how it works by c to linked in FPGA configuration bitstream data?

// This is the symbol name for the SOF file contents linked in.

extern char _binary_soc_system_dc_rbf_start;

extern char _binary_soc_system_dc_rbf_end;

// Use the above symbols to extract the FPGA image information.

const char * fpga_image = &_binary_soc_system_dc_rbf_start;

const uint32_t fpga_image_size = &_binary_soc_system_dc_rbf_end - &_binary_soc_system_dc_rbf_start;

how does it extract the FPGA image information ?

where the FPGA image ?

thanks!