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| -rw-r--r-- | src/arch/armv7/thread.c | 127 |
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; +} |