From: Cristian Marussi <cristian.marussi@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: linux-kselftest@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, shuah@kernel.org,
amit.kachhap@arm.com, andreyknvl@google.com
Subject: Re: [PATCH v7 05/11] kselftest: arm64: mangle_pstate_ssbs_regs
Date: Wed, 9 Oct 2019 08:52:37 +0100 [thread overview]
Message-ID: <13183627-4451-f6ee-35b0-2c12108de579@arm.com> (raw)
In-Reply-To: <20191008180112.GY27757@arm.com>
On 10/8/19 7:01 PM, Dave Martin wrote:
> On Mon, Oct 07, 2019 at 07:29:48pm +0100, Cristian Marussi wrote:
>> Add a simple mangle testcase which messes with the ucontext_t from within
>> the signal handler, trying to set the PSTATE SSBS bit and verify that
>> SSBS bit set is preserved across sigreturn.
>> Lookup PSTATE.SSBS directly using dedicated helper to grab PSTATE from a
>> live sigframe.
>>
>> Additionally, in order to support this test specific needs:
>> - extend signal testing framework to allow the definition of a custom
>> per test initialization function to be run at the end of test setup
>> and before test run routine. This will support also test SKIP.
>> - introduce also a new common utility function: get_current_context()
>> which can be used to grab a ucontext without the help of libc, and
>> detect if such ucontext has been actively used to jump back.
>>
>> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
>> ---
>> v6 --> v7
>> - fixed missing header for memcpy
>> - fixed misleading comment in get_current_context()
>> - fixed retvalue checks on get_current_context() invocation
>> - extend test_init()/test_result() and .init to report KSFT_SKIP
>> - SKIP mangle_pstate_ssbs_regs if SSBS not supported at all
>> - check SSBS support looking up ID_AA64PFR1_EL1.SSBS in test_init()
>> instead of using MRS/MSR
>
> [...]
>
>> diff --git a/tools/testing/selftests/arm64/signal/test_signals.c b/tools/testing/selftests/arm64/signal/test_signals.c
>> index cb970346b280..416b1ff43199 100644
>> --- a/tools/testing/selftests/arm64/signal/test_signals.c
>> +++ b/tools/testing/selftests/arm64/signal/test_signals.c
>> @@ -19,11 +19,11 @@ int main(int argc, char *argv[])
>> current = &tde;
>>
>> ksft_print_msg("%s :: %s\n", current->name, current->descr);
>> - if (test_setup(current)) {
>> + if (test_setup(current) && test_init(current)) {
>> test_run(current);
>> - test_result(current);
>> test_cleanup(current);
>> }
>> + test_result(current);
>>
>> - return current->pass ? KSFT_PASS : KSFT_FAIL;
>> + return current->result;
>> }
>> diff --git a/tools/testing/selftests/arm64/signal/test_signals.h b/tools/testing/selftests/arm64/signal/test_signals.h
>> index f712b5daa10b..ad8175806034 100644
>> --- a/tools/testing/selftests/arm64/signal/test_signals.h
>> +++ b/tools/testing/selftests/arm64/signal/test_signals.h
>> @@ -27,13 +27,25 @@
>> : "memory"); \
>> }
>>
>> +#define set_regval(regname, in) \
>> +{ \
>> + asm volatile("msr " __stringify(regname) ", %0" \
>> + : \
>> + : "r" (in) \
>> + : "memory"); \
>> +}
>
> Unused macro? Now that the test doesn't try to change the SSBS state
> via MSR, I don't think anything else is using this.
>
> [...]
>
Removing that in V8 (I left it on purpose since it's general and maybe could
have been used again for other tests...but now is effectively unused)
>> diff --git a/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c b/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c
>> new file mode 100644
>> index 000000000000..780161dbd7c0
>> --- /dev/null
>> +++ b/tools/testing/selftests/arm64/signal/testcases/mangle_pstate_ssbs_regs.c
>> @@ -0,0 +1,92 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2019 ARM Limited
>> + *
>> + * Try to mangle the ucontext from inside a signal handler, setting the
>> + * SSBS bit to 1 and veryfing that such modification is preserved.
>> + */
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <signal.h>
>> +#include <ucontext.h>
>> +
>> +#include <kselftest.h>
>> +
>> +#include "test_signals_utils.h"
>> +#include "testcases.h"
>> +
>> +static bool mangle_invalid_pstate_ssbs_init(struct tdescr *td)
>> +{
>> + bool ret;
>> +
>> + ret = feats_ok(td);
>> + if (!ret) {
>> + fprintf(stderr, "%s: unsupported feature - SKIP.\n", td->name);
>> + td->result = KSFT_SKIP;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static int mangle_invalid_pstate_ssbs_run(struct tdescr *td,
>> + siginfo_t *si, ucontext_t *uc)
>> +{
>> + ASSERT_GOOD_CONTEXT(uc);
>> +
>> + /* set bit value ... should NOT be cleared by Kernel on sigreturn */
>> + uc->uc_mcontext.pstate |= PSR_SSBS_BIT;
>> + fprintf(stderr, "SSBS set to 1 -- PSTATE: 0x%016llX\n",
>> + uc->uc_mcontext.pstate);
>> + /* Save after mangling...it should be preserved */
>> + td->saved_uc = *uc;
>
> Hmmm, now I'm wondering about how things like
> prctl(PR_SET_SPECULATION_CTRL) are supposed to interact with other ways
> of manipulating PSTATE.SSBS. Before we've answered this, we don't know
> what result to expect from this test in various configurations...
>
> To avoid this series depending on answering that question immediately,
> can we drop this test from the series for now?
>
> To reduce rework effort, maybe keep this patch in its current position
> in the series, with just the utility code, but drop the testcase.
Ok, but I'll split the remnants of this patch in two distinct patches:
one containing the get_current_context() and the other containing some test
initialization improvements that was also part of this patch.
Thanks
Cristian
>
> Sorry for the churn -- I didn't think of this issue earlier :(
>
> [...]
>
> Cheers
> ---Dave
>
next prev parent reply other threads:[~2019-10-09 7:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 18:29 [PATCH v7 00/11] Add arm64/signal initial kselftest support Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 01/11] kselftest: arm64: extend toplevel skeleton Makefile Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 02/11] kselftest: arm64: mangle_pstate_invalid_compat_toggle and common utils Cristian Marussi
2019-10-08 18:01 ` Dave Martin
2019-10-09 7:47 ` Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 03/11] kselftest: arm64: mangle_pstate_invalid_daif_bits Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 04/11] kselftest: arm64: mangle_pstate_invalid_mode_el[123][ht] Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 05/11] kselftest: arm64: mangle_pstate_ssbs_regs Cristian Marussi
2019-10-08 18:01 ` Dave Martin
2019-10-09 7:52 ` Cristian Marussi [this message]
2019-10-07 18:29 ` [PATCH v7 06/11] kselftest: arm64: fake_sigreturn_bad_magic Cristian Marussi
2019-10-08 18:01 ` Dave Martin
2019-10-07 18:29 ` [PATCH v7 07/11] kselftest: arm64: fake_sigreturn_bad_size_for_magic0 Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 08/11] kselftest: arm64: fake_sigreturn_missing_fpsimd Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 09/11] kselftest: arm64: fake_sigreturn_duplicated_fpsimd Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 10/11] kselftest: arm64: fake_sigreturn_bad_size Cristian Marussi
2019-10-07 18:29 ` [PATCH v7 11/11] kselftest: arm64: fake_sigreturn_misaligned_sp Cristian Marussi
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