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Message-ID: <f2a2755f-6742-7e5c-a9a6-f416bc01a871@dereferenced.org>
Date: Tue, 29 Sep 2020 14:38:30 -0600
From: Ariadne Conill <ariadne@...eferenced.org>
To: libc-coord@...ts.openwall.com
Subject: [RFC] Add posix_spawnattr_chroot_np()
Hello,
Package managers frequently have a feature where you can use the package
manager to build a new filesystem image in a sub-directory (usually
exposed as the --root option in the package manager). However, to
achieve this, we have to be able to chroot into the sub-directory to run
maintainer scripts.
Right now, package managers usually do fork() + chroot() + execve() to
implement this. I find it desirable to migrate apk from this fork() +
chroot() + execve() pattern toward using posix_spawn() as that allows
for the underlying libc to take care of spawning the maintainer scripts
for us (and I assume posix_spawn() will always use the most efficient
method available for doing so).
Accordingly, I propose adding the following interface:
int posix_spawnattr_chroot_np(posix_spawnattr_t *attr, const char *chroot);
This will, of course, set a chroot attribute in posix_spawnattr_t.
Like the other interfaces, it will return 0 or an appropriate error number.
Doing so would allow us to migrate maintainer script handling in package
managers to use posix_spawn, at least in apk this is the only missing
functionality we require.
I plan on introducing this to musl shortly if there is consensus that
the proposed interface is acceptable. I can also contribute a glibc
implementation and FreeBSD libc implementation if that would be helpful.
Ariadne
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