Setup for cross-platform development and support

* Import compiler builtin crate to fix issue with _umod and _udiv
* Trim unnecessary Makefile variables and flags
* Keep the BLOCK and ALIGN commands in linker.ld for now
* Fix linking error `undefiend reference to rust_begin_unwind`
  * `panic_fmt` was mangled through optimization
  * `panic_fmt` becomes `rust_begin_unwind`
  * Solution: add `#[no_mangle]` before `panic_fmt`
  * [Rust Issue](rust-lang/rust#38281)

Author: robert-w-gries

Cargo.toml

@@ -8,6 +8,7 @@ authors = [ "[email protected]" ]
 crate-type = ["staticlib"]
 
 [dependencies]
+compiler_builtins = { git = "https://github.com/rust-lang-nursery/compiler-builtins" }
 rlibc = "1.0.0"
 spin = "0.3.4"
 volatile = "0.1.0"

Makefile

@@ -1,20 +1,17 @@
 # Target and build files
 arch ?= x86
 target ?= i386
-system ?= linux
 build ?= debug
 
 # Flags
 CFLAGS := --target=$(target)-unknown-none-elf -ffreestanding
 ASFLAGS := -masm=intel
-LDFLAGS := -n -nostdlib --gc-sections -melf_$(target)
+LDFLAGS := -n --gc-sections -melf_$(target)
 
 # Rust target
 rust_arch := $(target)
 ifeq ($(rust_arch),i386)
 	rust_arch := i686
-else
-	CFLAGS += -mno-red-zone
 endif
 
 # Debug flags
@@ -28,15 +25,7 @@ kernel := build/rxinu-$(arch)-$(target).bin
 iso := build/rxinu-$(arch)-$(target).iso
 
 # Rust Binaries
-
-# Target
-ifeq ($(system),linux)
-	rust_target ?= $(rust_arch)-unknown-linux-gnu
-endif
-ifeq ($(system),apple)
-	rust_target ?= $(rust_arch)-apple-darwin
-endif
-
+rust_target ?= $(rust_arch)-unknown-linux-gnu
 rust_os := target/$(rust_target)/debug/librxinu.a
 
 # Source files

src/arch/x86/linker.ld

@@ -13,31 +13,31 @@ SECTIONS
 	/* First put the multiboot header, as it is required to be put very early
 	   early in the image or the bootloader won't recognize the file format.
 	   Next we'll put the .text section. */
-	.text :
+	.text BLOCK(4K) : ALIGN(4K)
 	{
 		KEEP(*(.multiboot_header))
 		*(.text .text.*)
 	}
 
 	/* Read-only data. */
-	.rodata :
+	.rodata BLOCK(4K) : ALIGN(4K)
 	{
 		*(.rodata .rodata.*)
 	}
 
-        .data.rel.ro :
-        {
-                *(.data.rel.ro.local*) *(.data.rel.ro .data.rel.ro.*)
-        }
-
 	/* Read-write data (initialized) */
-	.data :
+	.data BLOCK(4K) : ALIGN(4K)
+	{
+		*(.data .data.*)
+	}
+
+	.data.rel.ro BLOCK(4K) : ALIGN(4K)
 	{
-		*(.data)
+		*(.data.rel.ro.local*) *(.data.rel.ro .data.rel.ro.*)
 	}
 
 	/* Read-write data (uninitialized) and stack */
-	.bss :
+	.bss BLOCK(4K) : ALIGN(4K)
 	{
 		*(COMMON)
 		*(.bss)

src/lib.rs

@@ -3,6 +3,9 @@
 #![feature(unique)]
 #![no_std]
 
+#![feature(compiler_builtins_lib)]
+extern crate compiler_builtins;
+
 extern crate rlibc;
 extern crate spin;
 extern crate volatile;
@@ -20,7 +23,8 @@ pub extern fn rust_main() {
 }
 
 #[lang = "eh_personality"] extern fn eh_personality() {}
-#[lang = "panic_fmt"] extern fn panic_fmt() -> ! {loop{}}
+
+#[lang = "panic_fmt"] #[no_mangle] extern fn panic_fmt() -> ! {loop{}}
 
 #[allow(non_snake_case)]
 #[no_mangle]