when i build px4/firmware locally，flash overflowed. In the ld.script file, Only 1MB flash is configured.
There is a silicon errata on some of the older STM32F4 chips out there which means only 1MB can be safely used.
For more info check out: https://docs.px4.io/en/flight_controller/silicon_errata.html
But note that not every board that is limited to 1MB has the errata. Some boards are capable of running FMUv3 (which does not have the limit) but have an old bootloader that cannot detect that FMUv3 can be installed. You can upload the bootloader to find out: https://docs.px4.io/en/advanced_config/bootloader_update.html