Refactored linker script and boot to be more architecture agnostic.

Moved the linker script dependency to a dependency of i386. Added
--spawn_strategy=standalone to the qemu.sh script. Unfortunately, there
is a bug in bazel seen here,
bazelbuild/bazel#716, that requires sandboxing
to be disabled to allow the linker script dependency to persist to the
main kernel dependency. It's not ideal but if they ever fix this bug,
the code as is should function with sandboxing.

kernel/BUILD

@@ -9,12 +9,8 @@ cc_binary (
     "//kernel/arch:gdt",
     "//kernel/arch:tty",
     "//kernel/arch:memory_detection",
-    "//kernel/arch/i386:linker.ld",
     ":crt"
   ],
-  linkopts = [
-    "-T kernel/arch/i386/linker.ld"
-  ],
   visibility = ["//visibility:public"],
 )
 

kernel/arch/BUILD

@@ -8,9 +8,5 @@ arch_library(name = "gdt")
 
 arch_library(name = "memory_detection")
 
-cc_library(
-  name = "boot",
-  deps = select({
-    "//tools:i386" : ["//kernel/arch/i386/boot"],
-  }),
-)
+arch_library(name = "boot")
+

kernel/arch/boot.h

@@ -0,0 +1,4 @@
+#ifndef KERNEL_ARCH_BOOT_H
+#define KERNEL_ARCH_BOOT_H
+
+#endif // KERNEL_ARCH_BOOT_H

kernel/arch/i386/boot/BUILD

@@ -5,10 +5,14 @@ cc_library(
   srcs = [
     "boot.S",
     "crti.S",
-    "crtn.S"
+    "crtn.S",
   ],
   deps = [
     ":multiboot",
+    "linker.ld"
+  ],
+  linkopts = [
+    "-T $(location linker.ld)"
   ],
   alwayslink = 1,
 )
@@ -21,6 +25,5 @@ cc_library(
   hdrs = [
     "meminfo.h",
     "multiboot.h"
-  ],
-  alwayslink = 1,
+  ]
 )

kernel/arch/i386/linker.ld → kernel/arch/i386/boot/linker.ld

@@ -9,35 +9,35 @@ SECTIONS
 	/* Begin putting sections at 1 MiB, a conventional place for kernels to be
 	   loaded at by the bootloader. */
 	. = 1M;
+  kernel_start = .;
 
 	/* 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 BLOCK(4K) : ALIGN(4K)
+	.text ALIGN(4K) :
 	{
 		*(.multiboot)
 		*(.text)
 	}
 
 	/* Read-only data. */
-	.rodata BLOCK(4K) : ALIGN(4K)
+	.rodata ALIGN(4K) :
 	{
 		*(.rodata)
 	}
 
 	/* Read-write data (initialized) */
-	.data BLOCK(4K) : ALIGN(4K)
+	.data ALIGN(4K) :
 	{
 		*(.data)
 	}
 
 	/* Read-write data (uninitialized) and stack */
-	.bss BLOCK(4K) : ALIGN(4K)
+	.bss ALIGN(4K) :
 	{
 		*(COMMON)
 		*(.bss)
 	}
 
-	/* The compiler may produce other sections, put them in the proper place in
-	   in this file, if you'd like to include them in the final kernel. */
+  kernel_end = .;
 }

qemu.sh

@@ -13,5 +13,5 @@ if [ ! -d "tools/compilers/$TARGET" ]; then
   ./tools/install.sh $TARGET || exit $?;
 fi
 
-bazel build :iso --crosstool_top=//tools:toolchain --cpu=$1 --host_cpu=$1 --strip=never || exit $?
+bazel build :iso --spawn_strategy=standalone --crosstool_top=//tools:toolchain --cpu=$1 --host_cpu=$1 --strip=never --verbose_failures || exit $?
 qemu-system-$1 -cdrom bazel-genfiles/os.iso -monitor stdio -s