LoongArch: Record pc instead of offset in la_abs relocation

To clarify, the previous version functioned flawlessly. However, it's
worth noting that the LLVM's LoongArch backend currently lacks support
for cross-section label calculations. With this patch, we enable the use
of clang to compile relocatable kernels.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add Loongson Binary Translation (LBT) extension support

Loongson Binary Translation (LBT) is used to accelerate binary translation,
which contains 4 scratch registers (scr0 to scr3), x86/ARM eflags (eflags)
and x87 fpu stack pointer (ftop).

This patch support kernel to save/restore these registers, handle the LBT
exception and maintain sigcontext.

Signed-off-by: Qi Hu <huqi@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Drop unused parse_r and parse_v macros

When building with CONFIG_LTO_CLANG_FULL, there are several errors due
to the way that parse_r is defined with an __asm__ statement in a
header:

ld.lld: error: ld-temp.o <inline asm>:105:1: macro 'parse_r' is already defined
.macro parse_r var r
^

This was an issue for arch/mips as well, which was resolved by commit
67512a8cf5a7 ("MIPS: Avoid macro redefinitions").

However, parse_r is unused in arch/loongarch after commit 83d8b38967d2
("LoongArch: Simplify the invtlb wrappers"), so doing the same change
does not make much sense now. Just remove parse_r (and parse_v, which
is also unused) to resolve the redefinition error. If it needs to be
brought back due to an actual use, it should be brought back with the
same changes as the aforementioned arch/mips commit.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1924
Reviewed-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add vector extensions support

Add LoongArch's vector extensions support, which including 128bit LSX
(i.e., Loongson SIMD eXtension) and 256bit LASX (i.e., Loongson Advanced
SIMD eXtension).

Linux kernel doesn't use vector itself, it only handle exceptions and
context save/restore. So it only needs a subset of these instructions:

* Vector load/store: vld vst vldx vstx xvld xvst xvldx xvstx
* 8bit-elements move: vpickve2gr.b xvpickve2gr.b vinsgr2vr.b xvinsgr2vr.b
* 16bit-elements move: vpickve2gr.h xvpickve2gr.h vinsgr2vr.h xvinsgr2vr.h
* 32bit-elements move: vpickve2gr.w xvpickve2gr.w vinsgr2vr.w xvinsgr2vr.w
* 64bit-elements move: vpickve2gr.d xvpickve2gr.d vinsgr2vr.d xvinsgr2vr.d
* Elements permute: vpermi.w vpermi.d xvpermi.w xvpermi.d xvpermi.q

Introduce AS_HAS_LSX_EXTENSION and AS_HAS_LASX_EXTENSION to avoid non-
vector toolchains complains unsupported instructions.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add support for kernel relocation

This config allows to compile kernel as PIE and to relocate it at any
virtual address at runtime: this paves the way to KASLR.

Runtime relocation is possible since relocation metadata are embedded
into the kernel.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Xi Ruoyao <xry111@xry111.site> # Use arch_initcall
Signed-off-by: Jinyang He <hejinyang@loongson.cn> # Provide la_abs relocation code
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add la_abs macro implementation

Use the "la_abs macro" instead of the "la.abs pseudo instruction" to
prepare for the subsequent PIE kernel. When PIE is not enabled, la_abs
is equivalent to la.abs.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Remove several syntactic sugar macros for branches

These syntactic sugars have been supported by upstream binutils from the
beginning, so no need to patch them locally.

Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add other common headers

Add some other common headers for basic LoongArch support.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>