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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i7fDO-0005zp-Ob; Tue, 10 Sep 2019 12:25:46 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i7fDH-0005zD-Es for linux-arm-kernel@lists.infradead.org; Tue, 10 Sep 2019 12:25:45 +0000 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 21E2C1000; Tue, 10 Sep 2019 05:25:38 -0700 (PDT) Received: from [10.1.197.50] (e120937-lin.cambridge.arm.com [10.1.197.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 50E5D3F59C; Tue, 10 Sep 2019 05:25:37 -0700 (PDT) Subject: Re: [PATCH v5 00/11] Add arm64/signal initial kselftest support To: Dave Martin References: <20190902112932.36129-1-cristian.marussi@arm.com> <20190904114722.GQ27757@arm.com> From: Cristian Marussi Message-ID: <74165b2e-eb4c-994f-20ca-b69f71f3f5bc@arm.com> Date: Tue, 10 Sep 2019 13:25:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190904114722.GQ27757@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190910_052543_502205_F3BCD384 X-CRM114-Status: GOOD ( 24.34 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: amit.kachhap@arm.com, andreyknvl@google.com, shuah@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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) > [...] > > Cheers > ---Dave > Cheers Cristian _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel