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 CAE5521FF2A for ; Tue, 15 Sep 2026 23:37:59 +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=1789515481; cv=none; b=boQNsVRQLBtqe+vTLi/N6ZoNIeDEyufeL7oeyNmlOFkPmWamfx0nWexv4FnpuYQXgZv50NXkTHO3uLn0vXsK3pKErqPKA7dkEL5B8n2RumayVKB8uk9q1D4aJpQbOOL5mCA8gTqLAeOurzZ20saGoAM7444M8znByPYaf1H9C4c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789515481; c=relaxed/simple; bh=lNHMFbs3ekNTFi+lZW1nnZaV8Y1OaF3nX61Z9cWyXVY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AsZM4wYkHQWgoULMHIaGWpLdn1kNS3h7Qq4OO9qdSFc6e+WcN4Awn/VbRC1IGHJ+HZBpJct9H241bMKkKj2F0Z272qF7cwcVBoP/Q06sXmT29dVfeKVS+v/6hYCLUQRuQ2vR+mCdzCgno2BtPnomq+G0h1tnURsxJUDO8CrK+bQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WWzGWFVj; 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="WWzGWFVj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C71431F000FF; Tue, 15 Sep 2026 23:37:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789515479; bh=DsnCtOqOOXiZ4gl1TewM260+vYJkxZbvt9RG8a4ou3w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WWzGWFVjCMRXhvHEBaFsl654VXl+H96eZsb9cJmdOj0w8IkpsOGwp/vA/b0MNPtud l5fK/AEJrOeEgOmqrDx/+QtCcTqehzmiqOMPES4NDDcvEiFYA/YYnWlNbWxcErvqrk wubvaN6aaXIljHuwQmgyGGEsWCvGcWRrfO6jI/941t3KmnjBploqQNCQY45O35jHn0 2pS3bag5tGNZsYoD1NY90wrJI0alj21XzLrdlEQCecvSnArzwTOGrp7oAyQNmNjoxB yfFChdzod/ars1Y16clen5FQAr3klge2ffUG9Yyi7V5MntBIefpVoKMGMf2siCDQrs nhoGpCnvdyk4Q== 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 v4 33/58] objtool/klp: Add test for new references to exported symbols Date: Tue, 15 Sep 2026 16:34:29 -0700 Message-ID: <20260915233454.2405019-34-song@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260915233454.2405019-1-song@kernel.org> References: <20260915233454.2405019-1-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