1 files changed, 338 insertions, 0 deletions
diff --git a/backends/plugins/elf/mips-loader.cpp b/backends/plugins/elf/mips-loader.cpp
new file mode 100644
index 0000000000..af8c70fcf6
--- /dev/null
+++ b/backends/plugins/elf/mips-loader.cpp
@@ -0,0 +1,338 @@
+/* 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(MIPS_TARGET)
+
+#include "backends/plugins/elf/mips-loader.h"
+
+#include "common/debug.h"
+
+#define DEBUG_NUM 2
+
+bool MIPSDLObject::relocate(Elf32_Off offset, Elf32_Word size, byte *relSegment) {
+	Elf32_Rel *rel = 0;	// relocation entry
+
+	// Allocate memory for relocation table
+	if (!(rel = (Elf32_Rel *)malloc(size))) {
+		warning("elfloader: Out of memory.");
+		return false;
+	}
+
+	// Read in our relocation table
+	if (!_file->seek(offset, SEEK_SET) || _file->read(rel, size) != size) {
+		warning("elfloader: Relocation table load failed.");
+		free(rel);
+		return false;
+	}
+
+	// Treat each relocation entry. Loop over all of them
+	uint32 cnt = size / sizeof(*rel);
+
+	debug(2, "elfloader: Loaded relocation table. %d entries. base address=%p", cnt, relSegment);
+
+	bool seenHi16 = false;			// For treating HI/LO16 commands
+	int32 firstHi16 = -1;			// Mark the point of the first hi16 seen
+	Elf32_Addr ahl = 0;				// Calculated addend
+	int32 a = 0;					// Addend: taken from the target
+
+	uint32 *lastTarget = 0;			// For processing hi16 when lo16 arrives
+	uint32 relocation = 0;
+	uint debugRelocs[10] = { 0 };	// For debugging
+	uint extendedHi16 = 0;			// Count extended hi16 treatments
+	Elf32_Addr lastHiSymVal = 0;
+	bool hi16InShorts = false;
+
+	// Loop over relocation entries
+	for (uint32 i = 0; i < cnt; i++) {
+		// Get the symbol this relocation entry is referring to
+		Elf32_Sym *sym = _symtab + (REL_INDEX(rel[i].r_info));
+
+		// Get the target instruction in the code. TODO: repect _segmentVMA
+		uint32 *target = (uint32 *)((byte *)relSegment + rel[i].r_offset);
+
+		uint32 origTarget = *target;	// Save for debugging
+
+		// Act differently based on the type of relocation
+		switch (REL_TYPE(rel[i].r_info)) {
+		case R_MIPS_HI16:							// Absolute addressing.
+			if (sym->st_shndx < SHN_LOPROC &&		// Only shift for plugin section (ie. has a real section index)
+				firstHi16 < 0) {					// Only process first in block of HI16s
+				firstHi16 = i;						// Keep the first Hi16 we saw
+				seenHi16 = true;
+				ahl = (*target & 0xffff) << 16;		// Take lower 16 bits shifted up
+
+				lastHiSymVal = sym->st_value;
+				hi16InShorts = ShortsMan.inGeneralSegment((char *)sym->st_value); // Fix for problem with switching btw segments
+				if (debugRelocs[0]++ < DEBUG_NUM)	// Print only a set number
+					debug(8, "elfloader: R_MIPS_HI16: i=%d, offset=%x, ahl = %x, target = %x",
+							i, rel[i].r_offset, ahl, *target);
+			}
+			break;
+
+		case R_MIPS_LO16:							// Absolute addressing. Needs a HI16 to come before it
+			if (sym->st_shndx < SHN_LOPROC) {		// Only shift for plugin section. (ie. has a real section index)
+				if (!seenHi16) {					// We MUST have seen HI16 first
+					debug(8, "elfloader: R_MIPS_LO16 w/o preceding R_MIPS_HI16 at relocation %d!", i);
+					free(rel);
+					return false;
+				}
+
+				// Fix: bug in gcc makes LO16s connect to wrong HI16s sometimes (shorts and regular segment)
+				// Note that we can check the entire shorts segment because the executable's shorts don't belong to this plugin section
+				// and will be screened out above
+				bool lo16InShorts = ShortsMan.inGeneralSegment((char *)sym->st_value);
+
+				// Correct the bug by getting the proper value in ahl (taken from the current symbol)
+				if ((hi16InShorts && !lo16InShorts) || (!hi16InShorts && lo16InShorts)) {
+					ahl -= (lastHiSymVal & 0xffff0000);		// We assume gcc meant the same offset
+					ahl += (sym->st_value & 0xffff0000);
+				}
+
+				ahl &= 0xffff0000;				// Clean lower 16 bits for repeated LO16s
+				a = *target & 0xffff;			// Take lower 16 bits of the target
+				a = (a << 16) >> 16;			// Sign extend them
+				ahl += a;						// Add lower 16 bits. AHL is now complete
+
+				// Fix: we can have LO16 access to the short segment sometimes
+				if (lo16InShorts)
+					relocation = ahl + _shortsSegment->getOffset();		// Add in the short segment offset
+				else	// It's in the regular segment
+					relocation = ahl + Elf32_Addr(_segment);			// Add in the new offset for the segment
+
+				if (firstHi16 >= 0) {					// We haven't treated the HI16s yet so do it now
+					for (uint32 j = firstHi16; j < i; j++) {
+						if (REL_TYPE(rel[j].r_info) != R_MIPS_HI16)
+							continue;	// Skip over non-Hi16s
+
+						lastTarget = (uint32 *)((char *)relSegment + rel[j].r_offset);	// get hi16 target
+						*lastTarget &= 0xffff0000;		// Clear the lower 16 bits of the last target
+						*lastTarget |= (relocation >> 16) & 0xffff;	// Take the upper 16 bits of the relocation
+						if (relocation & 0x8000)
+							(*lastTarget)++;	// Subtle: we need to add 1 to the HI16 in this case
+					}
+
+					firstHi16 = -1;						// Reset so we'll know we treated it
+				} else {
+					extendedHi16++;
+				}
+
+				*target &= 0xffff0000;						// Clear the lower 16 bits of current target
+				*target |= relocation & 0xffff;				// Take the lower 16 bits of the relocation
+
+				if (debugRelocs[1]++ < DEBUG_NUM)
+					debug(8, "elfloader: R_MIPS_LO16: i=%d, offset=%x, a=%x, ahl = %x, "
+							"lastTarget = %x, origt = %x, target = %x",
+							i, rel[i].r_offset, a, ahl, *lastTarget, origTarget, *target);
+
+				if (lo16InShorts && debugRelocs[2]++ < DEBUG_NUM)
+					debug(8, "elfloader: R_MIPS_LO16s: i=%d, offset=%x, a=%x, ahl = %x, "
+							"lastTarget = %x, origt = %x, target = %x",
+							i, rel[i].r_offset, a, ahl, *lastTarget, origTarget, *target);
+			}
+			break;
+
+		case R_MIPS_26:													// Absolute addressing (for jumps and branches only)
+			if (sym->st_shndx < SHN_LOPROC) {							// Only relocate for main segment
+				a = *target & 0x03ffffff;								// Get 26 bits' worth of the addend
+				a = (a << 6) >> 6; 										// Sign extend a
+				relocation = ((a << 2) + Elf32_Addr(_segment)) >> 2;	// a already points to the target. Subtract our offset
+				*target &= 0xfc000000;									// Clean lower 26 target bits
+				*target |= (relocation & 0x03ffffff);
+
+				if (debugRelocs[3]++ < DEBUG_NUM)
+					debug(8, "elfloader: R_MIPS_26: i=%d, offset=%x, symbol=%d, stinfo=%x, "
+							"a=%x, origTarget=%x, target=%x",
+							i, rel[i].r_offset, REL_INDEX(rel[i].r_info), sym->st_info, a, origTarget, *target);
+			} else {
+				if (debugRelocs[4]++ < DEBUG_NUM)
+					debug(8, "elfloader: R_MIPS_26: i=%d, offset=%x, symbol=%d, stinfo=%x, "
+							"a=%x, origTarget=%x, target=%x",
+							i, rel[i].r_offset, REL_INDEX(rel[i].r_info), sym->st_info, a, origTarget, *target);
+			}
+			break;
+
+		case R_MIPS_GPREL16:												// GP Relative addressing
+			if (_shortsSegment->getOffset() != 0 &&							// Only relocate if we shift the shorts section
+					ShortsMan.inGeneralSegment((char *) sym->st_value)) {	// Only relocate things in the plugin hole
+				a = *target & 0xffff;										// Get 16 bits' worth of the addend
+				a = (a << 16) >> 16;										// Sign extend it
+
+				relocation = a + _shortsSegment->getOffset();
+
+				*target &= 0xffff0000;					// Clear the lower 16 bits of the target
+				*target |= relocation & 0xffff;
+
+				if (debugRelocs[5]++ < DEBUG_NUM)
+					debug(8, "elfloader: R_MIPS_GPREL16: i=%d, a=%x, gpVal=%x, origTarget=%x, "
+							"target=%x, offset=%x",
+							i, a, _gpVal, origTarget, *target, _shortsSegment->getOffset());
+			}
+
+			break;
+
+		case R_MIPS_32:									// Absolute addressing
+			if (sym->st_shndx < SHN_LOPROC) {			// Only shift for plugin section.
+				a = *target;							// Get full 32 bits of addend
+
+				if (ShortsMan.inGeneralSegment((char *)sym->st_value))	// Check if we're in the shorts segment
+					relocation = a + _shortsSegment->getOffset();		// Shift by shorts offset
+				else													// We're in the main section
+					relocation = a + Elf32_Addr(_segment);				// Shift by main offset
+
+				*target = relocation;
+
+				if (debugRelocs[6]++ < DEBUG_NUM)
+					debug("8, elfloader: R_MIPS_32: i=%d, a=%x, origTarget=%x, target=%x",
+							i, a, origTarget, *target);
+			}
+
+			break;
+
+		default:
+			warning("elfloader: Unknown relocation type %x at relocation %d.", REL_TYPE(rel[i].r_info), i);
+			free(rel);
+			return false;
+		}
+	}
+
+	debug(2, "elfloader: Done with relocation. extendedHi16=%d", extendedHi16);
+
+	free(rel);
+	return true;
+}
+
+bool MIPSDLObject::relocateRels(Elf32_Ehdr *ehdr, Elf32_Shdr *shdr) {
+	// Loop over sections, finding relocation sections
+	for (uint32 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 &&							// Check for a relocation section
+				curShdr->sh_entsize == sizeof(Elf32_Rel) &&			// Check for proper relocation size
+				int32(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 (!ShortsMan.inGeneralSegment((char *)shdr[curShdr->sh_info].sh_addr)) {			// regular segment
+				if (!relocate(curShdr->sh_offset, curShdr->sh_size, _segment))
+					return false;
+			} else {	// In Shorts segment
+				if (!relocate(curShdr->sh_offset, curShdr->sh_size, (byte *)_shortsSegment->getOffset()))
+					return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+void MIPSDLObject::relocateSymbols(Elf32_Addr offset) {
+	// Loop over symbols, add relocation offset
+	Elf32_Sym *s = _symtab;
+
+	for (uint32 c = _symbol_cnt; c--; s++) {
+		// Make sure we don't relocate special valued symbols
+		if (s->st_shndx < SHN_LOPROC) {
+			if (!ShortsMan.inGeneralSegment((char *)s->st_value)) {
+				s->st_value += offset;
+
+				if (s->st_value < Elf32_Addr(_segment) || s->st_value > Elf32_Addr(_segment) + _segmentSize)
+					warning("elfloader: Symbol out of bounds! st_value = %x", s->st_value);
+			} else {	// shorts section
+				s->st_value += _shortsSegment->getOffset();
+				if (!_shortsSegment->inSegment((char *)s->st_value))
+					warning("elfloader: Symbol out of bounds! st_value = %x", s->st_value);
+			}
+		}
+	}
+}
+
+bool MIPSDLObject::loadSegment(Elf32_Phdr *phdr) {
+	byte *baseAddress = 0;
+
+	// We need to take account of non-allocated segment for shorts
+	if (phdr->p_flags & PF_X) {	// This is a relocated segment
+		if (phdr->p_align < 0x10000)
+			phdr->p_align = 0x10000;	// Fix for wrong alignment on e.g. AGI
+
+		_segment = (byte *)allocSegment(phdr->p_align, phdr->p_memsz);
+
+		if (!_segment) {
+			warning("elfloader: Out of memory.");
+			return false;
+		}
+
+		debug(2, "elfloader: Allocated segment @ %p", _segment);
+
+		// Get offset to load segment into
+		baseAddress = _segment + phdr->p_vaddr;
+		_segmentSize = phdr->p_memsz;
+		_segmentVMA = phdr->p_vaddr;
+
+		// Set .bss segment to 0 if necessary
+		if (phdr->p_memsz > phdr->p_filesz) {
+			debug(2, "elfloader: Setting %p to %p to 0 for bss",
+					_segment + phdr->p_filesz, _segment + phdr->p_memsz);
+			memset(_segment + phdr->p_filesz, 0, phdr->p_memsz - phdr->p_filesz);
+		}
+	} else {						// This is a shorts section.
+		_shortsSegment = ShortsMan.newSegment(phdr->p_memsz, (char *)phdr->p_vaddr);
+
+		baseAddress = (byte *)_shortsSegment->getStart();
+		debug(2, "elfloader: Shorts segment @ %p to %p. Segment wants to be at %x. Offset=%x",
+				_shortsSegment->getStart(), _shortsSegment->getEnd(), phdr->p_vaddr,
+				_shortsSegment->getOffset());
+	}
+
+	// Set .sbss segment to 0 if necessary
+	if (phdr->p_memsz > phdr->p_filesz) {
+		debug(2, "elfloader: Setting %p to %p to 0 for bss", baseAddress + phdr->p_filesz,
+				baseAddress + phdr->p_memsz);
+		memset(baseAddress + phdr->p_filesz, 0, phdr->p_memsz - phdr->p_filesz);
+	}
+
+	debug(2, "elfloader: Reading the segment into memory");
+
+	// Read the segment into memory
+	if (!_file->seek(phdr->p_offset, SEEK_SET) ||
+			_file->read(baseAddress, phdr->p_filesz) != phdr->p_filesz) {
+		warning("elfloader: Segment load failed.");
+		return false;
+	}
+
+	debug(2, "elfloader: Segment has been read into memory");
+
+	return true;
+}
+
+// Unload all objects from memory
+void MIPSDLObject::unload() {
+	if (_shortsSegment) {
+		ShortsMan.deleteSegment(_shortsSegment);
+		_shortsSegment = 0;
+	}
+}
+
+#endif /* defined(DYNAMIC_MODULES) && defined(MIPS_TARGET) */
+