The auditing code always starts by checking if we're in one of the
ignored code ranges (malloc, free, realloc, syscall, etc.)
To reduce the number of checks needed, we can cache the bounds of
the LibC text segment. This allows us to fast-reject addresses that
cannot possibly be a LibC function.
This returns ENOSYS if you are running in the real kernel, and some
other result if you are running in UserspaceEmulator.
There are other ways we could check if we're inside an emulator, but
it seemed easier to just ask. :^)
This patch brings Kernel::RangeAllocator to UserspaceEmulator in a
slightly simplified form.
It supports the basic three allocation types needed by virt$mmap():
allocate_anywhere, allocate_specific, and allocate_randomized.
Porting virt$mmap() and virt$munmap() to use the allocator makes
UE work correctly once again. :^)
All users of this mechanism have been switched to anonymous files and
passing file descriptors with sendfd()/recvfd().
Shbufs got us where we are today, but it's time we say good-bye to them
and welcome a much more idiomatic replacement. :^)
