Finished initial abstraction of ELF-loader (works for DS)

svn-id: r51233

1 files changed, 464 insertions, 0 deletions

diff --git a/backends/plugins/elf-loader.cpp b/backends/plugins/elf-loader.cpp
new file mode 100644
index 0000000000..f675386df9
--- /dev/null
+++ b/backends/plugins/elf-loader.cpp
@@ -0,0 +1,464 @@
+/* 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) // TODO: && defined ELF loader target
+
+#include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <malloc.h>
+#include <unistd.h>
+#include <sys/_default_fcntl.h>
+
+//#include "backends/fs/stdiostream.h"
+//#include "backends/fs/ds/ds-fs.h"
+#include "dsmain.h"
+
+#include "elf-loader.h"
+
+#define __DEBUG_PLUGINS__
+
+#ifdef __DEBUG_PLUGINS__
+#define DBG(x,...) printf(x, ## __VA_ARGS__)
+#else
+#define DBG(x,...)
+#endif
+
+#define seterror(x,...) printf(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 DLFile 	 SeekableReadStream of File
+ * @param offset 	 Offset into the File
+ * @param size   	 Size of relocation section
+ *
+ */
+bool DLObject::relocate(Common::SeekableReadStream* DLFile, unsigned long offset, unsigned long size, void *relSegment) {
+	dlRelocate(DLFile, offset, size, relSegment);
+}
+
+bool DLObject::readElfHeader(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr) {
+
+	// Start reading the elf header. Check for errors
+	if (DLFile->read(ehdr, sizeof(*ehdr)) != sizeof(*ehdr) ||
+	        memcmp(ehdr->e_ident, ELFMAG, SELFMAG) ||			// Check MAGIC
+	        ehdr->e_type != ET_EXEC ||							// Check for executable
+	        ehdr->e_machine != EM_ARM ||						// Check for ARM machine type
+	        ehdr->e_phentsize < sizeof(Elf32_Phdr)	 ||			// Check for size of program header
+	        ehdr->e_shentsize != sizeof(Elf32_Shdr)) {			// Check for size of section header
+		seterror("Invalid file type.");
+		return false;
+	}
+
+	DBG("phoff = %d, phentsz = %d, phnum = %d\n",
+	    ehdr->e_phoff, ehdr->e_phentsize, ehdr->e_phnum);
+
+	return true;
+}
+
+bool DLObject::readProgramHeaders(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr, Elf32_Phdr *phdr, int num) {
+
+	// Read program header
+	if (DLFile->seek(ehdr->e_phoff + sizeof(*phdr)*num, SEEK_SET) < 0 ||
+	    DLFile->read(phdr, sizeof(*phdr)) != sizeof(*phdr)) {
+		seterror("Program header load failed.");
+		return false;
+	}
+
+	// Check program header values
+	if (phdr->p_type != PT_LOAD  || phdr->p_filesz > phdr->p_memsz) {
+		seterror("Invalid program header.");
+		return false;
+	}
+
+	DBG("offs = %x, filesz = %x, memsz = %x, align = %x\n",
+	    phdr->p_offset, phdr->p_filesz, phdr->p_memsz, phdr->p_align);
+
+	return true;
+
+}
+
+bool DLObject::loadSegment(Common::SeekableReadStream* DLFile, Elf32_Phdr *phdr) {
+
+	char *baseAddress = 0;
+
+	// Attempt to allocate memory for segment
+	int extra = phdr->p_vaddr % phdr->p_align;	// Get extra length TODO: check logic here
+	DBG("extra mem is %x\n", extra);
+
+	if (!(_segment = (char *)memalign(phdr->p_align, phdr->p_memsz + extra))) {
+		seterror("Out of memory.\n");
+		return false;
+	}
+
+	DBG("allocated segment @ %p\n", _segment);
+
+	// Get offset to load segment into
+	baseAddress = (char *)_segment + phdr->p_vaddr;
+	_segmentSize = phdr->p_memsz + extra;
+
+	DBG("base address is %p\n", baseAddress);
+	DBG("_segmentSize is %p\n", _segmentSize);
+
+	// Set bss segment to 0 if necessary (assumes bss is at the end)
+	if (phdr->p_memsz > phdr->p_filesz) {
+		DBG("Setting %p to %p to 0 for bss\n", baseAddress + phdr->p_filesz, baseAddress + phdr->p_memsz);
+		memset(baseAddress + phdr->p_filesz, 0, phdr->p_memsz - phdr->p_filesz);
+	}
+
+	DBG("Reading the segment into memory\n");
+
+	// Read the segment into memory
+	if (DLFile->seek(phdr->p_offset, SEEK_SET) < 0 ||
+	        DLFile->read(baseAddress, phdr->p_filesz) != (ssize_t)phdr->p_filesz) {
+		seterror("Segment load failed.");
+		return false;
+	}
+
+	DBG("Segment has been read into memory\n");
+
+	return true;
+}
+
+Elf32_Shdr * DLObject::loadSectionHeaders(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr) {
+
+	Elf32_Shdr *shdr = NULL;
+
+	// Allocate memory for section headers
+	if (!(shdr = (Elf32_Shdr *)malloc(ehdr->e_shnum * sizeof(*shdr)))) {
+		seterror("Out of memory.");
+		return NULL;
+	}
+
+	// Read from file into section headers
+	if (DLFile->seek(ehdr->e_shoff, SEEK_SET) < 0 ||
+	        DLFile->read(shdr, ehdr->e_shnum * sizeof(*shdr)) !=
+	        (ssize_t)(ehdr->e_shnum * sizeof(*shdr))) {
+		seterror("Section headers load failed.");
+		return NULL;
+	}
+
+	return shdr;
+}
+
+int DLObject::loadSymbolTable(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
+
+	// Loop over sections, looking for symbol table linked to a string table
+	for (int i = 0; i < ehdr->e_shnum; i++) {
+		if (shdr[i].sh_type == SHT_SYMTAB &&
+		        shdr[i].sh_entsize == sizeof(Elf32_Sym) &&
+		        shdr[i].sh_link < ehdr->e_shnum &&
+		        shdr[shdr[i].sh_link].sh_type == SHT_STRTAB &&
+		        _symtab_sect < 0) {
+			_symtab_sect = i;
+		}
+	}
+
+	// Check for no symbol table
+	if (_symtab_sect < 0) {
+		seterror("No symbol table.");
+		return -1;
+	}
+
+	DBG("Symbol section at section %d, size %x\n", _symtab_sect, shdr[_symtab_sect].sh_size);
+
+	// Allocate memory for symbol table
+	if (!(_symtab = malloc(shdr[_symtab_sect].sh_size))) {
+		seterror("Out of memory.");
+		return -1;
+	}
+
+	// Read symbol table into memory
+	if (DLFile->seek(shdr[_symtab_sect].sh_offset, SEEK_SET) < 0 ||
+	        DLFile->read(_symtab, shdr[_symtab_sect].sh_size) !=
+	        (ssize_t)shdr[_symtab_sect].sh_size) {
+		seterror("Symbol table load failed.");
+		return -1;
+	}
+
+	// Set number of symbols
+	_symbol_cnt = shdr[_symtab_sect].sh_size / sizeof(Elf32_Sym);
+	DBG("Loaded %d symbols.\n", _symbol_cnt);
+
+	return _symtab_sect;
+
+}
+
+bool DLObject::loadStringTable(Common::SeekableReadStream* DLFile, Elf32_Shdr *shdr) {
+
+	int string_sect = shdr[_symtab_sect].sh_link;
+
+	// Allocate memory for string table
+	if (!(_strtab = (char *)malloc(shdr[string_sect].sh_size))) {
+		seterror("Out of memory.");
+		return false;
+	}
+
+	// Read string table into memory
+	if (DLFile->seek(shdr[string_sect].sh_offset, SEEK_SET) < 0 ||
+	        DLFile->read(_strtab, shdr[string_sect].sh_size) !=
+	        (ssize_t)shdr[string_sect].sh_size) {
+		seterror("Symbol table strings load failed.");
+		return false;
+	}
+
+	return true;
+}
+
+void DLObject::relocateSymbols(Elf32_Addr offset) {
+
+	int relocCount = 0;
+	DBG("Relocating symbols by %x\n", offset);
+
+	// Loop over symbols, add relocation offset
+	Elf32_Sym *s = (Elf32_Sym *)_symtab;
+	for (int c = _symbol_cnt; c--; s++) {
+		// Make sure we don't relocate special valued symbols
+		if (s->st_shndx < SHN_LOPROC) {
+				relocCount++;
+				s->st_value += offset;
+				if (s->st_value < (Elf32_Addr)_segment || s->st_value > (Elf32_Addr)_segment + _segmentSize)
+					seterror("Symbol out of bounds! st_value = %x\n", s->st_value);
+
+		}
+
+	}
+
+	DBG("Relocated %d symbols.\n",relocCount);
+}
+
+bool DLObject::relocateRels(Common::SeekableReadStream* DLFile, Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
+
+	// Loop over sections, finding relocation sections
+	for (int i = 0; i < ehdr->e_shnum; i++) {
+
+		Elf32_Shdr *curShdr = &(shdr[i]);
+		//Elf32_Shdr *linkShdr = &(shdr[curShdr->sh_info]);
+
+		if ((curShdr->sh_type == SHT_REL || curShdr->sh_type == SHT_RELA) &&		// Check for a relocation section
+		        curShdr->sh_entsize == sizeof(Elf32_Rel) &&		// Check for proper relocation size
+		        (int)curShdr->sh_link == _symtab_sect &&			// Check that the sh_link connects to our symbol table
+		        curShdr->sh_info < ehdr->e_shnum &&					// Check that the relocated section exists
+		        (shdr[curShdr->sh_info].sh_flags & SHF_ALLOC)) {  	// Check if relocated section resides in memory
+
+			if (curShdr->sh_type == SHT_RELA) {
+				seterror("RELA entries not supported yet!\n");
+				return false;
+			}
+
+			if (!relocate(DLFile, curShdr->sh_offset, curShdr->sh_size, _segment)) {
+				return false;
+			}
+
+		}
+	}
+
+	return true;
+}
+
+bool DLObject::load(Common::SeekableReadStream* DLFile) {
+	Elf32_Ehdr ehdr;
+	Elf32_Phdr phdr;
+	Elf32_Shdr *shdr;
+	bool ret = true;
+
+	if (readElfHeader(DLFile, &ehdr) == false) {
+		return false;
+	}
+
+	for (int i = 0; i < ehdr.e_phnum; i++) {	//Load our segments
+
+		DBG("Loading segment %d\n", i);
+
+		if (readProgramHeaders(DLFile, &ehdr, &phdr, i) == false)
+			return false;
+
+		if (!loadSegment(DLFile, &phdr))
+			return false;
+	}
+
+	if ((shdr = loadSectionHeaders(DLFile, &ehdr)) == NULL)
+		ret = false;
+
+	if (ret && ((_symtab_sect = loadSymbolTable(DLFile, &ehdr, shdr)) < 0))
+		ret = false;
+
+	if (ret && (loadStringTable(DLFile, shdr) == false))
+		ret = false;
+
+	if (ret)
+		relocateSymbols((Elf32_Addr)_segment);	// Offset by our segment allocated address
+
+	if (ret && (relocateRels(DLFile, &ehdr, shdr) == false))
+		ret = false;
+
+	free(shdr);
+
+	return ret;
+
+}
+
+bool DLObject::open(const char *path) {
+
+	Common::SeekableReadStream* DLFile;
+	void *ctors_start, *ctors_end;
+
+	DBG("open(\"%s\")\n", path);
+
+	Common::FSNode file(path);
+
+	if (!(DLFile = file.createReadStream())) {
+		seterror("%s not found.", path);
+		return false;
+	}
+
+	DBG("%s found!\n", path);
+
+	/*Try to load and relocate*/
+	if (!load(DLFile)) {
+		unload();
+		return false;
+	}
+
+	DBG("loaded!/n");
+
+	flushDataCache();
+
+	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++)
+
+		// We can only import symbols that are global or weak in the plugin
+		if ((SYM_BIND(s->st_info) == STB_GLOBAL || SYM_BIND(s->st_info) == STB_WEAK) &&
+		       !strcmp(name, _strtab + s->st_name)) {
+
+			// 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 */
+