DynamicLoader+LibC: Link LibC into DynamicLoader --as-sane-people

In particular, define a static LibC library *in LibC's CMakeLists* and
use it in DynamicLoader. This is similar to the way LibELF is included
in DynamicLoader.

Additionally, compile DynamicLoader with -ffunction-sections,
-fdata-sections, and -Wl,--gc-sections. This brings the loader size from
~2Mb to ~1Mb with debug symbols and from ~500Kb to ~150Kb without. Also,
this makes linking DynamicLoader with LibTimeZone unnecessary.

Userland/DynamicLoader/CMakeLists.txt

@@ -4,60 +4,21 @@ set(LOADER_SOURCES
 )
 
 add_library(DynamicLoader_CompileOptions INTERFACE)
-target_compile_options(DynamicLoader_CompileOptions INTERFACE -fno-rtti -fpie)
-target_link_options(DynamicLoader_CompileOptions INTERFACE -nostdlib -fpie)
-target_compile_definitions(DynamicLoader_CompileOptions INTERFACE NO_TLS)
+target_compile_definitions(DynamicLoader_CompileOptions INTERFACE NO_TLS _DYNAMIC_LOADER)
+target_compile_options(DynamicLoader_CompileOptions INTERFACE -fno-rtti -fpie -ffunction-sections -fdata-sections)
+target_link_options(DynamicLoader_CompileOptions INTERFACE -nolibc -nostdlib++ -nostartfiles -static-libgcc -fpie -Wl,--gc-sections)
+target_link_options(DynamicLoader_CompileOptions INTERFACE -fno-sanitize=undefined) # Sanitizer runtime is linked in manually
 add_dependencies(DynamicLoader_CompileOptions install_libc_headers)
 
-file(GLOB LIBC_SOURCES1 "../Libraries/LibC/*.cpp")
-file(GLOB LIBC_SOURCES2 "../Libraries/LibC/*/*.cpp")
-
-set(ARCH_FOLDER "${SERENITY_ARCH}")
-
-file(GLOB LIBC_SOURCES3 "../Libraries/LibC/arch/${ARCH_FOLDER}/*.S")
-set(LIBC_SOURCES3 ${LIBC_SOURCES3} "../Libraries/LibC/arch/${ARCH_FOLDER}/fenv.cpp")
-if ("${SERENITY_ARCH}" STREQUAL "x86_64")
-    set(LIBC_SOURCES3 ${LIBC_SOURCES3} "../Libraries/LibC/arch/x86_64/memset.cpp")
-endif()
-
-file(GLOB LIBSYSTEM_SOURCES "../Libraries/LibSystem/*.cpp")
-
 if (ENABLE_UNDEFINED_SANITIZER)
     set(LOADER_SOURCES ${LOADER_SOURCES} ../Libraries/LibSanitizer/UBSanitizer.cpp)
 endif()
 
-# pthread requires thread local storage, which DynamicLoader does not have.
-list(FILTER LIBC_SOURCES1 EXCLUDE REGEX ".*/LibC/(pthread|semaphore)\\.cpp")
-
-add_definitions(-D_DYNAMIC_LOADER)
-
-set(SOURCES ${LOADER_SOURCES} ${AK_SOURCES} ${LIBC_SOURCES1} ${LIBC_SOURCES2} ${LIBC_SOURCES3} ${LIBSYSTEM_SOURCES})
-
-if (("${SERENITY_ARCH}" STREQUAL "aarch64") OR ("${SERENITY_ARCH}" STREQUAL "riscv64"))
-    # On aarch64 and riscv64 the stack protector would be accessed before the Loader can relocate itself.
-    set_source_files_properties(main.cpp PROPERTIES COMPILE_FLAGS "-fno-stack-protector")
-endif()
-
-set_source_files_properties(../Libraries/LibC/ssp.cpp PROPERTIES COMPILE_FLAGS "-fno-stack-protector")
-# Prevent GCC from removing null checks by marking the `FILE*` argument non-null
-set_source_files_properties(../Libraries/LibC/stdio.cpp PROPERTIES COMPILE_FLAGS "-fno-builtin-fputc -fno-builtin-fputs -fno-builtin-fwrite")
-
-# Prevent naively implemented string functions (like strlen) from being "optimized" into a call to themselves.
-if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    set_source_files_properties(../Libraries/LibC/string.cpp ../Libraries/LibC/wchar.cpp
-        PROPERTIES COMPILE_FLAGS "-fno-tree-loop-distribution -fno-tree-loop-distribute-patterns")
-endif()
+set(SOURCES ${LOADER_SOURCES})
 
 add_executable(Loader.so ${SOURCES})
-add_dependencies(Loader.so install_libc_headers)
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    target_link_libraries(Loader.so PRIVATE gcc)
-elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang$")
-    target_link_libraries(Loader.so PRIVATE clang_rt.builtins)
-endif ()
-
-target_link_libraries(Loader.so PRIVATE DynamicLoader_CompileOptions DynamicLoader_LibELF LibTimeZone)
+target_link_libraries(Loader.so PRIVATE DynamicLoader_CompileOptions DynamicLoader_LibELF)
 target_link_options(Loader.so PRIVATE LINKER:--no-dynamic-linker)
 # Don't confuse the coverage results by instrumenting Loader
 target_link_libraries(Loader.so PRIVATE NoCoverage)

Userland/DynamicLoader/main.cpp

@@ -91,7 +91,7 @@ ALWAYS_INLINE static void optimizer_fence()
     asm("" ::: "memory");
 }
 
-void _entry(int argc, char** argv, char** envp)
+[[gnu::no_stack_protector]] void _entry(int argc, char** argv, char** envp)
 {
     char** env;
     for (env = envp; *env; ++env) {

Userland/Libraries/LibC/CMakeLists.txt

@@ -291,6 +291,13 @@ file(WRITE "${CMAKE_STAGING_PREFIX}/${CMAKE_INSTALL_LIBDIR}/libdl.so" "INPUT(lib
 file(WRITE "${CMAKE_STAGING_PREFIX}/${CMAKE_INSTALL_LIBDIR}/libm.so" "INPUT(libc.so)")
 file(WRITE "${CMAKE_STAGING_PREFIX}/${CMAKE_INSTALL_LIBDIR}/libssp.so" "INPUT(libc.so)")
 
+# ===== LibC for DynamicLoader =====
+add_library(DynamicLoader_LibC STATIC ${SOURCES})
+target_link_libraries(DynamicLoader_LibC
+    PUBLIC DynamicLoader_CompileOptions
+    PRIVATE DynamicLoader_LibSystem
+)
+
 # ===== Compatibility with the GCC toolchain without TARGET_LIBC_PROVIDES_SSP =====
 # FIXME: Remove this on the next GCC toolchain version bump
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")

Userland/Libraries/LibC/pthread.cpp

@@ -161,6 +161,7 @@ void pthread_exit(void* value_ptr)
     pthread_exit_without_cleanup_handlers(value_ptr);
 }
 
+#ifndef _DYNAMIC_LOADER
 void __pthread_maybe_cancel()
 {
     // Check if we have cancellations enabled.
@@ -175,6 +176,7 @@ void __pthread_maybe_cancel()
     // return value and calling the cleanup handlers for us.
     pthread_exit(PTHREAD_CANCELED);
 }
+#endif
 
 // https://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_cleanup_push.html
 void pthread_cleanup_push(void (*routine)(void*), void* arg)

Userland/Libraries/LibELF/CMakeLists.txt

@@ -25,7 +25,10 @@ if (SERENITYOS)
     endif()
 
     add_library(DynamicLoader_LibELF STATIC ${SOURCES})
-    target_link_libraries(DynamicLoader_LibELF PUBLIC DynamicLoader_CompileOptions)
+    target_link_libraries(DynamicLoader_LibELF
+        PUBLIC DynamicLoader_CompileOptions
+        PRIVATE DynamicLoader_LibC
+    )
 endif()
 
 serenity_lib(LibELF elf ${SOURCES})

Userland/Libraries/LibSystem/CMakeLists.txt

@@ -5,3 +5,6 @@ set(SOURCES
 serenity_libc(LibSystem system)
 add_dependencies(LibSystem install_libc_headers)
 target_link_options(LibSystem PRIVATE -nostdlib)
+
+add_library(DynamicLoader_LibSystem STATIC ${SOURCES})
+target_link_libraries(DynamicLoader_LibSystem PUBLIC DynamicLoader_CompileOptions)