From mboxrd@z Thu Jan 1 00:00:00 1970 From: mulyadi.santosa@gmail.com (Mulyadi Santosa) Date: Sun, 2 Oct 2016 00:45:39 +0700 Subject: Error reading /dev/mem In-Reply-To: References: Message-ID: To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org On Wed, Sep 28, 2016 at 2:49 AM, Paddie O'Brien 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20161002/b87fa50e/attachment.html