linker - virtual and physical addresses of sections in elf files

Question

How does objdump compute the physical address (LMA) of elf sections? As far as I can tell, elf section headers only contain the virtual address (VMA) of sections [1].

Usually, VMA and LMA are the same. But for initialized data sections (.data), the VMA is the RAM location of the variables and LMA is the ROM location where the initial values are located. Crt0 is responsible for copying the initial values into RAM before main() is called. For example:

$ objdump -h my.elf
Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0003c3d0  00080000  00080000  00010000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  5 .data         000008d0  40000000  000d08d4  00060000  2**3
                  CONTENTS, ALLOC, LOAD, DATA

-Tom

[1] http://www.ouah.org/RevEng/x430.htm

Answer 1

Find this about LMA: http://www-zeuthen.desy.de/dv/documentation/unixguide/infohtml/binutils/docs/ld/Basic-Script-Concepts.html#Basic-Script-Concepts

The important is following:

Every loadable or allocatable output section has two addresses. The first is the VMA, or virtual memory address. This is the address the section will have when the output file is run. The second is the LMA, or load memory address. This is the address at which the section will be loaded. In most cases the two addresses will be the same. An example of when they might be different is when a data section is loaded into ROM, and then copied into RAM when the program starts up (this technique is often used to initialize global variables in a ROM based system). In this case the ROM address would be the LMA, and the RAM address would be the VMA