1 files changed, 127 insertions, 0 deletions
diff --git a/src/arch/arm/armv7/thread.c b/src/arch/arm/armv7/thread.c
new file mode 100644
index 000000000000..d0c23ff92d36
--- /dev/null
+++ b/src/arch/arm/armv7/thread.c
@@ -0,0 +1,127 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2013 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <console/console.h>
+#include <thread.h>
+
+/* The stack frame looks like the following. */
+struct pushed_regs {
+	u32 r4;
+	u32 r5;
+	u32 r6;
+	u32 r7;
+	u32 r8;
+	u32 r9;
+	u32 r10;
+	u32 r11;
+	u32 lr;
+};
+
+static inline uintptr_t push_stack(uintptr_t cur_stack, uintptr_t value)
+{
+	uintptr_t *addr;
+
+	cur_stack -= sizeof(value);
+	addr = (uintptr_t *)cur_stack;
+	*addr = value;
+	return cur_stack;
+}
+
+void arch_prepare_thread(struct thread *t,
+                         void asmlinkage (*thread_entry)(void *), void *arg)
+{
+	uintptr_t stack = t->stack_current;
+	int i;
+	uintptr_t poison = 0xdeadbeef;
+
+	/* Push the LR. thread_entry()
+	 * is assumed to never return.
+	 */
+	stack = push_stack(stack, (uintptr_t)thread_entry);
+	/* Make room for the registers.
+	 * Poison the initial stack. This is good hygiene and finds bugs.
+	 * Poisoning the stack with different values helps when you're
+	 * hunting for (e.g.) misaligned stacks or other such
+	 * weirdness. The -1 is because we already pushed lr.
+	 */
+	for(i = 0; i < sizeof(struct pushed_regs)/sizeof(u32)-1; i++)
+		stack = push_stack(stack, poison++);
+
+	t->stack_current = stack;
+}
+
+/* We could write this as a .S and the first time around that's how we
+ * did it. But there's always the question of matching our ARM
+ * directives in the .S with how gcc is doing things.  It seems best
+ * to follow the pattern of the rest of the ARM port and just use
+ * inline assembly and let gcc get all the ELF magic right.
+ */
+void __attribute__((naked))
+switch_to_thread(uintptr_t new_stack, uintptr_t *saved_stack)
+{
+	/* Defintions for those of us not totally familiar with ARM:
+	 * R15 -- PC, R14 -- LR, R13 -- SP
+	 * R0-R3 need not be saved, nor R12.
+	 * on entry, the only saved state is in LR -- the old PC.
+	 * The args are in R0,R1.
+	 * R0 is the new stack
+	 * R1 is a pointer to the old stack save location
+	 * Push R4-R11 and LR
+	 * then switch stacks
+	 * then pop R0-R12 and LR
+	 * then mov PC,LR
+	 *
+	 * stack layout
+	 * +------------+
+	 * |    LR      | <-- sp + 0x20
+	 * +------------+
+	 * |    R11     | <-- sp + 0x1c
+	 * +------------+
+	 * |    R10     | <-- sp + 0x18
+	 * +------------+
+	 * |    R9      | <-- sp + 0x14
+	 * +------------+
+	 * |    R8      | <-- sp + 0x10
+	 * +------------+
+	 * |    R7      | <-- sp + 0x0c
+	 * +------------+
+	 * |    R6      | <-- sp + 0x08
+	 * +------------+
+	 * |    R5      | <-- sp + 0x04
+	 * +------------+
+	 * |    R4      | <-- sp + 0x00
+	 * +------------+
+	 */
+        asm volatile (
+	/* save context. */
+	"push {r4-r11,lr}\n\t"
+	/* Save the current stack */
+	"str sp,[r1]\n\t"
+	/* switch to the new stack */
+	"mov sp,r0\n\t"
+	/* restore the registers */
+	"pop {r4-r11,lr}\n\t"
+	/* resume other thread. */
+	"mov pc,lr\n\t"
+	);
+}
+
+void *arch_get_thread_stackbase(void)
+{
+	return (void *)CONFIG_STACK_BOTTOM;
+}