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2 | pj | 1 | /* Project: OSLib |
2 | * Description: The OS Construction Kit |
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3 | * Date: 1.6.2000 |
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4 | * Idea by: Luca Abeni & Gerardo Lamastra |
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5 | * |
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6 | * OSLib is an SO project aimed at developing a common, easy-to-use |
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7 | * low-level infrastructure for developing OS kernels and Embedded |
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8 | * Applications; it partially derives from the HARTIK project but it |
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9 | * currently is independently developed. |
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10 | * |
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11 | * OSLib is distributed under GPL License, and some of its code has |
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12 | * been derived from the Linux kernel source; also some important |
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13 | * ideas come from studying the DJGPP go32 extender. |
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14 | * |
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15 | * We acknowledge the Linux Community, Free Software Foundation, |
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16 | * D.J. Delorie and all the other developers who believe in the |
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17 | * freedom of software and ideas. |
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18 | * |
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19 | * For legalese, check out the included GPL license. |
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20 | */ |
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21 | |||
22 | /* Safe abort routine & timer asm handler */ |
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23 | |||
24 | .title "Timer.S" |
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25 | |||
26 | #include <ll/i386/sel.h> |
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27 | #include <ll/i386/linkage.h> |
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28 | #include <ll/i386/defs.h> |
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29 | |||
30 | #include <ll/sys/ll/exc.h> |
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31 | |||
32 | .data |
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33 | |||
34 | ASMFILE(TimerHandler) |
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35 | |||
36 | .extern JmpSel |
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37 | .extern JmpZone |
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38 | .globl SYMBOL_NAME(ll_clock) |
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39 | .globl SYMBOL_NAME(last_handler) |
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40 | |||
41 | /* Used as JMP entry point to check if a real */ |
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42 | /* context switch is necessary */ |
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43 | |||
44 | SYMBOL_NAME_LABEL(ll_clock) .int 0 |
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45 | SYMBOL_NAME_LABEL(last_handler) .long 0 |
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46 | |||
47 | .extern SYMBOL_NAME(periodic_wake_up) |
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48 | .extern SYMBOL_NAME(oneshot_wake_up) |
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49 | |||
50 | .text |
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51 | .globl SYMBOL_NAME(ll_timer) |
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52 | /* This is the timer handler; it reloads for safety the DS register; this */ |
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53 | /* prevents from mess when timer interrupts linear access to memory (not in */ |
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54 | /* ELF address space); then EOI is sent in order to detect timer overrun */ |
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55 | /* The high level kernel procedure wake_up() is called to perform the */ |
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56 | /* preeption at higher level (process descriptos); the resulting context */ |
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57 | /* if different from the old one is used to trigger the task activation. */ |
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58 | |||
59 | SYMBOL_NAME_LABEL(ll_timer) |
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60 | pushal |
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61 | pushw %ds |
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62 | pushw %es |
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63 | pushw %fs |
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64 | pushw %gs |
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65 | |||
66 | movw $(X_FLATDATA_SEL),%ax |
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67 | movw %ax,%ds |
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68 | movw %ax,%es |
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69 | |||
70 | /* Send EOI to master PIC */ |
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71 | /* to perform later the overrun test */ |
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72 | movb $0x20,%al |
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73 | movl $0x20,%edx |
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74 | outb %al,%dx |
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75 | |||
76 | /* Call wake_up(actual_context) */ |
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77 | |||
78 | movl SYMBOL_NAME(ll_clock),%eax |
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79 | incl %eax |
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80 | movl %eax,SYMBOL_NAME(ll_clock) |
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81 | |||
82 | /* The following could be optimized a little... */ |
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83 | xorl %ebx, %ebx |
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84 | movw %ss, %bx |
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85 | /* We must switch to a ``safe stack'' */ |
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86 | /* |
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87 | * OK, this is the idea: in %esp we have the address of the |
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88 | * stack pointer in the APPLICATION address space... |
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89 | * We assume that address spaces are implemented through segments... |
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90 | * What we have to do is to add the segment base to %esp: |
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91 | * - Load the GDT base in a register |
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92 | * - Add DS * 8 to that value |
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93 | * - Read the corresponding GDT entry (the segment descriptor) |
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94 | * - Compute the base... |
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95 | * It is (*p & 0xFC) | (*(p +1) & 0x0F) << 16) | *(p + 2) |
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96 | */ |
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97 | movl SYMBOL_NAME(GDT_base), %edi |
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98 | addl %ebx, %edi |
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99 | xorl %ebx, %ebx |
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100 | movb 7(%edi), %bh |
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101 | movb 4(%edi), %bl |
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102 | shl $16, %ebx |
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103 | movw 2(%edi), %bx |
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104 | /* Is it correct? I think so... Test it!!! */ |
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105 | addl %ebx, %esp |
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106 | /* Save EBX for returning to our stack... */ |
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107 | movw %ds, %cx |
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108 | movw %ss, %dx |
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109 | movw %cx, %ss |
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110 | pushl %ebx |
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111 | pushl %edx |
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112 | cld |
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113 | movl SYMBOL_NAME(timermode), %eax |
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114 | cmpl $1, %eax |
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115 | je oneshot |
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116 | call SYMBOL_NAME(periodic_wake_up) |
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117 | jmp goon |
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118 | oneshot: call SYMBOL_NAME(oneshot_wake_up) |
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119 | goon: |
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120 | /* This is the overrun test */ |
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121 | /* Do it after sending EOI to master PIC */ |
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122 | |||
123 | movb $0x0A,%al |
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124 | movl $0x020,%edx |
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125 | outb %al,%dx |
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126 | inb %dx,%al |
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127 | testb $1,%al |
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128 | jz Timer_OK |
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129 | movl $(CLOCK_OVERRUN),%eax |
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130 | pushl %eax |
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131 | call SYMBOL_NAME(ll_abort) |
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132 | |||
133 | Timer_OK: |
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134 | /* Restore ESP */ |
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135 | popl %edx |
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136 | popl %ebx /* We must subtract it from ESP...*/ |
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137 | subl %ebx, %esp |
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138 | movw %dx, %ss |
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40 | pj | 139 | |
2 | pj | 140 | #ifdef __VIRCSW__ |
141 | |||
142 | movw SYMBOL_NAME(currCtx), %ax |
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143 | cmpw %ax,JmpSel |
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144 | je NoPreempt2 |
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145 | movw %ax,JmpSel |
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146 | ljmp JmpZone /* DISPATCH! */ |
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147 | #endif |
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148 | NoPreempt2: |
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149 | |||
150 | cmpl $0, SYMBOL_NAME(last_handler) |
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151 | je nohandler |
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152 | movl SYMBOL_NAME(last_handler), %ebx |
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153 | call *%ebx |
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154 | nohandler: |
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155 | popw %gs |
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156 | popw %fs |
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157 | popw %es |
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158 | popw %ds |
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159 | popal |
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160 | iret |