fastmodel: make gem5 fastmodel build hermetic

This CL makes fastmodel RPATH relative to $ORIGIN instead of absolute
path. In this way we can move build folder (installing), without
breaking gem5 run.

Change-Id: I8b16d749252b982e45dfe779a5df931015a0e07d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55085
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/fastmodel/SConscript

@@ -81,7 +81,16 @@ pvlib_flavor = env['PVLIB_FLAVOR']
 pvlib_lib_dir = pvlib_home.Dir('lib').Dir(pvlib_flavor)
 
 simulation_engine_name = 'libMAXCOREInitSimulationEngine.3.so'
-simulation_engine_lib = pvlib_lib_dir.File(simulation_engine_name)
+simulation_engine_lib = env.Command(
+            Dir(env['BUILDDIR']).File(simulation_engine_name),
+            pvlib_lib_dir.File(simulation_engine_name),
+            MakeAction("cp ${SOURCE} ${TARGET}", Transform('COPY')))
+
+arm_singleton_registry_name = 'arm_singleton_registry.so'
+arm_singleton_registry_lib = env.Command(
+            Dir(env['BUILDDIR']).File(arm_singleton_registry_name),
+            pvlib_lib_dir.File(arm_singleton_registry_name),
+            MakeAction("cp ${SOURCE} ${TARGET}", Transform('COPY')))
 
 
 def staticify(env, name):
@@ -95,9 +104,7 @@ def staticify(env, name):
         full_name = Dir(path).File(static_name).get_abspath()
         if os.path.isfile(full_name):
             return File(full_name)
-
-    return name
-
+    raise BuildError("Failed to find FM static lib: " + name)
 
 # Adjust the build environment to support building in Fast Models.
 
@@ -121,16 +128,20 @@ lib_paths = (
     pvlib_home.Dir('Iris').Dir(pvlib_flavor),
 )
 env.Append(LIBPATH=lib_paths)
-env.Append(RPATH=lib_paths)
 
-fm_libs = (
+# Per ARM's 11.16 release note, a platform build with simgen automatically
+# copies libraries into the build target directory along with the other
+# dependencies. Therefore, we only need to add each simgen result into rpath and
+# no other shared librarires are required here.
+fm_static_libs = (
     'components',
     'pvbus',
     'armctmodel',
     'fmruntime',
     'IrisSupport',
 )
-env.Append(LIBS=list(staticify(env, lib) for lib in fm_libs))
+env.Append(LIBS=list(staticify(env, lib) for lib in fm_static_libs))
+
 system_libs = (
     'atomic',
     'dl',
@@ -337,7 +348,8 @@ class ArmFastModelComponent(object):
         self.headerpaths = [gen_dir]
         self.libs = static_lib_nodes + shared_libs
         self.libpaths = [simgen_dir]
-        self.rpaths = [simgen_dir]
+        # Simgen also puts required share library under the project folder.
+        self.rpaths = [simgen_dir, project_file_dir]
         self.log = gen_dir.File('build_%s.log' % tlc)
         self.simgen_cmd = env.subst('${SIMGEN} -p %s --configuration %s -b ' +
             '--verbose off --num-build-cpus 100 --build-dir %s >%s') % \
@@ -364,6 +376,11 @@ class ArmFastModelComponent(object):
         # but the difference is probably not significant.
         env.SideEffect(next(license_cycle), lib_nodes[0])
 
+        # We need a copy of the simulation engine lib and arm_singleton_registry
+        # (introduced in 11.16) alongside the executable.
+        Depends(lib_nodes[0], simulation_engine_lib)
+        Depends(lib_nodes[0], arm_singleton_registry_lib)
+
     def prepare_env(self, env):
         env.Append(LIBPATH=self.libpaths)
         env.AddLocalRPATH(*self.rpaths)

src/arch/arm/fastmodel/arm_fast_model.py

@@ -42,21 +42,9 @@ def set_armlmd_license_file(force=False):
 # 7.6 of the Fast Models User Guide.
 
 def scx_initialize(id):
-    # Change our working directory to where the simulation engine library
-    # is so that the fast model code can find it. It looks in the binary
-    # directory and in the current working directory, and we can change
-    # the later. This avoids having to make copies of that library all
-    # over the place.
-    cwd = os.getcwd()
-    os.chdir(os.path.join(buildEnv['PVLIB_HOME'], 'lib',
-                          buildEnv['PVLIB_FLAVOR']))
-
     # Actually run scx_initialize.
     _m5.arm_fast_model.scx_initialize(id)
 
-    # Restore the previous working directory.
-    os.chdir(cwd)
-
 def scx_load_application(instance, application):
     _m5.arm_fast_model.scx_load_application(instance, application)