Building an ARM bare machine application

The following tools installed in /opt/STM/STLinux-2.4/bare/armv7/bin are used to build an ARM bare machine application:

• arm-none-eabi-addr2line
• arm-none-eabi-ar
• arm-none-eabi-as
• arm-none-eabi-c++
• arm-none-eabi-c++filt
• arm-none-eabi-cpp
• arm-none-eabi-elfedit
• arm-none-eabi-g++
• arm-none-eabi-gcc
• arm-none-eabi-gcov
• arm-none-eabi-gprof
• arm-none-eabi-ld
• arm-none-eabi-nm
• arm-none-eabi-objcopy
• arm-none-eabi-objdump
• arm-none-eabi-ranlib
• arm-none-eabi-readelf
• arm-none-eabi-size
• arm-none-eabi-strings
• arm-none-eabi-strip

For documentation on each of these tools please refer to their user manuals (installed in /opt/STM/STLinux-2.4/bare/armv7/info).

To build a simple hello, world application for a B2020-STiH415 target the use the following command:

host% arm-none-eabi-gcc hello.c -o hello.out -Wl,--defsym,__start=0x40000000,--defsym,__stack=0x60000000

where --defsym,__start=0x40000000 specifies the address where the application will be loaded and --defsym,__stack=0x60000000 specifies the address of the stack for the application. In this example the application has been allocated 512MB of RAM starting at the base of RAM.

Notes:

• The stack grows downward from the address specified by the __stack symbol and the heap grows upward from the end of the BSS section of the application (identified by the __end__ symbol).

  -------------------- 0x40000000
  | CODE             |
  --------------------
  | RO DATA          |
  --------------------
  | DATA             |
  --------------------
  | BSS              |
  --------------------
  | Heap             |
  |                  |
  |                  |
  | Stack            |
  -------------------- 0x60000000

• Only identity mapped virtual to physical addresses are supported.
• Hardware initialisation is limited to only that required by the C runtime library and to ensure safe execution. This means that only the following is performed:
  1. disable all interrupts (IRQ and FIQ),
  2. turn off the MMU and caches,
  3. ensure that only core 0 is executing,
     • the other cores enter sleep mode (by executing the wfe instruction)
     • the sleeping cores can be woken up by performing the following steps:
       1. write an address to the variable __cpu_nostack_init_holding_pen_release_address
       2. raise an event (by executing the sev instruction)
  4. turn on the ARM Neon floating point co-processor.