linux emulation: "/ " resolves to real root dir; why ?
Konrad Heuer
kheuer2 at gwdg.de
Fri Oct 22 04:18:54 PDT 2004
On Fri, 22 Oct 2004, Andriy Gapon wrote:
> Under Linux emulation "/" resolves to real root directory, not
> /compat/linux directory and I am very curious why this is so.
>
> I see that in linux_emul_convpath() there is a special check for this
> case with the following comment:
>
> /*
> * We now compare the vnode of the linux_root to the one
> * vnode asked. If they resolve to be the same, then we
> * ignore the match so that the real root gets used.
> * This avoids the problem of traversing "../.." to find the
> * root directory and never finding it, because "/" resolves
> * to the emulation root directory. This is expensive :-(
> */
>
>
> Because of such behavior "mkdir -p" (in linux base 7) is broken in cases
> where more than one path components needs to be created - mkdir first
> chdir()s to / and then iteratively mkdir()s and chdir()s to subdirectories.
>
> My rationale for throwing out that check is that no linux program should
> ever need to access real root directory, and in case of a user using an
> interactive linux shell he should be smart enough to break out of
> /compat/linux (very easy).
>
> I have already posted this question to freebsd-emulation list, but got
> no responses so far.
Linux binaries often need to access files outside the emulation directory
tree, just think of data files in the user's homes when running
applications like acroread, linux-mozilla, staroffice etc. So you
absolutely need to break out.
Regards
Konrad Heuer
GWDG, Am Fassberg, 37077 Goettingen, Germany, kheuer2 at gwdg.de
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