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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 | /* 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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| 227 | giacomo | 119 | jmp Timer_OK |
| 2 | pj | 120 | goon: |
| 121 | /* This is the overrun test */ |
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| 122 | /* Do it after sending EOI to master PIC */ |
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| 123 | |||
| 124 | movb $0x0A,%al |
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| 125 | movl $0x020,%edx |
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| 126 | outb %al,%dx |
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| 127 | inb %dx,%al |
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| 128 | testb $1,%al |
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| 129 | jz Timer_OK |
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| 130 | movl $(CLOCK_OVERRUN),%eax |
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| 131 | pushl %eax |
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| 132 | call SYMBOL_NAME(ll_abort) |
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| 133 | |||
| 134 | Timer_OK: |
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| 135 | /* Restore ESP */ |
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| 136 | popl %edx |
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| 137 | popl %ebx /* We must subtract it from ESP...*/ |
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| 138 | subl %ebx, %esp |
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| 139 | movw %dx, %ss |
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| 40 | pj | 140 | |
| 2 | pj | 141 | #ifdef __VIRCSW__ |
| 142 | |||
| 143 | movw SYMBOL_NAME(currCtx), %ax |
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| 144 | cmpw %ax,JmpSel |
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| 145 | je NoPreempt2 |
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| 146 | movw %ax,JmpSel |
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| 147 | ljmp JmpZone /* DISPATCH! */ |
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| 148 | #endif |
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| 149 | NoPreempt2: |
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| 150 | |||
| 151 | cmpl $0, SYMBOL_NAME(last_handler) |
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| 152 | je nohandler |
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| 153 | movl SYMBOL_NAME(last_handler), %ebx |
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| 154 | call *%ebx |
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| 155 | nohandler: |
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| 156 | popw %gs |
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| 157 | popw %fs |
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| 158 | popw %es |
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| 159 | popw %ds |
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| 160 | popal |
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| 161 | iret |