[LibOS] process current working directory is path-based instead of inode-based

[g2flyer]

Description of the problem

Currently, g_process.cwdis of type dentry, meaning that it always refer to a fixed path until fchdir changes that, even in presence of rename or unlink calls. However, in POSIX the current working directory is based on inodes. That said, probably unlikely in gramine that somebody would stumble over scenarios when the two behaviours diverge?

Steps to reproduce

Change the current directory with a rename and then create a new file: The new file should be associated with the renamed directory, not the current one (or more precisely, currently will fail as this path doesn't exist anymore?). Full disclosure, i didn't experimentally validate this but in discussion with Dmitrii (@dimakuv) we agreed there is a bug here and these kind of stuff would lead to divergence to POSIX.

(alternate scenario would be that cwd is unlinked and recreated, in which case no file created from this process without call to fchdir should be visible in the filesystem directory/namespace

Gramine commit hash

80377ca