options/rtld: Fix relr relocations

options/rtld/generic/linker.cpp

@@ -1734,6 +1734,11 @@ void Loader::_processStaticRelocations(SharedObject *object) {
 				*addr++ += object->baseAddress;
 			}else {
 				// Odd entry indicates entry is a bitmap of the subsequent locations to be relocated.
+
+				// The first bit of an entry is always a marker about whether the entry is an address or a bitmap,
+				// discard it.
+				entry >>= 1;
+
 				for(int i = 0; entry; ++i) {
 					if(entry & 1) {
 						addr[i] += object->baseAddress;

options/rtld/generic/main.cpp

@@ -148,6 +148,11 @@ extern "C" void relocateSelf() {
 			*addr++ += ldso_base;
 		}else {
 			// Odd entry indicates entry is a bitmap of the subsequent locations to be relocated.
+
+			// The first bit of an entry is always a marker about whether the entry is an address or a bitmap,
+			// discard it.
+			entry >>= 1;
+
 			for(int i = 0; entry; ++i) {
 				if(entry & 1) {
 					addr[i] += ldso_base;

tests/rtld/meson.build

@@ -12,6 +12,7 @@ rtld_test_cases = [
 	'scope4',
 	'scope5',
 	'tls_align',
+	'relr',
 ]
 
 host_libc_rtld_nosan_test_cases = [

tests/rtld/relr/meson.build

@@ -0,0 +1 @@
+test_additional_link_args += ['-Wl,-z,pack-relative-relocs']

tests/rtld/relr/test.c

@@ -0,0 +1,24 @@
+#include <stddef.h>
+#include <assert.h>
+
+const char* strings[] = {
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+	"", "", "", "", "", "", "", "",
+};
+
+int main() {
+	for(size_t i = 0; i < sizeof(strings) / sizeof(*strings); ++i) {
+		assert(strings[i][0] == 0);
+	}
+
+	return 0;
+}