From nobody Sun Jun 14 09:56:33 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 00987390202 for ; Thu, 2 Apr 2026 10:34:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775126095; cv=none; b=EVpjTW7MyQJp6hQ0JKrByf0QQuRL77aGXrPs9fJPVbrZnyX8GrdxW7O7uurB4IWPPPahdb73bRsB5udopxpY2lJOi9INQD8hAg2dBClLxRh8kItlYtpbsSZe9V5NNBIl5yxOb4u/7Lk1+/ifI8g0/Mk8Om0NBZfi/JXnsUMezJ0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775126095; c=relaxed/simple; bh=Oa6OfwqPvpLmZLovWO/G15zj+GpaA1PfOh/lLfGzlYM=; h=Message-ID:Subject:From:To:Cc:Date:Content-Type:MIME-Version; b=prO7CpTTPNKl8ZCg67DzZSNNFRkBNjLicNxwUuBX635a4BzMBf3PJhoVmH5PhEtPvhZB8lHFtp4a6lURDOtXqcy/t1rxeOlaz6W0SLuNMMQ5HHnxBsWst7U8LEBK2D+n9FSg2kt1HF/TmL8QfI+I0y0zHZY9vnAdB1oRqz6hcnE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=pikFBrh1; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="pikFBrh1" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=MIME-Version:Content-Type:Date:Cc:To: From:Subject:Message-ID:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:In-Reply-To:References; bh=yhlPryLtUWl4vrQUGB5h79kFDJR2GrwAqYKiYvpFnyU=; b=pikFBrh1FQ3phKtBsiJ1/LY86n 0i/n89I1PEtv7akOuy2ielV/2Lf+nk0Wo/fag13W828ukPKc+P2U9bpdlpzfz0Iw3Q5GUOWm5gbQH Yp4NijAzf+EnJ4djkOQXsmOqmxkvC0wruCfsrLRLQP4SB2MCGHzhszEwueW4h0eZDqQG9UK6nbyk4 qKjm1u0TqgYmkBLiQb3TVC8K3AJk6ITTSG8eAfvqDYrvrd/Bsawi7pjtBNESIQJL+UziJ7HRB6n+q OdrLOdu3lcZJjH7FyEiJZbsW300C8bVvxoL6GIZZRZ6/QP4lpgw0g4bXkW9UH0c9pX0M2NC5ZSIX3 PqT8ZJnA==; Received: from [172.31.31.148] (helo=u09cd745991455d.lumleys.internal) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1w8FNg-00000002FEu-1umJ; Thu, 02 Apr 2026 10:34:32 +0000 Message-ID: Subject: [PATCH] x86/kexec: Push kjump return address even for non-kjump kexec From: David Woodhouse To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , David Woodhouse , Kai Huang , Paolo Bonzini , Uros Bizjak , Sohil Mehta , linux-kernel@vger.kernel.org Cc: Rohan Kakulawaram , kexec Date: Thu, 02 Apr 2026 11:34:32 +0100 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-RJpuZZPWfXiEqlFNmFAK" User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html --=-RJpuZZPWfXiEqlFNmFAK Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: David Woodhouse The version of purgatory code shipped by kexec-tools attempts to look above the top of its stack to find a return address for a kjump, even in a non-kjump kexec. Since commit 2cacf7f23a02 ("x86/kexec: Fix stack and handling of re-entry point for ::preserve_context") the page above the stack might not be there, leading to a fault (which is at least now caught my by exception-handling code in kexec). That commit fixed things for the actual kjump path, but no longer "gratuitously" pushes the unused return address to the stack in the non-kjump path. Put that *back* in the non-kjump path, to prevent purgatory from crashing when trying to access it. Reported-by: Rohan Kakulawaram Tested-by: Rohan Kakulawaram Fixes: 2cacf7f23a02 ("x86/kexec: Fix stack and handling of re-entry point f= or ::preserve_context") Signed-off-by: David Woodhouse --- arch/x86/kernel/relocate_kernel_64.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocat= e_kernel_64.S index 4ffba68dc57b..301c586282aa 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -136,6 +136,8 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) * %r13 original CR4 when relocate_kernel() was invoked */ =20 + /* set return address to 0 if not preserving context */ + pushq $0 /* store the start address on the stack */ pushq %rdx =20 --=20 2.43.0 --=-RJpuZZPWfXiEqlFNmFAK Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 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