DynamicLoader/LibC: lazy malloc environ

This allows DynamicLoader to just set the value of global environ symbol
without libc needing to malloc it at startup

userspace/libraries/LibC/stdlib.cpp

@@ -14,11 +14,14 @@
 #include <strings.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
+#include <sys/weak_alias.h>
 #include <unistd.h>
 
 #include <icxxabi.h>
 
-extern "C" char** environ;
+char** __environ;
+weak_alias(__environ, environ);
+static bool s_environ_malloced = false;
 
 extern "C" __attribute__((weak)) void _fini();
 
@@ -516,27 +519,35 @@ int putenv(char* string)
 		return -1;
 	}
 
-	if (!environ)
+	if (!s_environ_malloced)
 	{
-		environ = (char**)malloc(sizeof(char*) * 2);
-		if (!environ)
+		size_t env_count = 0;
+		while (environ[env_count])
+			env_count++;
+
+		char** new_environ = static_cast<char**>(malloc((env_count + 1) * sizeof(char*)));
+		if (new_environ == nullptr)
 			return -1;
-		environ[0] = string;
-		environ[1] = nullptr;
-		return 0;
+		for (size_t i = 0; i < env_count; i++)
+		{
+			const size_t bytes = strlen(environ[i]) + 1;
+			new_environ[i] = (char*)malloc(bytes);
+			memcpy(new_environ[i], environ[i], bytes);
+		}
+		new_environ[env_count] = nullptr;
+
+		environ = new_environ;
+		s_environ_malloced = true;
 	}
 
-	int cnt = 0;
-	for (int i = 0; string[i]; i++)
-		if (string[i] == '=')
-			cnt++;
-	if (cnt != 1)
+	const char* eq_addr = strchr(string, '=');
+	if (eq_addr == nullptr)
 	{
 		errno = EINVAL;
 		return -1;
 	}
 
-	int namelen = strchr(string, '=') - string;
+	size_t namelen = eq_addr - string;
 	for (int i = 0; environ[i]; i++)
 	{
 		if (strncmp(environ[i], string, namelen + 1) == 0)
@@ -547,15 +558,15 @@ int putenv(char* string)
 		}
 	}
 
-	int env_count = 0;
+	size_t env_count = 0;
 	while (environ[env_count])
 		env_count++;
 
-	char** new_envp = (char**)malloc(sizeof(char*) * (env_count + 2));
+	char** new_envp = static_cast<char**>(malloc(sizeof(char*) * (env_count + 2)));
 	if (new_envp == nullptr)
 		return -1;
 
-	for (int i = 0; i < env_count; i++)
+	for (size_t i = 0; i < env_count; i++)
 		new_envp[i] = environ[i];
 	new_envp[env_count] = string;
 	new_envp[env_count + 1] = nullptr;

userspace/libraries/LibC/unistd.cpp

@@ -16,31 +16,12 @@
 #include <termios.h>
 #include <unistd.h>
 
-char** __environ;
-extern char** environ __attribute__((weak, alias("__environ")));
+extern "C" char** environ;
 
 extern "C" void _init_libc(char** _environ)
 {
-	static bool is_initialized = false;
-	if (is_initialized)
-		return;
-	is_initialized = true;
-
-	if (!_environ)
-		return;
-
-	size_t env_count = 0;
-	while (_environ[env_count])
-		env_count++;
-
-	environ = (char**)malloc(sizeof(char*) * env_count + 1);
-	for (size_t i = 0; i < env_count; i++)
-	{
-		size_t bytes = strlen(_environ[i]) + 1;
-		environ[i] = (char*)malloc(bytes);
-		memcpy(environ[i], _environ[i], bytes);
-	}
-	environ[env_count] = nullptr;
+	if (::environ == nullptr)
+		::environ = environ;
 }
 
 void _exit(int status)

userspace/programs/DynamicLoader/main.cpp

@@ -857,16 +857,27 @@ static LoadedElf& load_elf(const char* path, int fd)
 	return elf;
 }
 
-static void call_init_libc(LoadedElf& elf, char** envp)
+static void initialize_environ(char** envp)
 {
-	const auto* _init_libc = find_symbol(elf, "_init_libc");
-	if (_init_libc == nullptr)
+	uintptr_t environ = SYM_NOT_FOUND;
+	for (size_t i = 0; i < s_loaded_file_count; i++)
+	{
+		const auto* match = find_symbol(s_loaded_files[i], "environ");
+		if (match == nullptr)
+			continue;
+		if (environ == SYM_NOT_FOUND || ELF_ST_BIND(match->st_info) != STB_WEAK)
+			environ = s_loaded_files[i].base + match->st_value;
+		if (ELF_ST_BIND(match->st_info) != STB_WEAK)
+			break;
+	}
+
+	if (environ == SYM_NOT_FOUND)
 		return;
-	using _init_libc_t = void(*)(char**);
-	reinterpret_cast<_init_libc_t>(elf.base + _init_libc->st_value)(envp);
+
+	*reinterpret_cast<char***>(environ) = envp;
 }
 
-static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
+static void call_init_funcs(LoadedElf& elf, bool is_main_elf)
 {
 	if (elf.has_called_init)
 		return;
@@ -879,11 +890,12 @@ static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
 			if (dynamic.d_tag == DT_NULL)
 				break;
 			if (dynamic.d_tag == DT_NEEDED)
-				call_init_funcs(*reinterpret_cast<LoadedElf*>(dynamic.d_un.d_ptr), envp, false);
+				call_init_funcs(*reinterpret_cast<LoadedElf*>(dynamic.d_un.d_ptr), false);
 		}
 	}
 
-	if (elf.has_called_init || skip)
+	// main executable calls its init functions in _start
+	if (elf.has_called_init || is_main_elf)
 		return;
 
 	using init_t = void(*)();
@@ -892,10 +904,7 @@ static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
 	for (size_t i = 0; i < elf.init_arraysz / sizeof(init_t); i++)
 		reinterpret_cast<init_t*>(elf.init_array)[i]();
 
-	if (strcmp(elf.path, "/usr/lib/libc.so") == 0)
-		call_init_libc(elf, envp);
 
-	elf.has_called_init = true;
 }
 
 extern "C"
@@ -922,6 +931,7 @@ int _entry(int argc, char** argv, char** envp, int fd)
 	fini_random();
 
 	relocate_elf(elf, true);
-	call_init_funcs(elf, envp, true);
+	initialize_environ(envp);
+	call_init_funcs(elf, true);
 	call_entry_point(argc, argv, envp, elf.base + elf.file_header.e_entry);
 }