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Date: Sat, 19 Sep 2020 17:14:41 -0700 From: Andy Lutomirski <luto@...nel.org> To: Al Viro <viro@...iv.linux.org.uk> Cc: Christoph Hellwig <hch@....de>, Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, Arnd Bergmann <arnd@...db.de>, David Howells <dhowells@...hat.com>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, "open list:MIPS" <linux-mips@...r.kernel.org>, Parisc List <linux-parisc@...r.kernel.org>, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, linux-s390 <linux-s390@...r.kernel.org>, sparclinux <sparclinux@...r.kernel.org>, linux-block <linux-block@...r.kernel.org>, Linux SCSI List <linux-scsi@...r.kernel.org>, Linux FS Devel <linux-fsdevel@...r.kernel.org>, linux-aio@...ck.org, io-uring@...r.kernel.org, linux-arch <linux-arch@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, Network Development <netdev@...r.kernel.org>, keyrings@...r.kernel.org, LSM List <linux-security-module@...r.kernel.org> Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag On Sat, Sep 19, 2020 at 4:24 PM Al Viro <viro@...iv.linux.org.uk> wrote: > > On Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote: > > > > It would not be a win - most of the syscalls don't give a damn > > > about 32bit vs. 64bit... > > > > Any reasonable implementation would optimize it out for syscalls that don’t care. Or it could be explicit: > > > > DEFINE_MULTIARCH_SYSCALL(...) > > 1) what would that look like? In effect, it would work like this: /* Arch-specific, but there's a generic case for sane architectures. */ enum syscall_arch { SYSCALL_NATIVE, SYSCALL_COMPAT, SYSCALL_X32, }; DEFINE_MULTIARCH_SYSCALLn(args, arch) { args are the args here, and arch is the arch. } > 2) have you counted the syscalls that do and do not need that? No. > 3) how many of those realistically *can* be unified with their > compat counterparts? [hint: ioctl(2) cannot] There would be no requirement to unify anything. The idea is that we'd get rid of all the global state flags. For ioctl, we'd have a new file_operation: long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch); I'm not saying this is easy, but I think it's possible and the result would be more obviously correct than what we have now.
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