Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
From:   Dimitri John Ledkov <dimitri.ledkov@canonical.com>
To:     Josh Poimboeuf <jpoimboe@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] objtool: Make objtool check actually fatal upon fatal errors
Date:   Tue, 12 Dec 2023 18:53:38 +0000
Message-Id: <20231212185339.1562967-1-dimitri.ledkov@canonical.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Currently function calls within check() are sensitive to fatal errors
(negative return codes) and abort execution prematurely. However, in
all such cases the check() function still returns 0, and thus
resulting in a successful kernel build.

The only correct code paths were the ones that escpae the control flow
with `return ret`.

Make the check() function return `ret` status code, and make all
negative return codes goto that instruction. This makes fatal errors
(not warnings) from various function calls actually fail the
build. E.g. if create_retpoline_sites_sections() fails to create elf
section pair retpoline_sites the tool now exits with an error code.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
---
 tools/objtool/check.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e94756e09c..9146177fc9 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4669,166 +4669,168 @@ static void free_insns(struct objtool_file *file)
 int check(struct objtool_file *file)
 {
 	int ret, warnings = 0;
 
 	arch_initial_func_cfi_state(&initial_func_cfi);
 	init_cfi_state(&init_cfi);
 	init_cfi_state(&func_cfi);
 	set_func_state(&func_cfi);
 	init_cfi_state(&force_undefined_cfi);
 	force_undefined_cfi.force_undefined = true;
 
-	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
+	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3))) {
+		ret = -1;
 		goto out;
+	}
 
 	cfi_hash_add(&init_cfi);
 	cfi_hash_add(&func_cfi);
 
 	ret = decode_sections(file);
 	if (ret < 0)
 		goto out;
 
 	warnings += ret;
 
 	if (!nr_insns)
 		goto out;
 
 	if (opts.retpoline) {
 		ret = validate_retpoline(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
 	if (opts.stackval || opts.orc || opts.uaccess) {
 		ret = validate_functions(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 
 		ret = validate_unwind_hints(file, NULL);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 
 		if (!warnings) {
 			ret = validate_reachable_instructions(file);
 			if (ret < 0)
 				goto out;
 			warnings += ret;
 		}
 
 	} else if (opts.noinstr) {
 		ret = validate_noinstr_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.unret) {
 		/*
 		 * Must be after validate_branch() and friends, it plays
 		 * further games with insn->visited.
 		 */
 		ret = validate_unrets(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
 	if (opts.ibt) {
 		ret = validate_ibt(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.sls) {
 		ret = validate_sls(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.static_call) {
 		ret = create_static_call_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.retpoline) {
 		ret = create_retpoline_sites_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.cfi) {
 		ret = create_cfi_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.rethunk) {
 		ret = create_return_sites_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 
 		if (opts.hack_skylake) {
 			ret = create_direct_call_sections(file);
 			if (ret < 0)
 				goto out;
 			warnings += ret;
 		}
 	}
 
 	if (opts.mcount) {
 		ret = create_mcount_loc_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.prefix) {
 		ret = add_prefix_symbols(file);
 		if (ret < 0)
-			return ret;
+			goto out;
 		warnings += ret;
 	}
 
 	if (opts.ibt) {
 		ret = create_ibt_endbr_seal_sections(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	if (opts.orc && nr_insns) {
 		ret = orc_create(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
 	free_insns(file);
 
 	if (opts.verbose)
 		disas_warned_funcs(file);
 
 	if (opts.stats) {
 		printf("nr_insns_visited: %ld\n", nr_insns_visited);
 		printf("nr_cfi: %ld\n", nr_cfi);
 		printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
 		printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
 	}
 
 out:
 	/*
 	 *  For now, don't fail the kernel build on fatal warnings.  These
 	 *  errors are still fairly common due to the growing matrix of
 	 *  supported toolchains and their recent pace of change.
 	 */
-	return 0;
+	return ret;
 }
-- 
2.34.1