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 BD5334D597E for ; Wed, 16 Sep 2026 18:47:20 +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=1789584444; cv=none; b=YyUNpEpw4+ytjDt/UUdQO3TfuoHOG2PXMaL6B+ABFAptOijr29NXW2H2U/O/oF6DqCTLq9WYwbs8VYJt9+8CMgB09elCvdkFgzOoBiFxUZ4KelzSOA2BDRx1+c3rwTWC/u9Shj2TcIIy1uSiitvWA+rnBk5ZnHu2KfbKt/2lhuY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789584444; c=relaxed/simple; bh=EUllrK2ob0byegLQraQasGEOHSPgqWzPpz89wAFozwg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XrqKBlbRNxjdSoRjkhvBGshpPDt4GrkYYX/xQzjRlIXhsTl/ySWMUxdWKm7PWVy+Hlddr5l/B01GvD/p+VoFi9FHdLejm/npdBdCKTogf2uUDFXvv3x5euN3BkHR73dj4tmQz6diAy8FhqysQQ7KbJcpeT/dGhTYqbR+Noo7Rck= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c79W60Iz; 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="c79W60Iz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AA571F008A2; Wed, 16 Sep 2026 18:47:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789584435; bh=v6CnK39IiT17AexXoU1tlXRI9DIx6WBmq+qkliR9b9g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=c79W60IzMUcQ+y+B9DtIOUPdSdFs7+qwYbP6jtVzmtFzrigh6yGy4rzYiuiOsldDd OGCBD5juyoLtxHkwARa+y/ScqrKkW70n5U9V9JJ/oKpyqda0UOI2QOXqnYTPalXHAQ 0QyN2JNbB6rSPFcSKuJd9X2jo1IV88Q0F3cKDeRFoz+Og/yBSggW4EAJPtHUU6GlOF 4O7yuw3YkiryCIVPcs+vM6DuSRSGHQ+2mKdS8L0m9g9ZHt4M6LEg1P3QgfMiWvO1yY pWZBs9LinICpnIgesS906NQFI+SVr2ykG5qNNCWBmAV7JLJ8MdYui1HSnD8dJohBj7 RkxtOTLCWKAWw== 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 v5 41/58] objtool/klp: Add test for kCFI prefix symbols and traps Date: Wed, 16 Sep 2026 11:43:34 -0700 Message-ID: <20260916184351.2720310-42-song@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260916184351.2720310-1-song@kernel.org> References: <20260916184351.2720310-1-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