3DS: Implement dynamic plugins

Allows a full build to run on old generation devices

4 files changed, 58 insertions, 14 deletions

diff --git a/backends/plugins/elf/arm-loader.cpp b/backends/plugins/elf/arm-loader.cpp
index 3aabf44452..3bbb5b2ee5 100644
--- a/backends/plugins/elf/arm-loader.cpp
+++ b/backends/plugins/elf/arm-loader.cpp
@@ -65,6 +65,7 @@ bool ARMDLObject::relocate(Elf32_Off offset, Elf32_Word size, byte *relSegment)
 		// Act differently based on the type of relocation
 		switch (REL_TYPE(rel[i].r_info)) {
 		case R_ARM_ABS32:
+		case R_ARM_TARGET1:
 			if (sym->st_shndx < SHN_LOPROC) {			// Only shift for plugin section.
 				a = *target;							// Get full 32 bits of addend
 				relocation = a + Elf32_Addr(_segment);	// Shift by main offset
@@ -80,13 +81,36 @@ bool ARMDLObject::relocate(Elf32_Off offset, Elf32_Word size, byte *relSegment)
 			break;
 
 		case R_ARM_CALL:
-			debug(8, "elfloader: R_ARM_CALL: PC-relative jump, ld takes care of necessary relocation work for us.");
-			break;
-
 		case R_ARM_JUMP24:
-			debug(8, "elfloader: R_ARM_JUMP24: PC-relative jump, ld takes care of all relocation work for us.");
-			break;
+			if (sym->st_shndx == SHN_ABS) { // Absolute symbols used in PC-relative instructions need to be relocated
+				// Extract the PC offset from the instruction
+				int32 pcOffset = *target;
+				pcOffset = (pcOffset & 0x00ffffff) << 2;
+
+				if (pcOffset & 0x02000000)
+					pcOffset -= 0x04000000;
+
+				// Shift by the segment offset
+				pcOffset -= Elf32_Addr(_segment);
 
+				// Check the relocated offset is valid for the instruction
+				if (pcOffset <= (int32)0xfe000000 ||
+					pcOffset >= (int32)0x02000000) {
+					warning("elfloader: R_ARM_CALL/R_ARM_JUMP24: Out of range relocation i=%d, target=%p, pcOffset=%d", i, target, pcOffset);
+					free(rel);
+					return false;
+				}
+
+				// Put the relocated offset back in the instruction
+				pcOffset >>= 2;
+				pcOffset &= 0x00ffffff;
+
+				*target &= (uint32)0xff000000;
+				*target |= (uint32)pcOffset;
+
+				debug(8, "elfloader: R_ARM_CALL/R_ARM_JUMP24: i=%d, origTarget=%x, target=%x", i, origTarget, *target);
+			}
+			break;
 		case R_ARM_V4BX:
 			debug(8, "elfloader: R_ARM_V4BX: No relocation calculation necessary.");
 			break;
diff --git a/backends/plugins/elf/elf-loader.cpp b/backends/plugins/elf/elf-loader.cpp
index 5198fa8088..39f1f7dfa5 100644
--- a/backends/plugins/elf/elf-loader.cpp
+++ b/backends/plugins/elf/elf-loader.cpp
@@ -50,8 +50,7 @@ DLObject::DLObject() :
 
 DLObject::~DLObject() {
 	discardSymtab();
-	ELFMemMan.pluginDeallocate(_segment);
-	_segment = 0;
+	discardSegment();
 }
 
 // Expel the symbol table from memory
@@ -65,11 +64,12 @@ void DLObject::discardSymtab() {
 	_symbol_cnt = 0;
 }
 
-// Unload all objects from memory
-void DLObject::unload() {
-	discardSymtab();
-
-	ELFMemMan.pluginDeallocate(_segment);
+void DLObject::discardSegment() {
+	if (_segment) {
+		// Restore default protection before returning memory
+		protectMemory(_segment, _segmentSize, PF_R | PF_W);
+		deallocateMemory(_segment, _segmentSize);
+	}
 
 	_segment = 0;
 	_segmentSize = 0;
@@ -77,6 +77,12 @@ void DLObject::unload() {
 	_segmentVMA = 0;
 }
 
+// Unload all objects from memory
+void DLObject::unload() {
+	discardSymtab();
+	discardSegment();
+}
+
 bool DLObject::readElfHeader(Elf32_Ehdr *ehdr) {
 	assert(_file);
 
@@ -163,7 +169,7 @@ bool DLObject::readProgramHeaders(Elf32_Ehdr *ehdr, Elf32_Phdr *phdr, Elf32_Half
 }
 
 bool DLObject::loadSegment(Elf32_Phdr *phdr) {
-	_segment = (byte *)ELFMemMan.pluginAllocate(phdr->p_align, phdr->p_memsz);
+	_segment = (byte *)allocateMemory(phdr->p_align, phdr->p_memsz);
 
 	if (!_segment) {
 		warning("elfloader: Out of memory.");
@@ -402,6 +408,8 @@ bool DLObject::load() {
 		return false;
 	}
 
+	protectMemory(_segment, _segmentSize, phdr.p_flags);
+
 	return true;
 }
 
@@ -488,4 +496,12 @@ void *DLObject::symbol(const char *name) {
 	return 0;
 }
 
+void *DLObject::allocateMemory(uint32 align, uint32 size) {
+	return ELFMemMan.pluginAllocate(align, size);
+}
+
+void DLObject::deallocateMemory(void *ptr, uint32 size) {
+	ELFMemMan.pluginDeallocate(ptr);
+}
+
 #endif /* defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) */
diff --git a/backends/plugins/elf/elf-loader.h b/backends/plugins/elf/elf-loader.h
index 17ca35482a..1730338807 100644
--- a/backends/plugins/elf/elf-loader.h
+++ b/backends/plugins/elf/elf-loader.h
@@ -68,6 +68,7 @@ protected:
 	int loadSymbolTable(Elf32_Ehdr *ehdr, Elf32_Shdr *shdr);
 	bool loadStringTable(Elf32_Shdr *shdr);
 	virtual void relocateSymbols(ptrdiff_t offset);
+	void discardSegment();
 
 	// architecture specific
 
@@ -83,6 +84,9 @@ protected:
 
 	// platform specific
 	virtual void flushDataCache(void *ptr, uint32 len) const = 0;
+	virtual void *allocateMemory(uint32 align, uint32 size);
+	virtual void deallocateMemory(void *ptr, uint32 size);
+	virtual void protectMemory(void *ptr, uint32 len, int prot) const {};
 
 public:
 	DLObject();
diff --git a/backends/plugins/elf/mips-loader.cpp b/backends/plugins/elf/mips-loader.cpp
index 47ae00a8ea..e1e62234d5 100644
--- a/backends/plugins/elf/mips-loader.cpp
+++ b/backends/plugins/elf/mips-loader.cpp
@@ -279,7 +279,7 @@ bool MIPSDLObject::loadSegment(Elf32_Phdr *phdr) {
 	// We need to take account of non-allocated segment for shorts
 	if (phdr->p_flags & PF_X) {	// This is a relocated segment
 		// Attempt to allocate memory for segment
-		_segment = (byte *)ELFMemMan.pluginAllocate(phdr->p_align, phdr->p_memsz);
+		_segment = (byte *)allocateMemory(phdr->p_align, phdr->p_memsz);
 
 		if (!_segment) {
 			warning("elfloader: Out of memory.");