What address does the text section start?

Question

I read in a book (can't recollect the name) that in a 32 bit system text section always starts at 0x0848000. But when I do readelf -S example_executable it does not reflect the same information. Why is that? Do other sections (bss,data,rodata etc) also start at fixed addresses? How can I find the alignment boundary for these sections?

Answer 1

There is a good explanation here of how Linux virtual memory works when allocating storage for a particular program. ua alberta - linux memory allocation

The designers of the compiler/linker tool chain need to allocate an arbitary address for particular blocks of memory. In order to make it easier for other components of the tool chain like debuggers and profilers they always allocatate the same block to the same addresses. The actual addresses chosen are completely arbitrary.

When the program is loaded the virtual address will be mapped to some random piece of free memory (this is mostly done in hardware). This mapping is done on a per process basis to several programs can address virtual address x'0848000' but be pointed at different "real" memory addresses.