Date: Mon, 14 Sep 2020 10:00:57 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Xin LI <delphij@gmail.com>, FreeBSD Current <freebsd-current@freebsd.org> Cc: phk@freebsd.org, jilles@freebsd.org, Doug Rabson <dfr@rabson.org>, Xin Li <delphij@freebsd.org> Subject: Re: ioctl argument type [Was Re: svn commit: r359968 - head/sys/kern] Message-ID: <aa44cdff-d3e9-c87d-fc1b-c7bc7144de30@selasky.org> In-Reply-To: <CAGMYy3uQA5byFvu=Zyc9g2tgY4MhZ8WyRvBS795PcqNh6CO=fw@mail.gmail.com> References: <202004151320.03FDKqT7027080@repo.freebsd.org> <CAGMYy3uQA5byFvu=Zyc9g2tgY4MhZ8WyRvBS795PcqNh6CO=fw@mail.gmail.com>
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On 2020-09-14 09:44, Xin LI wrote: > Hi, > > I have seen Chromium trigger the warning (I run -CURRENT with INVARIANTS) > and looked into the code history a little bit. > > It seems that the command was changed to u_long in r36846 > <https://svnweb.freebsd.org/base?view=revision&revision=36846>; with a > follow up commit of r38517 > <https://svnweb.freebsd.org/base?view=revision&revision=38517>; , possibly > because ioctl was defined to take an unsigned long command before FreeBSD. > > Internally, we have truncated it to 32-bit since 2005 (r140406 > <https://svnweb.freebsd.org/base?view=revision&revision=140406>), and this > recent change made it a silent behavior. POSIX, on the other hand, defined > <https://pubs.opengroup.org/onlinepubs/9699919799/functions/ioctl.html>; > ioctl as taking an int as its second parameter, but neither Linux (glibc in > particular, despite its documentation says > <https://www.gnu.org/software/libc/manual/html_node/IOCTLs.html>; > differently) nor macOS appear to define it that way, but Solaris seems > <https://docs.oracle.com/cd/E23824_01/html/821-1463/ioctl-2.html>; to be > defining it as an int. > > What was the motivation to keep the prototype definition as > > int > ioctl(int fd, unsigned long request, ...); > > instead of: > > int > ioctl(int fd, int request, ...); > > Other than to make existing code happy? Alternatively, will it be a good > idea to give compiler some hints (e.g. by using __attribute__(enable_if)) > to emit errors, if we insist keeping the existing signature? > > > On Wed, Apr 15, 2020 at 6:21 AM Hans Petter Selasky <hselasky@freebsd.org> > wrote: > >> Author: hselasky >> Date: Wed Apr 15 13:20:51 2020 >> New Revision: 359968 >> URL: https://svnweb.freebsd.org/changeset/base/359968 >> >> Log: >> Cast all ioctl command arguments through uint32_t internally. >> >> Hide debug print showing use of sign extended ioctl command argument >> under INVARIANTS. The print is available to all and can easily fill >> up the logs. >> >> No functional change intended. >> >> MFC after: 1 week >> Sponsored by: Mellanox Technologies >> >> Modified: >> head/sys/kern/sys_generic.c >> >> Modified: head/sys/kern/sys_generic.c >> >> ============================================================================== >> --- head/sys/kern/sys_generic.c Wed Apr 15 13:13:46 2020 (r359967) >> +++ head/sys/kern/sys_generic.c Wed Apr 15 13:20:51 2020 (r359968) >> @@ -652,18 +652,19 @@ int >> sys_ioctl(struct thread *td, struct ioctl_args *uap) >> { >> u_char smalldata[SYS_IOCTL_SMALL_SIZE] >> __aligned(SYS_IOCTL_SMALL_ALIGN); >> - u_long com; >> + uint32_t com; >> int arg, error; >> u_int size; >> caddr_t data; >> >> +#ifdef INVARIANTS >> if (uap->com > 0xffffffff) { >> printf( >> "WARNING pid %d (%s): ioctl sign-extension ioctl >> %lx\n", >> td->td_proc->p_pid, td->td_name, uap->com); >> - uap->com &= 0xffffffff; >> } >> - com = uap->com; >> +#endif >> + com = (uint32_t)uap->com; >> >> /* >> * Interpret high order word to find amount of data to be >> Hi, Using unsigned long is not cross platform compatible, especially when you have 32-bit compat shim layers. On 64-bit platforms long is usually 64-bit and on 32-bit platforms long is usually 32-bit. You've brought up a good question with a good history line. Maybe we should just "#if 0" the INVARIANTS check and remove that code? --HPS
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