user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/rtld/loongarch64/elf.hpp

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <elf.h>
+
+#define ELF_CLASS ELFCLASS64
+#define ELF_MACHINE EM_LOONGARCH
+
+using elf_ehdr = Elf64_Ehdr;
+using elf_phdr = Elf64_Phdr;
+using elf_dyn = Elf64_Dyn;
+using elf_rel = Elf64_Rel;
+using elf_rela = Elf64_Rela;
+using elf_relr = Elf64_Relr;
+using elf_sym = Elf64_Sym;
+using elf_addr = Elf64_Addr;
+
+using elf_info = Elf64_Xword;
+using elf_addend = Elf64_Sxword;
+
+using elf_version = Elf64_Half;
+using elf_verdef = Elf64_Verdef;
+using elf_verdaux = Elf64_Verdaux;
+using elf_verneed = Elf64_Verneed;
+using elf_vernaux = Elf64_Vernaux;
+
+#define ELF_R_SYM ELF64_R_SYM
+#define ELF_R_TYPE ELF64_R_TYPE
+#define ELF_ST_BIND ELF64_ST_BIND
+#define ELF_ST_TYPE ELF64_ST_TYPE
+
+#define R_NONE R_LARCH_NONE
+#define R_JUMP_SLOT R_LARCH_JUMP_SLOT
+#define R_ABSOLUTE R_LARCH_64
+#define R_GLOB_DAT R_LARCH_64
+#define R_RELATIVE R_LARCH_RELATIVE
+#define R_IRELATIVE R_LARCH_IRELATIVE
+#define R_COPY R_LARCH_COPY
+#define R_TLS_DTPMOD R_LARCH_TLS_DTPMOD64
+#define R_TLS_DTPREL R_LARCH_TLS_DTPREL64
+#define R_TLS_TPREL R_LARCH_TLS_TPREL64
+// There appears to be no R_TLSDESC-equivalent
+
+struct ifunc_arg {
+	unsigned long _size;
+	unsigned long _hwcap;
+};
+
+using ifunc_handler = elf_addr (*)(ifunc_arg *);

user/include/mlibc/options/rtld/loongarch64/entry.S

@@ -0,0 +1,16 @@
+#include "mlibc-asm/helpers.h"
+
+PROC_START(_start)
+	pcaddu18i $ra, %call36(relocateSelf)
+	jirl $ra, $ra, 0
+
+	move $fp, $zero
+	move $a0, $sp
+	pcaddu18i $ra, %call36(interpreterMain)
+	jirl $ra, $ra, 0
+
+	jr $a0
+PROC_END(_start)
+
+GNU_STACK_NOTE()
+

user/include/mlibc/options/rtld/loongarch64/runtime.S

@@ -0,0 +1,5 @@
+.global pltRelocateStub
+pltRelocateStub:
+	break 0 // TODO
+.section .note.GNU-stack,"",%progbits
+