diff options
author | gVisor bot <gvisor-bot@google.com> | 2019-06-02 06:44:55 +0000 |
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committer | gVisor bot <gvisor-bot@google.com> | 2019-06-02 06:44:55 +0000 |
commit | ceb0d792f328d1fc0692197d8856a43c3936a571 (patch) | |
tree | 83155f302eff44a78bcc30a3a08f4efe59a79379 /pkg/sentry/platform/ring0/pagetables/walker_empty.go | |
parent | deb7ecf1e46862d54f4b102f2d163cfbcfc37f3b (diff) | |
parent | 216da0b733dbed9aad9b2ab92ac75bcb906fd7ee (diff) |
Merge 216da0b7 (automated)
Diffstat (limited to 'pkg/sentry/platform/ring0/pagetables/walker_empty.go')
-rwxr-xr-x | pkg/sentry/platform/ring0/pagetables/walker_empty.go | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/pkg/sentry/platform/ring0/pagetables/walker_empty.go b/pkg/sentry/platform/ring0/pagetables/walker_empty.go new file mode 100755 index 000000000..417784e17 --- /dev/null +++ b/pkg/sentry/platform/ring0/pagetables/walker_empty.go @@ -0,0 +1,255 @@ +package pagetables + +// Walker walks page tables. +type emptyWalker struct { + // pageTables are the tables to walk. + pageTables *PageTables + + // Visitor is the set of arguments. + visitor emptyVisitor +} + +// iterateRange iterates over all appropriate levels of page tables for the given range. +// +// If requiresAlloc is true, then Set _must_ be called on all given PTEs. The +// exception is super pages. If a valid super page (huge or jumbo) cannot be +// installed, then the walk will continue to individual entries. +// +// This algorithm will attempt to maximize the use of super pages whenever +// possible. Whether a super page is provided will be clear through the range +// provided in the callback. +// +// Note that if requiresAlloc is true, then no gaps will be present. However, +// if alloc is not set, then the iteration will likely be full of gaps. +// +// Note that this function should generally be avoided in favor of Map, Unmap, +// etc. when not necessary. +// +// Precondition: start must be page-aligned. +// +// Precondition: start must be less than end. +// +// Precondition: If requiresAlloc is true, then start and end should not span +// non-canonical ranges. If they do, a panic will result. +// +//go:nosplit +func (w *emptyWalker) iterateRange(start, end uintptr) { + if start%pteSize != 0 { + panic("unaligned start") + } + if end < start { + panic("start > end") + } + if start < lowerTop { + if end <= lowerTop { + w.iterateRangeCanonical(start, end) + } else if end > lowerTop && end <= upperBottom { + if w.visitor.requiresAlloc() { + panic("alloc spans non-canonical range") + } + w.iterateRangeCanonical(start, lowerTop) + } else { + if w.visitor.requiresAlloc() { + panic("alloc spans non-canonical range") + } + w.iterateRangeCanonical(start, lowerTop) + w.iterateRangeCanonical(upperBottom, end) + } + } else if start < upperBottom { + if end <= upperBottom { + if w.visitor.requiresAlloc() { + panic("alloc spans non-canonical range") + } + } else { + if w.visitor.requiresAlloc() { + panic("alloc spans non-canonical range") + } + w.iterateRangeCanonical(upperBottom, end) + } + } else { + w.iterateRangeCanonical(start, end) + } +} + +// next returns the next address quantized by the given size. +// +//go:nosplit +func emptynext(start uintptr, size uintptr) uintptr { + start &= ^(size - 1) + start += size + return start +} + +// iterateRangeCanonical walks a canonical range. +// +//go:nosplit +func (w *emptyWalker) iterateRangeCanonical(start, end uintptr) { + for pgdIndex := uint16((start & pgdMask) >> pgdShift); start < end && pgdIndex < entriesPerPage; pgdIndex++ { + var ( + pgdEntry = &w.pageTables.root[pgdIndex] + pudEntries *PTEs + ) + if !pgdEntry.Valid() { + if !w.visitor.requiresAlloc() { + + start = emptynext(start, pgdSize) + continue + } + + pudEntries = w.pageTables.Allocator.NewPTEs() + pgdEntry.setPageTable(w.pageTables, pudEntries) + } else { + pudEntries = w.pageTables.Allocator.LookupPTEs(pgdEntry.Address()) + } + + clearPUDEntries := uint16(0) + + for pudIndex := uint16((start & pudMask) >> pudShift); start < end && pudIndex < entriesPerPage; pudIndex++ { + var ( + pudEntry = &pudEntries[pudIndex] + pmdEntries *PTEs + ) + if !pudEntry.Valid() { + if !w.visitor.requiresAlloc() { + + clearPUDEntries++ + start = emptynext(start, pudSize) + continue + } + + if start&(pudSize-1) == 0 && end-start >= pudSize { + pudEntry.SetSuper() + w.visitor.visit(uintptr(start), pudEntry, pudSize-1) + if pudEntry.Valid() { + start = emptynext(start, pudSize) + continue + } + } + + pmdEntries = w.pageTables.Allocator.NewPTEs() + pudEntry.setPageTable(w.pageTables, pmdEntries) + + } else if pudEntry.IsSuper() { + + if w.visitor.requiresSplit() && (start&(pudSize-1) != 0 || end < emptynext(start, pudSize)) { + + pmdEntries = w.pageTables.Allocator.NewPTEs() + for index := uint16(0); index < entriesPerPage; index++ { + pmdEntries[index].SetSuper() + pmdEntries[index].Set( + pudEntry.Address()+(pmdSize*uintptr(index)), + pudEntry.Opts()) + } + pudEntry.setPageTable(w.pageTables, pmdEntries) + } else { + + w.visitor.visit(uintptr(start), pudEntry, pudSize-1) + + if !pudEntry.Valid() { + clearPUDEntries++ + } + + start = emptynext(start, pudSize) + continue + } + } else { + pmdEntries = w.pageTables.Allocator.LookupPTEs(pudEntry.Address()) + } + + clearPMDEntries := uint16(0) + + for pmdIndex := uint16((start & pmdMask) >> pmdShift); start < end && pmdIndex < entriesPerPage; pmdIndex++ { + var ( + pmdEntry = &pmdEntries[pmdIndex] + pteEntries *PTEs + ) + if !pmdEntry.Valid() { + if !w.visitor.requiresAlloc() { + + clearPMDEntries++ + start = emptynext(start, pmdSize) + continue + } + + if start&(pmdSize-1) == 0 && end-start >= pmdSize { + pmdEntry.SetSuper() + w.visitor.visit(uintptr(start), pmdEntry, pmdSize-1) + if pmdEntry.Valid() { + start = emptynext(start, pmdSize) + continue + } + } + + pteEntries = w.pageTables.Allocator.NewPTEs() + pmdEntry.setPageTable(w.pageTables, pteEntries) + + } else if pmdEntry.IsSuper() { + + if w.visitor.requiresSplit() && (start&(pmdSize-1) != 0 || end < emptynext(start, pmdSize)) { + + pteEntries = w.pageTables.Allocator.NewPTEs() + for index := uint16(0); index < entriesPerPage; index++ { + pteEntries[index].Set( + pmdEntry.Address()+(pteSize*uintptr(index)), + pmdEntry.Opts()) + } + pmdEntry.setPageTable(w.pageTables, pteEntries) + } else { + + w.visitor.visit(uintptr(start), pmdEntry, pmdSize-1) + + if !pmdEntry.Valid() { + clearPMDEntries++ + } + + start = emptynext(start, pmdSize) + continue + } + } else { + pteEntries = w.pageTables.Allocator.LookupPTEs(pmdEntry.Address()) + } + + clearPTEEntries := uint16(0) + + for pteIndex := uint16((start & pteMask) >> pteShift); start < end && pteIndex < entriesPerPage; pteIndex++ { + var ( + pteEntry = &pteEntries[pteIndex] + ) + if !pteEntry.Valid() && !w.visitor.requiresAlloc() { + clearPTEEntries++ + start += pteSize + continue + } + + w.visitor.visit(uintptr(start), pteEntry, pteSize-1) + if !pteEntry.Valid() { + if w.visitor.requiresAlloc() { + panic("PTE not set after iteration with requiresAlloc!") + } + clearPTEEntries++ + } + + start += pteSize + continue + } + + if clearPTEEntries == entriesPerPage { + pmdEntry.Clear() + w.pageTables.Allocator.FreePTEs(pteEntries) + clearPMDEntries++ + } + } + + if clearPMDEntries == entriesPerPage { + pudEntry.Clear() + w.pageTables.Allocator.FreePTEs(pmdEntries) + clearPUDEntries++ + } + } + + if clearPUDEntries == entriesPerPage { + pgdEntry.Clear() + w.pageTables.Allocator.FreePTEs(pudEntries) + } + } +} |