added pretty skeletal loader

svn-id: r50036

1 files changed, 255 insertions, 0 deletions

diff --git a/backends/platform/gp2xwiz/gp2xwiz-loader.cpp b/backends/platform/gp2xwiz/gp2xwiz-loader.cpp
new file mode 100644
index 0000000000..7acc4ee0d0
--- /dev/null
+++ b/backends/platform/gp2xwiz/gp2xwiz-loader.cpp
@@ -0,0 +1,255 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * $URL$
+ * $Id$
+ *
+ */
+
+#if defined(DYNAMIC_MODULES) && defined(__GP2X__)
+
+#include <string.h>
+#include <stdarg.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <malloc.h>
+#include <unistd.h>
+
+#include "gp2xwiz-loader.h"
+
+#ifdef __WIZ_DEBUG_PLUGINS__
+#define DBG(x) printf(x, ## __VA_ARGS__)
+#else
+#define DBG(x)
+#endif
+
+#define seterror(x,...) fprintf(stderr,x, ## __VA_ARGS__)
+
+// Expel the symbol table from memory
+void DLObject::discard_symtab()
+{
+  free(_symtab);
+  free(_strtab);
+  _symtab = NULL;
+  _strtab = NULL;
+  _symbol_cnt = 0;
+}
+
+// Unload all objects from memory
+void DLObject::unload()
+{
+  discard_symtab();
+  free(_segment);
+  segment = NULL;
+}
+
+/**
+ * Follow the instruction of a relocation section.
+ *
+ * @param fd 		 File Descriptor
+ * @param offset 	 Offset into the File
+ * @param size   	 Size of relocation section
+ *
+ */
+bool DLObject::relocate(int fd, unsigned long offset, unsigned long size)
+{
+  Elf32_Rela *rela; //relocation entry
+
+  // Allocate memory for relocation table
+  if (!(rela = (Elf32_Rela *)malloc(size))) {
+    seterror("Out of memory.");
+    return false;
+  }
+
+  // Read in our relocation table
+  if (lseek(fd, offset, SEEK_SET)<0 ||
+      read(fd, rela, size) != (ssize_t)size) {
+    seterror("Relocation table load failed.");
+    free(rela);
+    return false;
+  }
+
+  // Treat each relocation entry. Loop over all of them
+  int cnt = size / sizeof(*rela);
+
+  // TODO: Loop over relocation entries
+  for (int i=0; i<cnt; i++) {
+
+    Elf32_Sym *sym = ???;
+
+    void *target = ???;
+
+    switch(/*relocation type*/) {
+    case ???:
+      //TODO: Cases for each relocation type.
+      break;
+    default:
+      seterror("Unknown relocation type %d.", ???);
+      free(rela);
+      return false;
+    }
+
+  }
+
+  free(rela);
+  return true;
+}
+
+
+bool DLObject::load(int fd)
+{
+  Elf32_Ehdr ehdr; // ELF header
+  Elf32_Phdr phdr; // Program header
+  Elf32_Shdr *shdr; // Section header
+
+  //TODO: fill this out!
+
+  free(shdr);
+
+  return true;
+}
+
+bool DLObject::open(const char *path)
+{
+  int fd;
+  void *ctors_start, *ctors_end;
+
+  DBG(("open(\"%s\")\n", path));
+
+  if ((fd = ::open(path, O_RDONLY))<0) {
+    seterror("%s not found.", path);
+    return false;
+  }
+
+  // Try to load and relocate
+  if (!load(fd)) {
+    ::close(fd);
+    unload();
+    return false;
+  }
+
+  ::close(fd);
+
+  //TODO: flush data cache
+
+  ctors_start = symbol("___plugin_ctors");
+  ctors_end = symbol("___plugin_ctors_end");
+  _dtors_start = symbol("___plugin_dtors");
+  _dtors_end = symbol("___plugin_dtors_end");
+
+  if (ctors_start == NULL || ctors_end == NULL || _dtors_start == NULL ||
+     _dtors_end == NULL) {
+    seterror("Missing ctors/dtors.");
+    _dtors_start = _dtors_end = NULL;
+    unload();
+    return false;
+  }
+
+  DBG(("Calling constructors.\n"));
+  for (void (**f)(void) = (void (**)(void))ctors_start; f != ctors_end; f++)
+    (**f)();
+
+  DBG(("%s opened ok.\n", path));
+  return true;
+}
+
+bool DLObject::close()
+{
+  if (_dtors_start != NULL && _dtors_end != NULL)
+    for (void (**f)(void) = (void (**)(void))_dtors_start; f != _dtors_end; f++)
+      (**f)();
+  _dtors_start = _dtors_end = NULL;
+  unload();
+  return true;
+}
+
+void *DLObject::symbol(const char *name)
+{
+  DBG(("symbol(\"%s\")\n", name));
+
+  if (_symtab == NULL || _strtab == NULL || _symbol_cnt < 1) {
+    seterror("No symbol table loaded.");
+    return NULL;
+  }
+
+  Elf32_Sym *s = (Elf32_Sym *)_symtab;
+  for (int c = symbol_cnt; c--; s++)
+
+    //TODO: Figure out which symbols should be detected here
+    if ((s->st_info>>4 == 1 || s->st_info>>4 == 2) &&
+       strtab[s->st_name] == '_' && !strcmp(name, strtab+s->st_name+1)) {
+
+      // We found the symbol
+      DBG(("=> %p\n", (void*)s->st_value));
+      return (void*)s->st_value;
+    }
+  
+  // We didn't find the symbol
+  seterror("Symbol \"%s\" not found.", name);
+  return NULL;
+}
+
+
+static char dlerr[MAXDLERRLEN];
+
+void *dlopen(const char *filename, int flags)
+{
+  DLObject *obj = new DLObject(dlerr);
+  if (obj->open(filename))
+    return (void *)obj;
+  delete obj;
+  return NULL;
+}
+
+int dlclose(void *handle)
+{
+  DLObject *obj = (DLObject *)handle;
+  if (obj == NULL) {
+    strcpy(dlerr, "Handle is NULL.");
+    return -1;
+  }
+  if (obj->close()) {
+    delete obj;
+    return 0;
+  }
+  return -1;
+}
+
+void *dlsym(void *handle, const char *symbol)
+{
+  if (handle == NULL) {
+    strcpy(dlerr, "Handle is NULL.");
+    return NULL;
+  }
+  return ((DLObject *)handle)->symbol(symbol);
+}
+
+const char *dlerror()
+{
+  return dlerr;
+}
+
+void dlforgetsyms(void *handle)
+{
+  if (handle != NULL)
+    ((DLObject *)handle)->discard_symtab();
+}
+
+#endif /* DYNAMIC_MODULES && __GP2X__WIZ__ */