配置和編譯

OpenSBI的配置選項位于不同平臺下的config.mk文件，例如platform/generic/config.mk：

# Blobs to build
FW_TEXT_START=0x80000000
FW_DYNAMIC=y
FW_JUMP=y
FW_PAYLOAD=y
ifeq ($(PLATFORM_RISCV_XLEN), 32)
  # This needs to be 4MB aligned for 32-bit system
  FW_JUMP_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x400000)))
else
  # This needs to be 2MB aligned for 64-bit system
  FW_JUMP_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x200000)))
endif
FW_JUMP_FDT_ADDR=$(shell printf "0x%X" $$(($(FW_TEXT_START) + 0x2200000)))

ifeq ($(PLATFORM_RISCV_XLEN), 32)
  # This needs to be 4MB aligned for 32-bit system
  FW_PAYLOAD_OFFSET=0x400000
else
  # This needs to be 2MB aligned for 64-bit system
  FW_PAYLOAD_OFFSET=0x200000
endif
FW_PAYLOAD_FDT_ADDR=$(FW_JUMP_FDT_ADDR)

選擇編譯需要的固件類型：

三種固件，根據自己的需求，在對應的固件類型配置為y：

• FW_DYNAMIC=y
• FW_JUMP=y
• FW_PAYLOAD=y

默認三種固件類型都編譯。

FW_TEXT_START

OpenSBI的運行地址，需要把OpenSBI下載到FW_TEXT_START指定的地址才能運行

FW_JUMP_ADDR

FW_JUMP固件的跳轉地址，對于RV32需要4M對齊，對于RV64需要2M對齊

FW_PAYLOAD_OFFSET

FW_PAYLOAD固件的偏移地址，對于RV32需要4對齊，對于RV64需要2M對齊

FW_JUMP_FDT_ADDR和FW_PAYLOAD_FDT_ADDR

設備樹的地址

這里可能有個疑問：為什么跳轉地址/偏移地址需要2M對齊或4M對齊？這個跟RISC-V Linux啟動時建立的頁表有關，需要深入分析才知道。