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https://github.com/taigrr/gopher-os
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The page table walker provides a mechanism for accessing the individual page table entries that correspond to a particular virtual memory address. This implementation will serve as the basis for implementing page mapping/unmapping and virtual to physical address translation.
77 lines
2.1 KiB
Go
77 lines
2.1 KiB
Go
package vmm
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import (
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"runtime"
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"testing"
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"unsafe"
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"github.com/achilleasa/gopher-os/kernel/mem"
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)
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func TestPtePtrFn(t *testing.T) {
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// Dummy test to keep coverage happy
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if exp, got := unsafe.Pointer(uintptr(123)), ptePtrFn(uintptr(123)); exp != got {
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t.Fatalf("expected ptePtrFn to return %v; got %v", exp, got)
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}
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}
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func TestWalkAmd64(t *testing.T) {
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if runtime.GOARCH != "amd64" {
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t.Skip("test requires amd64 runtime; skipping")
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}
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defer func(origPtePtr func(uintptr) unsafe.Pointer) {
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ptePtrFn = origPtePtr
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}(ptePtrFn)
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// This address breaks down to:
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// p4 index: 1
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// p3 index: 2
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// p2 index: 3
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// p1 index: 4
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// offset : 1024
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targetAddr := uintptr(0x8080604400)
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sizeofPteEntry := uintptr(unsafe.Sizeof(pageTableEntry(0)))
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expEntryAddrBits := [pageLevels][pageLevels + 1]uintptr{
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{511, 511, 511, 511, 1 * sizeofPteEntry},
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{511, 511, 511, 1, 2 * sizeofPteEntry},
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{511, 511, 1, 2, 3 * sizeofPteEntry},
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{511, 1, 2, 3, 4 * sizeofPteEntry},
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}
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pteCallCount := 0
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ptePtrFn = func(entry uintptr) unsafe.Pointer {
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if pteCallCount >= pageLevels {
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t.Fatalf("unexpected call to ptePtrFn; already called %d times", pageLevels)
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}
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for i := 0; i < pageLevels; i++ {
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pteIndex := (entry >> pageLevelShifts[i]) & ((1 << pageLevelBits[i]) - 1)
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if pteIndex != expEntryAddrBits[pteCallCount][i] {
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t.Errorf("[ptePtrFn call %d] expected pte entry for level %d to use offset %d; got %d", pteCallCount, i, expEntryAddrBits[pteCallCount][i], pteIndex)
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}
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}
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// Check the page offset
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pteIndex := entry & ((1 << mem.PageShift) - 1)
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if pteIndex != expEntryAddrBits[pteCallCount][pageLevels] {
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t.Errorf("[ptePtrFn call %d] expected pte offset to be %d; got %d", pteCallCount, expEntryAddrBits[pteCallCount][pageLevels], pteIndex)
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}
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pteCallCount++
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return unsafe.Pointer(uintptr(0xf00))
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}
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walkFnCallCount := 0
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walk(targetAddr, func(level uint8, entry *pageTableEntry) bool {
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walkFnCallCount++
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return walkFnCallCount != pageLevels
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})
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if pteCallCount != pageLevels {
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t.Errorf("expected ptePtrFn to be called %d times; got %d", pageLevels, pteCallCount)
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}
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}
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