpHrBv88yDA6IDe0E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BREFQPUE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BREFQPUE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9DD7C433C7; Fri, 16 Feb 2024 20:23:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708115038; bh=Sq/Mpf4CU1DDxAJaU5smyIB6OI93uNYISckA1rqgEqc=; h=From:To:Cc:Subject:Date:From; b=BREFQPUE+Lg3oFG94/XQbjW6/X+N9Fgw8T5AM64uUsoM72l6MQ59lraq2doPeAmw0 gDuJLNl+241uzB2b51z9SyZ4hC6DZvvm8yLd+PNsKAmnUOL68zlMmfjN0bfQWpM0pd Ars2RqyFjk6GCUfQyBKbiffJqgbSCHUu46VLLSCSBmyGaMUALsTwJlygoySG7izBUr 6eivxdVnqLOuY8O6W2m+xBwAjiQN5gdxr7EYCRV6hBsrzlx5tWGshcsXdz0XtpvgtM AepxHs04hMDnSrPQU+THAkdsqYO1fmCnnMVMRLhwc6uL3gfRhk411oeGOh0wolXfkP qZaPK+/EP9M6w== From: Arnd Bergmann To: Alexander Viro , Christian Brauner Cc: Arnd Bergmann , Jan Kara , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Kees Cook , Andrew Morton , Andi Kleen , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH] fs/select: rework stack allocation hack for clang Date: Fri, 16 Feb 2024 21:23:34 +0100 Message-Id: <20240216202352.2492798-1-arnd@kernel.org> X-Mailer: git-send-email 2.39.2 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Arnd Bergmann A while ago, we changed the way that select() and poll() preallocate a temporary buffer just under the size of the static warning limit of 1024 bytes, as clang was frequently going slightly above that limit. The warnings have recently returned and I took another look. As it turns out, clang is not actually inherently worse at reserving stack space, it just happens to inline do_select() into core_sys_select(), while gcc never inlines it. Annotate do_select() to never be inlined and in turn remove the special case for the allocation size. This should give the same behavior for both clang and gcc all the time and once more avoids those warnings. Fixes: ad312f95d41c ("fs/select: avoid clang stack usage warning") Signed-off-by: Arnd Bergmann Reviewed-by: Kees Cook Reviewed-by: Andi Kleen Reviewed-by: Jan Kara --- fs/select.c | 2 +- include/linux/poll.h | 4 ---- 2 files changed, 1 insertion(+), 5 deletions(-) diff --git a/fs/select.c b/fs/select.c index 11a3b1312abe..9515c3fa1a03 100644 --- a/fs/select.c +++ b/fs/select.c @@ -476,7 +476,7 @@ static inline void wait_key_set(poll_table *wait, unsigned long in, wait->_key |= POLLOUT_SET; } -static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) +static noinline_for_stack int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) { ktime_t expire, *to = NULL; struct poll_wqueues table; diff --git a/include/linux/poll.h b/include/linux/poll.h index a9e0e1c2d1f2..d1ea4f3714a8 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -14,11 +14,7 @@ /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating additional memory. */ -#ifdef __clang__ -#define MAX_STACK_ALLOC 768 -#else #define MAX_STACK_ALLOC 832 -#endif #define FRONTEND_STACK_ALLOC 256 #define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC #define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC