From: mulyadi.santosa@gmail.com (Mulyadi Santosa)
To: kernelnewbies@lists.kernelnewbies.org
Subject: Error reading /dev/mem
Date: Sun, 2 Oct 2016 00:45:39 +0700 [thread overview]
Message-ID: <CAGdaadYWufjisgaavHQex3-6QVJBCQZuBLME7-j9JoeRo3N-Sg@mail.gmail.com> (raw)
In-Reply-To: <CAOK12Db6OzJagTgXMNcpJFOSnvOqNL8RqH=5GUVoi66wn=rC_g@mail.gmail.com>
On Wed, Sep 28, 2016 at 2:49 AM, Paddie O'Brien <paddieobrien@gmail.com>
wrote:
> Hi,
>
> I have a system call that maps virtual to physical addresses. I have
> disabled CONFIG_STRICT_DEVMEM and am reading from /dev/mem to verify
> that the contents of the syscall-returned physical address match the
> contents of the virtual address. It works fine up to a point. Reading
> beyond byte 935321597 in /dev/mem throws a "bad address" error. Not
> sure it's relevant but I'm running on virtual box and specifying 1GB
> of RAM. Tried with 2GB of RAM and hit the same problem.
>
> Any idea why I can't read beyond the above point?
>
> Thanks.
>
>
Hi paddie
Is it 32 bit system?
If yes, it seems you are about to exceed boundary of kernel linear addres
range, which is 0-896 MiB. The upper 896-1024 MiB (1 GiB) is reserved for
dynamic mapping
CMIIW people.
--
regards,
Mulyadi Santosa
Freelance Linux trainer and consultant
blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com
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next prev parent reply other threads:[~2016-10-01 17:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 19:49 Error reading /dev/mem Paddie O'Brien
2016-10-01 17:45 ` Mulyadi Santosa [this message]
2016-10-03 10:00 ` Paddie O'Brien
2016-10-10 6:55 ` Mulyadi Santosa
2016-10-03 13:00 ` Arun Sudhilal
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