Embedded Linux System Design and Development

Getting Started 41

As we see along with the main program’s hello_world, a range of the

addresses is allocated to libc and the dynamic linker ld.so. The memory map

of the application is created at runtime and then the symbol resolution (in

our case the

printf) is done. This is done by a series of steps. The ELF

loader, which is built as a part of the kernel, scans the executable and finds

out that the process has shared library dependency; hence it calls the dynamic

linker ld.so. The ld.so, which is also implemented as a shared library, is a

bootstrap library; it loads itself and the rest of the shared libraries (libc.so)

into memory thus freezing the memory map of the application and does the

rest of the symbol resolution.

This leaves us with one last ...