into the 'ram' memory region.

     MEMORY
       {
         rom (rx)  : ORIGIN = 0, LENGTH = 256K
         ram (!rx) : org = 0x40000000, l = 4M
       }

   Once you define a memory region, you can direct the linker to place
specific output sections into that memory region by using the '>REGION'
output section attribute.  For example, if you have a memory region
named 'mem', you would use '>mem' in the output section definition.
*Note Output Section Region::.  If no address was specified for the
output section, the linker will set the address to the next available
address within the memory region.  If the combined output sections
directed to a memory region are too large for the region, the linker
will issue an error message.

   It is possible to access the origin and length of a memory in an
expression via the 'ORIGIN(MEMORY)' and 'LENGTH(MEMORY)' functions:

       _fstack = ORIGIN(ram) + LENGTH(ram) - 4;