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bh=NytFsz7TaWpQ0xHSi4FEPFoDMRh4D1j2c+g6k9t3n5Y=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Aq61Wmrq0K6xc/wL30oB3UkxyHJ6Uh9hXcZBrdPGcHI4q5pNWgufSkg5RwAAWDNoD MAn83CSWtOuNJbqAT0yyjyU4mzXMtKbDQ3OTB5r9iKHpO6HXDytYgtMlea7n8vQKkP LRBlUK9k2mYMbLsmmZ6RPvWFyz1LyUsMWhbDNPzk= Date: Wed, 17 May 2023 15:20:28 -0700 From: Andrew Morton To: David Laight Cc: 'Michael Ellerman' , "glider@google.com" , "elver@google.com" , "zhangpeng.00@bytedance.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "linuxppc-dev@lists.ozlabs.org" Subject: Re: [PATCH] mm: kfence: Fix false positives on big endian Message-Id: <20230517152028.86b6d2d5afa4541b4269131b@linux-foundation.org> In-Reply-To: <826f836f41db41eeb0fc32061994ac39@AcuMS.aculab.com> References: <20230505035127.195387-1-mpe@ellerman.id.au> <826f836f41db41eeb0fc32061994ac39@AcuMS.aculab.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: ecpmt3ih5tni5p78pcshe68dtctrx9o9 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 826E918000D X-Rspam-User: X-HE-Tag: 1684362031-639204 X-HE-Meta: U2FsdGVkX19yZHqmLkfueajHIemXzWVZdnnLso34D2LZ0Re+5KzKFAp/kFhD5RER/ceywCbSXeEJTVEIjndAzrQaswI5MX4qFGMKMLrDk8iqCYX5nxo85B0kWJTSNjQrPGWduICyReHrBP9PDNQ85n4pawkXXZNfQdx3BxA1gTwHtk4EzlHCpIFlxFtg4+8dj7WC2NRnzbmAB7zKM+8jGwcxJQtyobQJMZrAioPYB5ekoBo3yh+eAzOBz6AZGmklA5bqctjUd49Ld3XN2cFUN3+QLrvvx26v4JfGY1j8sC78kuvdzSrdsX/rb5MsR8uwuBd8bvpKwfUHvLEjWS+iWBTxp+3jHrjOge46Xd1yk5IwUEbKMm+eAmXhOaCqO/555LoTedGKNv5fYDACKE/T2PJi+NcoqT8t+FGToKJnwZ/FB9S0ANcweuVM9houV9YYcLSWW7DG6MDwwiZdLL7BoI+tWuLhldp6IdUcRR0t58PLZM9JrrTnGMvnqINq7avRHd6BjL8r7CIXxpmirQUYZ3uv0BZTaEDQ9kOLdxlrZcCXE631R9JrYfhCdKXQusHluxzcTTQKyoU3c8ghm8E3BSfOCiNlPDZoTrhd+/SHnzXo94T0Nxn9U0chWZaLsHKTOC0VfeR89T2bS5Okxm8q48jTr4RdYcCL7xfcIck4gbZwceIn2vaZ/RTrUP1NZvmK0mYKbkOKZgmdgl9gsil96Bq+z4vZn/1oAC9w2vJEMyJRuMJig47GCV54Sd5yqytDHD8I4RCDTlFUp9WOEXYJjZgtQthQ3nYzBgSYIRhgPoUda29E+xds0wEuvPKAOL3vc+12nywP6HLFU8gEIpU0n0jPBHH4RC60NPWRbv1ws4bv7rDtyvWMMs3sdpwjTcK4Wv4kkd4McafKoWJlxjt6prt69lNiXa3G8Dv2bmoa+KzDSRAF0bEUvFHLP8OPHwR7EvF6k3FgaYD5haVGbxx 4BbZTPBq 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 5 May 2023 16:02:17 +0000 David Laight wrote: > From: Michael Ellerman > > Sent: 05 May 2023 04:51 > > > > Since commit 1ba3cbf3ec3b ("mm: kfence: improve the performance of > > __kfence_alloc() and __kfence_free()"), kfence reports failures in > > random places at boot on big endian machines. > > > > The problem is that the new KFENCE_CANARY_PATTERN_U64 encodes the > > address of each byte in its value, so it needs to be byte swapped on big > > endian machines. > > > > The compiler is smart enough to do the le64_to_cpu() at compile time, so > > there is no runtime overhead. > > > > Fixes: 1ba3cbf3ec3b ("mm: kfence: improve the performance of __kfence_alloc() and __kfence_free()") > > Signed-off-by: Michael Ellerman > > --- > > mm/kfence/kfence.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h > > index 2aafc46a4aaf..392fb273e7bd 100644 > > --- a/mm/kfence/kfence.h > > +++ b/mm/kfence/kfence.h > > @@ -29,7 +29,7 @@ > > * canary of every 8 bytes is the same. 64-bit memory can be filled and checked > > * at a time instead of byte by byte to improve performance. > > */ > > -#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(0x0706050403020100)) > > +#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(le64_to_cpu(0x0706050403020100))) > > What at the (u64) casts for? > The constants should probably have a ul (or ull) suffix. > I tried that, didn't fix the sparse warnings described at https://lkml.kernel.org/r/202305132244.DwzBUcUd-lkp@intel.com. Michael, have you looked into this? I'll merge it upstream - I guess we can live with the warnings for a while.