On Fri, Feb 01, 2019 at 08:47:11AM +0100, Sascha Hauer 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 can confirm that it is possible to enable access to the whole 64 bit address space via /dev/mem after adjusting /dev/mem size and eliminating checks for negative offset/pos in lseek(). Yet the proper approach seems to be to add a dedicated lseek implementation for /dev/mem, as in Linux. Regards, Peter > > 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
