From: Will Deacon <will@kernel.org>
To: Petr Tesarik <petrtesarik@huaweicloud.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Petr Tesarik <petr.tesarik1@huawei-partners.com>,
Michael Kelley <mhklinux@outlook.com>,
open list <linux-kernel@vger.kernel.org>,
"open list:DMA MAPPING HELPERS" <iommu@lists.linux.dev>,
Roberto Sassu <roberto.sassu@huaweicloud.com>,
Petr Tesarik <petr@tesarici.cz>
Subject: Re: [PATCH v3 2/2] bug: introduce ASSERT_VAR_CAN_HOLD()
Date: Fri, 22 Mar 2024 15:37:38 +0000 [thread overview]
Message-ID: <20240322153738.GC5634@willie-the-truck> (raw)
In-Reply-To: <20240321171902.85-3-petrtesarik@huaweicloud.com>
On Thu, Mar 21, 2024 at 06:19:02PM +0100, Petr Tesarik wrote:
> From: Petr Tesarik <petr.tesarik1@huawei-partners.com>
>
> Introduce an ASSERT_VAR_CAN_HOLD() macro to check at build time that a
> variable can hold the given value.
>
> Use this macro in swiotlb to make sure that the list and pad_slots fields
> of struct io_tlb_slot are big enough to hold the maximum possible value of
> IO_TLB_SEGSIZE.
>
> Signed-off-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
> ---
> include/linux/build_bug.h | 10 ++++++++++
> kernel/dma/swiotlb.c | 2 ++
> 2 files changed, 12 insertions(+)
>
> diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
> index 3aa3640f8c18..6e2486508af0 100644
> --- a/include/linux/build_bug.h
> +++ b/include/linux/build_bug.h
> @@ -86,4 +86,14 @@
> "Offset of " #field " in " #type " has changed.")
>
>
> +/*
> + * Compile time check that a variable can hold the given value
> + */
> +#define ASSERT_VAR_CAN_HOLD(var, value) ({ \
> + typeof(value) __val = (value); \
> + typeof(var) __tmp = __val; \
> + BUILD_BUG_ON_MSG(__tmp != __val, \
> + #var " cannot hold " #value "."); \
> +})
nit, but I think this prevents putting negative values into unsigned
types. Not sure whether we care? Arguably it's even correct to complain.
e.g.
u16 s;
ASSERT_VAR_CAN_HOLD(s, -1);
explodes for me.
Will
next prev parent reply other threads:[~2024-03-22 15:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 17:19 [PATCH v3 0/2] swiotlb: allocate padding slots if necessary Petr Tesarik
2024-03-21 17:19 ` [PATCH v3 1/2] swiotlb: extend buffer pre-padding to alloc_align_mask " Petr Tesarik
2024-03-22 4:29 ` Michael Kelley
2024-03-22 10:29 ` Petr Tesarik
2024-03-21 17:19 ` [PATCH v3 2/2] bug: introduce ASSERT_VAR_CAN_HOLD() Petr Tesarik
2024-03-22 4:33 ` Michael Kelley
2024-03-22 15:37 ` Will Deacon [this message]
2024-03-22 17:33 ` Petr Tesařík
2024-03-22 15:09 ` [PATCH v3 0/2] swiotlb: allocate padding slots if necessary Will Deacon
2024-03-22 17:51 ` Petr Tesařík
2024-03-27 19:42 ` Will Deacon
2024-03-22 18:11 ` Michael Kelley
2024-03-22 19:31 ` Petr Tesařík
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