Message ID | 0f630a0eb4585ab4114e4eecaa6f166a1fd81d49.1681325924.git.jpoimboe@kernel.org |
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State | New |
Headers |
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[2620:137:e000::1:20]) by mx.google.com with ESMTP id s1-20020a170902c64100b001a64476e1eesi7337982pls.185.2023.04.12.12.46.14; Wed, 12 Apr 2023 12:46:33 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=UudiDOuj; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229877AbjDLTEJ (ORCPT <rfc822;peter110.wang@gmail.com> + 99 others); Wed, 12 Apr 2023 15:04:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229904AbjDLTDu (ORCPT <rfc822;linux-kernel@vger.kernel.org>); Wed, 12 Apr 2023 15:03:50 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DEC040F9 for <linux-kernel@vger.kernel.org>; Wed, 12 Apr 2023 12:03:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BBED66120A for <linux-kernel@vger.kernel.org>; Wed, 12 Apr 2023 19:03:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F105FC433D2; Wed, 12 Apr 2023 19:03:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1681326228; bh=vyrH7fWmcqWjltl/LdT1BsNQ9591BQaxXbDWTsC3pYs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UudiDOujlu3FC9gXbLoKD/o9qBM5vOmRVcq9RCfnH2a+m7zindDoVG0SirE95XWlP ffko4mKUAo/3phlkK9kJu7UDtNghhhf2IlLadhhKjqWD1C/RqDLnciHusi6+DtfynJ Bk8eZh04yv+8fUCVHlMGD01c1FS8YHuN3tNDp/50xZlMpMlvijlzImNgca7M0Mkri2 NchUqg8Kz0peoSFTWP1jBx1x86gKSmf+2cEKmPoMlQCE3UgLotOj7d3EjB0g6tj1GZ ZRSglLWvn9f/vwjWnk6qo3LfEpb2n4tJI4UYLIFHcpU9qATq+M5FSXkw5tqmKkX3AN q3B6E/dQaZSnw== From: Josh Poimboeuf <jpoimboe@kernel.org> To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Miroslav Benes <mbenes@suse.cz> Subject: [PATCH v2 8/9] objtool: Detect missing __noreturn annotations Date: Wed, 12 Apr 2023 12:03:23 -0700 Message-Id: <0f630a0eb4585ab4114e4eecaa6f166a1fd81d49.1681325924.git.jpoimboe@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <cover.1681325924.git.jpoimboe@kernel.org> References: <cover.1681325924.git.jpoimboe@kernel.org> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1763001020933561463?= X-GMAIL-MSGID: =?utf-8?q?1763001020933561463?= |
Series |
objtool: warning improvements
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Commit Message
Josh Poimboeuf
April 12, 2023, 7:03 p.m. UTC
Most "unreachable instruction" warnings these days seem to actually be
the result of a missing __noreturn annotation. Add an explicit check
for that.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
tools/objtool/Documentation/objtool.txt | 6 ++++++
tools/objtool/check.c | 14 +++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)
Comments
On Wed, Apr 12, 2023 at 12:03:23PM -0700, Josh Poimboeuf wrote: > Most "unreachable instruction" warnings these days seem to actually be > the result of a missing __noreturn annotation. Add an explicit check > for that. > > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> > --- > tools/objtool/Documentation/objtool.txt | 6 ++++++ > tools/objtool/check.c | 14 +++++++++++++- > 2 files changed, 19 insertions(+), 1 deletion(-) > > diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt > index 5a69c207a10e..2cd1fa16ed08 100644 > --- a/tools/objtool/Documentation/objtool.txt > +++ b/tools/objtool/Documentation/objtool.txt > @@ -303,6 +303,12 @@ the objtool maintainers. > If it's not actually in a callable function (e.g. kernel entry code), > change ENDPROC to END. > > +3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation > + > + The call from foo() to bar() doesn't return, but bar() is missing the > + __noreturn annotation. NOTE: In addition to adding the __noreturn > + annotation, the function name also needs to be added to > + 'global_noreturns' in tools/objtool/check.c. Do we want something like the below (except perhaps less horrible) ? --- tools/objtool/Makefile | 1 + tools/objtool/check.c | 27 +-------------------------- tools/objtool/noreturns | 26 ++++++++++++++++++++++++++ tools/objtool/noreturns.sh | 7 +++++++ 4 files changed, 35 insertions(+), 26 deletions(-) diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile index 83b100c1e7f6..50b6cd241571 100644 --- a/tools/objtool/Makefile +++ b/tools/objtool/Makefile @@ -63,6 +63,7 @@ include $(srctree)/tools/build/Makefile.include $(OBJTOOL_IN): fixdep $(LIBSUBCMD) FORCE $(Q)$(CONFIG_SHELL) ./sync-check.sh + $(Q)$(CONFIG_SHELL) ./noreturns.sh $(Q)$(MAKE) $(build)=objtool $(HOST_OVERRIDES) CFLAGS="$(OBJTOOL_CFLAGS)" \ LDFLAGS="$(OBJTOOL_LDFLAGS)" diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f937be1afe65..f558730c27b6 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -197,32 +197,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, * attribute isn't provided in ELF data. Keep 'em sorted. */ static const char * const global_noreturns[] = { - "__invalid_creds", - "__module_put_and_kthread_exit", - "__reiserfs_panic", - "__stack_chk_fail", - "__ubsan_handle_builtin_unreachable", - "cpu_bringup_and_idle", - "cpu_startup_entry", - "do_exit", - "do_group_exit", - "do_task_dead", - "ex_handler_msr_mce", - "fortify_panic", - "kthread_complete_and_exit", - "kthread_exit", - "kunit_try_catch_throw", - "lbug_with_loc", - "machine_real_restart", - "make_task_dead", - "panic", - "rewind_stack_and_make_dead", - "sev_es_terminate", - "snp_abort", - "stop_this_cpu", - "usercopy_abort", - "xen_cpu_bringup_again", - "xen_start_kernel", +#include "noreturns.h" }; if (!func) diff --git a/tools/objtool/noreturns b/tools/objtool/noreturns new file mode 100644 index 000000000000..75f35fbb34d1 --- /dev/null +++ b/tools/objtool/noreturns @@ -0,0 +1,26 @@ +__invalid_creds +__module_put_and_kthread_exit +__reiserfs_panic +__stack_chk_fail +__ubsan_handle_builtin_unreachable +cpu_bringup_and_idle +cpu_startup_entry +do_exit +do_group_exit +do_task_dead +ex_handler_msr_mce +fortify_panic +kthread_complete_and_exit +kthread_exit +kunit_try_catch_throw +lbug_with_loc +machine_real_restart +make_task_dead +panic +rewind_stack_and_make_dead +sev_es_terminate +snp_abort +stop_this_cpu +usercopy_abort +xen_cpu_bringup_again +xen_start_kernel diff --git a/tools/objtool/noreturns.sh b/tools/objtool/noreturns.sh new file mode 100755 index 000000000000..f728cb61e665 --- /dev/null +++ b/tools/objtool/noreturns.sh @@ -0,0 +1,7 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +cat noreturns | while read func +do + echo \"${func}\", +done > noreturns.h
> --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -4485,7 +4485,8 @@ static int validate_sls(struct objtool_file *file) > > static int validate_reachable_instructions(struct objtool_file *file) > { > - struct instruction *insn; > + struct instruction *insn, *prev_insn; > + struct symbol *call_dest; > int warnings = 0; > > if (file->ignore_unreachables) > @@ -4495,6 +4496,17 @@ static int validate_reachable_instructions(struct objtool_file *file) > if (insn->visited || ignore_unreachable_insn(file, insn)) > continue; > > + prev_insn = prev_insn_same_sec(file, insn); > + if (prev_insn && prev_insn->dead_end) { > + call_dest = insn_call_dest(prev_insn); > + if (call_dest) { > + WARN_INSN(insn, "%s() is missing a __noreturn annotation", > + call_dest->name); > + warnings++; > + continue; A nit but this and > + } > + } > + > WARN_INSN(insn, "unreachable instruction"); > warnings++; this makes me thinking. Wouldn't it be confusing to anyone that there is no correspondence between warnings and a number of actual reported warnings through WARN_INSN()? In the future when there would be a usage for warnings. It does not really matter now. Miroslav
On Thu, Apr 13, 2023 at 10:48:01AM +0200, Peter Zijlstra wrote: > On Wed, Apr 12, 2023 at 12:03:23PM -0700, Josh Poimboeuf wrote: > > Most "unreachable instruction" warnings these days seem to actually be > > the result of a missing __noreturn annotation. Add an explicit check > > for that. > > > > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> > > --- > > tools/objtool/Documentation/objtool.txt | 6 ++++++ > > tools/objtool/check.c | 14 +++++++++++++- > > 2 files changed, 19 insertions(+), 1 deletion(-) > > > > diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt > > index 5a69c207a10e..2cd1fa16ed08 100644 > > --- a/tools/objtool/Documentation/objtool.txt > > +++ b/tools/objtool/Documentation/objtool.txt > > @@ -303,6 +303,12 @@ the objtool maintainers. > > If it's not actually in a callable function (e.g. kernel entry code), > > change ENDPROC to END. > > > > +3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation > > + > > + The call from foo() to bar() doesn't return, but bar() is missing the > > + __noreturn annotation. NOTE: In addition to adding the __noreturn > > + annotation, the function name also needs to be added to > > + 'global_noreturns' in tools/objtool/check.c. > > Do we want something like the below (except perhaps less horrible) ? Yeah, maybe. Another possible way to do it: diff --git a/tools/objtool/check.c b/tools/objtool/check.c index cae6ac6ff246..a4e8ff9dabf1 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -192,39 +192,16 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, struct instruction *insn; bool empty = true; +#define NORETURN(func) "\"" __stringify(func) "\"", + /* * Unfortunately these have to be hard coded because the noreturn * attribute isn't provided in ELF data. Keep 'em sorted. */ static const char * const global_noreturns[] = { - "__invalid_creds", - "__module_put_and_kthread_exit", - "__reiserfs_panic", - "__stack_chk_fail", - "__ubsan_handle_builtin_unreachable", - "arch_cpu_idle_dead", - "cpu_bringup_and_idle", - "cpu_startup_entry", - "do_exit", - "do_group_exit", - "do_task_dead", - "ex_handler_msr_mce", - "fortify_panic", - "kthread_complete_and_exit", - "kthread_exit", - "kunit_try_catch_throw", - "lbug_with_loc", - "machine_real_restart", - "make_task_dead", - "panic", - "rewind_stack_and_make_dead", - "sev_es_terminate", - "snp_abort", - "stop_this_cpu", - "usercopy_abort", - "xen_cpu_bringup_again", - "xen_start_kernel", +#include "noreturns.h" }; +#undef NORETURN if (!func) return false; diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h new file mode 100644 index 000000000000..0f5e53fd9e7a --- /dev/null +++ b/tools/objtool/noreturns.h @@ -0,0 +1,27 @@ +NORETURN(__invalid_creds) +NORETURN(__module_put_and_kthread_exit) +NORETURN(__reiserfs_panic) +NORETURN(__stack_chk_fail) +NORETURN(__ubsan_handle_builtin_unreachable) +NORETURN(arch_cpu_idle_dead) +NORETURN(cpu_bringup_and_idle) +NORETURN(cpu_startup_entry) +NORETURN(do_exit) +NORETURN(do_group_exit) +NORETURN(do_task_dead) +NORETURN(ex_handler_msr_mce) +NORETURN(fortify_panic) +NORETURN(kthread_complete_and_exit) +NORETURN(kthread_exit) +NORETURN(kunit_try_catch_throw) +NORETURN(lbug_with_loc) +NORETURN(machine_real_restart) +NORETURN(make_task_dead) +NORETURN(panic) +NORETURN(rewind_stack_and_make_dead) +NORETURN(sev_es_terminate) +NORETURN(snp_abort) +NORETURN(stop_this_cpu) +NORETURN(usercopy_abort) +NORETURN(xen_cpu_bringup_again) +NORETURN(xen_start_kernel)
On Thu, Apr 13, 2023 at 04:19:10PM +0200, Miroslav Benes wrote: > > --- a/tools/objtool/check.c > > +++ b/tools/objtool/check.c > > @@ -4485,7 +4485,8 @@ static int validate_sls(struct objtool_file *file) > > > > static int validate_reachable_instructions(struct objtool_file *file) > > { > > - struct instruction *insn; > > + struct instruction *insn, *prev_insn; > > + struct symbol *call_dest; > > int warnings = 0; > > > > if (file->ignore_unreachables) > > @@ -4495,6 +4496,17 @@ static int validate_reachable_instructions(struct objtool_file *file) > > if (insn->visited || ignore_unreachable_insn(file, insn)) > > continue; > > > > + prev_insn = prev_insn_same_sec(file, insn); > > + if (prev_insn && prev_insn->dead_end) { > > + call_dest = insn_call_dest(prev_insn); > > + if (call_dest) { > > + WARN_INSN(insn, "%s() is missing a __noreturn annotation", > > + call_dest->name); > > + warnings++; > > + continue; > > A nit but this and > > > + } > > + } > > + > > WARN_INSN(insn, "unreachable instruction"); > > warnings++; > > this makes me thinking. Wouldn't it be confusing to anyone that there is > no correspondence between warnings and a number of actual reported > warnings through WARN_INSN()? In the future when there would be a usage > for warnings. It does not really matter now. True, maybe we need WARN_INSN_ONCE_PER_FUNC() or so ;-)
> diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h > new file mode 100644 > index 000000000000..0f5e53fd9e7a > --- /dev/null > +++ b/tools/objtool/noreturns.h > @@ -0,0 +1,27 @@ > +NORETURN(__invalid_creds) > +NORETURN(__module_put_and_kthread_exit) > +NORETURN(__reiserfs_panic) > +NORETURN(__stack_chk_fail) > +NORETURN(__ubsan_handle_builtin_unreachable) > +NORETURN(arch_cpu_idle_dead) > +NORETURN(cpu_bringup_and_idle) > +NORETURN(cpu_startup_entry) > +NORETURN(do_exit) > +NORETURN(do_group_exit) > +NORETURN(do_task_dead) > +NORETURN(ex_handler_msr_mce) > +NORETURN(fortify_panic) > +NORETURN(kthread_complete_and_exit) > +NORETURN(kthread_exit) > +NORETURN(kunit_try_catch_throw) > +NORETURN(lbug_with_loc) > +NORETURN(machine_real_restart) > +NORETURN(make_task_dead) > +NORETURN(panic) > +NORETURN(rewind_stack_and_make_dead) > +NORETURN(sev_es_terminate) > +NORETURN(snp_abort) > +NORETURN(stop_this_cpu) > +NORETURN(usercopy_abort) > +NORETURN(xen_cpu_bringup_again) > +NORETURN(xen_start_kernel) Not as convenient to edit, but much easier to use. A bit of a toss up I suppose.
diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt index 5a69c207a10e..2cd1fa16ed08 100644 --- a/tools/objtool/Documentation/objtool.txt +++ b/tools/objtool/Documentation/objtool.txt @@ -303,6 +303,12 @@ the objtool maintainers. If it's not actually in a callable function (e.g. kernel entry code), change ENDPROC to END. +3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation + + The call from foo() to bar() doesn't return, but bar() is missing the + __noreturn annotation. NOTE: In addition to adding the __noreturn + annotation, the function name also needs to be added to + 'global_noreturns' in tools/objtool/check.c. 4. file.o: warning: objtool: func(): can't find starting instruction or diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5e7d3c62fb9d..60f2d649f19f 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4485,7 +4485,8 @@ static int validate_sls(struct objtool_file *file) static int validate_reachable_instructions(struct objtool_file *file) { - struct instruction *insn; + struct instruction *insn, *prev_insn; + struct symbol *call_dest; int warnings = 0; if (file->ignore_unreachables) @@ -4495,6 +4496,17 @@ static int validate_reachable_instructions(struct objtool_file *file) if (insn->visited || ignore_unreachable_insn(file, insn)) continue; + prev_insn = prev_insn_same_sec(file, insn); + if (prev_insn && prev_insn->dead_end) { + call_dest = insn_call_dest(prev_insn); + if (call_dest) { + WARN_INSN(insn, "%s() is missing a __noreturn annotation", + call_dest->name); + warnings++; + continue; + } + } + WARN_INSN(insn, "unreachable instruction"); warnings++; }