1

When a program causes a .so file to be loaded into memory, does is get loaded as a whole, or or does it only load the necessary "chunks"?

2

No. First the .so file is opened, then mmap() creates the virtual address space necessary to hold the whole file contents. However, only when something tries to access a particular address in the space will the access cause a page fault, and the kernel will read a (4k) block from the file corresponding to the page's offset into real memory. When it is in actual memory, the access will be restarted. This is demand paging.

  • '... the kernel will read PAGE_SIZE block...' PAGE_SIZE depends on architecture – Serge Jun 1 '16 at 21:33
  • @Serge Sure, but all popular architectures use 4kB (and many obscure ones too). – Gilles Jun 1 '16 at 22:05
  • 1
    @Gilles I commented for the sake of completeness, nothing else. – Serge Jun 1 '16 at 22:07

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