On Sat, Dec 29, 2018 at 12:12:27AM +0000, Peter Maydell wrote: > On Fri, 28 Dec 2018 at 23:16, Andreas Dilger <adilger@xxxxxxxxx> wrot > > On Dec 28, 2018, at 4:18 AM, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote: > > > The problem is that there is no 32-bit API in some cases > > > (unless I have misunderstood the kernel code) -- not all > > > host architectures implement compat syscalls or allow them > > > to be called from 64-bit processes or implement all the older > > > syscall variants that had smaller offets. If there was a guaranteed > > > "this syscall always exists and always gives me 32-bit offsets" > > > we could use it. > > > > The "32bitapi" mount option would use 32-bit hash for seekdir > > and telldir, regardless of what kernel API was used. That would > > just set the FMODE_32BITHASH flag in the file->f_mode for all files. > > A mount option wouldn't be much use to QEMU -- we can't tell > our users how to mount their filesystems, which they're > often doing lots of other things with besides running QEMU. > (Otherwise we could just tell them "don't use ext4", which > would also solve the problem :-)) We need something we can > use at the individual-syscall level. Could you use a prctl to set whether you were running in 32 or 64 bit mode? Or do you change which kind of task you're emulating too often to make this a good idea?
