Self notes:
With "-mla-global-with-pcrel" in KBUILD_CFLAGS_KERNEL gone (even if I
don't remove it, it will be ineffective with binutils-2.40/gcc-13), the
kernel will use GOT to access the objects in other translation units.
It may cause a performance regression.
*If* such a performance regression is really observed, we need to change
GCC to use PC relative addressing (instead of GOT) for loading external
objects when -fno-PIC. Such a change will benefit userspace apps as
well, *if* PC relative addressing is really faster than GOT access.
(Emphasize "if" here: I've not run any benchmarks yet.)
I'll be mostly AFK in the following one or two weeks, apologize for
possible slow respond.
On Thu, 2022-07-28 at 00:24 +0800, Xi Ruoyao wrote:
> The version 2.00 of LoongArch ELF ABI specification introduced new
> relocation types, and the development tree of Binutils and GCC has
> started to use them. If the kernel is built with the latest snapshot of
> Binutils or GCC, it will fail to load the modules because of unrecognized
> relocation types in modules.
>
> Add support for GOT and new relocation types for the module loader, so
> the kernel (with modules) can be built with the "normal" code model and
> function properly.
>
> Tested by building the kernel with Binutils & GCC master branch, and
> running the kernel with 35 in-tree modules loaded.
>
> Link: https://github.com/loongson/LoongArch-Documentation/pull/57
> Link: https://gcc.gnu.org/r13-1834
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f09482a
>
> Xi Ruoyao (5):
> LoongArch: Add section of GOT for kernel module
> LoongArch: Support R_LARCH_SOP_PUSH_GPREL relocation type in kernel
> module
> LoongArch: Support relocation against _GLOBAL_OFFSET_TABLE_
> LoongArch: Stop using undocumented assembler options
> LoongArch: Support modules with new relocation types
>
> arch/loongarch/Makefile | 5 +-
> arch/loongarch/include/asm/elf.h | 37 ++++++++++
> arch/loongarch/include/asm/module.h | 23 ++++++
> arch/loongarch/include/asm/module.lds.h | 1 +
> arch/loongarch/kernel/head.S | 10 +--
> arch/loongarch/kernel/module-sections.c | 72 +++++++++++++++++--
> arch/loongarch/kernel/module.c | 94 +++++++++++++++++++++++++
> 7 files changed, 229 insertions(+), 13 deletions(-)
>
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University