The first stage bootloader, part of the ESP32 ROM, already sets up
a stack that's sufficient to execute C programs. So, instead of
implementing __stack() in assembly, do it in C to simplify things
slightly.
This ESP32-specific initialization will perform the following:
- Disable the watchdog timer that's enabled by the bootloader
- Move exception handlers to IRAM
- Disable normal interrupts
- Disable the second CPU
- Zero out the BSS segment
Things that might be performed in the future include setting up the
CPU frequency, memory protection regions, and enabling the flash
cache.
Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
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