Clobbering of flash contents when write address and/or size is not a multiple of 4k chunks. (ESPTOOL-147)

[Spanguole]

Bug Description

When using the write_flash function to an address that is not a multiple of 4k (e.g. writing to 0x2588) and/or with data which has a size that is not a multiple of 4k (e.g. 256 bytes), all the multiple-of-4k chunks that had any amount of data written end up with data being clobbered to 0xff in the regions that were NOT written to.

Example: running esptool.py write_flash 0x3360 0x80 smallchunk.bin will set all the bytes that were not touched in the 0x3000-0x4000 region to 0xff, while the 128 bytes that were written will be fine.

• Operating system: GNU/Linux
• Python version: Python 3.4.6
• ESP hardware in use: Esp-8266 on a Wemos D1 Mini

What is the expected behaviour?

What expected is that any data not explicitly touched by the write operation to be retained OR at least a diagnostic warning about data being clobbered should be issued.

[ghost]

This still needs fixing.