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author | Xi Ruoyao <xry111@xry111.site> | 2022-10-12 11:36:08 +0300 |
---|---|---|
committer | Huacai Chen <chenhuacai@loongson.cn> | 2022-10-12 11:36:08 +0300 |
commit | 11cd8a648301af0ad6937ed9493519d1e93fd4c8 (patch) | |
tree | 019dfcc50e578b49a86867f1ed22350f798144c8 /arch/loongarch/Makefile | |
parent | 0d8dad7048611e5ba02ae8519539ce4b8b1482d3 (diff) | |
download | linux-11cd8a648301af0ad6937ed9493519d1e93fd4c8.tar.xz |
LoongArch: Adjust symbol addressing for AS_HAS_EXPLICIT_RELOCS
If explicit relocation hints are used by the toolchain, -Wa,-mla-*
options will be useless for the C code. So only use them for the
!CONFIG_AS_HAS_EXPLICIT_RELOCS case.
Replace "la" with "la.pcrel" in head.S to keep the semantic consistent
with new and old toolchains for the low level startup code.
For per-CPU variables, the "address" of the symbol is actually an offset
from $r21. The value is near the loading address of main kernel image,
but far from the loading address of modules. So we use model("extreme")
attibute to tell the compiler that a PC-relative addressing with 32-bit
offset is not sufficient for local per-CPU variables.
The behavior with different assemblers and compilers are summarized in
the following table:
AS has CC has
explicit relocs explicit relocs * Behavior
==============================================================
No No Use la.* macros.
No change from Linux 6.0.
--------------------------------------------------------------
No Yes Disable explicit relocs.
No change from Linux 6.0.
--------------------------------------------------------------
Yes No Not supported.
--------------------------------------------------------------
Yes Yes Enable explicit relocs.
No -Wa,-mla* options used.
==============================================================
*: We assume CC must have model attribute if it has explicit relocs.
Both features are added in GCC 13 development cycle, so any GCC
release >= 13 should be OK. Using early GCC 13 development snapshots
may produce modules with unsupported relocations.
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f09482a
Link: https://gcc.gnu.org/r13-1834
Link: https://gcc.gnu.org/r13-2199
Tested-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch/loongarch/Makefile')
-rw-r--r-- | arch/loongarch/Makefile | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index 84689c3ee3af..42352f905858 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -43,10 +43,28 @@ 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 +KBUILD_CFLAGS_KERNEL += -mdirect-extern-access +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 +endif cflags-y += -ffreestanding cflags-y += $(call cc-option, -mno-check-zero-division) |