Rollback rustsbi && support debugging under release mode

os/Cargo.toml

@@ -7,3 +7,6 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+
+[profile.release]
+debug = true

os/Makefile

@@ -1,6 +1,6 @@
 # Building
 TARGET := riscv64gc-unknown-none-elf
-MODE := debug
+MODE ?= debug
 KERNEL_ELF := target/$(TARGET)/$(MODE)/os
 KERNEL_BIN := $(KERNEL_ELF).bin
 DISASM_TMP := target/$(TARGET)/$(MODE)/asm
@@ -100,6 +100,7 @@ gdbserver: build
 	@qemu-system-riscv64 -machine virt -nographic -bios $(BOOTLOADER) -device loader,file=$(KERNEL_BIN),addr=$(KERNEL_ENTRY_PA) -s -S
 
 gdbclient:
+	@echo $(KERNEL_ELF)
 	@riscv64-unknown-elf-gdb -ex 'file $(KERNEL_ELF)' -ex 'set arch riscv:rv64' -ex 'target remote localhost:1234'
 
-.PHONY: build env kernel clean disasm disasm-vim run-inner switch-check gdbserver
+.PHONY: build env kernel clean disasm disasm-vim run-inner switch-check gdbserver gdbclient