From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC8F9C49ED7 for ; Mon, 16 Sep 2019 12:14:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF21221670 for ; Mon, 16 Sep 2019 12:14:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727813AbfIPMOd (ORCPT ); Mon, 16 Sep 2019 08:14:33 -0400 Received: from foss.arm.com ([217.140.110.172]:44064 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726875AbfIPMOd (ORCPT ); Mon, 16 Sep 2019 08:14:33 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D7F53337; Mon, 16 Sep 2019 05:14:31 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EFC323F59C; Mon, 16 Sep 2019 05:14:30 -0700 (PDT) Date: Mon, 16 Sep 2019 13:14:28 +0100 From: Dave Martin To: Cristian Marussi Cc: amit.kachhap@arm.com, andreyknvl@google.com, shuah@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v5 00/11] Add arm64/signal initial kselftest support Message-ID: <20190916121428.GJ27757@arm.com> References: <20190902112932.36129-1-cristian.marussi@arm.com> <20190904114722.GQ27757@arm.com> <74165b2e-eb4c-994f-20ca-b69f71f3f5bc@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <74165b2e-eb4c-994f-20ca-b69f71f3f5bc@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Sep 10, 2019 at 01:25:31PM +0100, Cristian Marussi wrote: > On 04/09/2019 12:47, Dave Martin wrote: > > On Mon, Sep 02, 2019 at 12:29:21pm +0100, Cristian Marussi wrote: > >> Hi > >> > >> this patchset aims to add the initial arch-specific arm64 support to > >> kselftest starting with signals-related test-cases. > >> A common internal test-case layout is proposed which then it is anyway > >> wired-up to the toplevel kselftest Makefile, so that it should be possible > >> at the end to run it on an arm64 target in the usual way with KSFT. > > > > BTW, it's helpful to state the base branch / commit as clearly as > > possible near the top of the cover letter, say, > > > > --8<-- > > > > This series is based on arm64/for-next/core [1] > > commit 9ce1263033cd ("selftests, arm64: add a selftest for passing tagged pointers to kernel") > > > > [1] git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core > > > > -->8-- > > > > This is particularly important if you expect the maintainer to pick up > > the patches. > > > > You don't need to reference a specific commit unless there's a > > significant chance of conflicts if the wrong commit is used, but it can > > help provide a clue as to why you're basing on this alternate branch. > > > > Ok, thanks I'll do. > > >> ~/linux# make TARGETS=arm64 kselftest > >> > >> New KSFT arm64 testcases live inside tools/testing/selftests/arm64 grouped by > >> family inside subdirectories: arm64/signal is the first family proposed with > >> this series. > >> This series converts also to this subdirectory scheme the pre-existing > >> (already queued on arm64/for-next/core) KSFT arm64 tags tests, moving them > >> into arm64/tags. > >> > >> Thanks > >> > >> Cristian > >> > >> > >> Notes: > >> ----- > >> - further details in the included READMEs > >> > >> - more tests still to be written (current strategy is going through the related > >> Kernel signal-handling code and write a test for each possible and sensible code-path) > >> A few ideas for more TODO testcases: > >> - fake_sigreturn_unmapped_sp: SP into unmapped addrs > >> - fake_sigreturn_kernelspace_sp: SP into kernel addrs > >> - fake_sigreturn_sve_bad_extra_context: SVE extra context badly formed > >> - mangle_sve_invalid_extra_context: SVE extra_context invalid > >> > >> - SVE signal testcases and special handling will be part of an additional patch > >> still to be released > > > > What's your approach to checking that the test failure paths work? > > > > We could either hack the kernel or the tests to provoke "fake" failures, > > and I don't think it's necessary to test everything in this way, > > providing we have confidence that the test strategy and framework works > > in general. > > > > So my approach to testing the tests itself has been as follows: > > - PASS path: instrumented Kernel itself to print the exact line where the SEGV > is supposed to be called and manually check once for all (just redone now). > Something like: > > # FAKE_SIGRETURN_MISALIGNED_SP :: Triggers a sigreturn with a misaligned sigframe > Registered handlers for all signals. > Detected MINSTKSIGSZ:9984 > Testcase initialized. > uc context validated. > GOOD CONTEXT grabbed from sig_copyctx handler > Handled SIG_COPYCTX > Calling sigreturn with fake sigframe sized:4688 at SP @FFFFCAAE5253 > [ 188.206911] Kernel SEGV @ 571 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< > SIG_OK -- SP:0xFFFFCAAE5253 si_addr@:0xffffcaae5253 si_code:2 token@:0xffffcaae5253 offset:0 > ==>> completed. PASS(1) > > > - FAIL path: tried at first the same approach (instrument to avoid the SEGV), but thinking that > this could have led to general Kernel instability while processing bad sigframes, > I instead instrumented tests and utils as follows: > > - mangle_ TESTS: > > + removed the "mangling" for each test, and observed test FAIL (NO SEGV) > > # MANGLE_PSTATE_INVALID_MODE_EL1h :: Mangling uc_mcontext INVALID MODE EL1h > Registered handlers for all signals. > Detected MINSTKSIGSZ:9984 > Testcase initialized. > uc context validated. > Handled SIG_TRIG > ==>> completed. FAIL(0) > > + SSBS: being this a peculiar mangle_ test, where we check that SSBS is PRESERVED as it is > on Kernel restoring sigframe (no expected SEGV), I used a kernel patched to NOT preserve > the SSBS bit (so clearing it). Moreover I experimented with the various SSBS support levels > (no_supp/SSBS_BIT/MRS+SSBS_BIT) and observed how test behaved related to the detected SSBS support > > + verify that an anomalous SEGV (no SEGV_ACCER) is detected (say a *(* int)0x00= inside handler) > > # MANGLE_PSTATE_INVALID_DAIF_BITS :: Mangling uc_mcontext with INVALID DAIF_BITS > Registered handlers for all signals. > Detected MINSTKSIGSZ:9984 > Testcase initialized. > uc context validated. > SIG_OK -- SP:0xFFFFFBE96DA0 si_addr@:(nil) si_code:1 token@:(nil) offset:0 > si_code != SEGV_ACCERR...test is probably broken! <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< > -- RX UNEXPECTED SIGNAL: 6 > ==>> completed. FAIL(0) > > > - fake_sigreturn_ TESTS: > > + verify placing on the stack the good context grabbed from get_current_context() as it is > (GOOD), execution flow is anomalously restored inside get_current_context() and such > anomaly is spotted (without deadly loops) > > # FAKE_SIGRETURN_BAD_MAGIC :: Trigger a sigreturn with a sigframe with a bad magic > Registered handlers for all signals. > Detected MINSTKSIGSZ:9984 > Testcase initialized. > uc context validated. > GOOD CONTEXT grabbed from sig_copyctx handler > Handled SIG_COPYCTX > Calling sigreturn with fake sigframe sized:4688 at SP @FFFFCAC61F80 > Unexpected successful sigreturn detected: live_uc is stale ! <<<<<<<<<<<<<<<<<<<<<<<<<<< > ==>> completed. FAIL(0) > > + verify that an early SEGV is detected as anomalous (say a *(* int)0x00 before fake sigframe > has been placed on the stack) > > # FAKE_SIGRETURN_BAD_MAGIC :: Trigger a sigreturn with a sigframe with a bad magic > Registered handlers for all signals. > Detected MINSTKSIGSZ:9984 > Testcase initialized. > uc context validated. > GOOD CONTEXT grabbed from sig_copyctx handler > Handled SIG_COPYCTX > Available space:3552 > Using badly built context - ERR: BAD MAGIC ! > Calling sigreturn with fake sigframe sized:4688 at SP @FFFFE77C96D0 > SIG_OK -- SP:0xFFFFE77C96D0 si_addr@:(nil) si_code:1 token@:(nil) offset:0 > current->token ZEROED...test is probably broken! <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< > -- RX UNEXPECTED SIGNAL: 6 > ==>> completed. FAIL(0) OK, seems reasonable. I was just curious as to how you'd approached it. Cheers ---Dave