summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--src/arch/armv7/thread.c127
1 files changed, 127 insertions, 0 deletions
diff --git a/src/arch/armv7/thread.c b/src/arch/armv7/thread.c
new file mode 100644
index 0000000000..d0c23ff92d
--- /dev/null
+++ b/src/arch/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;
+}