We really don't want callers of this function to accidentally change
the jail, or even worse - remove the Process from an attached jail.
To ensure this never happens, we can just declare this method as const
so nobody can mutate it this way.
Only do so after a brief check if we are in a Jail or not. This fixes
SMP, because apparently it is crashing when calling try_generate()
from the SysFSGlobalInformation::refresh_data method, so the fix for
this is to simply not do that inside the Process' Jail spinlock scope,
because otherwise we will simply have a possible flow of taking
multiple conflicting Spinlocks (in the wrong order multiple times), for
the SysFSOverallProcesses generation code:
Process::current().jail(), and then Process::for_each_in_same_jail being
called, we take Process::all_instances(), and Process::current().jail()
again.
Therefore, we should at the very least eliminate the first taking of the
Process::current().jail() spinlock, in the refresh_data method of the
SysFSGlobalInformation class.
By default, disallow reading of values in that directory. Later on, we
will enable sparingly read access to specific files.
The idea that led to this mechanism was suggested by Jean-Baptiste
Boric (also known as boricj in GitHub), to prevent access to sensitive
information in the SysFS if someone adds a new file in the /sys/kernel
directory.
The ProcFS is an utter mess currently, so let's start move things that
are not related to processes-info. To ensure it's done in a sane manner,
we start by duplicating all /proc/ global nodes to the /sys/kernel/
directory, then we will move Userland to use the new directory so the
old directory nodes can be removed from the /proc directory.
