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Fri, 22 Mar 2024 04:33:27 +0000 Received: from SN6PR02MB4157.namprd02.prod.outlook.com ([fe80::67a9:f3c0:f57b:86dd]) by SN6PR02MB4157.namprd02.prod.outlook.com ([fe80::67a9:f3c0:f57b:86dd%5]) with mapi id 15.20.7386.030; Fri, 22 Mar 2024 04:33:27 +0000 From: Michael Kelley To: Petr Tesarik , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Petr Tesarik , Will Deacon , open list , "open list:DMA MAPPING HELPERS" CC: Roberto Sassu , Petr Tesarik Subject: RE: [PATCH v3 2/2] bug: introduce ASSERT_VAR_CAN_HOLD() Thread-Topic: [PATCH v3 2/2] bug: introduce ASSERT_VAR_CAN_HOLD() Thread-Index: AQHae7P8YK5+vxRKhkyT7q/3TX9dpbFDK5Ww Date: Fri, 22 Mar 2024 04:33:27 +0000 Message-ID: References: <20240321171902.85-1-petrtesarik@huaweicloud.com> <20240321171902.85-3-petrtesarik@huaweicloud.com> In-Reply-To: <20240321171902.85-3-petrtesarik@huaweicloud.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-tmn: [0gXHdzBXTUFNliKlEG2y8zBJkhBPp86n] x-ms-publictraffictype: Email x-ms-traffictypediagnostic: SN6PR02MB4157:EE_|LV8PR02MB10336:EE_ x-ms-office365-filtering-correlation-id: 48a961af-6a05-43bb-0171-08dc4a293839 x-microsoft-antispam: BCL:0; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SN6PR02MB4157.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-Network-Message-Id: 48a961af-6a05-43bb-0171-08dc4a293839 X-MS-Exchange-CrossTenant-rms-persistedconsumerorg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Mar 2024 04:33:27.6703 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR02MB10336 From: Petr Tesarik Sent: Thursday, March 21, = 2024 10:19 AM >=20 > Introduce an ASSERT_VAR_CAN_HOLD() macro to check at build time that a > variable can hold the given value. >=20 > 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 o= f > IO_TLB_SEGSIZE. >=20 > Signed-off-by: Petr Tesarik > --- > include/linux/build_bug.h | 10 ++++++++++ > kernel/dma/swiotlb.c | 2 ++ > 2 files changed, 12 insertions(+) >=20 > 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.") >=20 >=20 > +/* > + * Compile time check that a variable can hold the given value > + */ > +#define ASSERT_VAR_CAN_HOLD(var, value) ({ \ > + typeof(value) __val =3D (value); \ > + typeof(var) __tmp =3D __val; \ > + BUILD_BUG_ON_MSG(__tmp !=3D __val, \ > + #var " cannot hold " #value "."); \ > +}) > + > #endif /* _LINUX_BUILD_BUG_H */ > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 3779a48eec9b..8256fcdc0cf6 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -285,6 +285,8 @@ static void swiotlb_init_io_tlb_pool(struct io_tlb_po= ol *mem, phys_addr_t start, > mem->areas[i].used =3D 0; > } >=20 > + ASSERT_VAR_CAN_HOLD(mem->slots[0].list, IO_TLB_SEGSIZE); > + ASSERT_VAR_CAN_HOLD(mem->slots[0].pad_slots, IO_TLB_SEGSIZE); > for (i =3D 0; i < mem->nslabs; i++) { > mem->slots[i].list =3D min(IO_TLB_SEGSIZE - io_tlb_offset(i), > mem->nslabs - i); > -- > 2.34.1 This was tested implicitly as part of my broader testing of Patch 1 of the series. From a code review standpoint, I don't feel very competent to recognize potential problems in ASSERT_VAR_CAN_HOLD(), so I haven't given a "Reviewed-by:" for this patch. Tested-by: Michael Kelley