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> OS Construction > (solved) simple task switching mechanism |
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BAiC 18 Apr 2012, 00:44
I've written a task switching mechanism which uses the LAPICs' oscillator to trigger a task switch. the code includes a Front Side Bus calculator to determine the correct value to write into the Initial Count Register.. the state machine component uses a Linked List approach. each time it is supposed to switch a task it stores the registers onto the current tasks' stack and stores the RSP register into the state machine for the current task; Then it reads in the address of the next tasks' state machine (using the linked list component) and uses it to recover RSP. The code below is on line 7485 of ORB.asm
Code:
xor ecx, ecx
mov[dword APIC.EOI], ecx
; mov rbx,[rdi+orb.tasks];this is used as an index.
; add rbx, rbx
; mov ecx, 16
; min rcx, rbx, rax
; mov eax, NRQ.TSC, .init
; shr eax, 4
; mul[rcx*8+reciprocals]
; add edx, edx
; mov[dword APIC.LVTTimerICR], edx
;tsc
;cmp rax,[rdi+orb.timeout-128]
;jb .end.int
rali ., 16
.int.two:
;the empty condition.
mov rsi,[rdi+orb.current-128]
;cmp rsi,[rsi+orb.next]
;je .end.int
psh r08 r09 r10 r11 r12 r13 r14 r15
add rsp,-512-8
fxsave64 [rsp]
inc[rdi+ orb.count]
mov[rsi+ orb.rsp], rsp
or [rsi+ orb.int], 1
mov rsi,[rsi+orb.next]
mov rsp,[rsi+orb.rsp ]
mov[rdi+ orb.current-128],rsi
tst[rsi+ orb.int], 1
jz .start
fxrstor64 [rsp]
add rsp, 512+8
pop r15 r14 r13 r12 r11 r10 r09 r08
.end.int:
ret
rali ., line
.start:
psh NRQ.Flags, .init
popf
cal qword [rsi]
cli
lea rdi, 128 shl ORB.Multiplier + ORB.Controls, .init
dec[rdi+ orb.tasks]
mov rsi,[rdi+orb.current-128]
mov rdx,[rsi+orb.next]
mov rcx,[rsi+orb.prev]
mov[rdx+orb.prev], rcx
mov[rcx+orb.next], rdx
mov[rdi+orb.current-128],rdx
mov rax,[rsi+orb.stack]
psh rdx
psh rsi
cal ORB.Page.D, .init;deallocate the memory used for the processes' stack.
pop rax
cal ORB.Line.D, .init;deallocate the memory used for the linked list block.
pop rsi
mov rsp,[rsi+orb.rsp]
lea rdi, 128 shl ORB.Multiplier + ORB.Controls, .init
inc[rdi+orb.count]
tst[rsi+orb.int], 1
jz .start
fxrstor64 [rsp]
add rsp, 512+8
pop r15 r14 r13 r12 r11 r10 r09 r08
ret
Last edited by BAiC on 18 Apr 2012, 04:40; edited 1 time in total |
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18 Apr 2012, 00:44 |
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BAiC 18 Apr 2012, 00:55
CAL is a macro for CALL.
rali is a macro that performs Relative Alignment. since the code is copied elsewhere prior to executing the ALIGN directive doesn't generally work. fxsave64 is a macro for fxsave (with "db 0x48" to make it x64 compatible). FASM doesn't include this instruction in the version I'm using (I can't speak for current version). |
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18 Apr 2012, 00:55 |
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BAiC 18 Apr 2012, 04:39
found it. I was using the root link as a "union" and ended up writing over rsp. The code now works as it should.
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18 Apr 2012, 04:39 |
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bubach 18 Apr 2012, 20:45
Do you have a homepage, i would like to learn more about your system&goals as it looks like you are preforming some serious assembly wizardry in there..
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18 Apr 2012, 20:45 |
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BAiC 19 Apr 2012, 14:22
I will eventually make a webpage about Mathis, I'm simply not ready yet. when it comes to my goals for Mathis, they're not readily apparent: I'm actually working towards a fully integral Scripting Language.
I've been focused heavily on the algorithms needed to support a parser. my current version is nothing more than a character code loop that tokenizes the input string. |
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19 Apr 2012, 14:22 |
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