The qemu-rv use a small init code for M mode in kernel build.
It is hard-coding and is difficult to change. Due to the fact,
introduce a already mature SBI implement (e.g OpenSBI) to
replace existing code is a better choice.
This patch introduce some change for qemu-rv:
1. use SSTC to provide time interrupt in kernel build
2. remove uncessary M mode trap.
For simplicity, this patch does not add support for booting
nuttx for any core, but force boot core to start core 0 and
let core 0 do the initialization.
Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
When an application is being loaded `up_addrenv_create ` calls
`create_region` to create the address environment. Only the first
entry is mapped when the region is created. Virtual memory that is
not mapped will trigger an exception when accessed. Other memory
pages are allocated and mapped on-demand. This enables setting
larger heap and stack for the process without compromising the
overall system memory.
