When RISCV_ALWAYS_SWITCH_THROUGH_ECALL is enabled, do_swap() enables PMP
checking in is_kernel_syscall.
If the PMP stack guard is triggered and do_swap() is called from the
fault handler, a PMP error occurs because the stack usage violates the
previous PMP setting.
Remove the stack guard setting during a stack overflow handler to allow
enabling PMP checking safely in fault handler.
Signed-off-by: Jimmy Zheng <jimmyzhe@andestech.com>
The idea here is to compute the PMP register set on demand i.e. upon
scheduling in the affected threads, and only if changes occurred.
A simple sequence number is used to stay in sync with the latest update.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Stackguard uses the PMP to prevents many types of stack overflow by
making any access to the bottom stack area raise a CPU exception. Each
thread has its set of precomputed PMP entries and those are written to
PMP registers at context switch time.
This is the code to set it up. It will be connected later.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This is the core code to manage PMP entries with only the global entries
initialisation for now. It is not yet linked into the build.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
