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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 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 | /* These function provide access to hardware structutes GDT/IDT */ |
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| 23 | |||
| 24 | #include <ll/i386/cons.h> |
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| 25 | #include <ll/i386/mem.h> |
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| 26 | #include <ll/math.h> |
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| 27 | |||
| 28 | FILE(X - SysTab); |
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| 29 | |||
| 30 | extern GATE IDT[256]; |
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| 31 | |||
| 32 | /* We usually need to set-up an interrupt handler; to do this we have */ |
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| 33 | /* to fill a GATE structure & copy it into the Interrupt Descriptor */ |
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| 34 | /* Table or IDT; its phisical address is given by IDT_base */ |
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| 35 | |||
| 36 | void IDT_place(BYTE num, void (*handler) (void)) |
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| 37 | { |
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| 38 | DWORD offset = (DWORD) (handler); |
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| 39 | IDT[num].sel = X_FLATCODE_SEL; |
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| 40 | /* Set DPL = 3, to allow execution of the gate from any ring */ |
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| 41 | IDT[num].access = INT_GATE386 | 0x60; |
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| 42 | IDT[num].dword_cnt = 0; |
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| 43 | IDT[num].offset_lo = offset & 0xFFFF; |
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| 44 | offset >>= 16; |
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| 45 | IDT[num].offset_hi = offset & 0xFFFF; |
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| 46 | } |
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| 47 | |||
| 48 | /* Ok; the GDT is managed in the same way as the IDT */ |
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| 49 | /* When a descriptor is cleared using it will cause a SEGMENT FAULT */ |
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| 50 | /* to refer such descriptor */ |
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| 51 | |||
| 52 | void GDT_place(WORD sel, DWORD base, DWORD lim, BYTE acc, BYTE gran) |
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| 53 | { |
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| 54 | union gdt_entry x; |
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| 55 | /* This is declared in [wc32/gnu]\x0.[asm/s] */ |
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| 56 | extern LIN_ADDR GDT_base; |
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| 57 | /* DWORD offset = appl2linear(&x); */ |
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| 58 | x.d.base_lo = (base & 0x0000FFFF); |
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| 59 | x.d.base_med = ((base & 0x00FF0000) >> 16); |
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| 60 | x.d.base_hi = ((base & 0xFF000000) >> 24); |
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| 61 | x.d.access = acc; |
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| 62 | x.d.lim_lo = (lim & 0xFFFF); |
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| 63 | x.d.gran = (gran | ((lim >> 16) & 0x0F) | 0x40); |
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| 64 | memcpy(GDT_base + (sel & ~3), &x, sizeof(union gdt_entry)); |
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| 65 | } |
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| 66 | |||
| 67 | /* This function is used to read & format the descriptor data */ |
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| 68 | /* Anyway is better to use the hw 386 instruction to modify */ |
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| 69 | /* a descriptor rather than reading,modifying & updating with */ |
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| 70 | /* this high level functions! */ |
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| 71 | |||
| 72 | DWORD GDT_read(WORD sel, DWORD * lim, BYTE * acc, BYTE * gran) |
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| 73 | { |
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| 74 | union gdt_entry x; |
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| 75 | /* This is declared in [wc32/gnu]\x0.[asm/s] */ |
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| 76 | extern LIN_ADDR GDT_base; |
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| 77 | /*DWORD offset = appl2linear(&x); */ |
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| 78 | DWORD base; |
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| 79 | memcpy(&x, GDT_base + sel, sizeof(union gdt_entry)); |
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| 80 | base = x.d.base_hi; |
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| 81 | base <<= 8; |
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| 82 | base |= x.d.base_med; |
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| 83 | base <<= 16; |
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| 84 | base |= x.d.base_lo; |
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| 85 | if (lim != NULL) { |
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| 86 | *lim = (x.d.gran & 0x0F); |
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| 87 | *lim <<= 16; |
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| 88 | *lim |= x.d.lim_lo; |
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| 89 | } |
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| 90 | if (acc != NULL) |
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| 91 | *acc = x.d.access; |
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| 92 | if (gran != NULL) |
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| 93 | *gran = x.d.gran & 0xF0; |
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| 94 | return (base); |
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| 95 | } |