If address environments are in use, it is not possible to simply
memcpy from from one process to another. The current implementation
of env_dup does precisely this and thus, it fails at once when it is
attempted between two user processes.
The solution is to use the kernel's heap as an intermediate buffer.
This is a simple, effective and common way to do a fork().
Obviously this is not needed for kernel processes.
When the initial proxy task is duplicated into the first user task,
the environment exists in kernel memory and this must be copied to user
memory.
The memory allocated for the new task was allocated with the parent's
priority which is incorrect. Use the new task's priority instead.
Follow-up for: #5753
- User mode allocator was used for setting up the environment. This
works in flat mode and probably in protected mode as well, as there
is always a a single user allocator present
- This does not work in kernel mode, where each user task has its own
heap allocator. Also, when the idle tasks environment is being set,
no allocator is ready and the system crashes at once.
Fix this by using the group allocators instead:
- Idle task is a kernel task, so its group is privileged
- Add group_realloc
- Use the group_malloc/realloc functions instead of kumm_malloc
