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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 | /* Context switch code */ |
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23 | |||
24 | #include <ll/i386/sel.h> |
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25 | #include <ll/i386/linkage.h> |
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26 | #include <ll/i386/defs.h> |
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27 | |||
28 | .data |
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29 | |||
30 | ASMFILE(Context) |
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31 | |||
32 | .globl SYMBOL_NAME(currCtx) |
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33 | .globl JmpSel |
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34 | .globl JmpZone |
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35 | |||
36 | SYMBOL_NAME_LABEL(currCtx) .word 0 |
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37 | |||
38 | JmpZone: |
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39 | JmpOffset: |
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40 | .word 0 |
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41 | .word 0 |
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42 | JmpSel: |
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43 | .word 0 |
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44 | |||
45 | .text |
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46 | |||
47 | .globl SYMBOL_NAME(context_save) |
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48 | .globl SYMBOL_NAME(context_change) |
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49 | .globl SYMBOL_NAME(context_load) |
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50 | .globl SYMBOL_NAME(init_TR) |
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51 | |||
52 | /* This function assign a value to the TASK register of 386 architecture */ |
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53 | /* We MUST do this BEFORE we use the HW multitask */ |
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54 | |||
55 | SYMBOL_NAME_LABEL(init_TR) |
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56 | pushl %ebp |
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57 | movl %esp,%ebp |
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58 | movl 8(%ebp),%eax |
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59 | ltrw %ax |
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60 | movw %ax,JmpSel |
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61 | movw %ax,SYMBOL_NAME(currCtx) |
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62 | popl %ebp |
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63 | ret |
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64 | |||
65 | /* CONTEXT __cdecl context_save(void); */ |
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66 | /* The context is returned into AX; Interrupts are also cleared as we are */ |
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67 | /* entering into kernel primitives */ |
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68 | |||
69 | SYMBOL_NAME_LABEL(context_save) |
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70 | xorl %eax,%eax |
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71 | strw %ax |
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72 | ret |
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73 | |||
74 | /* void __cdecl context_change(CONTEXT c) */ |
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75 | /* Use 386 task switch ability. This is the last call of any preemption */ |
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76 | /* generating primitive; when the original task is re-activated the */ |
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77 | /* interrupt flag is restored with STI */ |
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78 | /* In 32 bit systems, context_load is an alias for context_change!*/ |
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79 | |||
80 | SYMBOL_NAME_LABEL(context_load) |
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81 | SYMBOL_NAME_LABEL(context_change) |
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82 | pushl %ebp |
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83 | movl %esp,%ebp |
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84 | movw $(X_FLATDATA_SEL),%ax |
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85 | movw %ax,%ds |
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86 | movw %ax,%es |
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87 | movl 8(%ebp),%eax |
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88 | cmpw JmpSel,%ax |
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89 | je NoPreempt |
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90 | movw %ax,JmpSel |
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91 | ljmp JmpZone |
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92 | NoPreempt: popl %ebp |
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93 | ret |
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94 |