root / prex-0.9.0 / bsp / hal / ppc / arch / context.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*-
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2 | * Copyright (c) 2009, Kohsuke Ohtani
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3 | * All rights reserved.
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4 | *
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5 | * Redistribution and use in source and binary forms, with or without
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6 | * modification, are permitted provided that the following conditions
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7 | * are met:
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8 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | * 3. Neither the name of the author nor the names of any co-contributors
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14 | * may be used to endorse or promote products derived from this software
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15 | * without specific prior written permission.
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16 | *
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 | * SUCH DAMAGE.
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28 | */
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29 | |||
30 | /*
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31 | * context.c - context management routines
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32 | */
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33 | |||
34 | /*
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35 | * The context consists of kernel/user mode registers, and kernel
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36 | * stack. The user mode registers are always saved to the kernel
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37 | * stack when processor enters kernel mode by H/W or S/W events.
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38 | *
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39 | * The user mode registers are located in the interrupt/trap
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40 | * frame at the top of the kernel stack. Before the control
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41 | * returns to user mode next time, these register value will be
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42 | * restored automatically.
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43 | *
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44 | * All thread owns its context to keep its execution state. The
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45 | * scheduler will switch the context to change an active thread.
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46 | */
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47 | |||
48 | #include <kernel.h> |
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49 | #include <kmem.h> |
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50 | #include <cpu.h> |
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51 | #include <context.h> |
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52 | #include <locore.h> |
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53 | #include <trap.h> |
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54 | |||
55 | /*
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56 | * Set user mode registers into the specific context.
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57 | *
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58 | * Note: When user mode program counter is set, all register
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59 | * values except a stack pointer are reset to default value.
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60 | */
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61 | void
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62 | context_set(context_t ctx, int type, register_t val)
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63 | { |
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64 | struct kern_regs *k;
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65 | struct cpu_regs *u;
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66 | uint32_t *argp; |
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67 | |||
68 | k = &ctx->kregs; |
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69 | |||
70 | switch (type) {
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71 | case CTX_KSTACK:
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72 | /* Adjust stack for C code */
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73 | val -= STKFRAME_LEN; |
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74 | |||
75 | /* Set kernel mode stack pointer */
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76 | ctx->uregs = (struct cpu_regs *)
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77 | ((uint32_t)val - sizeof(struct cpu_regs)); |
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78 | |||
79 | k->sp = (uint32_t)ctx->uregs; |
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80 | k->kstack = (uint32_t)val; |
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81 | |||
82 | /* Reset minimum user mode registers */
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83 | u = ctx->uregs; |
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84 | u->gr[3] = 0x11111111; |
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85 | u->gr[4] = 0x22222222; |
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86 | u->gr[5] = 0x33333333; |
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87 | u->srr1 = MSR_DFLT; |
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88 | break;
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89 | |||
90 | case CTX_KENTRY:
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91 | /* Kernel mode program counter */
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92 | k->lr = (uint32_t)val; |
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93 | break;
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94 | |||
95 | case CTX_KARG:
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96 | /* Kernel mode argument */
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97 | argp = (uint32_t *)(k->sp + sizeof(uint32_t) * 2); |
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98 | *argp = (uint32_t)val; |
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99 | break;
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100 | |||
101 | case CTX_USTACK:
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102 | /* User mode stack pointer */
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103 | u = ctx->uregs; |
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104 | u->gr[1] = (uint32_t)val;
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105 | break;
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106 | |||
107 | case CTX_UENTRY:
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108 | /* User mode program counter */
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109 | u = ctx->uregs; |
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110 | u->srr0 = (uint32_t)val; |
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111 | u->srr1 = MSR_DFLT; |
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112 | break;
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113 | |||
114 | case CTX_UARG:
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115 | /* User mode argument */
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116 | u = ctx->uregs; |
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117 | u->gr[3] = (uint32_t)val;
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118 | argp = (uint32_t *)(u->gr[1] + sizeof(uint32_t)); |
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119 | copyout(&val, argp, sizeof(uint32_t));
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120 | break;
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121 | |||
122 | default:
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123 | /* invalid */
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124 | break;
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125 | } |
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126 | } |
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127 | |||
128 | /*
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129 | * Switch to new context
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130 | *
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131 | * Kernel mode registers and kernel stack pointer are switched to
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132 | * the next context.
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133 | *
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134 | * It is assumed all interrupts are disabled by caller.
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135 | *
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136 | * TODO: FPU context is not switched as of now.
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137 | */
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138 | void
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139 | context_switch(context_t prev, context_t next) |
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140 | { |
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141 | |||
142 | cpu_switch(&prev->kregs, &next->kregs); |
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143 | } |
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144 | |||
145 | /*
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146 | * Save user mode context to handle exceptions.
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147 | *
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148 | * Copy current user mode registers in the kernel stack to the
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149 | * user mode stack. The user stack pointer is adjusted for this
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150 | * area. So that the exception handler can get the register
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151 | * state of the target thread.
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152 | *
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153 | * It builds arguments for the exception handler in the following
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154 | * format.
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155 | *
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156 | * void exception_handler(int exc, void *regs);
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157 | */
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158 | void
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159 | context_save(context_t ctx) |
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160 | { |
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161 | struct cpu_regs *cur, *sav;
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162 | |||
163 | /* Copy current register context into user mode stack */
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164 | cur = ctx->uregs; |
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165 | sav = (struct cpu_regs *)(cur->gr[1] - sizeof(struct cpu_regs)); |
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166 | copyout(cur, sav, sizeof(*sav));
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167 | |||
168 | ctx->saved_regs = sav; |
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169 | |||
170 | /* Adjust stack pointer */
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171 | cur->gr[1] = (uint32_t)sav - sizeof(uint32_t); |
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172 | } |
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173 | |||
174 | /*
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175 | * Restore register context to return from the exception handler.
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176 | */
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177 | void
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178 | context_restore(context_t ctx) |
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179 | { |
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180 | struct cpu_regs *cur;
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181 | |||
182 | /* Restore user mode context */
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183 | cur = ctx->uregs; |
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184 | copyin(ctx->saved_regs, cur, sizeof(*cur));
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185 | |||
186 | /* Correct some registers for fail safe */
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187 | cur->srr1 |= MSR_DFLT; |
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188 | } |
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189 | |||
190 | void
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191 | context_dump(context_t ctx) |
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192 | { |
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193 | |||
194 | #ifdef DEBUG
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195 | trap_dump(ctx->uregs); |
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196 | #endif
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197 | } |