On Fri, Aug 9, 2019 at 12:57 AM Konstantin Belousov <kostik...@gmail.com> wrote:
> On Thu, Aug 08, 2019 at 07:38:28PM -0600, Warner Losh wrote: > > On Thu, Aug 8, 2019, 4:59 PM Gleb Smirnoff <gleb...@freebsd.org> wrote: > > > > > Hi, > > > > > > why do we need COMPAT_43 for arm64 at all? I can't imagine an > > > application that would require this compatibility. > > > > > > A more general question is how far in the future are we going > > > to carry COMPAT_43 for i386/amd64? > > > > > > > COMPAT_43 is a weird option. It's a combo of both sys calls and kernel > > behavior modifications. Before we thinned the ABIs we supported, it was > > necessary for them as well. The biggest behavior change is around > signals. > > It is weird to sort out and nobody has done the deep analysis to see what > > is truly unused and what is there for compat with Linux and other SysV > > systems... > I am not aware of any changes that COMPAT_43 provides for the signal > handling semantic, except a minor adjustment for interpretation of > zero-sized stack for sigaltstack(2). > The onstack stuff was what I was thinking about, but we also have code in sys_getpid() that returns the ppid in the second retval register, and similar things for getuid and getgid, It also allows ioctl numbers that have IOC_IN set, but size == 0 (these would otherwise return ENOTTY). It also turns on the COMPAT_OLDSOCK code which generally only kicks in when compat bits are set, but in one place it allows a shorter unix domain socket path length to be compatible unconditionally. The compatibility TTY stuff, at least is under COMPAT_43TTY, but that's purely ioctl translation code. The COMPAT_43 option indeed enables lcall 7,0 syscall entry emulation, > on both i386 and amd64. We are able to run FreeBSD 1.1.8 (i386) on amd64 > kernel in chroot this way. Since sometimes I get bug reports about this > stuff, there are some users of it. I believe it is important to be able > to run any FreeBSD binary for PR purposes, to wave the flag of excellent > binary compatibility we offer. > > COMPAT_43 is there to stay as far as there are people willing to maintain > it. There are more than one. > I think it's safe to retain on i386. amd64 is less clear to me, but I'd lean yes. All the other platforms I'd agree with gleb: why do we need it in the kernels by default (and maybe why do we need to support it at all)? Warner _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
