rtdl: Add support for LD_LIBRARY_PATH

options/rtdl/generic/linker.cpp

@@ -8,6 +8,7 @@ enum {
 
 
 #include <frg/manual_box.hpp>
+#include <frg/small_vector.hpp>
 #include <mlibc/allocator.hpp>
 #include <mlibc/debug.hpp>
 #include <mlibc/rtdl-sysdeps.hpp>
@@ -27,6 +28,7 @@ constexpr bool verbose = false;
 constexpr bool stillSlightlyVerbose = false;
 constexpr bool logBaseAddresses = false;
 constexpr bool logRpath = false;
+constexpr bool logLdPath = false;
 constexpr bool eagerBinding = true;
 
 #if defined(__x86_64__) || defined(__i386__)
@@ -42,6 +44,8 @@ constexpr inline bool tlsAboveTp = true;
 extern DebugInterface globalDebugInterface;
 extern uintptr_t __stack_chk_guard;
 
+extern frg::manual_box<frg::small_vector<frg::string_view, 4, MemoryAllocator>> libraryPaths;
+
 #if MLIBC_STATIC_BUILD
 extern "C" size_t __init_array_start[];
 extern "C" size_t __init_array_end[];
@@ -157,13 +161,6 @@ SharedObject *ObjectRepository::requestObjectWithName(frg::string_view name,
 	if (auto obj = findLoadedObject(name))
 		return obj;
 
-	const char *libdirs[4] = {
-		"/lib/",
-		"/lib64/",
-		"/usr/lib/",
-		"/usr/lib64/"
-	};
-
 	auto tryToOpen = [&] (const char *path) {
 		int fd;
 		if(auto x = mlibc::sys_open(path, O_RDONLY, 0, &fd); x) {
@@ -233,8 +230,12 @@ SharedObject *ObjectRepository::requestObjectWithName(frg::string_view name,
 	} else if (logRpath) {
 		mlibc::infoLogger() << "rtdl: no rpath set for object" << frg::endlog;
 	}
-	for(int i = 0; i < 4 && fd == -1; i++) {
-		auto path = frg::string<MemoryAllocator>{getAllocator(), libdirs[i]} + name + '\0';
+
+	for(size_t i = 0; i < libraryPaths->size() && fd == -1; i++) {
+		auto ldPath = (*libraryPaths)[i];
+		auto path = frg::string<MemoryAllocator>{getAllocator(), ldPath} + '/' + name;
+		if(logLdPath)
+			mlibc::infoLogger() << "rtdl: Trying to load " << name << " from ldpath " << ldPath << frg::endlog;
 		fd = tryToOpen(path.data());
 		if(fd >= 0) {
 			chosenPath = std::move(path);

options/rtdl/generic/main.cpp

@@ -3,6 +3,7 @@
 #include <link.h>
 
 #include <frg/manual_box.hpp>
+#include <frg/small_vector.hpp>
 
 #include <abi-bits/auxv.h>
 #include <mlibc/debug.hpp>
@@ -47,6 +48,9 @@ frg::manual_box<Scope> globalScope;
 
 frg::manual_box<RuntimeTlsMap> runtimeTlsMap;
 
+// We use a small vector of size 4 to avoid memory allocation for the default library paths
+frg::manual_box<frg::small_vector<frg::string_view, 4, MemoryAllocator>> libraryPaths;
+
 static SharedObject *executableSO;
 extern HIDDEN char __ehdr_start[];
 
@@ -199,11 +203,27 @@ extern "C" [[gnu::alias("dl_debug_state"), gnu::visibility("default")]] void _dl
 // This symbol can be used by GDB to find the global interface structure
 [[ gnu::visibility("default") ]] DebugInterface *_dl_debug_addr = &globalDebugInterface;
 
+static void parseLibraryPaths(frg::string_view paths) {
+	size_t p = 0;
+	while(p < paths.size()) {
+		size_t s; // Offset of next colon or end of string.
+		if(size_t cs = paths.find_first(':', p); cs != size_t(-1)) {
+			s = cs;
+		}else{
+			s = paths.size();
+		}
+
+		libraryPaths->push_back(paths.sub_string(p, s - p));
+		p = s + 1;
+	}
+}
+
 extern "C" void *interpreterMain(uintptr_t *entry_stack) {
 	if(logEntryExit)
 		mlibc::infoLogger() << "Entering ld.so" << frg::endlog;
 	entryStack = entry_stack;
 	runtimeTlsMap.initialize();
+	libraryPaths.initialize(getAllocator());
 
 	void *phdr_pointer = 0;
 	size_t phdr_entry_size = 0;
@@ -282,16 +302,25 @@ extern "C" void *interpreterMain(uintptr_t *entry_stack) {
 		if(s == size_t(-1))
 			mlibc::panicLogger() << "rtdl: environment '" << env << "' is missing a '='" << frg::endlog;
 
+		auto name = view.sub_string(0, s);
 		auto value = const_cast<char *>(view.data() + s + 1);
 
-		if(view.sub_string(0, s) == "LD_SHOW_AUXV" && value && *value && *value != '0') {
+		if(name == "LD_SHOW_AUXV" && *value && *value != '0') {
 			ldShowAuxv = true;
+		}else if(name == "LD_LIBRARY_PATH" && *value) {
+			parseLibraryPaths(value);
 		}
 
 		aux++;
 	}
 	aux++;
 
+	// Add default library paths
+	libraryPaths->push_back("/lib/");
+	libraryPaths->push_back("/lib64/");
+	libraryPaths->push_back("/usr/lib/");
+	libraryPaths->push_back("/usr/lib64/");
+
 	// Parse the actual vector.
 	while(true) {
 		auto value = aux + 1;

tests/rtdl/ld_library_path/libfoo.c

@@ -0,0 +1 @@
+void foo() {}

tests/rtdl/ld_library_path/meson.build

@@ -0,0 +1,19 @@
+# Remove the RPATH and set the LD_LIBRARY_PATH environment variable
+# instead when running tests to make sure the library can be found
+# in a directory specified by the user at runtime
+
+test_rpath = '$ORIGIN/'
+
+test_ld_path = meson.build_root() / 'tests' / 'rtdl' / test_name
+test_env += ['LD_LIBRARY_PATH=' + test_ld_path]
+test_native_env += ['LD_LIBRARY_PATH=' + test_ld_path]
+
+libfoo = shared_library('foo', 'libfoo.c',
+	link_with: libc, include_directories: libc_include_dirs,
+	link_args: test_additional_link_args,
+)
+
+libfoo_native = shared_library('native-foo', 'libfoo.c',
+	link_args: ['-ldl'] + test_additional_link_args,
+	native: true
+)

tests/rtdl/ld_library_path/test.c

@@ -0,0 +1,16 @@
+#include <dlfcn.h>
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+
+#ifdef USE_HOST_LIBC
+#define LIBFOO "libnative-foo.so"
+#else
+#define LIBFOO "libfoo.so"
+#endif
+
+int main() {
+	void *foo = dlopen(LIBFOO, RTLD_NOW);
+	assert(foo);
+	dlclose(foo);
+}

tests/rtdl/meson.build

@@ -1,6 +1,7 @@
 rtdl_test_cases = [
 	'dl_iterate_phdr',
 	'dladdr_local',
+	'ld_library_path',
 	'noload-promote',
 	'rtld_next',
 	'soname',
@@ -17,8 +18,10 @@ foreach test_name : rtdl_test_cases
 	test_rpath = meson.build_root() / 'tests' / 'rtdl' / test_name / ''
 	test_rpath += ':$ORIGIN/' # Workaround old and buggy qemu-user on CI
 
+	test_env = []
 	test_link_with = []
 	test_depends = []
+	test_native_env = []
 	test_native_link_with = []
 	test_native_depends = []
 	test_additional_link_args = []
@@ -34,7 +37,7 @@ foreach test_name : rtdl_test_cases
 		c_args: test_c_args,
 		link_args: test_link_args + test_additional_link_args,
 	)
-	test(test_name, exec, suite: 'rtdl', depends: test_depends)
+	test(test_name, exec, env: test_env, suite: 'rtdl', depends: test_depends)
 
 	if build_tests_host_libc and not host_libc_excluded_test_cases.contains(test_name)
 		exec = executable('host-libc-' + test_name, test_name / 'test.c',
@@ -48,6 +51,6 @@ foreach test_name : rtdl_test_cases
 			link_args: ['-ldl'] + test_additional_link_args,
 			native: true,
 		)
-		test(test_name, exec, suite: ['host-libc', 'rtdl'], depends: test_native_depends)
+		test(test_name, exec, env: test_native_env, suite: ['host-libc', 'rtdl'], depends: test_native_depends)
 	endif
 endforeach