linprocfs proc/pid/mem Bad address

[Kostik Belousov]

On Fri, Feb 26, 2010 at 12:06:07PM +0100, Fernando Apestegu?a wrote:
> On Fri, Feb 26, 2010 at 11:41 AM, Kostik Belousov <kostikbel at gmail.com> wrote:
> > On Thu, Feb 25, 2010 at 10:54:02PM +0100, Fernando Apestegu?a wrote:
> >> Why /compat/linux/proc/<pid>/mem always reports "Bad address" ?
> >>
> >> I'm using 8.0-RELEASE-p2
> >>
> >> Thanks in advance.
> >
> > Reports when ? What is the operation you doing that causes this ?
> 
> Oops, sorry. When trying to cat the file for example. In Linux the
> error reported is something like
> "No such process"
> 
> >

mem provides access to the target process virtual address space as file.
Reading from the file at some offset returns corresponding sequence of
bytes present in the process virtual address space starting at the offset.
Since cat starts read at the file offset 0, and (almost) no processes
map the page at the address 0, you get this error.
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