On Fri, Feb 01, 2019 at 04:35:16PM -0800, Andrey Smirnov wrote: > On Thu, Jan 31, 2019 at 11:47 PM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote: > > > > On Thu, Jan 31, 2019 at 03:50:28PM +0300, Peter Mamonov wrote: > > > On Thu, Jan 31, 2019 at 01:54:52PM +0300, Peter Mamonov wrote: > > > > Hello, Andrey, > > > > > > > > > In order to allow access to second half of address space on 64-bit > > > > > machines, add code that creates /dev/highmem dedicated for that. > > > > > > > > > > Note that due to maximum file size being limited to MAX_LFS_FILESIZE > > > > > or 0x7fff_ffff_ffff_ffff bytes at addresses 0x7fff_ffff_ffff_ffff and > > > > > 0xffff_ffff_ffff_ffff cannot be access through /dev/mem and > > > > > /dev/hightmem correspondingly. > > > > > > > > Does it imply using `-s /dev/highmem` argument when accessing addresses beyond > > > > MAX_LFS_FILESIZE? That's not very convenient: > > > > > > > > $ git grep -l /dev/mem > > > > commands/crc.c > > > > commands/digest.c > > > > commands/disasm.c > > > > commands/md.c > > > > commands/memcmp.c > > > > commands/memcpy.c > > > > commands/memset.c > > > > commands/mm.c > > > > commands/mw.c > > > > > > I've forgotten to mention, that all meaningful MIPS64 virtual addresses > > > belong to the 2nd half of the address space. Except for user segment addresses > > > which are not used in barebox. > > > > In that case our only option seems to be to use an unsigned 64bit type > > for filesize. We would need an additional lseek like function which > > is able to reach the upper half of the address space and with regular > > lseek simply only the lower half would be reachable. > > > > Note that currently we don't seem to have a problem as even with Andreys > > series applied we can still 'md' the whole address space. The test if we > > lseek outside the file never triggers since the signed comparison of > > offset > f->size never evaluates to true for f->size == S64_MAX. > > > > I am a bit confused by this statement. I agree The check for pos > > f->size won't evaluate to true if f->size == S64_MAX, but the pos < 0, > will. On my i.MX8MQ board with all but "drivers: mem: Create file to > access second half of 64-bit memory" applied I have: Sorry, my bad. I accidently looked at a tree that didn't have the patches applied. You're right of course. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
