1 files changed, 43 insertions, 0 deletions
diff --git a/src/boot.c b/src/boot.c
new file mode 100644
index 0000000..ac08818
--- /dev/null
+++ b/src/boot.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ * Copyright (c) 2017 Jerko Lenstra.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <stdint.h>
+
+#include <lib/macros.h>
+
+#include "boot.h"
+
+/*
+ * This is the boot stack, used by the boot code to set the value of
+ * the ESP register very early once control is passed to the kernel.
+ *
+ * It is aligned to 4 bytes to comply with the System V Intel 386 ABI [1].
+ * While not strictly required since x86 supports unaligned accesses,
+ * aligned accesses are faster, and the compiler generates instructions
+ * accessing the stack that assume it's aligned.
+ *
+ * See the assembly code at the boot_start label in boot_asm.S.
+ *
+ * [1] http://www.sco.com/developers/devspecs/abi386-4.pdf
+ */
+uint8_t boot_stack[BOOT_STACK_SIZE] __aligned(4);