Messages in this thread | | | From | Huacai Chen <> | Date | Tue, 6 Sep 2022 09:52:43 +0800 | Subject | Re: [PATCH v7 0/5] LoongArch: Support toolchain with new relocation types |
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Hi, Ruoyao,
On Tue, Sep 6, 2022 at 8:32 AM Xi Ruoyao <xry111@xry111.site> wrote: > > On Thu, 2022-09-01 at 10:17 +0800, Huacai Chen wrote: > > > Now all global variable accesses are via got, I think the performance > > may be much worse than before when we didn't use explicit-relocs. > > I don't know whether "a new code model" or your "(1)(2)(3)" is easier > > to implement, but I think it is better to solve the performance issue > > before 6.1-rc1. > > Hi Huacai, > > We've added a GCC option for this at https://gcc.gnu.org/r13-2433. On > the kernel side we need a one-line change: > > diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile > index 92c4a52c4c3e..69b39ba3a09d 100644 > --- a/arch/loongarch/Makefile > +++ b/arch/loongarch/Makefile > @@ -54,6 +54,7 @@ LDFLAGS_vmlinux += -G0 -static -n -nostdlib > # upgrade the compiler or downgrade the assembler. > ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS > cflags-y += -mexplicit-relocs > +KBUILD_CFLAGS_KERNEL += -mdirect-extern-access > else > cflags-y += $(call cc-option,-mno-explicit-relocs) > KBUILD_AFLAGS_KERNEL += -Wa,-mla-global-with-pcrel > > And we also need a one-line change in the EFI stub patch (under review): > > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > index 8931ed24379e..8c1225b92492 100644 > --- a/drivers/firmware/efi/libstub/Makefile > +++ b/drivers/firmware/efi/libstub/Makefile > @@ -27,7 +27,7 @@ cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > -fpic > cflags-$(CONFIG_LOONGARCH) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > - -fpic > + -fpie > > cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt > > (Some explanation: -fpic does not only mean "generate position- > independent code", but "generate position-independent code *suitable for > use in a shared library*". On LoongArch -mdirect-extern-access cannot > work for a shared library so the "-fpic -mdirect-extern-access" > combination is rejected deliberately.) > > Not sure how to submit these changes properly... Do you prefer me to > send V8 of this series or a single patch on top of your tree on GitHub? Don't need V8, I will squash it into the previous patch myself. But can we keep efistub as is?
Huacai > > -- > Xi Ruoyao <xry111@xry111.site> > School of Aerospace Science and Technology, Xidian University >
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