libselinux.so will be unmounted when magiskd starts. If magiskd restarts (like it died before boot completed), the files we want to unmount is the original files because the modified files is unmounted in previous start, which will causes many crashes due to missing libselinux.so.
* There will be garbage output when executing `su` (#4016)
* Failed to check root status and showing N/A in status (#4005)
Signed-off-by: Shaka Huang <shakalaca@gmail.com>
- Block signals in logging routine (fix#3976)
- Prevent possible deadlock after fork (stdio locks internally)
by creating a new FILE pointer per logging call (thread/stack local)
When detecting device is booting as Safe Mode, disable all modules and
MagiskHide and skip all operations. The only thing that'll be available
in this state is root (Magisk Manager will also be disabled by system).
Since the next normal boot will also have all modules disabled, this can
be used to rescue a device in the case when a rogue module causes
bootloop and no custom recovery is available (or recoveries without
the ability to decrypt data).
Previously, we use either BroadcastReceivers or Activities to receive
messages from our native daemon, but both have their own downsides.
Some OEMs blocks broadcasts if the app is not running in the background,
regardless of who the caller is. Activities on the other hand, despite
working 100% of the time, will steal the focus of the current foreground
app, even though we are just doing some logging and showing a toast.
In addition, since stubs for hiding Magisk Manager is introduced, our
only communication method is left with the broadcast option, as
only broadcasting allows targeting a specific package name, not a
component name (which will be obfuscated in the case of stubs).
To make sure root requests will work on all devices, Magisk had to do
some experiments every boot to test whether broadcast is deliverable or
not. This makes the whole thing even more complicated then ever.
So lets take a look at another kind of component in Android apps:
ContentProviders. It is a vital part of Android's ecosystem, and as far
as I know no OEMs will block requests to ContentProviders (or else
tons of functionality will break catastrophically). Starting at API 11,
the system supports calling a specific method in ContentProviders,
optionally sending extra data along with the method call. This is
perfect for the native daemon to start a communication with Magisk
Manager. Another cool thing is that we no longer need to know the
component name of the reciever, as ContentProviders identify themselves
with an "authority" name, which in Magisk Manager's case is tied to the
package name. We already have a mechanism to keep track of our current
manager package name, so this works out of the box.
So yay! No more flaky broadcast tests, no more stupid OEMs blocking
broadcasts for some bizzare reasons. This method should in theory
work on almost all devices and situations.
According to this comment in #1880:
https://github.com/topjohnwu/Magisk/issues/1880#issuecomment-546657588
If Linux recycled our PPID, and coincidentally the process that reused
the PPID is root, AND init wants to kill the whole process group,
magiskd will get killed as a result.
There is no real way to block a SIGKILL signal, so we simply make sure
our daemon PID is the process group leader by renaming the directory.
Close#1880
