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-rw-r--r--pkg/sentry/mm/pma.go1036
1 files changed, 1036 insertions, 0 deletions
diff --git a/pkg/sentry/mm/pma.go b/pkg/sentry/mm/pma.go
new file mode 100644
index 000000000..ece561ff0
--- /dev/null
+++ b/pkg/sentry/mm/pma.go
@@ -0,0 +1,1036 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mm
+
+import (
+ "fmt"
+
+ "gvisor.googlesource.com/gvisor/pkg/sentry/context"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/platform/safecopy"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/usage"
+ "gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+ "gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// existingPMAsLocked checks that pmas exist for all addresses in ar, and
+// support access of type (at, ignorePermissions). If so, it returns an
+// iterator to the pma containing ar.Start. Otherwise it returns a terminal
+// iterator.
+//
+// Preconditions: mm.activeMu must be locked. ar.Length() != 0.
+func (mm *MemoryManager) existingPMAsLocked(ar usermem.AddrRange, at usermem.AccessType, ignorePermissions bool, needInternalMappings bool) pmaIterator {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ }
+
+ first := mm.pmas.FindSegment(ar.Start)
+ pseg := first
+ for pseg.Ok() {
+ pma := pseg.ValuePtr()
+ perms := pma.effectivePerms
+ if ignorePermissions {
+ perms = pma.maxPerms
+ }
+ if !perms.SupersetOf(at) {
+ return pmaIterator{}
+ }
+ if needInternalMappings && pma.internalMappings.IsEmpty() {
+ return pmaIterator{}
+ }
+
+ if ar.End <= pseg.End() {
+ return first
+ }
+ pseg, _ = pseg.NextNonEmpty()
+ }
+
+ // Ran out of pmas before reaching ar.End.
+ return pmaIterator{}
+}
+
+// existingVecPMAsLocked returns true if pmas exist for all addresses in ars,
+// and support access of type (at, ignorePermissions).
+//
+// Preconditions: mm.activeMu must be locked.
+func (mm *MemoryManager) existingVecPMAsLocked(ars usermem.AddrRangeSeq, at usermem.AccessType, ignorePermissions bool, needInternalMappings bool) bool {
+ for ; !ars.IsEmpty(); ars = ars.Tail() {
+ if ar := ars.Head(); ar.Length() != 0 && !mm.existingPMAsLocked(ar, at, ignorePermissions, needInternalMappings).Ok() {
+ return false
+ }
+ }
+ return true
+}
+
+// getPMAsLocked ensures that pmas exist for all addresses in ar, and support
+// access of type at. It returns:
+//
+// - An iterator to the pma containing ar.Start. If no pma contains ar.Start,
+// the iterator is unspecified.
+//
+// - An iterator to the gap after the last pma containing an address in ar. If
+// pmas exist for no addresses in ar, the iterator is to a gap that begins
+// before ar.Start.
+//
+// - An error that is non-nil if pmas exist for only a subset of ar.
+//
+// Preconditions: mm.mappingMu must be locked. mm.activeMu must be locked for
+// writing. ar.Length() != 0. vseg.Range().Contains(ar.Start). vmas must exist
+// for all addresses in ar, and support accesses of type at (i.e. permission
+// checks must have been performed against vmas).
+func (mm *MemoryManager) getPMAsLocked(ctx context.Context, vseg vmaIterator, ar usermem.AddrRange, at usermem.AccessType) (pmaIterator, pmaGapIterator, error) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ if !vseg.Ok() {
+ panic("terminal vma iterator")
+ }
+ if !vseg.Range().Contains(ar.Start) {
+ panic(fmt.Sprintf("initial vma %v does not cover start of ar %v", vseg.Range(), ar))
+ }
+ }
+
+ // Page-align ar so that all AddrRanges are aligned.
+ end, ok := ar.End.RoundUp()
+ var alignerr error
+ if !ok {
+ end = ar.End.RoundDown()
+ alignerr = syserror.EFAULT
+ }
+ ar = usermem.AddrRange{ar.Start.RoundDown(), end}
+
+ pstart, pend, perr := mm.getPMAsInternalLocked(ctx, vseg, ar, at)
+ if pend.Start() <= ar.Start {
+ return pmaIterator{}, pend, perr
+ }
+ // getPMAsInternalLocked may not have returned pstart due to iterator
+ // invalidation.
+ if !pstart.Ok() {
+ pstart = mm.findOrSeekPrevUpperBoundPMA(ar.Start, pend)
+ }
+ if perr != nil {
+ return pstart, pend, perr
+ }
+ return pstart, pend, alignerr
+}
+
+// getVecPMAsLocked ensures that pmas exist for all addresses in ars, and
+// support access of type at. It returns the subset of ars for which pmas
+// exist. If this is not equal to ars, it returns a non-nil error explaining
+// why.
+//
+// Preconditions: mm.mappingMu must be locked. mm.activeMu must be locked for
+// writing. vmas must exist for all addresses in ars, and support accesses of
+// type at (i.e. permission checks must have been performed against vmas).
+func (mm *MemoryManager) getVecPMAsLocked(ctx context.Context, ars usermem.AddrRangeSeq, at usermem.AccessType) (usermem.AddrRangeSeq, error) {
+ for arsit := ars; !arsit.IsEmpty(); arsit = arsit.Tail() {
+ ar := arsit.Head()
+ if ar.Length() == 0 {
+ continue
+ }
+ if checkInvariants {
+ if !ar.WellFormed() {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ }
+
+ // Page-align ar so that all AddrRanges are aligned.
+ end, ok := ar.End.RoundUp()
+ var alignerr error
+ if !ok {
+ end = ar.End.RoundDown()
+ alignerr = syserror.EFAULT
+ }
+ ar = usermem.AddrRange{ar.Start.RoundDown(), end}
+
+ _, pend, perr := mm.getPMAsInternalLocked(ctx, mm.vmas.FindSegment(ar.Start), ar, at)
+ if perr != nil {
+ return truncatedAddrRangeSeq(ars, arsit, pend.Start()), perr
+ }
+ if alignerr != nil {
+ return truncatedAddrRangeSeq(ars, arsit, pend.Start()), alignerr
+ }
+ }
+
+ return ars, nil
+}
+
+// getPMAsInternalLocked is equivalent to getPMAsLocked, with the following
+// exceptions:
+//
+// - getPMAsInternalLocked returns a pmaIterator on a best-effort basis (that
+// is, the returned iterator may be terminal, even if a pma that contains
+// ar.Start exists). Returning this iterator on a best-effort basis allows
+// callers that require it to use it when it's cheaply available, while also
+// avoiding the overhead of retrieving it when it's not.
+//
+// - getPMAsInternalLocked additionally requires that ar is page-aligned.
+//
+// getPMAsInternalLocked is an implementation helper for getPMAsLocked and
+// getVecPMAsLocked; other clients should call one of those instead.
+func (mm *MemoryManager) getPMAsInternalLocked(ctx context.Context, vseg vmaIterator, ar usermem.AddrRange, at usermem.AccessType) (pmaIterator, pmaGapIterator, error) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 || !ar.IsPageAligned() {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ if !vseg.Ok() {
+ panic("terminal vma iterator")
+ }
+ if !vseg.Range().Contains(ar.Start) {
+ panic(fmt.Sprintf("initial vma %v does not cover start of ar %v", vseg.Range(), ar))
+ }
+ }
+
+ mf := mm.mfp.MemoryFile()
+ // Limit the range we allocate to ar, aligned to privateAllocUnit.
+ maskAR := privateAligned(ar)
+ didUnmapAS := false
+ // The range in which we iterate vmas and pmas is still limited to ar, to
+ // ensure that we don't allocate or COW-break a pma we don't need.
+ pseg, pgap := mm.pmas.Find(ar.Start)
+ pstart := pseg
+ for {
+ // Get pmas for this vma.
+ vsegAR := vseg.Range().Intersect(ar)
+ vma := vseg.ValuePtr()
+ pmaLoop:
+ for {
+ switch {
+ case pgap.Ok() && pgap.Start() < vsegAR.End:
+ // Need a pma here.
+ optAR := vseg.Range().Intersect(pgap.Range())
+ if checkInvariants {
+ if optAR.Length() <= 0 {
+ panic(fmt.Sprintf("vseg %v and pgap %v do not overlap", vseg, pgap))
+ }
+ }
+ if vma.mappable == nil {
+ // Private anonymous mappings get pmas by allocating.
+ allocAR := optAR.Intersect(maskAR)
+ fr, err := mf.Allocate(uint64(allocAR.Length()), usage.Anonymous)
+ if err != nil {
+ return pstart, pgap, err
+ }
+ if checkInvariants {
+ if !fr.WellFormed() || fr.Length() != uint64(allocAR.Length()) {
+ panic(fmt.Sprintf("Allocate(%v) returned invalid FileRange %v", allocAR.Length(), fr))
+ }
+ }
+ mm.addRSSLocked(allocAR)
+ mm.incPrivateRef(fr)
+ mf.IncRef(fr)
+ pseg, pgap = mm.pmas.Insert(pgap, allocAR, pma{
+ file: mf,
+ off: fr.Start,
+ translatePerms: usermem.AnyAccess,
+ effectivePerms: vma.effectivePerms,
+ maxPerms: vma.maxPerms,
+ // Since we just allocated this memory and have the
+ // only reference, the new pma does not need
+ // copy-on-write.
+ private: true,
+ }).NextNonEmpty()
+ pstart = pmaIterator{} // iterators invalidated
+ } else {
+ // Other mappings get pmas by translating.
+ optMR := vseg.mappableRangeOf(optAR)
+ reqAR := optAR.Intersect(ar)
+ reqMR := vseg.mappableRangeOf(reqAR)
+ perms := at
+ if vma.private {
+ // This pma will be copy-on-write; don't require write
+ // permission, but do require read permission to
+ // facilitate the copy.
+ //
+ // If at.Write is true, we will need to break
+ // copy-on-write immediately, which occurs after
+ // translation below.
+ perms.Read = true
+ perms.Write = false
+ }
+ ts, err := vma.mappable.Translate(ctx, reqMR, optMR, perms)
+ if checkInvariants {
+ if err := memmap.CheckTranslateResult(reqMR, optMR, perms, ts, err); err != nil {
+ panic(fmt.Sprintf("Mappable(%T).Translate(%v, %v, %v): %v", vma.mappable, reqMR, optMR, perms, err))
+ }
+ }
+ // Install a pma for each translation.
+ if len(ts) == 0 {
+ return pstart, pgap, err
+ }
+ pstart = pmaIterator{} // iterators invalidated
+ for _, t := range ts {
+ newpmaAR := vseg.addrRangeOf(t.Source)
+ newpma := pma{
+ file: t.File,
+ off: t.Offset,
+ translatePerms: t.Perms,
+ effectivePerms: vma.effectivePerms.Intersect(t.Perms),
+ maxPerms: vma.maxPerms.Intersect(t.Perms),
+ }
+ if vma.private {
+ newpma.effectivePerms.Write = false
+ newpma.maxPerms.Write = false
+ newpma.needCOW = true
+ }
+ mm.addRSSLocked(newpmaAR)
+ t.File.IncRef(t.FileRange())
+ // This is valid because memmap.Mappable.Translate is
+ // required to return Translations in increasing
+ // Translation.Source order.
+ pseg = mm.pmas.Insert(pgap, newpmaAR, newpma)
+ pgap = pseg.NextGap()
+ }
+ // The error returned by Translate is only significant if
+ // it occurred before ar.End.
+ if err != nil && vseg.addrRangeOf(ts[len(ts)-1].Source).End < ar.End {
+ return pstart, pgap, err
+ }
+ // Rewind pseg to the first pma inserted and continue the
+ // loop to check if we need to break copy-on-write.
+ pseg, pgap = mm.findOrSeekPrevUpperBoundPMA(vseg.addrRangeOf(ts[0].Source).Start, pgap), pmaGapIterator{}
+ continue
+ }
+
+ case pseg.Ok() && pseg.Start() < vsegAR.End:
+ oldpma := pseg.ValuePtr()
+ if at.Write && mm.isPMACopyOnWriteLocked(vseg, pseg) {
+ // Break copy-on-write by copying.
+ if checkInvariants {
+ if !oldpma.maxPerms.Read {
+ panic(fmt.Sprintf("pma %v needs to be copied for writing, but is not readable: %v", pseg.Range(), oldpma))
+ }
+ }
+ // The majority of copy-on-write breaks on executable pages
+ // come from:
+ //
+ // - The ELF loader, which must zero out bytes on the last
+ // page of each segment after the end of the segment.
+ //
+ // - gdb's use of ptrace to insert breakpoints.
+ //
+ // Neither of these cases has enough spatial locality to
+ // benefit from copying nearby pages, so if the vma is
+ // executable, only copy the pages required.
+ var copyAR usermem.AddrRange
+ if vseg.ValuePtr().effectivePerms.Execute {
+ copyAR = pseg.Range().Intersect(ar)
+ } else {
+ copyAR = pseg.Range().Intersect(maskAR)
+ }
+ // Get internal mappings from the pma to copy from.
+ if err := pseg.getInternalMappingsLocked(); err != nil {
+ return pstart, pseg.PrevGap(), err
+ }
+ // Copy contents.
+ fr, err := mf.AllocateAndFill(uint64(copyAR.Length()), usage.Anonymous, &safemem.BlockSeqReader{mm.internalMappingsLocked(pseg, copyAR)})
+ if _, ok := err.(safecopy.BusError); ok {
+ // If we got SIGBUS during the copy, deliver SIGBUS to
+ // userspace (instead of SIGSEGV) if we're breaking
+ // copy-on-write due to application page fault.
+ err = &memmap.BusError{err}
+ }
+ if fr.Length() == 0 {
+ return pstart, pseg.PrevGap(), err
+ }
+ // Unmap all of maskAR, not just copyAR, to minimize host
+ // syscalls. AddressSpace mappings must be removed before
+ // mm.decPrivateRef().
+ if !didUnmapAS {
+ mm.unmapASLocked(maskAR)
+ didUnmapAS = true
+ }
+ // Replace the pma with a copy in the part of the address
+ // range where copying was successful. This doesn't change
+ // RSS.
+ copyAR.End = copyAR.Start + usermem.Addr(fr.Length())
+ if copyAR != pseg.Range() {
+ pseg = mm.pmas.Isolate(pseg, copyAR)
+ pstart = pmaIterator{} // iterators invalidated
+ }
+ oldpma = pseg.ValuePtr()
+ if oldpma.private {
+ mm.decPrivateRef(pseg.fileRange())
+ }
+ oldpma.file.DecRef(pseg.fileRange())
+ mm.incPrivateRef(fr)
+ mf.IncRef(fr)
+ oldpma.file = mf
+ oldpma.off = fr.Start
+ oldpma.translatePerms = usermem.AnyAccess
+ oldpma.effectivePerms = vma.effectivePerms
+ oldpma.maxPerms = vma.maxPerms
+ oldpma.needCOW = false
+ oldpma.private = true
+ oldpma.internalMappings = safemem.BlockSeq{}
+ // Try to merge the pma with its neighbors.
+ if prev := pseg.PrevSegment(); prev.Ok() {
+ if merged := mm.pmas.Merge(prev, pseg); merged.Ok() {
+ pseg = merged
+ pstart = pmaIterator{} // iterators invalidated
+ }
+ }
+ if next := pseg.NextSegment(); next.Ok() {
+ if merged := mm.pmas.Merge(pseg, next); merged.Ok() {
+ pseg = merged
+ pstart = pmaIterator{} // iterators invalidated
+ }
+ }
+ // The error returned by AllocateAndFill is only
+ // significant if it occurred before ar.End.
+ if err != nil && pseg.End() < ar.End {
+ return pstart, pseg.NextGap(), err
+ }
+ // Ensure pseg and pgap are correct for the next iteration
+ // of the loop.
+ pseg, pgap = pseg.NextNonEmpty()
+ } else if !oldpma.translatePerms.SupersetOf(at) {
+ // Get new pmas (with sufficient permissions) by calling
+ // memmap.Mappable.Translate again.
+ if checkInvariants {
+ if oldpma.private {
+ panic(fmt.Sprintf("private pma %v has non-maximal pma.translatePerms: %v", pseg.Range(), oldpma))
+ }
+ }
+ // Allow the entire pma to be replaced.
+ optAR := pseg.Range()
+ optMR := vseg.mappableRangeOf(optAR)
+ reqAR := optAR.Intersect(ar)
+ reqMR := vseg.mappableRangeOf(reqAR)
+ perms := oldpma.translatePerms.Union(at)
+ ts, err := vma.mappable.Translate(ctx, reqMR, optMR, perms)
+ if checkInvariants {
+ if err := memmap.CheckTranslateResult(reqMR, optMR, perms, ts, err); err != nil {
+ panic(fmt.Sprintf("Mappable(%T).Translate(%v, %v, %v): %v", vma.mappable, reqMR, optMR, perms, err))
+ }
+ }
+ // Remove the part of the existing pma covered by new
+ // Translations, then insert new pmas. This doesn't change
+ // RSS. Note that we don't need to call unmapASLocked: any
+ // existing AddressSpace mappings are still valid (though
+ // less permissive than the new pmas indicate) until
+ // Invalidate is called, and will be replaced by future
+ // calls to mapASLocked.
+ if len(ts) == 0 {
+ return pstart, pseg.PrevGap(), err
+ }
+ transMR := memmap.MappableRange{ts[0].Source.Start, ts[len(ts)-1].Source.End}
+ transAR := vseg.addrRangeOf(transMR)
+ pseg = mm.pmas.Isolate(pseg, transAR)
+ pseg.ValuePtr().file.DecRef(pseg.fileRange())
+ pgap = mm.pmas.Remove(pseg)
+ pstart = pmaIterator{} // iterators invalidated
+ for _, t := range ts {
+ newpmaAR := vseg.addrRangeOf(t.Source)
+ newpma := pma{
+ file: t.File,
+ off: t.Offset,
+ translatePerms: t.Perms,
+ effectivePerms: vma.effectivePerms.Intersect(t.Perms),
+ maxPerms: vma.maxPerms.Intersect(t.Perms),
+ }
+ if vma.private {
+ newpma.effectivePerms.Write = false
+ newpma.maxPerms.Write = false
+ newpma.needCOW = true
+ }
+ t.File.IncRef(t.FileRange())
+ pseg = mm.pmas.Insert(pgap, newpmaAR, newpma)
+ pgap = pseg.NextGap()
+ }
+ // The error returned by Translate is only significant if
+ // it occurred before ar.End.
+ if err != nil && pseg.End() < ar.End {
+ return pstart, pgap, err
+ }
+ // Ensure pseg and pgap are correct for the next iteration
+ // of the loop.
+ if pgap.Range().Length() == 0 {
+ pseg, pgap = pgap.NextSegment(), pmaGapIterator{}
+ } else {
+ pseg = pmaIterator{}
+ }
+ } else {
+ // We have a usable pma; continue.
+ pseg, pgap = pseg.NextNonEmpty()
+ }
+
+ default:
+ break pmaLoop
+ }
+ }
+ // Go to the next vma.
+ if ar.End <= vseg.End() {
+ if pgap.Ok() {
+ return pstart, pgap, nil
+ }
+ return pstart, pseg.PrevGap(), nil
+ }
+ vseg = vseg.NextSegment()
+ }
+}
+
+const (
+ // When memory is allocated for a private pma, align the allocated address
+ // range to a privateAllocUnit boundary when possible. Larger values of
+ // privateAllocUnit may reduce page faults by allowing fewer, larger pmas
+ // to be mapped, but may result in larger amounts of wasted memory in the
+ // presence of fragmentation. privateAllocUnit must be a power-of-2
+ // multiple of usermem.PageSize.
+ privateAllocUnit = usermem.HugePageSize
+
+ privateAllocMask = privateAllocUnit - 1
+)
+
+func privateAligned(ar usermem.AddrRange) usermem.AddrRange {
+ aligned := usermem.AddrRange{ar.Start &^ privateAllocMask, ar.End}
+ if end := (ar.End + privateAllocMask) &^ privateAllocMask; end >= ar.End {
+ aligned.End = end
+ }
+ if checkInvariants {
+ if !aligned.IsSupersetOf(ar) {
+ panic(fmt.Sprintf("aligned AddrRange %#v is not a superset of ar %#v", aligned, ar))
+ }
+ }
+ return aligned
+}
+
+// isPMACopyOnWriteLocked returns true if the contents of the pma represented
+// by pseg must be copied to a new private pma to be written to.
+//
+// If the pma is a copy-on-write private pma, and holds the only reference on
+// the memory it maps, isPMACopyOnWriteLocked will take ownership of the memory
+// and update the pma to indicate that it does not require copy-on-write.
+//
+// Preconditions: vseg.Range().IsSupersetOf(pseg.Range()). mm.mappingMu must be
+// locked. mm.activeMu must be locked for writing.
+func (mm *MemoryManager) isPMACopyOnWriteLocked(vseg vmaIterator, pseg pmaIterator) bool {
+ pma := pseg.ValuePtr()
+ if !pma.needCOW {
+ return false
+ }
+ if !pma.private {
+ return true
+ }
+ // If we have the only reference on private memory to be copied, just take
+ // ownership of it instead of copying. If we do hold the only reference,
+ // additional references can only be taken by mm.Fork(), which is excluded
+ // by mm.activeMu, so this isn't racy.
+ mm.privateRefs.mu.Lock()
+ defer mm.privateRefs.mu.Unlock()
+ fr := pseg.fileRange()
+ // This check relies on mm.privateRefs.refs being kept fully merged.
+ rseg := mm.privateRefs.refs.FindSegment(fr.Start)
+ if rseg.Ok() && rseg.Value() == 1 && fr.End <= rseg.End() {
+ pma.needCOW = false
+ // pma.private => pma.translatePerms == usermem.AnyAccess
+ vma := vseg.ValuePtr()
+ pma.effectivePerms = vma.effectivePerms
+ pma.maxPerms = vma.maxPerms
+ return false
+ }
+ return true
+}
+
+// Invalidate implements memmap.MappingSpace.Invalidate.
+func (mm *MemoryManager) Invalidate(ar usermem.AddrRange, opts memmap.InvalidateOpts) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 || !ar.IsPageAligned() {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ }
+
+ mm.activeMu.Lock()
+ defer mm.activeMu.Unlock()
+ if mm.captureInvalidations {
+ mm.capturedInvalidations = append(mm.capturedInvalidations, invalidateArgs{ar, opts})
+ return
+ }
+ mm.invalidateLocked(ar, opts.InvalidatePrivate, true)
+}
+
+// invalidateLocked removes pmas and AddressSpace mappings of those pmas for
+// addresses in ar.
+//
+// Preconditions: mm.activeMu must be locked for writing. ar.Length() != 0. ar
+// must be page-aligned.
+func (mm *MemoryManager) invalidateLocked(ar usermem.AddrRange, invalidatePrivate, invalidateShared bool) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 || !ar.IsPageAligned() {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ }
+
+ var didUnmapAS bool
+ pseg := mm.pmas.LowerBoundSegment(ar.Start)
+ for pseg.Ok() && pseg.Start() < ar.End {
+ pma := pseg.ValuePtr()
+ if (invalidatePrivate && pma.private) || (invalidateShared && !pma.private) {
+ pseg = mm.pmas.Isolate(pseg, ar)
+ pma = pseg.ValuePtr()
+ if !didUnmapAS {
+ // Unmap all of ar, not just pseg.Range(), to minimize host
+ // syscalls. AddressSpace mappings must be removed before
+ // mm.decPrivateRef().
+ mm.unmapASLocked(ar)
+ didUnmapAS = true
+ }
+ if pma.private {
+ mm.decPrivateRef(pseg.fileRange())
+ }
+ mm.removeRSSLocked(pseg.Range())
+ pma.file.DecRef(pseg.fileRange())
+ pseg = mm.pmas.Remove(pseg).NextSegment()
+ } else {
+ pseg = pseg.NextSegment()
+ }
+ }
+}
+
+// Pin returns the platform.File ranges currently mapped by addresses in ar in
+// mm, acquiring a reference on the returned ranges which the caller must
+// release by calling Unpin. If not all addresses are mapped, Pin returns a
+// non-nil error. Note that Pin may return both a non-empty slice of
+// PinnedRanges and a non-nil error.
+//
+// Pin does not prevent mapped ranges from changing, making it unsuitable for
+// most I/O. It should only be used in contexts that would use get_user_pages()
+// in the Linux kernel.
+//
+// Preconditions: ar.Length() != 0. ar must be page-aligned.
+func (mm *MemoryManager) Pin(ctx context.Context, ar usermem.AddrRange, at usermem.AccessType, ignorePermissions bool) ([]PinnedRange, error) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 || !ar.IsPageAligned() {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ }
+
+ // Ensure that we have usable vmas.
+ mm.mappingMu.RLock()
+ vseg, vend, verr := mm.getVMAsLocked(ctx, ar, at, ignorePermissions)
+ if vendaddr := vend.Start(); vendaddr < ar.End {
+ if vendaddr <= ar.Start {
+ mm.mappingMu.RUnlock()
+ return nil, verr
+ }
+ ar.End = vendaddr
+ }
+
+ // Ensure that we have usable pmas.
+ mm.activeMu.Lock()
+ pseg, pend, perr := mm.getPMAsLocked(ctx, vseg, ar, at)
+ mm.mappingMu.RUnlock()
+ if pendaddr := pend.Start(); pendaddr < ar.End {
+ if pendaddr <= ar.Start {
+ mm.activeMu.Unlock()
+ return nil, perr
+ }
+ ar.End = pendaddr
+ }
+
+ // Gather pmas.
+ var prs []PinnedRange
+ for pseg.Ok() && pseg.Start() < ar.End {
+ psar := pseg.Range().Intersect(ar)
+ f := pseg.ValuePtr().file
+ fr := pseg.fileRangeOf(psar)
+ f.IncRef(fr)
+ prs = append(prs, PinnedRange{
+ Source: psar,
+ File: f,
+ Offset: fr.Start,
+ })
+ pseg = pseg.NextSegment()
+ }
+ mm.activeMu.Unlock()
+
+ // Return the first error in order of progress through ar.
+ if perr != nil {
+ return prs, perr
+ }
+ return prs, verr
+}
+
+// PinnedRanges are returned by MemoryManager.Pin.
+type PinnedRange struct {
+ // Source is the corresponding range of addresses.
+ Source usermem.AddrRange
+
+ // File is the mapped file.
+ File platform.File
+
+ // Offset is the offset into File at which this PinnedRange begins.
+ Offset uint64
+}
+
+// FileRange returns the platform.File offsets mapped by pr.
+func (pr PinnedRange) FileRange() platform.FileRange {
+ return platform.FileRange{pr.Offset, pr.Offset + uint64(pr.Source.Length())}
+}
+
+// Unpin releases the reference held by prs.
+func Unpin(prs []PinnedRange) {
+ for i := range prs {
+ prs[i].File.DecRef(prs[i].FileRange())
+ }
+}
+
+// movePMAsLocked moves all pmas in oldAR to newAR.
+//
+// Preconditions: mm.activeMu must be locked for writing. oldAR.Length() != 0.
+// oldAR.Length() <= newAR.Length(). !oldAR.Overlaps(newAR).
+// mm.pmas.IsEmptyRange(newAR). oldAR and newAR must be page-aligned.
+func (mm *MemoryManager) movePMAsLocked(oldAR, newAR usermem.AddrRange) {
+ if checkInvariants {
+ if !oldAR.WellFormed() || oldAR.Length() <= 0 || !oldAR.IsPageAligned() {
+ panic(fmt.Sprintf("invalid oldAR: %v", oldAR))
+ }
+ if !newAR.WellFormed() || newAR.Length() <= 0 || !newAR.IsPageAligned() {
+ panic(fmt.Sprintf("invalid newAR: %v", newAR))
+ }
+ if oldAR.Length() > newAR.Length() {
+ panic(fmt.Sprintf("old address range %v may contain pmas that will not fit in new address range %v", oldAR, newAR))
+ }
+ if oldAR.Overlaps(newAR) {
+ panic(fmt.Sprintf("old and new address ranges overlap: %v, %v", oldAR, newAR))
+ }
+ // mm.pmas.IsEmptyRange is checked by mm.pmas.Insert.
+ }
+
+ type movedPMA struct {
+ oldAR usermem.AddrRange
+ pma pma
+ }
+ var movedPMAs []movedPMA
+ pseg := mm.pmas.LowerBoundSegment(oldAR.Start)
+ for pseg.Ok() && pseg.Start() < oldAR.End {
+ pseg = mm.pmas.Isolate(pseg, oldAR)
+ movedPMAs = append(movedPMAs, movedPMA{
+ oldAR: pseg.Range(),
+ pma: pseg.Value(),
+ })
+ pseg = mm.pmas.Remove(pseg).NextSegment()
+ // No RSS change is needed since we're re-inserting the same pmas
+ // below.
+ }
+
+ off := newAR.Start - oldAR.Start
+ pgap := mm.pmas.FindGap(newAR.Start)
+ for i := range movedPMAs {
+ mpma := &movedPMAs[i]
+ pmaNewAR := usermem.AddrRange{mpma.oldAR.Start + off, mpma.oldAR.End + off}
+ pgap = mm.pmas.Insert(pgap, pmaNewAR, mpma.pma).NextGap()
+ }
+
+ mm.unmapASLocked(oldAR)
+}
+
+// getPMAInternalMappingsLocked ensures that pmas for all addresses in ar have
+// cached internal mappings. It returns:
+//
+// - An iterator to the gap after the last pma with internal mappings
+// containing an address in ar. If internal mappings exist for no addresses in
+// ar, the iterator is to a gap that begins before ar.Start.
+//
+// - An error that is non-nil if internal mappings exist for only a subset of
+// ar.
+//
+// Preconditions: mm.activeMu must be locked for writing.
+// pseg.Range().Contains(ar.Start). pmas must exist for all addresses in ar.
+// ar.Length() != 0.
+//
+// Postconditions: getPMAInternalMappingsLocked does not invalidate iterators
+// into mm.pmas.
+func (mm *MemoryManager) getPMAInternalMappingsLocked(pseg pmaIterator, ar usermem.AddrRange) (pmaGapIterator, error) {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ if !pseg.Range().Contains(ar.Start) {
+ panic(fmt.Sprintf("initial pma %v does not cover start of ar %v", pseg.Range(), ar))
+ }
+ }
+
+ for {
+ if err := pseg.getInternalMappingsLocked(); err != nil {
+ return pseg.PrevGap(), err
+ }
+ if ar.End <= pseg.End() {
+ return pseg.NextGap(), nil
+ }
+ pseg, _ = pseg.NextNonEmpty()
+ }
+}
+
+// getVecPMAInternalMappingsLocked ensures that pmas for all addresses in ars
+// have cached internal mappings. It returns the subset of ars for which
+// internal mappings exist. If this is not equal to ars, it returns a non-nil
+// error explaining why.
+//
+// Preconditions: mm.activeMu must be locked for writing. pmas must exist for
+// all addresses in ar.
+//
+// Postconditions: getVecPMAInternalMappingsLocked does not invalidate iterators
+// into mm.pmas.
+func (mm *MemoryManager) getVecPMAInternalMappingsLocked(ars usermem.AddrRangeSeq) (usermem.AddrRangeSeq, error) {
+ for arsit := ars; !arsit.IsEmpty(); arsit = arsit.Tail() {
+ ar := arsit.Head()
+ if ar.Length() == 0 {
+ continue
+ }
+ if pend, err := mm.getPMAInternalMappingsLocked(mm.pmas.FindSegment(ar.Start), ar); err != nil {
+ return truncatedAddrRangeSeq(ars, arsit, pend.Start()), err
+ }
+ }
+ return ars, nil
+}
+
+// internalMappingsLocked returns internal mappings for addresses in ar.
+//
+// Preconditions: mm.activeMu must be locked. Internal mappings must have been
+// previously established for all addresses in ar. ar.Length() != 0.
+// pseg.Range().Contains(ar.Start).
+func (mm *MemoryManager) internalMappingsLocked(pseg pmaIterator, ar usermem.AddrRange) safemem.BlockSeq {
+ if checkInvariants {
+ if !ar.WellFormed() || ar.Length() <= 0 {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ if !pseg.Range().Contains(ar.Start) {
+ panic(fmt.Sprintf("initial pma %v does not cover start of ar %v", pseg.Range(), ar))
+ }
+ }
+
+ if ar.End <= pseg.End() {
+ // Since only one pma is involved, we can use pma.internalMappings
+ // directly, avoiding a slice allocation.
+ offset := uint64(ar.Start - pseg.Start())
+ return pseg.ValuePtr().internalMappings.DropFirst64(offset).TakeFirst64(uint64(ar.Length()))
+ }
+
+ var ims []safemem.Block
+ for {
+ pr := pseg.Range().Intersect(ar)
+ for pims := pseg.ValuePtr().internalMappings.DropFirst64(uint64(pr.Start - pseg.Start())).TakeFirst64(uint64(pr.Length())); !pims.IsEmpty(); pims = pims.Tail() {
+ ims = append(ims, pims.Head())
+ }
+ if ar.End <= pseg.End() {
+ break
+ }
+ pseg = pseg.NextSegment()
+ }
+ return safemem.BlockSeqFromSlice(ims)
+}
+
+// vecInternalMappingsLocked returns internal mappings for addresses in ars.
+//
+// Preconditions: mm.activeMu must be locked. Internal mappings must have been
+// previously established for all addresses in ars.
+func (mm *MemoryManager) vecInternalMappingsLocked(ars usermem.AddrRangeSeq) safemem.BlockSeq {
+ var ims []safemem.Block
+ for ; !ars.IsEmpty(); ars = ars.Tail() {
+ ar := ars.Head()
+ if ar.Length() == 0 {
+ continue
+ }
+ for pims := mm.internalMappingsLocked(mm.pmas.FindSegment(ar.Start), ar); !pims.IsEmpty(); pims = pims.Tail() {
+ ims = append(ims, pims.Head())
+ }
+ }
+ return safemem.BlockSeqFromSlice(ims)
+}
+
+// incPrivateRef acquires a reference on private pages in fr.
+func (mm *MemoryManager) incPrivateRef(fr platform.FileRange) {
+ mm.privateRefs.mu.Lock()
+ defer mm.privateRefs.mu.Unlock()
+ refSet := &mm.privateRefs.refs
+ seg, gap := refSet.Find(fr.Start)
+ for {
+ switch {
+ case seg.Ok() && seg.Start() < fr.End:
+ seg = refSet.Isolate(seg, fr)
+ seg.SetValue(seg.Value() + 1)
+ seg, gap = seg.NextNonEmpty()
+ case gap.Ok() && gap.Start() < fr.End:
+ seg, gap = refSet.InsertWithoutMerging(gap, gap.Range().Intersect(fr), 1).NextNonEmpty()
+ default:
+ refSet.MergeAdjacent(fr)
+ return
+ }
+ }
+}
+
+// decPrivateRef releases a reference on private pages in fr.
+func (mm *MemoryManager) decPrivateRef(fr platform.FileRange) {
+ var freed []platform.FileRange
+
+ mm.privateRefs.mu.Lock()
+ refSet := &mm.privateRefs.refs
+ seg := refSet.LowerBoundSegment(fr.Start)
+ for seg.Ok() && seg.Start() < fr.End {
+ seg = refSet.Isolate(seg, fr)
+ if old := seg.Value(); old == 1 {
+ freed = append(freed, seg.Range())
+ seg = refSet.Remove(seg).NextSegment()
+ } else {
+ seg.SetValue(old - 1)
+ seg = seg.NextSegment()
+ }
+ }
+ refSet.MergeAdjacent(fr)
+ mm.privateRefs.mu.Unlock()
+
+ mf := mm.mfp.MemoryFile()
+ for _, fr := range freed {
+ mf.DecRef(fr)
+ }
+}
+
+// addRSSLocked updates the current and maximum resident set size of a
+// MemoryManager to reflect the insertion of a pma at ar.
+//
+// Preconditions: mm.activeMu must be locked for writing.
+func (mm *MemoryManager) addRSSLocked(ar usermem.AddrRange) {
+ mm.curRSS += uint64(ar.Length())
+ if mm.curRSS > mm.maxRSS {
+ mm.maxRSS = mm.curRSS
+ }
+}
+
+// removeRSSLocked updates the current resident set size of a MemoryManager to
+// reflect the removal of a pma at ar.
+//
+// Preconditions: mm.activeMu must be locked for writing.
+func (mm *MemoryManager) removeRSSLocked(ar usermem.AddrRange) {
+ mm.curRSS -= uint64(ar.Length())
+}
+
+// pmaSetFunctions implements segment.Functions for pmaSet.
+type pmaSetFunctions struct{}
+
+func (pmaSetFunctions) MinKey() usermem.Addr {
+ return 0
+}
+
+func (pmaSetFunctions) MaxKey() usermem.Addr {
+ return ^usermem.Addr(0)
+}
+
+func (pmaSetFunctions) ClearValue(pma *pma) {
+ pma.file = nil
+ pma.internalMappings = safemem.BlockSeq{}
+}
+
+func (pmaSetFunctions) Merge(ar1 usermem.AddrRange, pma1 pma, ar2 usermem.AddrRange, pma2 pma) (pma, bool) {
+ if pma1.file != pma2.file ||
+ pma1.off+uint64(ar1.Length()) != pma2.off ||
+ pma1.translatePerms != pma2.translatePerms ||
+ pma1.effectivePerms != pma2.effectivePerms ||
+ pma1.maxPerms != pma2.maxPerms ||
+ pma1.needCOW != pma2.needCOW ||
+ pma1.private != pma2.private {
+ return pma{}, false
+ }
+
+ // Discard internal mappings instead of trying to merge them, since merging
+ // them requires an allocation and getting them again from the
+ // platform.File might not.
+ pma1.internalMappings = safemem.BlockSeq{}
+ return pma1, true
+}
+
+func (pmaSetFunctions) Split(ar usermem.AddrRange, p pma, split usermem.Addr) (pma, pma) {
+ newlen1 := uint64(split - ar.Start)
+ p2 := p
+ p2.off += newlen1
+ if !p.internalMappings.IsEmpty() {
+ p.internalMappings = p.internalMappings.TakeFirst64(newlen1)
+ p2.internalMappings = p2.internalMappings.DropFirst64(newlen1)
+ }
+ return p, p2
+}
+
+// findOrSeekPrevUpperBoundPMA returns mm.pmas.UpperBoundSegment(addr), but may do
+// so by scanning linearly backward from pgap.
+//
+// Preconditions: mm.activeMu must be locked. addr <= pgap.Start().
+func (mm *MemoryManager) findOrSeekPrevUpperBoundPMA(addr usermem.Addr, pgap pmaGapIterator) pmaIterator {
+ if checkInvariants {
+ if !pgap.Ok() {
+ panic("terminal pma iterator")
+ }
+ if addr > pgap.Start() {
+ panic(fmt.Sprintf("can't seek backward to %#x from %#x", addr, pgap.Start()))
+ }
+ }
+ // Optimistically check if pgap.PrevSegment() is the PMA we're looking for,
+ // which is the case if findOrSeekPrevUpperBoundPMA is called to find the
+ // start of a range containing only a single PMA.
+ if pseg := pgap.PrevSegment(); pseg.Start() <= addr {
+ return pseg
+ }
+ return mm.pmas.UpperBoundSegment(addr)
+}
+
+// getInternalMappingsLocked ensures that pseg.ValuePtr().internalMappings is
+// non-empty.
+//
+// Preconditions: mm.activeMu must be locked for writing.
+func (pseg pmaIterator) getInternalMappingsLocked() error {
+ pma := pseg.ValuePtr()
+ if pma.internalMappings.IsEmpty() {
+ // This must use maxPerms (instead of perms) because some permission
+ // constraints are only visible to vmas; for example, mappings of
+ // read-only files have vma.maxPerms.Write unset, but this may not be
+ // visible to the memmap.Mappable.
+ perms := pma.maxPerms
+ // We will never execute application code through an internal mapping.
+ perms.Execute = false
+ ims, err := pma.file.MapInternal(pseg.fileRange(), perms)
+ if err != nil {
+ return err
+ }
+ pma.internalMappings = ims
+ }
+ return nil
+}
+
+func (pseg pmaIterator) fileRange() platform.FileRange {
+ return pseg.fileRangeOf(pseg.Range())
+}
+
+// Preconditions: pseg.Range().IsSupersetOf(ar). ar.Length != 0.
+func (pseg pmaIterator) fileRangeOf(ar usermem.AddrRange) platform.FileRange {
+ if checkInvariants {
+ if !pseg.Ok() {
+ panic("terminal pma iterator")
+ }
+ if !ar.WellFormed() || ar.Length() <= 0 {
+ panic(fmt.Sprintf("invalid ar: %v", ar))
+ }
+ if !pseg.Range().IsSupersetOf(ar) {
+ panic(fmt.Sprintf("ar %v out of bounds %v", ar, pseg.Range()))
+ }
+ }
+
+ pma := pseg.ValuePtr()
+ pstart := pseg.Start()
+ return platform.FileRange{pma.off + uint64(ar.Start-pstart), pma.off + uint64(ar.End-pstart)}
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 19:45:46 +0000