On Sun, Jan 24, 2010 at 12:57 PM, ZelluX <zellux@xxxxxxxxx> wrote:
So actually dynamic linking has nothing to do with kernel, or there's no special system calls or other mechanisms provided by kernel to support dynamic linking, is it right?
Why would you need special support in the kernel? As long as userspace has write access to the memory segments (relocation tables and other information to support dynamic linking), it will always work.
Take the cat program:
readelf -l /bin/cat
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x006f08 0x0804ff08 0x0804ff08 0x001d8 0x0035c RW 0x1000
DYNAMIC 0x006f1c 0x0804ff1c 0x0804ff1c 0x000d0 0x000d0 RW 0x4
Section to Segment mapping:
03 .ctors .dtors .jcr .dynamic .got .got.plt .data .bss
04 .dynamic
Notice that the 3rd segment contains the .got and .got.plt tables which are required by the dynamic linker. These segments are marked with the flags "RW" so they can be written to in userspace after they've been loaded.
-Joel
