Subject: Re: [PATCH v5 09/11] kselftest: arm64: fake_sigreturn_duplicated_fpsimd

From: Dave Martin <[email-masked]>
Date: Thu, 5 Sep 2019 15:20:24 +0100

On Thu, Sep 05, 2019 at 02:32:09PM +0100, Cristian Marussi wrote:
> On 05/09/2019 13:39, Dave Martin wrote:
> > On Thu, Sep 05, 2019 at 01:15:58PM +0100, Cristian Marussi wrote:
> >> Hi
> >>
> >> On 04/09/2019 12:49, Dave Martin wrote:
> >>> On Mon, Sep 02, 2019 at 12:29:30pm +0100, Cristian Marussi wrote:
> >>>> Add a simple fake_sigreturn testcase which builds a ucontext_t with
> >>>> an anomalous additional fpsimd_context and place it onto the stack.
> >>>> Expects a SIGSEGV on test PASS.
> >>>>
> >>>> Signed-off-by: Cristian Marussi <[email-masked]>
> >>>> ---
> >>>> v3 --> v4
> >>>> - fix commit
> >>>> - missing include
> >>>> - using new get_starting_head() helper
> >>>> - added test description
> >>>> ---
> >>>>  .../fake_sigreturn_duplicated_fpsimd.c        | 52 +++++++++++++++++++
> >>>>  1 file changed, 52 insertions(+)
> >>>>  create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_duplicated_fpsimd.c
> >>>>
> >>>> diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_duplicated_fpsimd.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_duplicated_fpsimd.c
> >>>> new file mode 100644
> >>>> index 000000000000..c7122c44f53f
> >>>> --- /dev/null
> >>>> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_duplicated_fpsimd.c
> >>>> @@ -0,0 +1,52 @@
> >>>> +// SPDX-License-Identifier: GPL-2.0
> >>>> +/*
> >>>> + * Copyright (C) 2019 ARM Limited
> >>>> + *
> >>>> + * Place a fake sigframe on the stack including an additional FPSIMD
> >>>> + * record: on sigreturn Kernel must spot this attempt and the test
> >>>> + * case is expected to be terminated via SEGV.
> >>>> + */
> >>>> +
> >>>> +#include <signal.h>
> >>>> +#include <ucontext.h>
> >>>> +
> >>>> +#include "test_signals_utils.h"
> >>>> +#include "testcases.h"
> >>>> +
> >>>> +struct fake_sigframe sf;
> >>>> +
> >>>> +static int fake_sigreturn_duplicated_fpsimd_run(struct tdescr *td,
> >>>> +						siginfo_t *si, ucontext_t *uc)
> >>>> +{
> >>>> +	size_t resv_sz, need_sz;
> >>>> +	struct _aarch64_ctx *shead = GET_SF_RESV_HEAD(sf), *head;
> >>>> +
> >>>> +	/* just to fill the ucontext_t with something real */
> >>>> +	if (!get_current_context(td, &sf.uc))
> >>>> +		return 1;
> >>>> +
> >>>> +	resv_sz = GET_SF_RESV_SIZE(sf);
> >>>> +	need_sz = HDR_SZ + sizeof(struct fpsimd_context);
> >>>
> >>> Nit: Maybe write this sum in the same order as the records we're going 
> >>> o append, i.e.:
> >>>
> >>> 	need_sz = sizeof(struct fpsimd_context) + HDR_SZ; /* for terminator */
> >>
> >> Ok
> >>
> >>>
> >>> Also, maybe fail this test if there is no fpsimd_context in the initial
> >>> frame from get_current_context(): that would be a kernel bug, but we
> >>> wouldn't be giving fake_sigreturn() duplicate fpsimd_contexts in that
> >>> case -- so this test wouldn't test the thing it's supposed to test.
> >>>
> >>
> >> Any context grabbed by get_current_context() is verified at first to be sane
> >> when is copied in the handler by ASSERT_GOOD_CONTEXT()
> >>
> >>>   } else if (signum == sig_copyctx && current->live_uc) {
> >>>                 memcpy(current->live_uc, uc, current->live_sz);
> >>>                 ASSERT_GOOD_CONTEXT(current->live_uc);
> >>>                 current->live_uc_valid = 1;
> >>
> >> A missing fpsimd in the original sigframe would lead to an abort()
> >> straight away while preparing the test, and the test will fail.
> > 
> > OK, but there is no abort() in ASSERT_GOOD_CONTEXT(), only assert(0).
> > Can you add an abort() after the assert() in there in patch 2?
> > 
> Ok yes, I meant the abort coming from assert(0) in fact....I'll review all
> the critical asserts for additional aborts in V6

OK -- I guess this only matters for things that should be reported as
test failures.  Things that are purely bugs in the test are less of a
concern.

Cheers
---Dave

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