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Rev | Author | Line No. | Line |
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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 | /* 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 | } |