Messages in this thread Patch in this message | | | From | Xi Ruoyao <> | Subject | [PATCH v6 2/6] LoongArch: Adjust CFLAGS for CONFIG_AS_HAS_EXPLICIT_RELOCS | Date | Mon, 29 Aug 2022 21:31:42 +0800 |
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If explicit relocation hints is used by the toolchain, -Wa,-mla-* options will be useless for C code. Only use them for !CONFIG_AS_HAS_EXPLICIT_RELOCS.
Replace "la" with "la.pcrel" in head.S to keep the semantic consistent with new and old toolchains for the low level startup code.
Remove -fplt because it's the default for all known LoongArch C compilers.
The behavior with different assemblers and compilers are summarized in the following table:
AS has CC has explicit reloc explicit reloc Behavior ============================================================== No No Use la.* macros. No change from Linux 6.0. -------------------------------------------------------------- No Yes Disable explicit reloc. No change from Linux 6.0. -------------------------------------------------------------- Yes No Not supported. -------------------------------------------------------------- Yes Yes Use explicit relocs. No -Wa,-mla* options. ==============================================================
Signed-off-by: Xi Ruoyao <xry111@xry111.site> --- arch/loongarch/Makefile | 19 ++++++++++++++++++- arch/loongarch/kernel/head.S | 10 +++++----- 2 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index 7051a95f7f31..1563747c4fa8 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -40,10 +40,27 @@ endif cflags-y += -G0 -pipe -msoft-float LDFLAGS_vmlinux += -G0 -static -n -nostdlib + +# When the assembler supports explicit relocation hint, we must use it. +# GCC may have -mexplicit-relocs off by default if it was built with an old +# assembler, so we force it via an option. +# +# When the assembler does not supports explicit relocation hint, we can't use +# it. Disable it if the compiler supports it. +# +# If you've seen "unknown reloc hint" message building the kernel and you are +# now wondering why "-mexplicit-relocs" is not wrapped with cc-option: the +# combination of a "new" assembler and "old" compiler is not supported. Either +# upgrade the compiler or downgrade the assembler. +ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS +cflags-y += -mexplicit-relocs +else +cflags-y += $(call cc-option,-mno-explicit-relocs) KBUILD_AFLAGS_KERNEL += -Wa,-mla-global-with-pcrel KBUILD_CFLAGS_KERNEL += -Wa,-mla-global-with-pcrel KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs -KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs +KBUILD_CFLAGS_MODULE += -Wa,-mla-global-with-abs,-mla-local-with-abs +endif cflags-y += -ffreestanding cflags-y += $(call cc-option, -mno-check-zero-division) diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S index 01bac62a6442..eb3f641d5915 100644 --- a/arch/loongarch/kernel/head.S +++ b/arch/loongarch/kernel/head.S @@ -55,17 +55,17 @@ SYM_CODE_START(kernel_entry) # kernel entry point li.w t0, 0x00 # FPE=0, SXE=0, ASXE=0, BTE=0 csrwr t0, LOONGARCH_CSR_EUEN - la t0, __bss_start # clear .bss + la.pcrel t0, __bss_start # clear .bss st.d zero, t0, 0 - la t1, __bss_stop - LONGSIZE + la.pcrel t1, __bss_stop - LONGSIZE 1: addi.d t0, t0, LONGSIZE st.d zero, t0, 0 bne t0, t1, 1b - la t0, fw_arg0 + la.pcrel t0, fw_arg0 st.d a0, t0, 0 # firmware arguments - la t0, fw_arg1 + la.pcrel t0, fw_arg1 st.d a1, t0, 0 /* KSave3 used for percpu base, initialized as 0 */ @@ -73,7 +73,7 @@ SYM_CODE_START(kernel_entry) # kernel entry point /* GPR21 used for percpu base (runtime), initialized as 0 */ move u0, zero - la tp, init_thread_union + la.pcrel tp, init_thread_union /* Set the SP after an empty pt_regs. */ PTR_LI sp, (_THREAD_SIZE - 32 - PT_SIZE) PTR_ADD sp, sp, tp -- 2.37.0
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