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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