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Date: Thu, 28 Jul 2022 00:46:53 +0800 From: Xi Ruoyao <xry111@...111.site> To: loongarch@...ts.linux.dev Cc: linux-kernel@...r.kernel.org, WANG Xuerui <kernel@...0n.name>, Huacai Chen <chenhuacai@...nel.org> Subject: Re: [PATCH 0/5] LoongArch: Support new relocation types 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@...111.site> School of Aerospace Science and Technology, Xidian University
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