Use base location of runtime source files, not compiled location (#319)

When debugging in GDB, it can be helpful to use tools such as `layout
src` in order to use the source files for a specific runtime. However,
the embedded debugging information points to the copied source directory
in the build directory rather than the canonical source under
`runtime/`. This PR adds a compile flag, `-fdebug-prefix-map`, which
embeds debugging information that points to the canonical runtime
source. This is useful in exotic (but seen!) debugging configurations
where the runtime build directory may have moved or no longer exists.

runtime/CMakeLists.txt

@@ -42,6 +42,10 @@ rt_option(ENV_SETUP "Set up stack environments like glibc expects" OFF)
 rt_option(INTERNAL_STRACE "Debug syscalls" OFF)
 rt_option(DEBUG "Enable debugging" OFF)
 
+if(DEFINED EYRIE_SRCDIR)
+    add_compile_options(-fdebug-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}=${EYRIE_SRCDIR})
+endif()
+
 include_directories($ENV{KEYSTONE_SDK_DIR}/include/edge)
 include_directories(tmplib)
 include_directories(include)

sdk/macros.cmake

@@ -80,6 +80,17 @@ macro(add_files FILE_LIST DIRWORK)
   endforeach()
 endmacro()
 
+macro(get_runtime_dir var)
+  get_filename_component(SRCDIR ${CMAKE_SOURCE_DIR} NAME)
+  if(${SRCDIR} STREQUAL "sdk")
+    get_filename_component(${var} ../runtime REALPATH BASE_DIR "${CMAKE_SOURCE_DIR}")
+  elseif(${SRCDIR} STREQUAL "keystone")
+    get_filename_component(${var} ./runtime REALPATH BASE_DIR "${CMAKE_SOURCE_DIR}")
+  else()
+    message(FATAL_ERROR "Don't know how to find runtime from current directory" ${SRCDIR})
+  endif()
+endmacro()
+
 # CMake macro for Eyrie runtime and Keystone Package
 macro(add_eyrie_runtime target_name plugins) # the files are passed via ${ARGN}
   set(runtime_prefix runtime)
@@ -95,19 +106,12 @@ macro(add_eyrie_runtime target_name plugins) # the files are passed via ${ARGN}
   list(APPEND PLUGIN_FLAGS "-DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}")
   list(APPEND PLUGIN_FLAGS "-DCMAKE_OBJCOPY=${CMAKE_OBJCOPY}")
 
-  get_filename_component(SRCDIR ${CMAKE_SOURCE_DIR} NAME)
-  if(${SRCDIR} STREQUAL "sdk")
-    set(EYRIE_SRCDIR ${CMAKE_SOURCE_DIR}/../runtime)
-  elseif(${SRCDIR} STREQUAL "keystone")
-    set(EYRIE_SRCDIR ${CMAKE_SOURCE_DIR}/runtime)
-  else()
-    message(FATAL_ERROR "Don't know how to find runtime from current directory" ${SRCDIR})
-  endif()
+  get_runtime_dir(EYRIE_SRCDIR)
 
   ExternalProject_Add(eyrie-${target_name}
     PREFIX ${runtime_prefix}
     DOWNLOAD_COMMAND rm -rf ${eyrie_src} && cp -ar ${EYRIE_SRCDIR} ${eyrie_src}
-    CMAKE_ARGS "${PLUGIN_FLAGS}"
+    CMAKE_ARGS "${PLUGIN_FLAGS}" -DEYRIE_SRCDIR=${EYRIE_SRCDIR}
     BUILD_IN_SOURCE TRUE
     BUILD_BYPRODUCTS ${eyrie_src}/eyrie-rt ${eyrie_src}/.options_log
     INSTALL_COMMAND "")