From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Date: Sat, 17 Jun 2017 05:23:38 +0000 Subject: Re: endian bitshift defects [ was: staging: fusb302: don't bitshift __le16 type ] Message-Id: MIME-Version: 1 Content-Type: multipart/mixed; boundary="8323329-1575079896-1497677019=:2045" List-Id: References: <20170616174556.2358-1-fransklaver@gmail.com> <1497653077.10546.23.camel@perches.com> In-Reply-To: <1497653077.10546.23.camel@perches.com> To: Joe Perches Cc: Frans Klaver , Greg Kroah-Hartman , kernel-janitors , Guenter Roeck , Yueyao Zhu , Rui Miguel Silva , Guru Das Srinagesh , Javier Martinez Canillas , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1575079896-1497677019=:2045 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable On Fri, 16 Jun 2017, Joe Perches wrote: > On Fri, 2017-06-16 at 19:45 +0200, Frans Klaver wrote: > > The header field in struct pd_message is declared as an __le16 type. The > > data in the message is supposed to be little endian. This means we don't > > have to go and shift the individual bytes into position when we're > > filling the buffer, we can just copy the contents right away. As an > > added benefit we don't get fishy results on big endian systems anymore. > > Thanks for pointing this out. > > There are several instances of this class of error. > > Here's a cocci script to find them. > > This is best used with cocci's --all-includes option like: > > $ spatch --all-includes --very-quiet --sp-file lebe_bitshifts.cocci . > [ many defects...] > > $ cat lebe_bitshifts.cocci > @@ > typedef __le16, __le32, __le64,=A0=A0__be16, __be32, __be64; > { __le16, __le32, __le64,=A0=A0__be16, __be32, __be64 } a; > expression b; > @@ > > * a << b > > @@ > { __le16, __le32, __le64,=A0=A0__be16, __be32, __be64 } a; > expression b; > @@ > > * a <<=3D b > > @@ > { __le16, __le32, __le64,=A0=A0__be16, __be32, __be64 } a; > expression b; > @@ > > * a >> b > > @@ > { __le16, __le32, __le64,=A0=A0__be16, __be32, __be64 } a; > expression b; > @@ > > * a >>=3D b Is this always a problem? Would it be useful to add this to the scripts in the kernel? julia --8323329-1575079896-1497677019=:2045--