mkdir -p /opt/src
cd /opt/src
git clone https://code.google.com/p/stm32flash/
cd stm32flash
make
make install

This test was on the STM32 Value line discovery board using PA10/PA9. Boot was pulled high via 220R.

It took a few attempts to synchronise.

stm32flash -b 115200 /dev/ttyCP2102
stm32flash 0.4

http://stm32flash.googlecode.com/

Interface serial_posix: 115200 8E1
Version      : 0x22
Option 1     : 0x00
Option 2     : 0x00
Device ID    : 0x0420 (Medium-density VL)
- RAM        : 8KiB  (512b reserved by bootloader)
- Flash      : 128KiB (sector size: 4x1024)
- Option RAM : 16b
- System RAM : 2KiB