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https://github.com/taigrr/gopher-os
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Implement API for mapping virtual addresses to physical frames
The API provides the Map() and MapTemporary() functions that establish virtual -> physical address mappings using the currently active page directory table. Mapped pages can be unmapped using the Unmap() function. When unmapping virtual addresses, the page tables leading to them will not be automatically released even if they are empty. This will be addressed by a future commit.
This commit is contained in:
Achilleas Anagnostopoulos
251
kernel/mem/vmm/map_test.go
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251
kernel/mem/vmm/map_test.go
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@@ -0,0 +1,251 @@
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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"
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"github.com/achilleasa/gopher-os/kernel/mem"
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"github.com/achilleasa/gopher-os/kernel/mem/pmm"
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)
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func TestNextAddrFn(t *testing.T) {
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// Dummy test to keep coverage happy
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if exp, got := uintptr(123), nextAddrFn(uintptr(123)); exp != got {
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t.Fatalf("expected nextAddrFn to return %v; got %v", exp, got)
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}
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}
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func TestMapTemporaryAmd64(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, origNextAddrFn func(uintptr) uintptr, origFlushTLBEntryFn func(uintptr)) {
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ptePtrFn = origPtePtr
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nextAddrFn = origNextAddrFn
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flushTLBEntryFn = origFlushTLBEntryFn
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}(ptePtrFn, nextAddrFn, flushTLBEntryFn)
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var physPages [pageLevels][mem.PageSize >> mem.PointerShift]pageTableEntry
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nextPhysPage := 0
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// allocFn returns pages from index 1; we keep index 0 for the P4 entry
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allocFn := func(_ mem.PageOrder) (pmm.Frame, *kernel.Error) {
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nextPhysPage++
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pageAddr := unsafe.Pointer(&physPages[nextPhysPage][0])
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return pmm.Frame(uintptr(pageAddr) >> mem.PageShift), nil
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}
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pteCallCount := 0
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ptePtrFn = func(entry uintptr) unsafe.Pointer {
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pteCallCount++
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// The last 12 bits encode the page table offset in bytes
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// which we need to convert to a uint64 entry
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pteIndex := (entry & uintptr(mem.PageSize-1)) >> mem.PointerShift
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return unsafe.Pointer(&physPages[pteCallCount-1][pteIndex])
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}
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nextAddrFn = func(entry uintptr) uintptr {
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return uintptr(unsafe.Pointer(&physPages[nextPhysPage][0]))
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}
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flushTLBEntryCallCount := 0
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flushTLBEntryFn = func(uintptr) {
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flushTLBEntryCallCount++
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}
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// The temporary mappin address breaks down to:
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// p4 index: 510
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// p3 index: 511
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// p2 index: 511
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// p1 index: 511
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frame := pmm.Frame(123)
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levelIndices := []uint{510, 511, 511, 511}
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page, err := MapTemporary(frame, allocFn)
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if err != nil {
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t.Fatal(err)
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}
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if got := page.Address(); got != tempMappingAddr {
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t.Fatalf("expected temp mapping virtual address to be %x; got %x", tempMappingAddr, got)
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}
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for level, physPage := range physPages {
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pte := physPage[levelIndices[level]]
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if !pte.HasFlags(FlagPresent | FlagRW) {
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t.Errorf("[pte at level %d] expected entry to have FlagPresent and FlagRW set", level)
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}
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switch {
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case level < pageLevels-1:
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if exp, got := pmm.Frame(uintptr(unsafe.Pointer(&physPages[level+1][0]))>>mem.PageShift), pte.Frame(); got != exp {
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t.Errorf("[pte at level %d] expected entry frame to be %d; got %d", level, exp, got)
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}
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default:
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// The last pte entry should point to frame
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if got := pte.Frame(); got != frame {
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t.Errorf("[pte at level %d] expected entry frame to be %d; got %d", level, frame, got)
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}
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}
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}
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if exp := 1; flushTLBEntryCallCount != exp {
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t.Errorf("expected flushTLBEntry to be called %d times; got %d", exp, flushTLBEntryCallCount)
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}
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}
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func TestMapTemporaryErrorsAmd64(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, origNextAddrFn func(uintptr) uintptr, origFlushTLBEntryFn func(uintptr)) {
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ptePtrFn = origPtePtr
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nextAddrFn = origNextAddrFn
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flushTLBEntryFn = origFlushTLBEntryFn
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}(ptePtrFn, nextAddrFn, flushTLBEntryFn)
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var physPages [pageLevels][mem.PageSize >> mem.PointerShift]pageTableEntry
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// The reserved virt address uses the following page level indices: 510, 511, 511, 511
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p4Index := 510
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frame := pmm.Frame(123)
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t.Run("encounter huge page", func(t *testing.T) {
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physPages[0][p4Index].SetFlags(FlagPresent | FlagHugePage)
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ptePtrFn = func(entry uintptr) unsafe.Pointer {
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// The last 12 bits encode the page table offset in bytes
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// which we need to convert to a uint64 entry
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pteIndex := (entry & uintptr(mem.PageSize-1)) >> mem.PointerShift
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return unsafe.Pointer(&physPages[0][pteIndex])
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}
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if _, err := MapTemporary(frame, nil); err != errNoHugePageSupport {
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t.Fatalf("expected to get errNoHugePageSupport; got %v", err)
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}
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})
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t.Run("allocFn returns an error", func(t *testing.T) {
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physPages[0][p4Index] = 0
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expErr := &kernel.Error{Module: "test", Message: "out of memory"}
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allocFn := func(_ mem.PageOrder) (pmm.Frame, *kernel.Error) {
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return 0, expErr
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}
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if _, err := MapTemporary(frame, allocFn); err != expErr {
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t.Fatalf("got unexpected error %v", err)
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}
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})
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}
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func TestUnmapAmd64(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, origFlushTLBEntryFn func(uintptr)) {
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ptePtrFn = origPtePtr
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flushTLBEntryFn = origFlushTLBEntryFn
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}(ptePtrFn, flushTLBEntryFn)
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var (
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physPages [pageLevels][mem.PageSize >> mem.PointerShift]pageTableEntry
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frame = pmm.Frame(123)
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)
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// Emulate a page mapped to virtAddr 0 across all page levels
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for level := 0; level < pageLevels; level++ {
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physPages[level][0].SetFlags(FlagPresent | FlagRW)
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if level < pageLevels-1 {
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physPages[level][0].SetFrame(pmm.Frame(uintptr(unsafe.Pointer(&physPages[level+1][0])) >> mem.PageShift))
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} else {
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physPages[level][0].SetFrame(frame)
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}
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}
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pteCallCount := 0
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ptePtrFn = func(entry uintptr) unsafe.Pointer {
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pteCallCount++
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return unsafe.Pointer(&physPages[pteCallCount-1][0])
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}
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flushTLBEntryCallCount := 0
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flushTLBEntryFn = func(uintptr) {
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flushTLBEntryCallCount++
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}
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if err := Unmap(PageFromAddress(0)); err != nil {
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t.Fatal(err)
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}
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for level, physPage := range physPages {
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pte := physPage[0]
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switch {
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case level < pageLevels-1:
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if !pte.HasFlags(FlagPresent) {
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t.Errorf("[pte at level %d] expected entry to retain have FlagPresent set", level)
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}
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if exp, got := pmm.Frame(uintptr(unsafe.Pointer(&physPages[level+1][0]))>>mem.PageShift), pte.Frame(); got != exp {
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t.Errorf("[pte at level %d] expected entry frame to still be %d; got %d", level, exp, got)
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}
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default:
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if pte.HasFlags(FlagPresent) {
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t.Errorf("[pte at level %d] expected entry not to have FlagPresent set", level)
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}
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// The last pte entry should still point to frame
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if got := pte.Frame(); got != frame {
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t.Errorf("[pte at level %d] expected entry frame to be %d; got %d", level, frame, got)
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}
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}
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}
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if exp := 1; flushTLBEntryCallCount != exp {
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t.Errorf("expected flushTLBEntry to be called %d times; got %d", exp, flushTLBEntryCallCount)
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}
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}
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func TestUnmapErrorsAmd64(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, origNextAddrFn func(uintptr) uintptr, origFlushTLBEntryFn func(uintptr)) {
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ptePtrFn = origPtePtr
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nextAddrFn = origNextAddrFn
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flushTLBEntryFn = origFlushTLBEntryFn
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}(ptePtrFn, nextAddrFn, flushTLBEntryFn)
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var physPages [pageLevels][mem.PageSize >> mem.PointerShift]pageTableEntry
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t.Run("encounter huge page", func(t *testing.T) {
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physPages[0][0].SetFlags(FlagPresent | FlagHugePage)
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ptePtrFn = func(entry uintptr) unsafe.Pointer {
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// The last 12 bits encode the page table offset in bytes
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// which we need to convert to a uint64 entry
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pteIndex := (entry & uintptr(mem.PageSize-1)) >> mem.PointerShift
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return unsafe.Pointer(&physPages[0][pteIndex])
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}
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if err := Unmap(PageFromAddress(0)); err != errNoHugePageSupport {
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t.Fatalf("expected to get errNoHugePageSupport; got %v", err)
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}
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})
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t.Run("virtual address not mapped", func(t *testing.T) {
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physPages[0][0].ClearFlags(FlagPresent)
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if err := Unmap(PageFromAddress(0)); err != ErrInvalidMapping {
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t.Fatalf("expected to get ErrInvalidMapping; got %v", err)
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}
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})
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}
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