From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 188CE247DF9; Tue, 15 Jul 2025 15:53:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752594798; cv=none; b=OXuZxz6FOxJT8Q+N0W0+ZEs1W+KoMlT4B23yDEjeYM8tYULuhesggVd3AXaXR5ak1tJBY7AMkIC/EedIdriol29MxmrJ6pN2rg/Py8cwUB5XPTFRVQtOKc0amqRqSOYTM4jDNaECLy6YG5HMoGzDeIWmIHfX6Z51Aark4bV817w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752594798; c=relaxed/simple; bh=wU3e9HJeH/DY7sTOVhInQNEvtGjh+kj5oo/xKVxRTfU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Ahzh7U75ceZQQ66QLs4h6Au+pRXurGHaotZKymEqTlpH4msHd9+xITTOgB+5bkYYqNbAkEx+HhdGLTa1i7VXkLeayir1uxZpT/u+Yof2iN9xU64iWpe7D9VTu4unbwTeDUn4WQToDXA4YsCrCApYKbUF+JT5tsPhUJ2760j0xew= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=m3HV9td4; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="m3HV9td4" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 56FFqgiW1035906 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 15 Jul 2025 08:52:45 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 56FFqgiW1035906 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025062101; t=1752594766; bh=SEcCsOO82E/DNVVnYdIJVwGaG0aOw/9Zah1U8zubMuc=; h=From:To:Cc:Subject:Date:From; b=m3HV9td4PvA3VbMqe5VpDebvtgVYxf93FH1D9Ot/x3sxdkoWp3hEONsWsvzyFsSQA hcC8uV1mZDzn1A9uiciZf24GTfe46DuOQDXJnq+KyJjN4oWn7FkxhiGgAjE6Enb9ii rT3vaX9kKRBR4K/9jH3yGIClQa3xydfYFV273pVh8NmsJjffCrJZ2NfE7XVSZLfgBz lV5rU8H4TlpqP/CWRHSdpCAeMsSotw88JK4QeJXBqm6OZdzjgQ5YPRGC1tAnPfYd/c wpqmpyVvJMShVaBgVwHPK3l9FQEdaDkuRiyad9Rz7q9cuDlf+PnhG3Dip/XWAwkydQ ofB/cJQDla3qQ== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org Cc: luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, jmill@asu.edu, peterz@infradead.org, andrew.cooper3@citrix.com, stable@vger.kernel.org Subject: [PATCH v2 1/1] x86/fred: Remove ENDBR64 from FRED entry points Date: Tue, 15 Jul 2025 08:52:42 -0700 Message-ID: <20250715155242.1035896-1-xin@zytor.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The FRED specification v9.0 states that there is no need for FRED event handlers to begin with ENDBR64, because in the presence of supervisor indirect branch tracking, FRED event delivery does not enter the WAIT_FOR_ENDBRANCH state. As a result, remove ENDBR64 from FRED entry points. Then add ANNOTATE_NOENDBR to indicate that FRED entry points will never be used for indirect calls to suppress an objtool warning. This change implies that any indirect CALL/JMP to FRED entry points causes #CP in the presence of supervisor indirect branch tracking. Credit goes to Jennifer Miller and other contributors from Arizona State University whose work led to this change. Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code") Link: https://lore.kernel.org/linux-hardening/Z60NwR4w%2F28Z7XUa@ubun/ Reviewed-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li (Intel) Cc: Jennifer Miller Cc: Peter Zijlstra Cc: Andrew Cooper Cc: H. Peter Anvin Cc: stable@vger.kernel.org # v6.9+ --- Change in v2: *) CC stable and add a fixes tag (PeterZ). --- arch/x86/entry/entry_64_fred.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S index 29c5c32c16c3..907bd233c6c1 100644 --- a/arch/x86/entry/entry_64_fred.S +++ b/arch/x86/entry/entry_64_fred.S @@ -16,7 +16,7 @@ .macro FRED_ENTER UNWIND_HINT_END_OF_STACK - ENDBR + ANNOTATE_NOENDBR PUSH_AND_CLEAR_REGS movq %rsp, %rdi /* %rdi -> pt_regs */ .endm -- 2.50.1