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 B31424D09F4 for ; Tue, 15 Sep 2026 23:38:45 +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=1789515526; cv=none; b=XXKsPR5c4bpPwa6GRgrSA6GsAZi92K17pFIO9im52ux2zeytiF7AAUQP/qlnQ4Ehz6SdThUKjh+eGwWMQAEBKLLmdUbtFzl9nK2zlq2rIMiuL3S5Ib7cWOSzjVo2tM7D8z9wvnJ/7ElurxZsHp/kyXQ3mWcQJqmWNIRh53pm6+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789515526; c=relaxed/simple; bh=EUllrK2ob0byegLQraQasGEOHSPgqWzPpz89wAFozwg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pjlVIMh9VfJzkDHIJvDbg/Rrgb1t6Mda73pl61gaTboHai3L06CI7dxSIIAGaPR3PWfDDQ357ZDHINw+nw3m5vi7uiNXobYYIoItq/EQs0D5D1/weYB8QgtlmV2oot+291vXiEUGFr21xzxNLE6s4fWIvh2CuA0XQusWnr095uo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J52TVKiq; 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="J52TVKiq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D0C41F000FF; Tue, 15 Sep 2026 23:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789515525; bh=v6CnK39IiT17AexXoU1tlXRI9DIx6WBmq+qkliR9b9g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=J52TVKiqc60I22Z4PXvtzdw0EGiGxaEafGAzmXnvAiilTxBUz7/2sYzjqRfjcdUO/ 725FrUNGQvegiqoIJoiGqW/kAGMYh9uEQ/WIVB6hWypEVVDry1DKHlqMzDvhUdPaOO YKJcHpMjA86MynqY1X5wZTsuUvLHPuUrVfw8nuNZEVbsZGkIAtOk0pYOyg1UaMpMLq kqWdKeot9MpfF4W20KJxOarcS2jHPWGIij5rTh2yxnSESaNzqMNZvwOw+njSNgzBo9 +rBYCdDAd7+jlJZeZ9KAfvfY0YSKIv9FBFkY3wPZQWcPFyGUG2/dyncMdik3EKqLDw smcHPuIJconUQ== 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 41/58] objtool/klp: Add test for kCFI prefix symbols and traps Date: Tue, 15 Sep 2026 16:34:37 -0700 Message-ID: <20260915233454.2405019-42-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 Two properties, asserted separately because they fail differently: - the __cfi_ prefix symbol has to be carried with the patched function, or the function has no type identity and indirect calls to it trap; - its .kcfi_traps entry has to be extracted, or the trap is not recognised as a CFI failure and a clean report becomes an oops. test-special-section hand-assembles a .kcfi_traps entry, which is what makes it catch commit 7df1638df97b ("objtool/klp: Fix .kcfi_traps special section extraction"). Nothing until now built real kCFI code. This tests the behavior of commit da4326573ae8 ("objtool/klp: Fix kCFI trap handling"). Commit f7ceffd21a8a ("objtool/klp: Fix kCFI prefix finding/cloning") cannot be tested as such, its code having been rewritten by commit fe6a87e0abac ("objtool: Improve and simplify prefix symbol detection"); this guards the current implementation's behaviour instead. Assisted-by: Claude:claude-opus-4 Based-on-test-by: Joe Lawrence Assisted-by: Claude:claude-opus-5 Signed-off-by: Song Liu --- tools/objtool/tests/x86/fixtures/kcfi.c | 39 +++++++++++++++++++++++++ tools/objtool/tests/x86/test-kcfi.sh | 39 +++++++++++++++++++++++++ 2 files changed, 78 insertions(+) create mode 100644 tools/objtool/tests/x86/fixtures/kcfi.c create mode 100755 tools/objtool/tests/x86/test-kcfi.sh diff --git a/tools/objtool/tests/x86/fixtures/kcfi.c b/tools/objtool/tests/x86/fixtures/kcfi.c new file mode 100644 index 000000000000..b62fc60634cf --- /dev/null +++ b/tools/objtool/tests/x86/fixtures/kcfi.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * An indirect call, which under kCFI is preceded by a type check and a trap. + * + * Clang emits a __cfi_ prefix symbol carrying the type hash ahead of + * every address-taken function, and records the trap site in .kcfi_traps. + * Both belong to the function and both have to come with it into a patch. + * + * Needs -fsanitize=kcfi, which only Clang has. + */ + +static const char __modinfo[] + __attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux"; + +static int impl_a(int x) +{ + return x + 1; +} + +static int impl_b(int x) +{ + return x * 2; +} + +__attribute__((noinline)) int (*pick(int x))(int) +{ + return (x & 1) ? impl_a : impl_b; +} + +int target(int x) +{ + int (*fn)(int arg) = pick(x); + +#ifdef PATCHED + return fn(x) + 2; +#else + return fn(x) + 1; +#endif +} diff --git a/tools/objtool/tests/x86/test-kcfi.sh b/tools/objtool/tests/x86/test-kcfi.sh new file mode 100755 index 000000000000..b583ef608747 --- /dev/null +++ b/tools/objtool/tests/x86/test-kcfi.sh @@ -0,0 +1,39 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Under kCFI an indirect call checks a type hash before jumping, and traps on a +# mismatch. Two things belong to the calling function and must come with it +# into a patch: +# +# - the __cfi_ prefix symbol holding the hash. Lose it and the patched +# function has no type identity, so indirect calls to it trap. +# - its .kcfi_traps entry. Lose that and the trap is not recognised as a +# CFI failure, so what should be a clean report becomes an oops. +# +# Neither shows up at build time. + +. "$(dirname "$0")/../lib.sh" + +clang_only "kCFI is a Clang feature" + +setup + +# Declared above that this is Clang's; a given Clang may still be too old. +cc_supports -fsanitize=kcfi || + probe_skip "this clang does not support -fsanitize=kcfi" + +build_pair kcfi.c -fsanitize=kcfi + +assert_input_section .kcfi_traps +assert_input_symbol __cfi_target + +run_diff + +assert_patched target + +# The prefix symbol comes with its function ... +assert_symbol __cfi_target +# ... and so does the trap entry. +assert_section .kcfi_traps + +pass "kCFI prefix symbol and trap entry carried with the patched function" -- 2.53.0-Meta