Re: 回复：[PATCH v5] LoongArch: add movable attribute

[Xi Ruoyao <xry111@xry111.site>]

On Fri, 2022-08-05 at 10:38 +0800, Lulu Cheng wrote:

> > > I'm working on the implementation of specifing attributes of variables for other architectures.
> > > If the address is obtained through the GOT table and 4 instructions, there is not much difference in performance.
> > In this case I still prefer a GOT table entry because for 4-instruction
> > absolute addressing sequence we'll need to implement 4 new relocation
> > types in the kernel module loader.
> If it is accessed through the GOT table, dynamic relocation is required when the module is loaded.

Dynamic relocation is required when the module is loaded anyway.  The
.ko modules are actually relocatable ELF objects (produced by ld -r) and
the module loader has to perform some work of a normal linker.

> And accessing the got table may have a cache miss.

/* snip */

> So my idea is "model(normal)","model (large)" etc.

Then should we have an option to disable GOT globally?  Maybe for kernel
we'll just "-mno-got -mcmodel=large" (or "extreme"?  The kernel image is
loaded at 0x9000000000000000 and the modules are above
0xffff000000000000 so we need to handle 64-bit offset).
-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University