Revert #1 

Merge #1 from ZonePG/dev

add spinlock_t and muit-core startup support.

1. linker.ld
  change the secionts position

2. kvm.c
  map all secionts with PTE_XWR_SET

1. kvm.c
  add virtio-blk map

1. Makefile
  add qemu options, to disable virtio-blk legacy

2. virtio
  basic defs

3. kustd
  fix memcpy and memmove

1. spinlock.c spinlock.h
  add spinlock
2. earlylog.c earlylog.h
  add spinlock for printf
3. main.c
  change muticore call printf for spinlock

1. CMakeLists.txt
  add QEMU and K210 macro which are passed to gcc

2. Makefile
  add QEMU and K210 args passed to CMakeLists

1. main.c sbi.h
  add muticore start

2. gdbinit.py
  change display src and asm window

1. entry.s
  bug fix about stack address

2. swtch.s
  add swtch funtion

1. riscv
  functions to read write set and clear specifed csr
2. kvec
  kernel interrupt handler works now.
3. timer interrupt
  it works now.

1. add ranged map and ranged unmap function.

1. change linker script for page mapping.
2. add more bootinfo
3. optimize style of extdef.h

1. vmem.h vmem.c
  works now, simple tested. (1GiB is not tested)

2. pg.h
  add riscv sv39 paging related macro and defines.

1. add basic defs for riscv sv39 paging
2. add more utils in utils.h

1. add interface: kmalloc() kfree(), to be consistent with linux
2. remove some meaningless output in kmem_test()
3. kmem_cache_destory() should work(not tested)

1. expose interface of kmem_cache
2. add dev guide section on README.md
3. kmem_shrink() and kmem_cache_shrink() works
4. kmem_add() and kmem_del() works

1. list
  bug fix in list_del
  rename list_empty() to list_is_empty() to be consistent with linux's
  list impl

2. slab
  bug fix in slab_contain()
  slab_create() add new args 'adat' which is passed to buddy

3. gdbinit.py, layout src

4. kmem_free() and kmem_alloc() works.
  add manual test to kmem

1. Buddy allocator: add "used" field in buddy_block to indicate whether
   it is used, add check when do the free.
2. Buddy allocator: add "adat"(additional data) field in buddy_block for
   future use.
3. add a manual test for Buddy allocator.

1. fix bug in buddy_debug_print()
2. add kmem as a wrapper of slab
3. slab almost works now
4. add powerful list

1. make slab more flexible
2. make pmem interface more clear

1. Add simplifed slab allocator and simple test case(need human
   check...)
2. typo fix.
3. optimize constant position.

1. use file command to add source file instead of hard-coded in CMakeLists
2. add a brand new buddy system, simple tested, it needs more test.
3. fix bug in v_sprintf by adding a break.
4. add a unified kernel panic macro "KERNEL_PANIC()"
5. add a physical memory allocator abstruction layer, currently backed
   by buddy system.
6. add some simple utils.

2. toolchain.cmake can detect riscv64 tools in PATH
3. README.md
4. add rustsbi binaries
5. add more feature in Makefile, see comment in Makefile