when a current thread is added to a memory domain the pages/sections
must be configured immediately.
A problem occurs when we add a thread to current and then drop
down to usermode. In such a case memory domain will become active
the next time a swap occurs.
Signed-off-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>
Added arch specific calls to handle memory domain destroy
and removal of partition.
GH-3852
Signed-off-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>
This adds CONFIG_EXECUTE_XOR_WRITE, which is enabled by default on
systems that support controlling whether a page can contain executable
code. This is also known as W^X[1].
Trying to add a memory domain with a page that is both executable and
writable, either for supervisor mode threads, or for user mode threads,
will result in a kernel panic.
There are few cases where a writable page should also be executable
(JIT compilers, which are most likely out of scope for Zephyr), so an
option is provided to disable the check.
Since the memory domain APIs are executed in supervisor mode, a
determined person could bypass these checks with ease. This is seen
more as a way to avoid people shooting themselves in the foot.
[1] https://en.wikipedia.org/wiki/W%5EX
Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
Added arch specific calls to handle memory domain destroy
and removal of partition.
GH-3852
Signed-off-by: Adithya Baglody <adithya.nagaraj.baglody@intel.com>
Add the following application-facing memory domain APIs:
k_mem_domain_init() - to initialize a memory domain
k_mem_domain_destroy() - to destroy a memory domain
k_mem_domain_add_partition() - to add a partition into a domain
k_mem_domain_remove_partition() - to remove a partition from a domain
k_mem_domain_add_thread() - to add a thread into a domain
k_mem_domain_remove_thread() - to remove a thread from a domain
A memory domain would contain some number of memory partitions.
A memory partition is a memory region (might be RAM, peripheral
registers, flash...) with specific attributes (access permission,
e.g. privileged read/write, unprivileged read-only, execute never...).
Memory partitions would be defined by set of MPU regions or MMU tables
underneath.
A thread could only belong to a single memory domain any point in time
but a memory domain could contain multiple threads.
Threads in the same memory domain would have the same access permission
to the memory partitions belong to the memory domain.
The memory domain APIs are used by unprivileged threads to share data
to the threads in the same memory and protect sensitive data from
threads outside their domain. It is not only for improving the security
but also useful for debugging (unexpected access would cause exception).
Jira: ZEP-2281
Signed-off-by: Chunlin Han <chunlin.han@linaro.org>
