From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 27CC3351C0B for ; Mon, 14 Sep 2026 06:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789367306; cv=none; b=qyXLHthAI6w37bof1uMB+HgIvG7TNx80VNHF78MfrLdhjVT6Ubj6NLW2mlMr7yXtkJ/HcCQxAni7B1iluHof+tOSw2kxdfnpiLWd5peQGMGIeVMuR+lr7BKhF5CTImlOpnkB7gNxU/okM2421Z4oCGzSD/ccXul+yWtBjDzj8vY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789367306; c=relaxed/simple; bh=lNHMFbs3ekNTFi+lZW1nnZaV8Y1OaF3nX61Z9cWyXVY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tFde1xt9TxDJXYmrNxfaVLNq6O8SXteeYviIUhu/mdJV+BwnkuOkh7xUto8xNQaujd5pJgX/sXAlo3R7yrsx94nfvwVaGml9bvldJVnlIlY9gCgBP5BonyT4EUGAApNlJ/7lN1qNFqSHbHIBCmURGA5ePbKagRXlXNU7fE+Vs44= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J/1H2w+g; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J/1H2w+g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBBFD1F000FF; Mon, 14 Sep 2026 06:28:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789367305; bh=DsnCtOqOOXiZ4gl1TewM260+vYJkxZbvt9RG8a4ou3w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=J/1H2w+gs8bAsSWR1OJEScKku9uM90NgFhBcRTlQhA7Ik1YcOtFNc6D2w99p4tcmT bOZAjUBWw4dIZzZLmx2kN5o7hUtEkQxIQ8tyKNgFCFMEc0ges4V+LIg1D2NQjSRlbI GUSvs5Nsm4YwdW7Y7qQG2uBrfVxHrLq+YrL4xFRKu40p30tI9FC8MyegSsdBihfWPi /XDK9f4eAP5zEBaMP8lGPeLe+xfif+3H6Hbo8Y+tgho3rbE5D8Mj/a6zC2mh8sL0g/ D4TdIHb4B/42lz931obiOppcCjHYcVnt0L2Xz3nTNk3hQXDYzL5MirWLNgVDokfi90 F/gNLSGlibghQ== From: Song Liu To: live-patching@vger.kernel.org Cc: jpoimboe@kernel.org, peterz@infradead.org, jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, joe.lawrence@redhat.com, puranjay@kernel.org, kernel-team@meta.com, Song Liu Subject: [PATCH v2 33/58] objtool/klp: Add test for new references to exported symbols Date: Sun, 13 Sep 2026 23:24:49 -0700 Message-ID: <20260914062514.926997-34-song@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914062514.926997-1-song@kernel.org> References: <20260914062514.926997-1-song@kernel.org> Precedence: bulk X-Mailing-List: live-patching@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A patch may introduce a reference the original object did not have. That is fine when the export belongs to vmlinux, and not fine when it belongs to a module: the livepatch would gain a module dependency nobody declared, and late module patching lets the patch load first. This tests the behavior of commit 72d76d0c18eb ("objtool/klp: Allow new references to module exports"). Assisted-by: Claude:claude-opus-4 Based-on-test-by: Joe Lawrence Assisted-by: Claude:claude-opus-5 Signed-off-by: Song Liu --- .../tests/generic/fixtures/new_export_ref.c | 20 +++++++++++ .../tests/generic/test-new-export-ref.sh | 34 +++++++++++++++++++ 2 files changed, 54 insertions(+) create mode 100644 tools/objtool/tests/generic/fixtures/new_export_ref.c create mode 100755 tools/objtool/tests/generic/test-new-export-ref.sh diff --git a/tools/objtool/tests/generic/fixtures/new_export_ref.c b/tools/objtool/tests/generic/fixtures/new_export_ref.c new file mode 100644 index 000000000000..c046b9f87d0b --- /dev/null +++ b/tools/objtool/tests/generic/fixtures/new_export_ref.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * A reference which only exists in the patched build. The symbol has no twin + * in the original object, so what klp diff may do with it depends entirely on + * whether Module.symvers says it is exported, and by what. + */ + +static const char __modinfo[] + __attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux"; + +extern int newly_referenced(int x); + +int target(int x) +{ +#ifdef PATCHED + return newly_referenced(x); +#else + return x + 1; +#endif +} diff --git a/tools/objtool/tests/generic/test-new-export-ref.sh b/tools/objtool/tests/generic/test-new-export-ref.sh new file mode 100755 index 000000000000..ad6fa3979942 --- /dev/null +++ b/tools/objtool/tests/generic/test-new-export-ref.sh @@ -0,0 +1,34 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# A reference the patch adds has no counterpart in the original object. klp +# diff used to reject any such reference needing a klp relocation, which ruled +# out patches that call something they did not call before -- a common enough +# thing for a fix to do. +# +# Module.symvers is what makes it safe: it says the symbol exists and who owns +# it. But that is only sufficient for a vmlinux export. A new reference to a +# module's export is a dependency the patch module does not declare, and the +# relocation would resolve only if that module happened to be loaded, so it +# stays an error. + +. "$(dirname "$0")/../lib.sh" + +setup +build_pair new_export_ref.c + +# Exported by vmlinux, in a module: namespace so it needs a klp relocation +# rather than an ordinary one. Allowed. +export_syms +add_exports_ns vmlinux module:kvm newly_referenced +run_diff +assert_klp_sym newly_referenced vmlinux + +# Exported by a module the patched object does not depend on. Rejected, and +# for that reason rather than some other. +export_syms +add_exports other_mod newly_referenced +run_diff 255 +assert_diff_log 'undeclared module dependency' + +pass "new reference allowed to a vmlinux export, rejected for a module export" -- 2.53.0-Meta