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

From: Dave Martin <Dave.Martin@arm.com>
To: Cristian Marussi <cristian.marussi@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 v5 09/11] kselftest: arm64: fake_sigreturn_duplicated_fpsimd
Date: Wed, 4 Sep 2019 12:49:23 +0100	[thread overview]
Message-ID: <20190904114923.GZ27757@arm.com> (raw)
In-Reply-To: <20190902112932.36129-10-cristian.marussi@arm.com>

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 <cristian.marussi@arm.com>
> ---
> 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 */

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.

> +
> +	head = get_starting_head(shead, need_sz, resv_sz, NULL);
> +	if (head) {
> +		/* Add a spurios fpsimd_context */
> +		head->magic = FPSIMD_MAGIC;
> +		head->size = sizeof(struct fpsimd_context);
> +		/* and terminate */
> +		write_terminator_record(GET_RESV_NEXT_HEAD(head));
> +
> +		ASSERT_BAD_CONTEXT(&sf.uc);
> +		fake_sigreturn(&sf, sizeof(sf), 0);
> +	}
> +
> +	return 1;

[...]

Cheers
---Dave