Everywhere: Add RISC-V 64 target to the build system

This is a minimal set of changes to allow `serenity.sh build riscv64` to
successfully generate the build environment and start building. This
includes some, but not all, assembly stubs that will be needed later on;
they are currently empty.

Documentation/AdvancedBuildInstructions.md

@@ -65,7 +65,7 @@ There are some optional features that can be enabled during compilation that are
 - `INCLUDE_WASM_SPEC_TESTS`: downloads and includes the WebAssembly spec testsuite tests. In order to use this option, you will need to install `prettier` and `wabt`. wabt version 1.0.23 or higher is required to pre-process the WebAssembly spec testsuite.
 - `INCLUDE_FLAC_SPEC_TESTS`: downloads and includes the xiph.org FLAC test suite.
 - `SERENITY_TOOLCHAIN`: Specifies whether to use the established GNU toolchain, or the experimental Clang-based toolchain for building SerenityOS. See the [Clang-based toolchain](#clang-based-toolchain) section below.
-- `SERENITY_ARCH`: Specifies which architecture to build for. Currently supported options are `x86_64`.
+- `SERENITY_ARCH`: Specifies which architecture to build for. Currently supported options are `x86_64`, `aarch64`, `riscv64`.
 - `BUILD_<component>`: builds the specified component, e.g. `BUILD_HEARTS` (note: must be all caps). Check the components.ini file in your build directory for a list of available components. Make sure to run `ninja clean` and `rm -rf Build/x86_64/Root` after disabling components. These options can be easily configured by using the `ConfigureComponents` utility. See the [Component Configuration](#component-configuration) section below.
 - `BUILD_EVERYTHING`: builds all optional components, overrides other `BUILD_<component>` flags when enabled
 - `SERENITY_CACHE_DIR`: sets the location of a shared cache of downloaded files. Should not need to be set unless managing a distribution package.

Kernel/CMakeLists.txt

@@ -9,6 +9,8 @@ if ("${SERENITY_ARCH}" STREQUAL "aarch64")
     set(KERNEL_ARCH aarch64)
 elseif("${SERENITY_ARCH}" STREQUAL "x86_64")
     set(KERNEL_ARCH x86_64)
+elseif("${SERENITY_ARCH}" STREQUAL "riscv64")
+    set(KERNEL_ARCH riscv64)
 endif()
 
 set(KERNEL_HEAP_SOURCES
@@ -495,6 +497,14 @@ elseif("${SERENITY_ARCH}" STREQUAL "aarch64")
     # NOTE: These files cannot use a stack protector and sanitizers, as these will cause accesses to global variables to be inserted
     #       by the compiler. The CPU cannot access global variables without the MMU as the kernel is linked for a virtual address in high memory.
     set_source_files_properties(${SOURCES_RUNNING_WITHOUT_MMU} PROPERTIES COMPILE_FLAGS "-fno-stack-protector -fno-sanitize=all")
+elseif("${SERENITY_ARCH}" STREQUAL "riscv64")
+    set(KERNEL_SOURCES
+        ${KERNEL_SOURCES}
+        Arch/Processor.cpp
+        kprintf.cpp
+    )
+
+    add_compile_options(-fno-stack-protector -fno-sanitize=all)
 endif()
 
 set(AK_SOURCES
@@ -767,7 +777,7 @@ endif()
 serenity_install_headers(Kernel)
 serenity_install_sources(Kernel)
 
-# aarch64 does not need a Prekernel
-if (NOT "${SERENITY_ARCH}" STREQUAL "aarch64")
+# Only x86 needs a Prekernel
+if ("${SERENITY_ARCH}" STREQUAL "x86_64")
     add_subdirectory(Prekernel)
 endif()

Meta/ShellCompletions/zsh/_serenity

@@ -46,6 +46,7 @@ _serenity() {
     targets=(
         'x86_64:Target x86_64 or $SERENITY_ARCH (default)'
         'aarch64:Target aarch64'
+        'riscv64:Target riscv64'
         'lagom:Target host machine'
     )
 

Meta/serenity.sh

@@ -7,7 +7,7 @@ print_help() {
     NAME=$(basename "$ARG0")
     cat <<EOF
 Usage: $NAME COMMAND [TARGET] [TOOLCHAIN] [ARGS...]
-  Supported TARGETs: aarch64, x86_64, lagom. Defaults to SERENITY_ARCH, or x86_64 if not set.
+  Supported TARGETs: aarch64, x86_64, riscv64, lagom. Defaults to SERENITY_ARCH, or x86_64 if not set.
   Supported TOOLCHAINs: GNU, Clang. Defaults to SERENITY_TOOLCHAIN, or GNU if not set.
   Supported COMMANDs:
     build:      Compiles the target binaries, [ARGS...] are passed through to ninja
@@ -122,6 +122,10 @@ is_valid_target() {
         CMAKE_ARGS+=("-DSERENITY_ARCH=x86_64")
         return 0
     fi
+    if [ "$TARGET" = "riscv64" ]; then
+        CMAKE_ARGS+=("-DSERENITY_ARCH=riscv64")
+        return 0
+    fi
     if [ "$TARGET" = "lagom" ]; then
         CMAKE_ARGS+=("-DBUILD_LAGOM=ON")
         if [ "${CMD_ARGS[0]}" = "ladybird" ]; then

Toolchain/CMake/ClangToolchain.txt.in

@@ -40,3 +40,8 @@ set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
 set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
 set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
 set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE BOTH)
+
+# Sets a common default architecture for all toolchains. Be sure to update this in GNUToolchain as well!
+if("${SERENITY_ARCH}" STREQUAL "riscv64")
+    add_compile_options(-march=rv64gc)
+endif()

Toolchain/CMake/GNUToolchain.txt.in

@@ -37,3 +37,8 @@ set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
 set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
 set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
 set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE BOTH)
+
+# Sets a common default architecture for all toolchains. Be sure to update this in ClangToolchain as well!
+if("${SERENITY_ARCH}" STREQUAL "riscv64")
+    add_compile_options(-march=rv64gc)
+endif()

Userland/Libraries/LibC/CMakeLists.txt

@@ -109,6 +109,11 @@ elseif ("${SERENITY_ARCH}" STREQUAL "x86_64")
     set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/x86_64/entry.S ../LibELF/Arch/x86_64/plt_trampoline.S)
     set(CRTI_SOURCE "arch/x86_64/crti.S")
     set(CRTN_SOURCE "arch/x86_64/crtn.S")
+elseif ("${SERENITY_ARCH}" STREQUAL "riscv64")
+    set(ASM_SOURCES "arch/riscv64/setjmp.S")
+    set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/riscv64/entry.S ../LibELF/Arch/riscv64/plt_trampoline.S)
+    set(CRTI_SOURCE "arch/riscv64/crti.S")
+    set(CRTN_SOURCE "arch/riscv64/crtn.S")
 endif()
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unknown-warning-option")

Userland/Libraries/LibC/arch/riscv64/crti.S

@@ -0,0 +1 @@
+# Intentionally empty.

Userland/Libraries/LibC/arch/riscv64/crtn.S

@@ -0,0 +1 @@
+# Intentionally empty.

Userland/Libraries/LibC/arch/riscv64/setjmp.S

@@ -0,0 +1 @@
+# Intentionally empty.

Userland/Libraries/LibELF/Arch/riscv64/entry.S

@@ -0,0 +1 @@
+# Intentionally empty.

Userland/Libraries/LibELF/Arch/riscv64/plt_trampoline.S

@@ -0,0 +1 @@
+# Intentionally empty.