From: Sascha Hauer <s.hauer@pengutronix.de>
To: Peter Mamonov <pmamonov@gmail.com>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>,
Barebox List <barebox@lists.infradead.org>
Subject: Re: [PATCH v2 18/19] drivers: mem: Create file to access second half of 64-bit memory
Date: Fri, 1 Feb 2019 08:47:11 +0100 [thread overview]
Message-ID: <20190201074711.clrwidodo5hpqb7y@pengutronix.de> (raw)
In-Reply-To: <20190131125028.glbnt55zmhqowi6p@localhost.localdomain>
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.
Sascha
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next prev parent reply other threads:[~2019-02-01 7:47 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 6:55 [PATCH v2 00/19] 32-bit lseek and /dev/mem fixes/improvements Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 01/19] commands: Move mem_parse_options() to lib/misc.c Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 02/19] commands: Get rid of mem_rw_buf Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 03/19] commands: Move /dev/mem driver to drivers/misc Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 04/19] nvmem: Do not use DEVFS_IS_CHARACTER_DEV Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 05/19] common: firmware: Don't use FILE_SIZE_STREAM directly Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 06/19] devfs: Fix incorrect error check for cdev->ops->lseek() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 07/19] fs: Update FILE position in lseek() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 08/19] fs: Drop trivial .lseek() implementaitons in FS drivers Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 09/19] devfs: Drop dev_lseek_default() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 10/19] fs: devfs: Change .lseek callbacks to return 'int' Andrey Smirnov
2019-02-04 14:32 ` Sascha Hauer
2019-01-29 6:55 ` [PATCH v2 11/19] fs: Do not use IS_ERR_VALUE() to validate offset in lseek() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 12/19] fs: Simplify new position calculation " Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 13/19] fs: Share code between mem_write()/mem_read() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 14/19] fs: Avoid division in mem_copy() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 15/19] fs: Report actual data processed by mem_copy() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 16/19] fs: Introduce mem_read_nofail() Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 17/19] commands: md: Do not use memmap() Andrey Smirnov
2019-02-04 13:57 ` Sascha Hauer
2019-02-04 19:35 ` Andrey Smirnov
2019-01-29 6:55 ` [PATCH v2 18/19] drivers: mem: Create file to access second half of 64-bit memory Andrey Smirnov
2019-01-29 8:48 ` Sascha Hauer
2019-01-29 20:40 ` Andrey Smirnov
2019-01-29 21:09 ` Sam Ravnborg
2019-01-31 10:54 ` Peter Mamonov
2019-01-31 12:50 ` Peter Mamonov
2019-02-01 7:47 ` Sascha Hauer [this message]
2019-02-01 10:25 ` Peter Mamonov
2019-02-02 1:07 ` Andrey Smirnov
2019-02-02 0:35 ` Andrey Smirnov
2019-02-04 7:40 ` Sascha Hauer
2019-01-31 20:17 ` Andrey Smirnov
2019-02-01 10:14 ` Peter Mamonov
2019-01-29 6:55 ` [PATCH v2 19/19] libfile: Fix incorrect lseek check in open_and_lseek() Andrey Smirnov
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