Offset between beginning of a .got section and _gp symbols used in MIPS GOT relocations calculations. Usually the expression looks like VA + Offset - GP, where VA is the .got section address, Offset - offset of the GOT entry, GP - offset between .got and _gp. Also there two "magic" symbols _gp_disp and __gnu_local_gp which hold the offset mentioned above. These symbols might be referenced by MIPS relocations.
Now the linker always defines _gp symbol and uses hardcoded value for its initialization. So offset between .got and _gp is 0x7ff0. The _gp_disp and gnu_local_gp defined if required and initialized by 0x7ff0. In fact that is not correct because _gp symbol might be defined by a linker script and holds arbitrary value. In that case we need to use this value in relocation calculation and initialize _gp_disp and gnu_local_gp properly.
The patch fixes the problem and completes fixing the bug #30311.