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 212EC35F5ED for ; Mon, 14 Sep 2026 06:28:46 +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=1789367327; cv=none; b=ZQPmlyRce1CHsu3WLIauA68Mu6dLOjnDJTEBRdgBckOsPBEuZccxLYorzay3hLibmIA2XSsMvyy+McyK44GysIS1BWOUY40/1+X56iGEj3kMB69MP8HfKon5aYYPc0riIY0Zqp76rQ17t1v7fa4q4+cgAdFJ7EIG/2DhqGkZsw8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789367327; c=relaxed/simple; bh=3iVoK4BkPE7Ao2mIIlFXdexW1442xptVOxNVtYYEQ+8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LxRKZ2Tf0VJTE27oa/eVP2zd2se/NO5DZqEKSopsQGx+5pO8taTMUX/0hpLQMKN+tTyxi6Lesx/+Rnj+brAJMI5FvYDuCN2RadGLVeeTrWk6knpkuM1whDvWUfRB9JYVKg/f5Os37ZNrStM6DJ4xLcPGPZvSTiz+zHG6gFb1rhE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HyP63ysI; 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="HyP63ysI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC0511F000FF; Mon, 14 Sep 2026 06:28:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789367326; bh=qDD8qst+lNvXm1mMrcNe9/GCFXs/oxrzCZsX6CQt3qQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=HyP63ysISlYGwXEmxRKpeRq+15zLJyrQ2D7WFdTWy4f1HI+Mirsa2hvoiUPCdCr/W EfuVqldNlsDi0fu7Zmo91mQ+EJfw7rqN12OhxwVfSIfq4ooH30ivXjj6ox5YoeNZFM QrqMH9lWq0PIUiwhSz+RIVKuxbDaS0ZycT2Dxca8T/6SBBxzgT2i5EubYbCpgmXaQe +VIXlEdCgOguyct4eYA/7/mEn+99pRNbZxPsdvuSqBWDTkM9v3bjawOCuYDUZaJA62 zcajX04nLoiZsmVUpzWn/XFpLW2wVzqlJrGpJlLDzHFDrtosY1t7HCsW8t8PHla6h8 3vwGKCykJfmcQ== 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 37/58] objtool/klp: Add test for sympos in module objects Date: Sun, 13 Sep 2026 23:24:53 -0700 Message-ID: <20260914062514.926997-38-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 klp-sympos.c had no coverage at all. sympos disambiguates same-named symbols for livepatch, counting from 1, with 0 meaning the name is unique. Resolving to the wrong one is not a load failure -- it is a patch quietly wired to the wrong object. Covers the module path, where the position is a count in symbol table order and klp diff can work it out from the object alone. 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/sympos_dup.c | 32 ++++++++++++ tools/objtool/tests/generic/test-sympos.sh | 51 +++++++++++++++++++ 2 files changed, 83 insertions(+) create mode 100644 tools/objtool/tests/generic/fixtures/sympos_dup.c create mode 100755 tools/objtool/tests/generic/test-sympos.sh diff --git a/tools/objtool/tests/generic/fixtures/sympos_dup.c b/tools/objtool/tests/generic/fixtures/sympos_dup.c new file mode 100644 index 000000000000..7eded9b12cfc --- /dev/null +++ b/tools/objtool/tests/generic/fixtures/sympos_dup.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * A static whose name recurs in every translation unit that includes it. + * Compiled once for a single-copy object and twice, partially linked, for one + * with duplicates -- which is the only case where sympos is non-zero. + * + * FUNC_NAME keeps the referencing functions distinct so both get patched. + * Only the first copy carries .modinfo; two would be a second thing to + * disambiguate and is not what this fixture is about. + */ + +#ifndef FUNC_NAME +#define FUNC_NAME use_a +#endif + +#ifndef NO_MODINFO +static const char __modinfo[] + __attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux"; +#endif + +/* volatile so it survives as an STT_OBJECT rather than being folded away */ +static volatile int dup_counter = 1; + +int FUNC_NAME(int x) +{ + dup_counter += x; +#ifdef PATCHED + return dup_counter + 1; +#else + return dup_counter; +#endif +} diff --git a/tools/objtool/tests/generic/test-sympos.sh b/tools/objtool/tests/generic/test-sympos.sh new file mode 100755 index 000000000000..b71d4930a22a --- /dev/null +++ b/tools/objtool/tests/generic/test-sympos.sh @@ -0,0 +1,51 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# sympos is what livepatch uses to tell duplicate symbol names apart in the +# patched object: which "dup_counter" of several the relocation means. Get it +# wrong and the patch resolves to the wrong object at load time, silently. +# +# klp_find_sympos() reports 0 when a name is unique and a 1-based position when +# it is not, so both need checking -- always reporting a position, or never, +# each looks right in one of the two cases. +# +# This is the module path, counting symbol table order. vmlinux is reordered +# by the final link and goes through .klp.symid instead; that needs a linked +# vmlinux next to vmlinux.o and is not covered here. + +. "$(dirname "$0")/../lib.sh" + +setup + +# One copy: the name is unique, so there is nothing to disambiguate. +build_one sympos_dup.c orig.o -DFUNC_NAME=use_a +build_one sympos_dup.c patched.o -DFUNC_NAME=use_a -DPATCHED +run_diff + +assert_klp_sympos dup_counter 0 + +# Two copies: positions, in symbol table order. +for p in "" "-DPATCHED"; do + # shellcheck disable=SC2086 + build_one sympos_dup.c "a$p.o" -DFUNC_NAME=use_a $p + # shellcheck disable=SC2086 + build_one sympos_dup.c "b$p.o" -DFUNC_NAME=use_b -DNO_MODINFO $p +done +partial_link "$workdir/orig.o" "$workdir/a.o" "$workdir/b.o" || + probe_skip "partial link unavailable" +partial_link "$workdir/patched.o" "$workdir/a-DPATCHED.o" "$workdir/b-DPATCHED.o" || + probe_skip "partial link unavailable" + +# Without duplicates in the input there is nothing for sympos to number. +[ "$(count_input_symbols orig.o dup_counter)" = 2 ] || + fail "fixture did not produce two dup_counter symbols" + +run_diff + +assert_klp_sympos dup_counter 1 +assert_klp_sympos dup_counter 2 +# ... and nothing still claiming the name is unique +out_symbols | grep -qE '\.klp\.sym\.[^.]+\.dup_counter,0([[:space:]]|$)' && + fail "sympos 0 emitted for a duplicated symbol" + +pass "sympos numbers duplicate symbols and stays 0 for unique ones" -- 2.53.0-Meta