Android 源码签名路径分析

签名路径由DEFAULT_SYSTEM_DEV_CERTIFICATE或PRODUCT_DEFAULT_DEV_CERTIFICATE 决定

签名文件由LOCAL_CERTIFICATE 决定

文件 build/core/config.mk

# The default key if not set as LOCAL_CERTIFICATE
ifdef PRODUCT_DEFAULT_DEV_CERTIFICATE
  DEFAULT_SYSTEM_DEV_CERTIFICATE := $(PRODUCT_DEFAULT_DEV_CERTIFICATE)
else
  DEFAULT_SYSTEM_DEV_CERTIFICATE := build/target/product/security/testkey
endif

如上代码分析，如果没有定义PRODUCT_DEFAULT_DEV_CERTIFICATE（可以在产品mk中定义），默认签名使用“build/target/product/security/testkey”。

文件 build/make/core/prebuilt_internal.mk

# If this is not an absolute certificate, assign it to a generic one.
ifeq ($(dir $(strip $(LOCAL_CERTIFICATE))),./)
      LOCAL_CERTIFICATE := $(dir $(DEFAULT_SYSTEM_DEV_CERTIFICATE))$(LOCAL_CERTIFICATE)
endif

如果LOCAL_CERTIFICATE（在应用的Android.mk中定义）不是绝对值路径，则LOCAL_CERTIFICATE根据DEFAULT_SYSTEM_DEV_CERTIFICATE的目录找到对应的签名文件。

如LOCAL_CERTIFICATE:=platform 表示使用平台签名，则其值最终为LOCAL_CERTIFICATE = build/target/product/security/platform