Restoring IRIX 6.5 dynamic linking in binutils

Current binutils still knows about IRIX, but programs it links do not start on IRIX 6.5: the system’s runtime linker, rld, rejects or mishandles them. Four changes to binutils 2.47 were needed for IRIX 7 before a dynamically linked program built with a modern toolchain ran on the real operating system.

• Local entries in the global offset table are laid out the way rld expects.
• The .rld_map section is emitted. rld uses it to publish its map of loaded objects to debuggers.
• The newer DT_MIPS_RLD_MAP_REL dynamic tag is suppressed. Linux’s loader understands it; IRIX’s does not.
• A section alignment in the startup object crt1 is corrected.

With those, both o32 and n32 test programs run in an IRIX 6.5 guest.

The way they are tested matters as much as the patches. The same source is compiled twice inside an emulated Indy running IRIX: once with SGI’s own MIPSpro compiler and once with the new toolchain. Both programs run on the guest and their output is compared. MIPSpro’s result is treated as the definition of correct.