PyPANDA: directory overrides for PANDA constructor

Allow caller to specify location of libpanda shared object, pc-bios files,
and directory where plugins are installed.  If these arguments are left as
their default values PyPANDA will use the previous algorithm for finding
these files.

a773

panda/python/core/pandare/panda.py

@@ -61,7 +61,9 @@ def __init__(self, arch="i386", mem="128M",
             raw_monitor=False, # When set, don't specify a -monitor. arg Allows for use of -nographic in args with ctrl-A+C for interactive qemu prompt.
             extra_args=None,
             catch_exceptions=True, # Should we catch and end_analysis() when python code raises an exception?
-            libpanda_path=None):
+            libpanda_path=None,
+            biospath=None,
+            plugin_path=None):
         '''
         Construct a new `Panda` object.  Note that multiple Panda objects cannot coexist in the same Python instance.
         Args:
@@ -83,6 +85,9 @@ def __init__(self, arch="i386", mem="128M",
                     -nographic in args with ctrl-A+C for interactive qemu prompt. Experts only!
             extra_args: extra arguments to pass to PANDA as either a string or an
                     array. (e.g. "-nographic" or ["-nographic", "-net", "none"])
+            libpanda_path: path to panda shared object to load
+            biospath: directory that contains "pc-bios" files
+            plugin_path: directory that contains panda plugins
         Returns:
             Panda: the created panda object
         '''
@@ -99,6 +104,8 @@ def __init__(self, arch="i386", mem="128M",
         self.cdrom = None
         self.catch_exceptions=catch_exceptions
         self.qlog = QEMU_Log_Manager(self)
+        self.build_dir = None
+        self.plugin_path = plugin_path
 
         self.serial_unconsumed_data = b''
 
@@ -147,13 +154,10 @@ def __init__(self, arch="i386", mem="128M",
             raise ValueError(f"Unsupported architecture {self.arch_name}")
         self.bits, self.endianness, self.register_size = self.arch._determine_bits()
 
-        self.build_dir  = find_build_dir(self.arch_name)
-        environ["PANDA_DIR"] = self.build_dir
-
         if libpanda_path:
-            self.libpanda_path = libpanda_path
+            environ["PANDA_LIB"] = self.libpanda_path = libpanda_path
         else:
-            self.libpanda_path = pjoin(self.build_dir, "{0}-softmmu/libpanda-{0}.so".format(self.arch_name))
+            self.libpanda_path = pjoin(self.get_build_dir(), "{0}-softmmu/libpanda-{0}.so".format(self.arch_name))
         self.panda = self.libpanda_path # Necessary for realpath to work inside core-panda, may cause issues?
 
         self.ffi = self._do_types_import()
@@ -167,7 +171,9 @@ def __init__(self, arch="i386", mem="128M",
 
         # Setup argv for panda
         self.panda_args = [self.panda]
-        biospath = realpath(pjoin(self.build_dir, "pc-bios")) # XXX: necessary for network drivers for arm/mips, so 'pc-bios' is a misleading name
+
+        if biospath is None:
+            biospath = realpath(pjoin(self.get_build_dir(), "pc-bios")) # XXX: necessary for network drivers for arm/mips, so 'pc-bios' is a misleading name
         self.panda_args.append("-L")
         self.panda_args.append(biospath)
 
@@ -244,6 +250,17 @@ def __init__(self, arch="i386", mem="128M",
         progress ("Panda args: [" + (" ".join(self.panda_args)) + "]")
     # /__init__
 
+    def get_plugin_path(self):
+        if self.plugin_path is None:
+            self.plugin_path = pjoin(*[self.get_build_dir(), self.arch_name+"-softmmu", "panda", "plugins"])
+        return self.plugin_path
+
+    def get_build_dir(self):
+        if self.build_dir is None:
+            self.build_dir  = find_build_dir(self.arch_name)
+            environ["PANDA_DIR"] = self.build_dir
+        return self.build_dir
+
     def _do_types_import(self):
         '''
         Import objects from panda_datatypes which are configured by the environment variables(?)
@@ -908,9 +925,9 @@ def _load_plugin_library(self, name):
             libpanda_path_chr = self.ffi.new("char[]",bytes(self.libpanda_path, "UTF-8"))
             self.__did_load_libpanda = self.libpanda.panda_load_libpanda(libpanda_path_chr)
         if not name in self.plugins.keys():
-            assert(isfile(pjoin(*[self.build_dir, self.arch_name+"-softmmu", "panda/plugins/panda_{}.so".format(name)])))
-            library = self.ffi.dlopen(pjoin(*[self.build_dir, self.arch_name+"-softmmu", "panda/plugins/panda_{}.so".format(name)]))
-            self.plugins[name] = library
+            plugin = pjoin(*[self.get_plugin_path(), f"panda_{name}.so"])
+            assert(isfile(plugin))
+            self.plugins[name] = self.ffi.dlopen(plugin)
 
     def queue_async(self, f, internal=False):
         '''

panda/src/callbacks.c

@@ -201,23 +201,33 @@ bool _panda_load_plugin(const char *filename, const char *plugin_name, bool libr
       assert(0 && "Library dir unset but library mode is enabled - Unsupported architecture?");
 	  printf("Library dir not set");
 #endif
-      const char *lib_dir = g_getenv("PANDA_DIR");
-      char *library_path;
-      if (lib_dir != NULL) {
-        library_path = g_strdup_printf("%s%s", lib_dir, LIBRARY_DIR);
-      }else{
-        fprintf(stderr, "WARNING: using hacky dlopen code that will be removed soon\n");
-        library_path = g_strdup_printf("../../../build/%s", LIBRARY_DIR); // XXX This is bad, need a less hardcoded path
-      }
+      const char *panda_lib = g_getenv("PANDA_LIB");
+      if(panda_lib != NULL) {
+        void *libpanda = dlopen(panda_lib, RTLD_LAZY | RTLD_NOLOAD | RTLD_GLOBAL);
+
+        if (!libpanda) {
+          fprintf(stderr, "Failed to load libpanda: %s from %s\n", dlerror(), panda_lib);
+          return false;
+        }
+      } else {
+        const char *lib_dir = g_getenv("PANDA_DIR");
+        char *library_path;
+        if (lib_dir != NULL) {
+          library_path = g_strdup_printf("%s%s", lib_dir, LIBRARY_DIR);
+        }else{
+          fprintf(stderr, "WARNING: using hacky dlopen code that will be removed soon\n");
+          library_path = g_strdup_printf("../../../build/%s", LIBRARY_DIR); // XXX This is bad, need a less hardcoded path
+        }
 
-      void *libpanda = dlopen(library_path, RTLD_LAZY | RTLD_NOLOAD | RTLD_GLOBAL);
+        void *libpanda = dlopen(library_path, RTLD_LAZY | RTLD_NOLOAD | RTLD_GLOBAL);
 
-      if (!libpanda) {
-        fprintf(stderr, "Failed to load libpanda: %s from %s\n", dlerror(), library_path);
+        if (!libpanda) {
+          fprintf(stderr, "Failed to load libpanda: %s from %s\n", dlerror(), library_path);
+          g_free(library_path);
+          return false;
+        }
         g_free(library_path);
-        return false;
       }
-      g_free(library_path);
     }
 
     void *plugin = dlopen(filename, RTLD_NOW);