user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/sysdeps/linux/loongarch64/cp_syscall.S

@@ -0,0 +1,30 @@
+.section .text
+.global __mlibc_do_asm_cp_syscall
+.global __mlibc_syscall_begin
+.global __mlibc_syscall_end
+.type __mlibc_do_asm_cp_syscall, "function"
+__mlibc_do_asm_cp_syscall:
+	st.d $a7, $sp, -8
+	move $a7, $a0
+	move $a0, $a1
+	move $a1, $a2
+	move $a2, $a3
+	move $a3, $a4
+	move $a4, $a5
+	move $a5, $a6
+	move $a6, $a7
+	ld.w $t0, $tp, -96 // Tcb::cancelBits. See asserts in tcb.hpp.
+__mlibc_syscall_begin:
+	// tcbCancelEnableBit && tcbCancelTriggerBit
+	addi.d $t1, $r0, (1 << 0) | (1 << 2)
+	and $t0, $t0, $t1
+	beq $t0, $t1, cancel
+	syscall 0
+__mlibc_syscall_end:
+	ret
+
+cancel:
+	la.local $t2, __mlibc_do_cancel
+	jr $t2
+.section .note.GNU-stack,"",%progbits
+