Messages in this thread | | | Date | Thu, 25 Jun 2009 01:49:13 +0200 | Subject | Re: [PATCH] allow execve'ing "/proc/self/exe" even if /proc is not mounted | From | Denys Vlasenko <> |
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On Thu, Jun 25, 2009 at 1:21 AM, Andrew Morton<akpm@linux-foundation.org> wrote: > On Thu, 25 Jun 2009 01:00:56 +0200 > Denys Vlasenko <vda.linux@googlemail.com> wrote: >> In some circumstances running process needs to re-execute >> its image. ... >> More elegant way is to execute /proc/self/exe. >> This works just fine as long as /proc is mounted. >> >> But it breaks if /proc isn't mounted, and this can happen in real-world >> usage. For example, when shell invoked very early in initrd/initramfs. > > Why can't userspace mount /proc before doing the daemonization?
Some people want to unset CONFIG_PROC_FS, and still have working POSIX compatible shell. Coincidentally, NOMMU machines, ones which *require* re-execution of the shell to support that, tent to be the most memory starved machines too (thus most likely to be those where people desire to unset CONFIG_PROC_FS).
> Oh geeze. Hard-coded "/proc/self/exec" it the middle of the core exec > code? You're a brave man.
There are other alternatives. This looked to be the least ugly to me.
We can special-case execve(NULL, ...). But I feared people would say this will change previously-buggy userspace code into one acting weirdly; in come cases leading to infinite execve loops. Do you think it's better than "/proc/self/exe"?
Then I thought about using a special name to mean "re-execute me", like "", or "/./self" or whatever. Whatever I though about, it was either risking a collision with a real file, or was too ugly, or both.
Then it occurred to me that "/proc/self/exe" _already is_ such a name. It is _already used_ for this purpose, so the userspace does not need to be changed.
For the extra non-intrusiveness, the hack kicks in only if /proc/self/exe does not exist.
[code style notes skipped. I will re-write it in whatever form you like it most, when/if it will be agreed on in principle ]
> But don't do any of that yet. This will be an unpopular patch and I > fear for its future ;)
Propose some other way to make it possible to re-execute a binary without /proc. -- vda -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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