runtime_loader: Randomly position only relocatable code

The use of an unreliable test for relocatability effectively broke
runtime_loader's support for non-position-independent executables, as it
would insist on randomly positioning these files' segments in memory
anyway causing the program to quickly crash.

With this change runtime_loader uses the object type specified in the
file's header to determine whether its segments can be safely relocated,
restoring support for non-PI executables.

Fixes #12427.

Signed-off-by: Adrien Destugues <[email protected]>

headers/private/system/elf_common.h

@@ -31,6 +31,17 @@
 #define EI_VERSION	6
 #define EI_PAD		7
 
+// e_type (Object file type)
+#define ET_NONE			0 // No file type
+#define ET_REL			1 // Relocatable file
+#define ET_EXEC			2 // Executable file
+#define ET_DYN			3 // Shared object file
+#define ET_CORE			4 // Core file
+#define ET_LOOS			0xfe00 // OS-specific range start
+#define ET_HIOS			0xfeff // OS-specific range end
+#define ET_LOPROC		0xff00 // Processor-specific range start
+#define ET_HIPROC		0xffff // Processor-specific range end
+
 // e_machine (Architecture)
 #define EM_NONE			0 // No machine
 #define EM_M32			1 // AT&T WE 32100

src/system/runtime_loader/elf_load_image.cpp

@@ -527,7 +527,7 @@ load_image(char const* name, image_type type, const char* rpath,
 		goto err2;
 	}
 
-	status = map_image(fd, path, image);
+	status = map_image(fd, path, image, eheader.e_type == ET_EXEC);
 	if (status < B_OK) {
 		FATAL("%s: Could not map image: %s\n", image->path, strerror(status));
 		status = B_ERROR;

src/system/runtime_loader/images.cpp

@@ -169,9 +169,9 @@ topological_sort(image_t* image, uint32 slot, image_t** initList,
 */
 static void
 get_image_region_load_address(image_t* image, uint32 index, long lastDelta,
-	addr_t& loadAddress, uint32& addressSpecifier)
+	bool fixed, addr_t& loadAddress, uint32& addressSpecifier)
 {
-	if (image->dynamic_ptr != 0) {
+	if (!fixed) {
 		// relocatable image... we can afford to place wherever
 		if (index == 0) {
 			// but only the first segment gets a free ride
@@ -286,7 +286,7 @@ put_image(image_t* image)
 
 
 status_t
-map_image(int fd, char const* path, image_t* image)
+map_image(int fd, char const* path, image_t* image, bool fixed)
 {
 	// cut the file name from the path as base name for the created areas
 	const char* baseName = strrchr(path, '/');
@@ -304,10 +304,16 @@ map_image(int fd, char const* path, image_t* image)
 	uint32 addressSpecifier = B_RANDOMIZED_ANY_ADDRESS;
 
 	for (uint32 i = 0; i < image->num_regions; i++) {
+		// for BeOS compatibility: if we load an old BeOS executable, we
+		// have to relocate it, if possible - we recognize it because the
+		// vmstart is set to 0 (hopefully always)
+		if (fixed && image->regions[i].vmstart == 0)
+			fixed = false;
+
 		uint32 regionAddressSpecifier;
 		get_image_region_load_address(image, i,
 			i > 0 ? loadAddress - image->regions[i - 1].vmstart : 0,
-			loadAddress, regionAddressSpecifier);
+			fixed, loadAddress, regionAddressSpecifier);
 		if (i == 0) {
 			reservedAddress = loadAddress;
 			addressSpecifier = regionAddressSpecifier;
@@ -339,7 +345,7 @@ map_image(int fd, char const* path, image_t* image)
 			baseName, i, (image->regions[i].flags & RFLAG_RW) ? "rw" : "ro");
 
 		get_image_region_load_address(image, i,
-			i > 0 ? image->regions[i - 1].delta : 0, loadAddress,
+			i > 0 ? image->regions[i - 1].delta : 0, fixed, loadAddress,
 			addressSpecifier);
 
 		// If the image position is arbitrary, we must let it point to the start

src/system/runtime_loader/images.h

@@ -50,7 +50,7 @@ void		delete_image_struct(image_t* image);
 void		delete_image(image_t* image);
 void		put_image(image_t* image);
 
-status_t	map_image(int fd, char const* path, image_t* image);
+status_t	map_image(int fd, char const* path, image_t* image, bool fixed);
 void		unmap_image(image_t* image);
 void		remap_images();