Ronald G. Minnich | 62997e0 | 2013-08-23 11:22:42 -0700 | [diff] [blame] | 1 | /* |
| 2 | * This file is part of the coreboot project. |
| 3 | * |
| 4 | * Copyright (C) 2013 Google, Inc. |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; version 2 of the License. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
Ronald G. Minnich | 62997e0 | 2013-08-23 11:22:42 -0700 | [diff] [blame] | 14 | */ |
| 15 | #include <console/console.h> |
| 16 | #include <thread.h> |
| 17 | |
| 18 | /* The stack frame looks like the following. */ |
| 19 | struct pushed_regs { |
| 20 | u32 r4; |
| 21 | u32 r5; |
| 22 | u32 r6; |
| 23 | u32 r7; |
| 24 | u32 r8; |
| 25 | u32 r9; |
| 26 | u32 r10; |
| 27 | u32 r11; |
| 28 | u32 lr; |
| 29 | }; |
| 30 | |
| 31 | static inline uintptr_t push_stack(uintptr_t cur_stack, uintptr_t value) |
| 32 | { |
| 33 | uintptr_t *addr; |
| 34 | |
| 35 | cur_stack -= sizeof(value); |
| 36 | addr = (uintptr_t *)cur_stack; |
| 37 | *addr = value; |
| 38 | return cur_stack; |
| 39 | } |
| 40 | |
| 41 | void arch_prepare_thread(struct thread *t, |
| 42 | void asmlinkage (*thread_entry)(void *), void *arg) |
| 43 | { |
| 44 | uintptr_t stack = t->stack_current; |
| 45 | int i; |
| 46 | uintptr_t poison = 0xdeadbeef; |
| 47 | |
| 48 | /* Push the LR. thread_entry() |
| 49 | * is assumed to never return. |
| 50 | */ |
| 51 | stack = push_stack(stack, (uintptr_t)thread_entry); |
| 52 | /* Make room for the registers. |
| 53 | * Poison the initial stack. This is good hygiene and finds bugs. |
| 54 | * Poisoning the stack with different values helps when you're |
| 55 | * hunting for (e.g.) misaligned stacks or other such |
| 56 | * weirdness. The -1 is because we already pushed lr. |
| 57 | */ |
| 58 | for(i = 0; i < sizeof(struct pushed_regs)/sizeof(u32)-1; i++) |
| 59 | stack = push_stack(stack, poison++); |
| 60 | |
| 61 | t->stack_current = stack; |
| 62 | } |
| 63 | |
| 64 | /* We could write this as a .S and the first time around that's how we |
| 65 | * did it. But there's always the question of matching our ARM |
| 66 | * directives in the .S with how gcc is doing things. It seems best |
| 67 | * to follow the pattern of the rest of the ARM port and just use |
| 68 | * inline assembly and let gcc get all the ELF magic right. |
| 69 | */ |
| 70 | void __attribute__((naked)) |
| 71 | switch_to_thread(uintptr_t new_stack, uintptr_t *saved_stack) |
| 72 | { |
| 73 | /* Defintions for those of us not totally familiar with ARM: |
| 74 | * R15 -- PC, R14 -- LR, R13 -- SP |
| 75 | * R0-R3 need not be saved, nor R12. |
| 76 | * on entry, the only saved state is in LR -- the old PC. |
| 77 | * The args are in R0,R1. |
| 78 | * R0 is the new stack |
| 79 | * R1 is a pointer to the old stack save location |
| 80 | * Push R4-R11 and LR |
| 81 | * then switch stacks |
| 82 | * then pop R0-R12 and LR |
| 83 | * then mov PC,LR |
| 84 | * |
| 85 | * stack layout |
| 86 | * +------------+ |
| 87 | * | LR | <-- sp + 0x20 |
| 88 | * +------------+ |
| 89 | * | R11 | <-- sp + 0x1c |
| 90 | * +------------+ |
| 91 | * | R10 | <-- sp + 0x18 |
| 92 | * +------------+ |
| 93 | * | R9 | <-- sp + 0x14 |
| 94 | * +------------+ |
| 95 | * | R8 | <-- sp + 0x10 |
| 96 | * +------------+ |
| 97 | * | R7 | <-- sp + 0x0c |
| 98 | * +------------+ |
| 99 | * | R6 | <-- sp + 0x08 |
| 100 | * +------------+ |
| 101 | * | R5 | <-- sp + 0x04 |
| 102 | * +------------+ |
| 103 | * | R4 | <-- sp + 0x00 |
| 104 | * +------------+ |
| 105 | */ |
| 106 | asm volatile ( |
| 107 | /* save context. */ |
| 108 | "push {r4-r11,lr}\n\t" |
| 109 | /* Save the current stack */ |
| 110 | "str sp,[r1]\n\t" |
| 111 | /* switch to the new stack */ |
| 112 | "mov sp,r0\n\t" |
| 113 | /* restore the registers */ |
| 114 | "pop {r4-r11,lr}\n\t" |
| 115 | /* resume other thread. */ |
| 116 | "mov pc,lr\n\t" |
| 117 | ); |
| 118 | } |
| 119 | |
| 120 | void *arch_get_thread_stackbase(void) |
| 121 | { |
| 122 | return (void *)CONFIG_STACK_BOTTOM; |
| 123 | } |