Subject: Re: [PATCH v5 08/11] kselftest: arm64: fake_sigreturn_missing_fpsimd

From: Dave Martin <[email-masked]>
Date: Wed, 4 Sep 2019 12:49:10 +0100

On Mon, Sep 02, 2019 at 12:29:29pm +0100, Cristian Marussi wrote:
> Add a simple fake_sigreturn testcase which builds a ucontext_t without
> the required 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
> - added signal.h
> - added test description
> ---
>  .../testcases/fake_sigreturn_missing_fpsimd.c | 50 +++++++++++++++++++
>  1 file changed, 50 insertions(+)
>  create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_missing_fpsimd.c
> 
> diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_missing_fpsimd.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_missing_fpsimd.c
> new file mode 100644
> index 000000000000..08ecd8073a1a
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_missing_fpsimd.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 ARM Limited
> + *
> + * Place a fake sigframe on the stack missing the mandatory FPSIMD
> + * record: on sigreturn Kernel must spot this attempt and the test
> + * case is expected to be terminated via SEGV.
> + */
> +
> +#include <stdio.h>
> +#include <signal.h>
> +#include <ucontext.h>
> +
> +#include "test_signals_utils.h"
> +#include "testcases.h"
> +
> +struct fake_sigframe sf;
> +
> +static int fake_sigreturn_missing_fpsimd_run(struct tdescr *td,
> +					     siginfo_t *si, ucontext_t *uc)
> +{
> +	size_t resv_sz, offset;
> +	struct _aarch64_ctx *head = GET_SF_RESV_HEAD(sf);
> +
> +	/* 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);
> +	head = get_header(head, FPSIMD_MAGIC, resv_sz, &offset);
> +	if (head && resv_sz - offset >= HDR_SZ) {
> +		fprintf(stderr, "Mangling template header. Spare space:%zd\n",
> +			resv_sz - offset);
> +		/* Just overwrite fpsmid_context */
> +		write_terminator_record(head);

Strictly speaking, we may be throwing away more than just the
fpsimd_context record here.

But I think the test works nonetheless.  fpsimd_context is the only
record that's mandatory in any case.

> +
> +		ASSERT_BAD_CONTEXT(&sf.uc);
> +		fake_sigreturn(&sf, sizeof(sf), 0);
> +	}
> +
> +	return 1;
> +}
> +
> +struct tdescr tde = {
> +		.name = "FAKE_SIGRETURN_MISSING_FPSIMD",
> +		.descr = "Triggers a sigreturn with a missing fpsimd_context",
> +		.sig_ok = SIGSEGV,
> +		.timeout = 3,
> +		.run = fake_sigreturn_missing_fpsimd_run,
> +};

Assuming the comment I just posted on v3 of this patch makes sense to you,

Reviewed-by: Dave Martin <[email-masked]>

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