Move platform.File in memmap

The subsequent systrap changes will need to import memmap from
the platform package.

PiperOrigin-RevId: 323409486

29 files changed, 205 insertions, 223 deletions

diff --git a/pkg/sentry/fs/fsutil/BUILD b/pkg/sentry/fs/fsutil/BUILD
index 789369220..5fb419bcd 100644
--- a/pkg/sentry/fs/fsutil/BUILD
+++ b/pkg/sentry/fs/fsutil/BUILD
@@ -8,7 +8,6 @@ go_template_instance(
     out = "dirty_set_impl.go",
     imports = {
         "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
     },
     package = "fsutil",
     prefix = "Dirty",
@@ -25,14 +24,14 @@ go_template_instance(
     name = "frame_ref_set_impl",
     out = "frame_ref_set_impl.go",
     imports = {
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
+        "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
     },
     package = "fsutil",
     prefix = "FrameRef",
     template = "//pkg/segment:generic_set",
     types = {
         "Key": "uint64",
-        "Range": "platform.FileRange",
+        "Range": "memmap.FileRange",
         "Value": "uint64",
         "Functions": "FrameRefSetFunctions",
     },
@@ -43,7 +42,6 @@ go_template_instance(
     out = "file_range_set_impl.go",
     imports = {
         "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
     },
     package = "fsutil",
     prefix = "FileRange",
@@ -86,7 +84,6 @@ go_library(
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
-        "//pkg/sentry/platform",
         "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/state",
diff --git a/pkg/sentry/fs/fsutil/dirty_set.go b/pkg/sentry/fs/fsutil/dirty_set.go
index c6cd45087..2c9446c1d 100644
--- a/pkg/sentry/fs/fsutil/dirty_set.go
+++ b/pkg/sentry/fs/fsutil/dirty_set.go
@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -159,7 +158,7 @@ func (ds *DirtySet) AllowClean(mr memmap.MappableRange) {
 // repeatedly until all bytes have been written. max is the true size of the
 // cached object; offsets beyond max will not be passed to writeAt, even if
 // they are marked dirty.
-func SyncDirty(ctx context.Context, mr memmap.MappableRange, cache *FileRangeSet, dirty *DirtySet, max uint64, mem platform.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
+func SyncDirty(ctx context.Context, mr memmap.MappableRange, cache *FileRangeSet, dirty *DirtySet, max uint64, mem memmap.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
 	var changedDirty bool
 	defer func() {
 		if changedDirty {
@@ -194,7 +193,7 @@ func SyncDirty(ctx context.Context, mr memmap.MappableRange, cache *FileRangeSet
 // successful partial write, SyncDirtyAll will call it repeatedly until all
 // bytes have been written. max is the true size of the cached object; offsets
 // beyond max will not be passed to writeAt, even if they are marked dirty.
-func SyncDirtyAll(ctx context.Context, cache *FileRangeSet, dirty *DirtySet, max uint64, mem platform.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
+func SyncDirtyAll(ctx context.Context, cache *FileRangeSet, dirty *DirtySet, max uint64, mem memmap.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
 	dseg := dirty.FirstSegment()
 	for dseg.Ok() {
 		if err := syncDirtyRange(ctx, dseg.Range(), cache, max, mem, writeAt); err != nil {
@@ -210,7 +209,7 @@ func SyncDirtyAll(ctx context.Context, cache *FileRangeSet, dirty *DirtySet, max
 }
 
 // Preconditions: mr must be page-aligned.
-func syncDirtyRange(ctx context.Context, mr memmap.MappableRange, cache *FileRangeSet, max uint64, mem platform.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
+func syncDirtyRange(ctx context.Context, mr memmap.MappableRange, cache *FileRangeSet, max uint64, mem memmap.File, writeAt func(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)) error {
 	for cseg := cache.LowerBoundSegment(mr.Start); cseg.Ok() && cseg.Start() < mr.End; cseg = cseg.NextSegment() {
 		wbr := cseg.Range().Intersect(mr)
 		if max < wbr.Start {
diff --git a/pkg/sentry/fs/fsutil/file_range_set.go b/pkg/sentry/fs/fsutil/file_range_set.go
index 5643cdac9..bbafebf03 100644
--- a/pkg/sentry/fs/fsutil/file_range_set.go
+++ b/pkg/sentry/fs/fsutil/file_range_set.go
@@ -23,13 +23,12 @@ import (
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // FileRangeSet maps offsets into a memmap.Mappable to offsets into a
-// platform.File. It is used to implement Mappables that store data in
+// memmap.File. It is used to implement Mappables that store data in
 // sparsely-allocated memory.
 //
 // type FileRangeSet <generated by go_generics>
@@ -65,20 +64,20 @@ func (FileRangeSetFunctions) Split(mr memmap.MappableRange, frstart uint64, spli
 }
 
 // FileRange returns the FileRange mapped by seg.
-func (seg FileRangeIterator) FileRange() platform.FileRange {
+func (seg FileRangeIterator) FileRange() memmap.FileRange {
 	return seg.FileRangeOf(seg.Range())
 }
 
 // FileRangeOf returns the FileRange mapped by mr.
 //
 // Preconditions: seg.Range().IsSupersetOf(mr). mr.Length() != 0.
-func (seg FileRangeIterator) FileRangeOf(mr memmap.MappableRange) platform.FileRange {
+func (seg FileRangeIterator) FileRangeOf(mr memmap.MappableRange) memmap.FileRange {
 	frstart := seg.Value() + (mr.Start - seg.Start())
-	return platform.FileRange{frstart, frstart + mr.Length()}
+	return memmap.FileRange{frstart, frstart + mr.Length()}
 }
 
 // Fill attempts to ensure that all memmap.Mappable offsets in required are
-// mapped to a platform.File offset, by allocating from mf with the given
+// mapped to a memmap.File offset, by allocating from mf with the given
 // memory usage kind and invoking readAt to store data into memory. (If readAt
 // returns a successful partial read, Fill will call it repeatedly until all
 // bytes have been read.) EOF is handled consistently with the requirements of
@@ -141,7 +140,7 @@ func (frs *FileRangeSet) Fill(ctx context.Context, required, optional memmap.Map
 }
 
 // Drop removes segments for memmap.Mappable offsets in mr, freeing the
-// corresponding platform.FileRanges.
+// corresponding memmap.FileRanges.
 //
 // Preconditions: mr must be page-aligned.
 func (frs *FileRangeSet) Drop(mr memmap.MappableRange, mf *pgalloc.MemoryFile) {
@@ -154,7 +153,7 @@ func (frs *FileRangeSet) Drop(mr memmap.MappableRange, mf *pgalloc.MemoryFile) {
 }
 
 // DropAll removes all segments in mr, freeing the corresponding
-// platform.FileRanges.
+// memmap.FileRanges.
 func (frs *FileRangeSet) DropAll(mf *pgalloc.MemoryFile) {
 	for seg := frs.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
 		mf.DecRef(seg.FileRange())
diff --git a/pkg/sentry/fs/fsutil/frame_ref_set.go b/pkg/sentry/fs/fsutil/frame_ref_set.go
index dd6f5aba6..a808894df 100644
--- a/pkg/sentry/fs/fsutil/frame_ref_set.go
+++ b/pkg/sentry/fs/fsutil/frame_ref_set.go
@@ -17,7 +17,7 @@ package fsutil
 import (
 	"math"
 
-	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 )
 
@@ -39,7 +39,7 @@ func (FrameRefSetFunctions) ClearValue(val *uint64) {
 }
 
 // Merge implements segment.Functions.Merge.
-func (FrameRefSetFunctions) Merge(_ platform.FileRange, val1 uint64, _ platform.FileRange, val2 uint64) (uint64, bool) {
+func (FrameRefSetFunctions) Merge(_ memmap.FileRange, val1 uint64, _ memmap.FileRange, val2 uint64) (uint64, bool) {
 	if val1 != val2 {
 		return 0, false
 	}
@@ -47,13 +47,13 @@ func (FrameRefSetFunctions) Merge(_ platform.FileRange, val1 uint64, _ platform.
 }
 
 // Split implements segment.Functions.Split.
-func (FrameRefSetFunctions) Split(_ platform.FileRange, val uint64, _ uint64) (uint64, uint64) {
+func (FrameRefSetFunctions) Split(_ memmap.FileRange, val uint64, _ uint64) (uint64, uint64) {
 	return val, val
 }
 
 // IncRefAndAccount adds a reference on the range fr. All newly inserted segments
 // are accounted as host page cache memory mappings.
-func (refs *FrameRefSet) IncRefAndAccount(fr platform.FileRange) {
+func (refs *FrameRefSet) IncRefAndAccount(fr memmap.FileRange) {
 	seg, gap := refs.Find(fr.Start)
 	for {
 		switch {
@@ -74,7 +74,7 @@ func (refs *FrameRefSet) IncRefAndAccount(fr platform.FileRange) {
 
 // DecRefAndAccount removes a reference on the range fr and untracks segments
 // that are removed from memory accounting.
-func (refs *FrameRefSet) DecRefAndAccount(fr platform.FileRange) {
+func (refs *FrameRefSet) DecRefAndAccount(fr memmap.FileRange) {
 	seg := refs.FindSegment(fr.Start)
 
 	for seg.Ok() && seg.Start() < fr.End {
diff --git a/pkg/sentry/fs/fsutil/host_file_mapper.go b/pkg/sentry/fs/fsutil/host_file_mapper.go
index e82afd112..ef0113b52 100644
--- a/pkg/sentry/fs/fsutil/host_file_mapper.go
+++ b/pkg/sentry/fs/fsutil/host_file_mapper.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -126,7 +125,7 @@ func (f *HostFileMapper) DecRefOn(mr memmap.MappableRange) {
 // offsets in fr or until the next call to UnmapAll.
 //
 // Preconditions: The caller must hold a reference on all offsets in fr.
-func (f *HostFileMapper) MapInternal(fr platform.FileRange, fd int, write bool) (safemem.BlockSeq, error) {
+func (f *HostFileMapper) MapInternal(fr memmap.FileRange, fd int, write bool) (safemem.BlockSeq, error) {
 	chunks := ((fr.End + chunkMask) >> chunkShift) - (fr.Start >> chunkShift)
 	f.mapsMu.Lock()
 	defer f.mapsMu.Unlock()
@@ -146,7 +145,7 @@ func (f *HostFileMapper) MapInternal(fr platform.FileRange, fd int, write bool)
 }
 
 // Preconditions: f.mapsMu must be locked.
-func (f *HostFileMapper) forEachMappingBlockLocked(fr platform.FileRange, fd int, write bool, fn func(safemem.Block)) error {
+func (f *HostFileMapper) forEachMappingBlockLocked(fr memmap.FileRange, fd int, write bool, fn func(safemem.Block)) error {
 	prot := syscall.PROT_READ
 	if write {
 		prot |= syscall.PROT_WRITE
diff --git a/pkg/sentry/fs/fsutil/host_mappable.go b/pkg/sentry/fs/fsutil/host_mappable.go
index 78fec553e..c15d8a946 100644
--- a/pkg/sentry/fs/fsutil/host_mappable.go
+++ b/pkg/sentry/fs/fsutil/host_mappable.go
@@ -21,18 +21,17 @@ import (
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
-// HostMappable implements memmap.Mappable and platform.File over a
+// HostMappable implements memmap.Mappable and memmap.File over a
 // CachedFileObject.
 //
 // Lock order (compare the lock order model in mm/mm.go):
 //   truncateMu ("fs locks")
 //     mu ("memmap.Mappable locks not taken by Translate")
-//       ("platform.File locks")
+//       ("memmap.File locks")
 //   	     backingFile ("CachedFileObject locks")
 //
 // +stateify savable
@@ -124,24 +123,24 @@ func (h *HostMappable) NotifyChangeFD() error {
 	return nil
 }
 
-// MapInternal implements platform.File.MapInternal.
-func (h *HostMappable) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+// MapInternal implements memmap.File.MapInternal.
+func (h *HostMappable) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
 	return h.hostFileMapper.MapInternal(fr, h.backingFile.FD(), at.Write)
 }
 
-// FD implements platform.File.FD.
+// FD implements memmap.File.FD.
 func (h *HostMappable) FD() int {
 	return h.backingFile.FD()
 }
 
-// IncRef implements platform.File.IncRef.
-func (h *HostMappable) IncRef(fr platform.FileRange) {
+// IncRef implements memmap.File.IncRef.
+func (h *HostMappable) IncRef(fr memmap.FileRange) {
 	mr := memmap.MappableRange{Start: fr.Start, End: fr.End}
 	h.hostFileMapper.IncRefOn(mr)
 }
 
-// DecRef implements platform.File.DecRef.
-func (h *HostMappable) DecRef(fr platform.FileRange) {
+// DecRef implements memmap.File.DecRef.
+func (h *HostMappable) DecRef(fr memmap.FileRange) {
 	mr := memmap.MappableRange{Start: fr.Start, End: fr.End}
 	h.hostFileMapper.DecRefOn(mr)
 }
diff --git a/pkg/sentry/fs/fsutil/inode_cached.go b/pkg/sentry/fs/fsutil/inode_cached.go
index 800c8b4e1..fe8b0b6ac 100644
--- a/pkg/sentry/fs/fsutil/inode_cached.go
+++ b/pkg/sentry/fs/fsutil/inode_cached.go
@@ -26,7 +26,6 @@ import (
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -934,7 +933,7 @@ func maxFillRange(required, optional memmap.MappableRange) memmap.MappableRange
 
 // InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
 func (c *CachingInodeOperations) InvalidateUnsavable(ctx context.Context) error {
-	// Whether we have a host fd (and consequently what platform.File is
+	// Whether we have a host fd (and consequently what memmap.File is
 	// mapped) can change across save/restore, so invalidate all translations
 	// unconditionally.
 	c.mapsMu.Lock()
@@ -999,10 +998,10 @@ func (c *CachingInodeOperations) Evict(ctx context.Context, er pgalloc.Evictable
 	}
 }
 
-// IncRef implements platform.File.IncRef. This is used when we directly map an
-// underlying host fd and CachingInodeOperations is used as the platform.File
+// IncRef implements memmap.File.IncRef. This is used when we directly map an
+// underlying host fd and CachingInodeOperations is used as the memmap.File
 // during translation.
-func (c *CachingInodeOperations) IncRef(fr platform.FileRange) {
+func (c *CachingInodeOperations) IncRef(fr memmap.FileRange) {
 	// Hot path. Avoid defers.
 	c.dataMu.Lock()
 	seg, gap := c.refs.Find(fr.Start)
@@ -1024,10 +1023,10 @@ func (c *CachingInodeOperations) IncRef(fr platform.FileRange) {
 	}
 }
 
-// DecRef implements platform.File.DecRef. This is used when we directly map an
-// underlying host fd and CachingInodeOperations is used as the platform.File
+// DecRef implements memmap.File.DecRef. This is used when we directly map an
+// underlying host fd and CachingInodeOperations is used as the memmap.File
 // during translation.
-func (c *CachingInodeOperations) DecRef(fr platform.FileRange) {
+func (c *CachingInodeOperations) DecRef(fr memmap.FileRange) {
 	// Hot path. Avoid defers.
 	c.dataMu.Lock()
 	seg := c.refs.FindSegment(fr.Start)
@@ -1046,15 +1045,15 @@ func (c *CachingInodeOperations) DecRef(fr platform.FileRange) {
 	c.dataMu.Unlock()
 }
 
-// MapInternal implements platform.File.MapInternal. This is used when we
+// MapInternal implements memmap.File.MapInternal. This is used when we
 // directly map an underlying host fd and CachingInodeOperations is used as the
-// platform.File during translation.
-func (c *CachingInodeOperations) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+// memmap.File during translation.
+func (c *CachingInodeOperations) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
 	return c.hostFileMapper.MapInternal(fr, c.backingFile.FD(), at.Write)
 }
 
-// FD implements platform.File.FD. This is used when we directly map an
-// underlying host fd and CachingInodeOperations is used as the platform.File
+// FD implements memmap.File.FD. This is used when we directly map an
+// underlying host fd and CachingInodeOperations is used as the memmap.File
 // during translation.
 func (c *CachingInodeOperations) FD() int {
 	return c.backingFile.FD()
diff --git a/pkg/sentry/fsimpl/gofer/regular_file.go b/pkg/sentry/fsimpl/gofer/regular_file.go
index 02317a133..09f142cfc 100644
--- a/pkg/sentry/fsimpl/gofer/regular_file.go
+++ b/pkg/sentry/fsimpl/gofer/regular_file.go
@@ -29,7 +29,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -221,12 +220,12 @@ func (fd *regularFileFD) pwriteLocked(ctx context.Context, src usermem.IOSequenc
 			return 0, syserror.EINVAL
 		}
 		mr := memmap.MappableRange{pgstart, pgend}
-		var freed []platform.FileRange
+		var freed []memmap.FileRange
 		d.dataMu.Lock()
 		cseg := d.cache.LowerBoundSegment(mr.Start)
 		for cseg.Ok() && cseg.Start() < mr.End {
 			cseg = d.cache.Isolate(cseg, mr)
-			freed = append(freed, platform.FileRange{cseg.Value(), cseg.Value() + cseg.Range().Length()})
+			freed = append(freed, memmap.FileRange{cseg.Value(), cseg.Value() + cseg.Range().Length()})
 			cseg = d.cache.Remove(cseg).NextSegment()
 		}
 		d.dataMu.Unlock()
@@ -821,7 +820,7 @@ func maxFillRange(required, optional memmap.MappableRange) memmap.MappableRange
 
 // InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
 func (d *dentry) InvalidateUnsavable(ctx context.Context) error {
-	// Whether we have a host fd (and consequently what platform.File is
+	// Whether we have a host fd (and consequently what memmap.File is
 	// mapped) can change across save/restore, so invalidate all translations
 	// unconditionally.
 	d.mapsMu.Lock()
@@ -869,8 +868,8 @@ func (d *dentry) Evict(ctx context.Context, er pgalloc.EvictableRange) {
 	}
 }
 
-// dentryPlatformFile implements platform.File. It exists solely because dentry
-// cannot implement both vfs.DentryImpl.IncRef and platform.File.IncRef.
+// dentryPlatformFile implements memmap.File. It exists solely because dentry
+// cannot implement both vfs.DentryImpl.IncRef and memmap.File.IncRef.
 //
 // dentryPlatformFile is only used when a host FD representing the remote file
 // is available (i.e. dentry.handle.fd >= 0), and that FD is used for
@@ -878,7 +877,7 @@ func (d *dentry) Evict(ctx context.Context, er pgalloc.EvictableRange) {
 type dentryPlatformFile struct {
 	*dentry
 
-	// fdRefs counts references on platform.File offsets. fdRefs is protected
+	// fdRefs counts references on memmap.File offsets. fdRefs is protected
 	// by dentry.dataMu.
 	fdRefs fsutil.FrameRefSet
 
@@ -890,29 +889,29 @@ type dentryPlatformFile struct {
 	hostFileMapperInitOnce sync.Once
 }
 
-// IncRef implements platform.File.IncRef.
-func (d *dentryPlatformFile) IncRef(fr platform.FileRange) {
+// IncRef implements memmap.File.IncRef.
+func (d *dentryPlatformFile) IncRef(fr memmap.FileRange) {
 	d.dataMu.Lock()
 	d.fdRefs.IncRefAndAccount(fr)
 	d.dataMu.Unlock()
 }
 
-// DecRef implements platform.File.DecRef.
-func (d *dentryPlatformFile) DecRef(fr platform.FileRange) {
+// DecRef implements memmap.File.DecRef.
+func (d *dentryPlatformFile) DecRef(fr memmap.FileRange) {
 	d.dataMu.Lock()
 	d.fdRefs.DecRefAndAccount(fr)
 	d.dataMu.Unlock()
 }
 
-// MapInternal implements platform.File.MapInternal.
-func (d *dentryPlatformFile) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+// MapInternal implements memmap.File.MapInternal.
+func (d *dentryPlatformFile) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
 	d.handleMu.RLock()
 	bs, err := d.hostFileMapper.MapInternal(fr, int(d.handle.fd), at.Write)
 	d.handleMu.RUnlock()
 	return bs, err
 }
 
-// FD implements platform.File.FD.
+// FD implements memmap.File.FD.
 func (d *dentryPlatformFile) FD() int {
 	d.handleMu.RLock()
 	fd := d.handle.fd
diff --git a/pkg/sentry/fsimpl/host/BUILD b/pkg/sentry/fsimpl/host/BUILD
index e86fbe2d5..bd701bbc7 100644
--- a/pkg/sentry/fsimpl/host/BUILD
+++ b/pkg/sentry/fsimpl/host/BUILD
@@ -34,7 +34,6 @@ go_library(
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/memmap",
-        "//pkg/sentry/platform",
         "//pkg/sentry/socket/control",
         "//pkg/sentry/socket/unix",
         "//pkg/sentry/socket/unix/transport",
diff --git a/pkg/sentry/fsimpl/host/mmap.go b/pkg/sentry/fsimpl/host/mmap.go
index 8545a82f0..65d3af38c 100644
--- a/pkg/sentry/fsimpl/host/mmap.go
+++ b/pkg/sentry/fsimpl/host/mmap.go
@@ -19,13 +19,12 @@ import (
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
-// inodePlatformFile implements platform.File. It exists solely because inode
-// cannot implement both kernfs.Inode.IncRef and platform.File.IncRef.
+// inodePlatformFile implements memmap.File. It exists solely because inode
+// cannot implement both kernfs.Inode.IncRef and memmap.File.IncRef.
 //
 // inodePlatformFile should only be used if inode.canMap is true.
 type inodePlatformFile struct {
@@ -34,7 +33,7 @@ type inodePlatformFile struct {
 	// fdRefsMu protects fdRefs.
 	fdRefsMu sync.Mutex
 
-	// fdRefs counts references on platform.File offsets. It is used solely for
+	// fdRefs counts references on memmap.File offsets. It is used solely for
 	// memory accounting.
 	fdRefs fsutil.FrameRefSet
 
@@ -45,32 +44,32 @@ type inodePlatformFile struct {
 	fileMapperInitOnce sync.Once
 }
 
-// IncRef implements platform.File.IncRef.
+// IncRef implements memmap.File.IncRef.
 //
 // Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) IncRef(fr platform.FileRange) {
+func (i *inodePlatformFile) IncRef(fr memmap.FileRange) {
 	i.fdRefsMu.Lock()
 	i.fdRefs.IncRefAndAccount(fr)
 	i.fdRefsMu.Unlock()
 }
 
-// DecRef implements platform.File.DecRef.
+// DecRef implements memmap.File.DecRef.
 //
 // Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) DecRef(fr platform.FileRange) {
+func (i *inodePlatformFile) DecRef(fr memmap.FileRange) {
 	i.fdRefsMu.Lock()
 	i.fdRefs.DecRefAndAccount(fr)
 	i.fdRefsMu.Unlock()
 }
 
-// MapInternal implements platform.File.MapInternal.
+// MapInternal implements memmap.File.MapInternal.
 //
 // Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+func (i *inodePlatformFile) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
 	return i.fileMapper.MapInternal(fr, i.hostFD, at.Write)
 }
 
-// FD implements platform.File.FD.
+// FD implements memmap.File.FD.
 func (i *inodePlatformFile) FD() int {
 	return i.hostFD
 }
diff --git a/pkg/sentry/kernel/shm/BUILD b/pkg/sentry/kernel/shm/BUILD
index bfd779837..c211fc8d0 100644
--- a/pkg/sentry/kernel/shm/BUILD
+++ b/pkg/sentry/kernel/shm/BUILD
@@ -20,7 +20,6 @@ go_library(
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
-        "//pkg/sentry/platform",
         "//pkg/sentry/usage",
         "//pkg/sync",
         "//pkg/syserror",
diff --git a/pkg/sentry/kernel/shm/shm.go b/pkg/sentry/kernel/shm/shm.go
index f66cfcc7f..55b4c2cdb 100644
--- a/pkg/sentry/kernel/shm/shm.go
+++ b/pkg/sentry/kernel/shm/shm.go
@@ -45,7 +45,6 @@ import (
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -370,7 +369,7 @@ type Shm struct {
 
 	// fr is the offset into mfp.MemoryFile() that backs this contents of this
 	// segment. Immutable.
-	fr platform.FileRange
+	fr memmap.FileRange
 
 	// mu protects all fields below.
 	mu sync.Mutex `state:"nosave"`
diff --git a/pkg/sentry/kernel/timekeeper.go b/pkg/sentry/kernel/timekeeper.go
index 5f3908d8b..7c4fefb16 100644
--- a/pkg/sentry/kernel/timekeeper.go
+++ b/pkg/sentry/kernel/timekeeper.go
@@ -21,8 +21,8 @@ import (
 
 	"gvisor.dev/gvisor/pkg/log"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	sentrytime "gvisor.dev/gvisor/pkg/sentry/time"
 	"gvisor.dev/gvisor/pkg/sync"
 )
@@ -90,7 +90,7 @@ type Timekeeper struct {
 // NewTimekeeper does not take ownership of paramPage.
 //
 // SetClocks must be called on the returned Timekeeper before it is usable.
-func NewTimekeeper(mfp pgalloc.MemoryFileProvider, paramPage platform.FileRange) (*Timekeeper, error) {
+func NewTimekeeper(mfp pgalloc.MemoryFileProvider, paramPage memmap.FileRange) (*Timekeeper, error) {
 	return &Timekeeper{
 		params: NewVDSOParamPage(mfp, paramPage),
 	}, nil
diff --git a/pkg/sentry/kernel/vdso.go b/pkg/sentry/kernel/vdso.go
index f1b3c212c..290c32466 100644
--- a/pkg/sentry/kernel/vdso.go
+++ b/pkg/sentry/kernel/vdso.go
@@ -19,8 +19,8 @@ import (
 
 	"gvisor.dev/gvisor/pkg/binary"
 	"gvisor.dev/gvisor/pkg/safemem"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -58,7 +58,7 @@ type vdsoParams struct {
 type VDSOParamPage struct {
 	// The parameter page is fr, allocated from mfp.MemoryFile().
 	mfp pgalloc.MemoryFileProvider
-	fr  platform.FileRange
+	fr  memmap.FileRange
 
 	// seq is the current sequence count written to the page.
 	//
@@ -81,7 +81,7 @@ type VDSOParamPage struct {
 // * VDSOParamPage must be the only writer to fr.
 //
 // * mfp.MemoryFile().MapInternal(fr) must return a single safemem.Block.
-func NewVDSOParamPage(mfp pgalloc.MemoryFileProvider, fr platform.FileRange) *VDSOParamPage {
+func NewVDSOParamPage(mfp pgalloc.MemoryFileProvider, fr memmap.FileRange) *VDSOParamPage {
 	return &VDSOParamPage{mfp: mfp, fr: fr}
 }
 
diff --git a/pkg/sentry/memmap/BUILD b/pkg/sentry/memmap/BUILD
index a98b66de1..2c95669cd 100644
--- a/pkg/sentry/memmap/BUILD
+++ b/pkg/sentry/memmap/BUILD
@@ -28,9 +28,21 @@ go_template_instance(
     },
 )
 
+go_template_instance(
+    name = "file_range",
+    out = "file_range.go",
+    package = "memmap",
+    prefix = "File",
+    template = "//pkg/segment:generic_range",
+    types = {
+        "T": "uint64",
+    },
+)
+
 go_library(
     name = "memmap",
     srcs = [
+        "file_range.go",
         "mappable_range.go",
         "mapping_set.go",
         "mapping_set_impl.go",
@@ -40,7 +52,7 @@ go_library(
     deps = [
         "//pkg/context",
         "//pkg/log",
-        "//pkg/sentry/platform",
+        "//pkg/safemem",
         "//pkg/syserror",
         "//pkg/usermem",
     ],
diff --git a/pkg/sentry/memmap/memmap.go b/pkg/sentry/memmap/memmap.go
index c6db9fc8f..c188f6c29 100644
--- a/pkg/sentry/memmap/memmap.go
+++ b/pkg/sentry/memmap/memmap.go
@@ -19,12 +19,12 @@ import (
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // Mappable represents a memory-mappable object, a mutable mapping from uint64
-// offsets to (platform.File, uint64 File offset) pairs.
+// offsets to (File, uint64 File offset) pairs.
 //
 // See mm/mm.go for Mappable's place in the lock order.
 //
@@ -74,7 +74,7 @@ type Mappable interface {
 	// Translations are valid until invalidated by a callback to
 	// MappingSpace.Invalidate or until the caller removes its mapping of the
 	// translated range. Mappable implementations must ensure that at least one
-	// reference is held on all pages in a platform.File that may be the result
+	// reference is held on all pages in a File that may be the result
 	// of a valid Translation.
 	//
 	// Preconditions: required.Length() > 0. optional.IsSupersetOf(required).
@@ -100,7 +100,7 @@ type Translation struct {
 	Source MappableRange
 
 	// File is the mapped file.
-	File platform.File
+	File File
 
 	// Offset is the offset into File at which this Translation begins.
 	Offset uint64
@@ -110,9 +110,9 @@ type Translation struct {
 	Perms usermem.AccessType
 }
 
-// FileRange returns the platform.FileRange represented by t.
-func (t Translation) FileRange() platform.FileRange {
-	return platform.FileRange{t.Offset, t.Offset + t.Source.Length()}
+// FileRange returns the FileRange represented by t.
+func (t Translation) FileRange() FileRange {
+	return FileRange{t.Offset, t.Offset + t.Source.Length()}
 }
 
 // CheckTranslateResult returns an error if (ts, terr) does not satisfy all
@@ -361,3 +361,49 @@ type MMapOpts struct {
 	// TODO(jamieliu): Replace entirely with MappingIdentity?
 	Hint string
 }
+
+// File represents a host file that may be mapped into an platform.AddressSpace.
+type File interface {
+	// All pages in a File are reference-counted.
+
+	// IncRef increments the reference count on all pages in fr.
+	//
+	// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
+	// 0. At least one reference must be held on all pages in fr. (The File
+	// interface does not provide a way to acquire an initial reference;
+	// implementors may define mechanisms for doing so.)
+	IncRef(fr FileRange)
+
+	// DecRef decrements the reference count on all pages in fr.
+	//
+	// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
+	// 0. At least one reference must be held on all pages in fr.
+	DecRef(fr FileRange)
+
+	// MapInternal returns a mapping of the given file offsets in the invoking
+	// process' address space for reading and writing.
+	//
+	// Note that fr.Start and fr.End need not be page-aligned.
+	//
+	// Preconditions: fr.Length() > 0. At least one reference must be held on
+	// all pages in fr.
+	//
+	// Postconditions: The returned mapping is valid as long as at least one
+	// reference is held on the mapped pages.
+	MapInternal(fr FileRange, at usermem.AccessType) (safemem.BlockSeq, error)
+
+	// FD returns the file descriptor represented by the File.
+	//
+	// The only permitted operation on the returned file descriptor is to map
+	// pages from it consistent with the requirements of AddressSpace.MapFile.
+	FD() int
+}
+
+// FileRange represents a range of uint64 offsets into a File.
+//
+// type FileRange <generated using go_generics>
+
+// String implements fmt.Stringer.String.
+func (fr FileRange) String() string {
+	return fmt.Sprintf("[%#x, %#x)", fr.Start, fr.End)
+}
diff --git a/pkg/sentry/mm/BUILD b/pkg/sentry/mm/BUILD
index a036ce53c..f9d0837a1 100644
--- a/pkg/sentry/mm/BUILD
+++ b/pkg/sentry/mm/BUILD
@@ -7,14 +7,14 @@ go_template_instance(
     name = "file_refcount_set",
     out = "file_refcount_set.go",
     imports = {
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
+        "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
     },
     package = "mm",
     prefix = "fileRefcount",
     template = "//pkg/segment:generic_set",
     types = {
         "Key": "uint64",
-        "Range": "platform.FileRange",
+        "Range": "memmap.FileRange",
         "Value": "int32",
         "Functions": "fileRefcountSetFunctions",
     },
diff --git a/pkg/sentry/mm/aio_context.go b/pkg/sentry/mm/aio_context.go
index 379148903..1999ec706 100644
--- a/pkg/sentry/mm/aio_context.go
+++ b/pkg/sentry/mm/aio_context.go
@@ -20,7 +20,6 @@ import (
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -243,7 +242,7 @@ type aioMappable struct {
 	refs.AtomicRefCount
 
 	mfp pgalloc.MemoryFileProvider
-	fr  platform.FileRange
+	fr  memmap.FileRange
 }
 
 var aioRingBufferSize = uint64(usermem.Addr(linux.AIORingSize).MustRoundUp())
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index 6db7c3d40..3e85964e4 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -25,7 +25,7 @@
 //           Locks taken by memmap.Mappable.Translate
 //             mm.privateRefs.mu
 //               platform.AddressSpace locks
-//                 platform.File locks
+//                 memmap.File locks
 //         mm.aioManager.mu
 //           mm.AIOContext.mu
 //
@@ -396,7 +396,7 @@ type pma struct {
 	// file is the file mapped by this pma. Only pmas for which file ==
 	// MemoryManager.mfp.MemoryFile() may be saved. pmas hold a reference to
 	// the corresponding file range while they exist.
-	file platform.File `state:"nosave"`
+	file memmap.File `state:"nosave"`
 
 	// off is the offset into file at which this pma begins.
 	//
@@ -436,7 +436,7 @@ type pma struct {
 	private bool
 
 	// If internalMappings is not empty, it is the cached return value of
-	// file.MapInternal for the platform.FileRange mapped by this pma.
+	// file.MapInternal for the memmap.FileRange mapped by this pma.
 	internalMappings safemem.BlockSeq `state:"nosave"`
 }
 
@@ -469,10 +469,10 @@ func (fileRefcountSetFunctions) MaxKey() uint64 {
 func (fileRefcountSetFunctions) ClearValue(_ *int32) {
 }
 
-func (fileRefcountSetFunctions) Merge(_ platform.FileRange, rc1 int32, _ platform.FileRange, rc2 int32) (int32, bool) {
+func (fileRefcountSetFunctions) Merge(_ memmap.FileRange, rc1 int32, _ memmap.FileRange, rc2 int32) (int32, bool) {
 	return rc1, rc1 == rc2
 }
 
-func (fileRefcountSetFunctions) Split(_ platform.FileRange, rc int32, _ uint64) (int32, int32) {
+func (fileRefcountSetFunctions) Split(_ memmap.FileRange, rc int32, _ uint64) (int32, int32) {
 	return rc, rc
 }
diff --git a/pkg/sentry/mm/pma.go b/pkg/sentry/mm/pma.go
index 62e4c20af..930ec895f 100644
--- a/pkg/sentry/mm/pma.go
+++ b/pkg/sentry/mm/pma.go
@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/safecopy"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -604,7 +603,7 @@ func (mm *MemoryManager) invalidateLocked(ar usermem.AddrRange, invalidatePrivat
 	}
 }
 
-// Pin returns the platform.File ranges currently mapped by addresses in ar in
+// Pin returns the memmap.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
@@ -674,15 +673,15 @@ type PinnedRange struct {
 	Source usermem.AddrRange
 
 	// File is the mapped file.
-	File platform.File
+	File memmap.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())}
+// FileRange returns the memmap.File offsets mapped by pr.
+func (pr PinnedRange) FileRange() memmap.FileRange {
+	return memmap.FileRange{pr.Offset, pr.Offset + uint64(pr.Source.Length())}
 }
 
 // Unpin releases the reference held by prs.
@@ -857,7 +856,7 @@ func (mm *MemoryManager) vecInternalMappingsLocked(ars usermem.AddrRangeSeq) saf
 }
 
 // incPrivateRef acquires a reference on private pages in fr.
-func (mm *MemoryManager) incPrivateRef(fr platform.FileRange) {
+func (mm *MemoryManager) incPrivateRef(fr memmap.FileRange) {
 	mm.privateRefs.mu.Lock()
 	defer mm.privateRefs.mu.Unlock()
 	refSet := &mm.privateRefs.refs
@@ -878,8 +877,8 @@ func (mm *MemoryManager) incPrivateRef(fr platform.FileRange) {
 }
 
 // decPrivateRef releases a reference on private pages in fr.
-func (mm *MemoryManager) decPrivateRef(fr platform.FileRange) {
-	var freed []platform.FileRange
+func (mm *MemoryManager) decPrivateRef(fr memmap.FileRange) {
+	var freed []memmap.FileRange
 
 	mm.privateRefs.mu.Lock()
 	refSet := &mm.privateRefs.refs
@@ -951,7 +950,7 @@ func (pmaSetFunctions) Merge(ar1 usermem.AddrRange, pma1 pma, ar2 usermem.AddrRa
 
 	// 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.
+	// memmap.File might not.
 	pma1.internalMappings = safemem.BlockSeq{}
 	return pma1, true
 }
@@ -1012,12 +1011,12 @@ func (pseg pmaIterator) getInternalMappingsLocked() error {
 	return nil
 }
 
-func (pseg pmaIterator) fileRange() platform.FileRange {
+func (pseg pmaIterator) fileRange() memmap.FileRange {
 	return pseg.fileRangeOf(pseg.Range())
 }
 
 // Preconditions: pseg.Range().IsSupersetOf(ar). ar.Length != 0.
-func (pseg pmaIterator) fileRangeOf(ar usermem.AddrRange) platform.FileRange {
+func (pseg pmaIterator) fileRangeOf(ar usermem.AddrRange) memmap.FileRange {
 	if checkInvariants {
 		if !pseg.Ok() {
 			panic("terminal pma iterator")
@@ -1032,5 +1031,5 @@ func (pseg pmaIterator) fileRangeOf(ar usermem.AddrRange) platform.FileRange {
 
 	pma := pseg.ValuePtr()
 	pstart := pseg.Start()
-	return platform.FileRange{pma.off + uint64(ar.Start-pstart), pma.off + uint64(ar.End-pstart)}
+	return memmap.FileRange{pma.off + uint64(ar.Start-pstart), pma.off + uint64(ar.End-pstart)}
 }
diff --git a/pkg/sentry/mm/special_mappable.go b/pkg/sentry/mm/special_mappable.go
index 9ad52082d..0e142fb11 100644
--- a/pkg/sentry/mm/special_mappable.go
+++ b/pkg/sentry/mm/special_mappable.go
@@ -19,7 +19,6 @@ import (
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -35,7 +34,7 @@ type SpecialMappable struct {
 	refs.AtomicRefCount
 
 	mfp  pgalloc.MemoryFileProvider
-	fr   platform.FileRange
+	fr   memmap.FileRange
 	name string
 }
 
@@ -44,7 +43,7 @@ type SpecialMappable struct {
 // SpecialMappable will use the given name in /proc/[pid]/maps.
 //
 // Preconditions: fr.Length() != 0.
-func NewSpecialMappable(name string, mfp pgalloc.MemoryFileProvider, fr platform.FileRange) *SpecialMappable {
+func NewSpecialMappable(name string, mfp pgalloc.MemoryFileProvider, fr memmap.FileRange) *SpecialMappable {
 	m := SpecialMappable{mfp: mfp, fr: fr, name: name}
 	m.EnableLeakCheck("mm.SpecialMappable")
 	return &m
@@ -126,7 +125,7 @@ func (m *SpecialMappable) MemoryFileProvider() pgalloc.MemoryFileProvider {
 
 // FileRange returns the offsets into MemoryFileProvider().MemoryFile() that
 // store the SpecialMappable's contents.
-func (m *SpecialMappable) FileRange() platform.FileRange {
+func (m *SpecialMappable) FileRange() memmap.FileRange {
 	return m.fr
 }
 
diff --git a/pkg/sentry/pgalloc/BUILD b/pkg/sentry/pgalloc/BUILD
index e1fcb175f..7a3311a70 100644
--- a/pkg/sentry/pgalloc/BUILD
+++ b/pkg/sentry/pgalloc/BUILD
@@ -36,14 +36,14 @@ go_template_instance(
         "trackGaps": "1",
     },
     imports = {
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
+        "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
     },
     package = "pgalloc",
     prefix = "usage",
     template = "//pkg/segment:generic_set",
     types = {
         "Key": "uint64",
-        "Range": "platform.FileRange",
+        "Range": "memmap.FileRange",
         "Value": "usageInfo",
         "Functions": "usageSetFunctions",
     },
@@ -56,14 +56,14 @@ go_template_instance(
         "minDegree": "10",
     },
     imports = {
-        "platform": "gvisor.dev/gvisor/pkg/sentry/platform",
+        "memmap": "gvisor.dev/gvisor/pkg/sentry/memmap",
     },
     package = "pgalloc",
     prefix = "reclaim",
     template = "//pkg/segment:generic_set",
     types = {
         "Key": "uint64",
-        "Range": "platform.FileRange",
+        "Range": "memmap.FileRange",
         "Value": "reclaimSetValue",
         "Functions": "reclaimSetFunctions",
     },
@@ -89,7 +89,7 @@ go_library(
         "//pkg/safemem",
         "//pkg/sentry/arch",
         "//pkg/sentry/hostmm",
-        "//pkg/sentry/platform",
+        "//pkg/sentry/memmap",
         "//pkg/sentry/usage",
         "//pkg/state",
         "//pkg/state/wire",
diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go
index afab97c0a..3243d7214 100644
--- a/pkg/sentry/pgalloc/pgalloc.go
+++ b/pkg/sentry/pgalloc/pgalloc.go
@@ -33,14 +33,14 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/hostmm"
-	"gvisor.dev/gvisor/pkg/sentry/platform"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
-// MemoryFile is a platform.File whose pages may be allocated to arbitrary
+// MemoryFile is a memmap.File whose pages may be allocated to arbitrary
 // users.
 type MemoryFile struct {
 	// opts holds options passed to NewMemoryFile. opts is immutable.
@@ -372,7 +372,7 @@ func (f *MemoryFile) Destroy() {
 // to Allocate.
 //
 // Preconditions: length must be page-aligned and non-zero.
-func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.FileRange, error) {
+func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (memmap.FileRange, error) {
 	if length == 0 || length%usermem.PageSize != 0 {
 		panic(fmt.Sprintf("invalid allocation length: %#x", length))
 	}
@@ -390,7 +390,7 @@ func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.Fi
 	// Find a range in the underlying file.
 	fr, ok := findAvailableRange(&f.usage, f.fileSize, length, alignment)
 	if !ok {
-		return platform.FileRange{}, syserror.ENOMEM
+		return memmap.FileRange{}, syserror.ENOMEM
 	}
 
 	// Expand the file if needed.
@@ -398,7 +398,7 @@ func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.Fi
 		// Round the new file size up to be chunk-aligned.
 		newFileSize := (int64(fr.End) + chunkMask) &^ chunkMask
 		if err := f.file.Truncate(newFileSize); err != nil {
-			return platform.FileRange{}, err
+			return memmap.FileRange{}, err
 		}
 		f.fileSize = newFileSize
 		f.mappingsMu.Lock()
@@ -416,7 +416,7 @@ func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.Fi
 				bs[i] = 0
 			}
 		}); err != nil {
-			return platform.FileRange{}, err
+			return memmap.FileRange{}, err
 		}
 	}
 	if !f.usage.Add(fr, usageInfo{
@@ -439,7 +439,7 @@ func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.Fi
 // space for mappings to be allocated downwards.
 //
 // Precondition: alignment must be a power of 2.
-func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint64) (platform.FileRange, bool) {
+func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint64) (memmap.FileRange, bool) {
 	alignmentMask := alignment - 1
 
 	// Search for space in existing gaps, starting at the current end of the
@@ -461,7 +461,7 @@ func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint6
 			break
 		}
 		if start := unalignedStart &^ alignmentMask; start >= gap.Start() {
-			return platform.FileRange{start, start + length}, true
+			return memmap.FileRange{start, start + length}, true
 		}
 
 		gap = gap.PrevLargeEnoughGap(length)
@@ -475,7 +475,7 @@ func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint6
 	min = (min + alignmentMask) &^ alignmentMask
 	if min+length < min {
 		// Overflow: allocation would exceed the range of uint64.
-		return platform.FileRange{}, false
+		return memmap.FileRange{}, false
 	}
 
 	// Determine the minimum file size required to fit this allocation at its end.
@@ -484,7 +484,7 @@ func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint6
 		if newFileSize <= fileSize {
 			if fileSize != 0 {
 				// Overflow: allocation would exceed the range of int64.
-				return platform.FileRange{}, false
+				return memmap.FileRange{}, false
 			}
 			newFileSize = chunkSize
 		}
@@ -496,7 +496,7 @@ func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint6
 			continue
 		}
 		if start := unalignedStart &^ alignmentMask; start >= min {
-			return platform.FileRange{start, start + length}, true
+			return memmap.FileRange{start, start + length}, true
 		}
 	}
 }
@@ -508,22 +508,22 @@ func findAvailableRange(usage *usageSet, fileSize int64, length, alignment uint6
 // by r.ReadToBlocks(), it returns that error.
 //
 // Preconditions: length > 0. length must be page-aligned.
-func (f *MemoryFile) AllocateAndFill(length uint64, kind usage.MemoryKind, r safemem.Reader) (platform.FileRange, error) {
+func (f *MemoryFile) AllocateAndFill(length uint64, kind usage.MemoryKind, r safemem.Reader) (memmap.FileRange, error) {
 	fr, err := f.Allocate(length, kind)
 	if err != nil {
-		return platform.FileRange{}, err
+		return memmap.FileRange{}, err
 	}
 	dsts, err := f.MapInternal(fr, usermem.Write)
 	if err != nil {
 		f.DecRef(fr)
-		return platform.FileRange{}, err
+		return memmap.FileRange{}, err
 	}
 	n, err := safemem.ReadFullToBlocks(r, dsts)
 	un := uint64(usermem.Addr(n).RoundDown())
 	if un < length {
 		// Free unused memory and update fr to contain only the memory that is
 		// still allocated.
-		f.DecRef(platform.FileRange{fr.Start + un, fr.End})
+		f.DecRef(memmap.FileRange{fr.Start + un, fr.End})
 		fr.End = fr.Start + un
 	}
 	return fr, err
@@ -540,7 +540,7 @@ const (
 // will read zeroes.
 //
 // Preconditions: fr.Length() > 0.
-func (f *MemoryFile) Decommit(fr platform.FileRange) error {
+func (f *MemoryFile) Decommit(fr memmap.FileRange) error {
 	if !fr.WellFormed() || fr.Length() == 0 || fr.Start%usermem.PageSize != 0 || fr.End%usermem.PageSize != 0 {
 		panic(fmt.Sprintf("invalid range: %v", fr))
 	}
@@ -560,7 +560,7 @@ func (f *MemoryFile) Decommit(fr platform.FileRange) error {
 	return nil
 }
 
-func (f *MemoryFile) markDecommitted(fr platform.FileRange) {
+func (f *MemoryFile) markDecommitted(fr memmap.FileRange) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	// Since we're changing the knownCommitted attribute, we need to merge
@@ -581,8 +581,8 @@ func (f *MemoryFile) markDecommitted(fr platform.FileRange) {
 	f.usage.MergeRange(fr)
 }
 
-// IncRef implements platform.File.IncRef.
-func (f *MemoryFile) IncRef(fr platform.FileRange) {
+// IncRef implements memmap.File.IncRef.
+func (f *MemoryFile) IncRef(fr memmap.FileRange) {
 	if !fr.WellFormed() || fr.Length() == 0 || fr.Start%usermem.PageSize != 0 || fr.End%usermem.PageSize != 0 {
 		panic(fmt.Sprintf("invalid range: %v", fr))
 	}
@@ -600,8 +600,8 @@ func (f *MemoryFile) IncRef(fr platform.FileRange) {
 	f.usage.MergeAdjacent(fr)
 }
 
-// DecRef implements platform.File.DecRef.
-func (f *MemoryFile) DecRef(fr platform.FileRange) {
+// DecRef implements memmap.File.DecRef.
+func (f *MemoryFile) DecRef(fr memmap.FileRange) {
 	if !fr.WellFormed() || fr.Length() == 0 || fr.Start%usermem.PageSize != 0 || fr.End%usermem.PageSize != 0 {
 		panic(fmt.Sprintf("invalid range: %v", fr))
 	}
@@ -637,8 +637,8 @@ func (f *MemoryFile) DecRef(fr platform.FileRange) {
 	}
 }
 
-// MapInternal implements platform.File.MapInternal.
-func (f *MemoryFile) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+// MapInternal implements memmap.File.MapInternal.
+func (f *MemoryFile) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
 	if !fr.WellFormed() || fr.Length() == 0 {
 		panic(fmt.Sprintf("invalid range: %v", fr))
 	}
@@ -664,7 +664,7 @@ func (f *MemoryFile) MapInternal(fr platform.FileRange, at usermem.AccessType) (
 
 // forEachMappingSlice invokes fn on a sequence of byte slices that
 // collectively map all bytes in fr.
-func (f *MemoryFile) forEachMappingSlice(fr platform.FileRange, fn func([]byte)) error {
+func (f *MemoryFile) forEachMappingSlice(fr memmap.FileRange, fn func([]byte)) error {
 	mappings := f.mappings.Load().([]uintptr)
 	for chunkStart := fr.Start &^ chunkMask; chunkStart < fr.End; chunkStart += chunkSize {
 		chunk := int(chunkStart >> chunkShift)
@@ -944,7 +944,7 @@ func (f *MemoryFile) updateUsageLocked(currentUsage uint64, checkCommitted func(
 					continue
 				case !populated && populatedRun:
 					// Finish the run by changing this segment.
-					runRange := platform.FileRange{
+					runRange := memmap.FileRange{
 						Start: r.Start + uint64(populatedRunStart*usermem.PageSize),
 						End:   r.Start + uint64(i*usermem.PageSize),
 					}
@@ -1009,7 +1009,7 @@ func (f *MemoryFile) File() *os.File {
 	return f.file
 }
 
-// FD implements platform.File.FD.
+// FD implements memmap.File.FD.
 func (f *MemoryFile) FD() int {
 	return int(f.file.Fd())
 }
@@ -1090,13 +1090,13 @@ func (f *MemoryFile) runReclaim() {
 //
 // Note that there returned range will be removed from tracking. It
 // must be reclaimed (removed from f.usage) at this point.
-func (f *MemoryFile) findReclaimable() (platform.FileRange, bool) {
+func (f *MemoryFile) findReclaimable() (memmap.FileRange, bool) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	for {
 		for {
 			if f.destroyed {
-				return platform.FileRange{}, false
+				return memmap.FileRange{}, false
 			}
 			if f.reclaimable {
 				break
@@ -1120,7 +1120,7 @@ func (f *MemoryFile) findReclaimable() (platform.FileRange, bool) {
 	}
 }
 
-func (f *MemoryFile) markReclaimed(fr platform.FileRange) {
+func (f *MemoryFile) markReclaimed(fr memmap.FileRange) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	seg := f.usage.FindSegment(fr.Start)
@@ -1222,11 +1222,11 @@ func (usageSetFunctions) MaxKey() uint64 {
 func (usageSetFunctions) ClearValue(val *usageInfo) {
 }
 
-func (usageSetFunctions) Merge(_ platform.FileRange, val1 usageInfo, _ platform.FileRange, val2 usageInfo) (usageInfo, bool) {
+func (usageSetFunctions) Merge(_ memmap.FileRange, val1 usageInfo, _ memmap.FileRange, val2 usageInfo) (usageInfo, bool) {
 	return val1, val1 == val2
 }
 
-func (usageSetFunctions) Split(_ platform.FileRange, val usageInfo, _ uint64) (usageInfo, usageInfo) {
+func (usageSetFunctions) Split(_ memmap.FileRange, val usageInfo, _ uint64) (usageInfo, usageInfo) {
 	return val, val
 }
 
@@ -1270,10 +1270,10 @@ func (reclaimSetFunctions) MaxKey() uint64 {
 func (reclaimSetFunctions) ClearValue(val *reclaimSetValue) {
 }
 
-func (reclaimSetFunctions) Merge(_ platform.FileRange, _ reclaimSetValue, _ platform.FileRange, _ reclaimSetValue) (reclaimSetValue, bool) {
+func (reclaimSetFunctions) Merge(_ memmap.FileRange, _ reclaimSetValue, _ memmap.FileRange, _ reclaimSetValue) (reclaimSetValue, bool) {
 	return reclaimSetValue{}, true
 }
 
-func (reclaimSetFunctions) Split(_ platform.FileRange, _ reclaimSetValue, _ uint64) (reclaimSetValue, reclaimSetValue) {
+func (reclaimSetFunctions) Split(_ memmap.FileRange, _ reclaimSetValue, _ uint64) (reclaimSetValue, reclaimSetValue) {
 	return reclaimSetValue{}, reclaimSetValue{}
 }
diff --git a/pkg/sentry/platform/BUILD b/pkg/sentry/platform/BUILD
index 453241eca..209b28053 100644
--- a/pkg/sentry/platform/BUILD
+++ b/pkg/sentry/platform/BUILD
@@ -1,39 +1,21 @@
 load("//tools:defs.bzl", "go_library")
-load("//tools/go_generics:defs.bzl", "go_template_instance")
 
 package(licenses = ["notice"])
 
-go_template_instance(
-    name = "file_range",
-    out = "file_range.go",
-    package = "platform",
-    prefix = "File",
-    template = "//pkg/segment:generic_range",
-    types = {
-        "T": "uint64",
-    },
-)
-
 go_library(
     name = "platform",
     srcs = [
         "context.go",
-        "file_range.go",
         "mmap_min_addr.go",
         "platform.go",
     ],
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",
-        "//pkg/atomicbitops",
         "//pkg/context",
-        "//pkg/log",
-        "//pkg/safecopy",
-        "//pkg/safemem",
         "//pkg/seccomp",
         "//pkg/sentry/arch",
-        "//pkg/sentry/usage",
-        "//pkg/syserror",
+        "//pkg/sentry/memmap",
         "//pkg/usermem",
     ],
 )
diff --git a/pkg/sentry/platform/kvm/BUILD b/pkg/sentry/platform/kvm/BUILD
index 10a10bfe2..b5d27a72a 100644
--- a/pkg/sentry/platform/kvm/BUILD
+++ b/pkg/sentry/platform/kvm/BUILD
@@ -47,6 +47,7 @@ go_library(
         "//pkg/safecopy",
         "//pkg/seccomp",
         "//pkg/sentry/arch",
+        "//pkg/sentry/memmap",
         "//pkg/sentry/platform",
         "//pkg/sentry/platform/interrupt",
         "//pkg/sentry/platform/ring0",
diff --git a/pkg/sentry/platform/kvm/address_space.go b/pkg/sentry/platform/kvm/address_space.go
index faf1d5e1c..98a3e539d 100644
--- a/pkg/sentry/platform/kvm/address_space.go
+++ b/pkg/sentry/platform/kvm/address_space.go
@@ -18,6 +18,7 @@ import (
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/atomicbitops"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sync"
@@ -150,7 +151,7 @@ func (as *addressSpace) mapLocked(addr usermem.Addr, m hostMapEntry, at usermem.
 }
 
 // MapFile implements platform.AddressSpace.MapFile.
-func (as *addressSpace) MapFile(addr usermem.Addr, f platform.File, fr platform.FileRange, at usermem.AccessType, precommit bool) error {
+func (as *addressSpace) MapFile(addr usermem.Addr, f memmap.File, fr memmap.FileRange, at usermem.AccessType, precommit bool) error {
 	as.mu.Lock()
 	defer as.mu.Unlock()
 
diff --git a/pkg/sentry/platform/platform.go b/pkg/sentry/platform/platform.go
index 171513f3f..4b13eec30 100644
--- a/pkg/sentry/platform/platform.go
+++ b/pkg/sentry/platform/platform.go
@@ -22,9 +22,9 @@ import (
 	"os"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/seccomp"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -207,7 +207,7 @@ type AddressSpace interface {
 	// Preconditions: addr and fr must be page-aligned. fr.Length() > 0.
 	// at.Any() == true. At least one reference must be held on all pages in
 	// fr, and must continue to be held as long as pages are mapped.
-	MapFile(addr usermem.Addr, f File, fr FileRange, at usermem.AccessType, precommit bool) error
+	MapFile(addr usermem.Addr, f memmap.File, fr memmap.FileRange, at usermem.AccessType, precommit bool) error
 
 	// Unmap unmaps the given range.
 	//
@@ -310,52 +310,6 @@ func (f SegmentationFault) Error() string {
 	return fmt.Sprintf("segmentation fault at %#x", f.Addr)
 }
 
-// File represents a host file that may be mapped into an AddressSpace.
-type File interface {
-	// All pages in a File are reference-counted.
-
-	// IncRef increments the reference count on all pages in fr.
-	//
-	// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
-	// 0. At least one reference must be held on all pages in fr. (The File
-	// interface does not provide a way to acquire an initial reference;
-	// implementors may define mechanisms for doing so.)
-	IncRef(fr FileRange)
-
-	// DecRef decrements the reference count on all pages in fr.
-	//
-	// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
-	// 0. At least one reference must be held on all pages in fr.
-	DecRef(fr FileRange)
-
-	// MapInternal returns a mapping of the given file offsets in the invoking
-	// process' address space for reading and writing.
-	//
-	// Note that fr.Start and fr.End need not be page-aligned.
-	//
-	// Preconditions: fr.Length() > 0. At least one reference must be held on
-	// all pages in fr.
-	//
-	// Postconditions: The returned mapping is valid as long as at least one
-	// reference is held on the mapped pages.
-	MapInternal(fr FileRange, at usermem.AccessType) (safemem.BlockSeq, error)
-
-	// FD returns the file descriptor represented by the File.
-	//
-	// The only permitted operation on the returned file descriptor is to map
-	// pages from it consistent with the requirements of AddressSpace.MapFile.
-	FD() int
-}
-
-// FileRange represents a range of uint64 offsets into a File.
-//
-// type FileRange <generated using go_generics>
-
-// String implements fmt.Stringer.String.
-func (fr FileRange) String() string {
-	return fmt.Sprintf("[%#x, %#x)", fr.Start, fr.End)
-}
-
 // Requirements is used to specify platform specific requirements.
 type Requirements struct {
 	// RequiresCurrentPIDNS indicates that the sandbox has to be started in the
diff --git a/pkg/sentry/platform/ptrace/BUILD b/pkg/sentry/platform/ptrace/BUILD
index 30402c2df..29fd23cc3 100644
--- a/pkg/sentry/platform/ptrace/BUILD
+++ b/pkg/sentry/platform/ptrace/BUILD
@@ -30,6 +30,7 @@ go_library(
         "//pkg/seccomp",
         "//pkg/sentry/arch",
         "//pkg/sentry/hostcpu",
+        "//pkg/sentry/memmap",
         "//pkg/sentry/platform",
         "//pkg/sentry/platform/interrupt",
         "//pkg/sync",
diff --git a/pkg/sentry/platform/ptrace/subprocess.go b/pkg/sentry/platform/ptrace/subprocess.go
index 2389423b0..c990f3454 100644
--- a/pkg/sentry/platform/ptrace/subprocess.go
+++ b/pkg/sentry/platform/ptrace/subprocess.go
@@ -24,6 +24,7 @@ import (
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/procid"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -616,7 +617,7 @@ func (s *subprocess) syscall(sysno uintptr, args ...arch.SyscallArgument) (uintp
 }
 
 // MapFile implements platform.AddressSpace.MapFile.
-func (s *subprocess) MapFile(addr usermem.Addr, f platform.File, fr platform.FileRange, at usermem.AccessType, precommit bool) error {
+func (s *subprocess) MapFile(addr usermem.Addr, f memmap.File, fr memmap.FileRange, at usermem.AccessType, precommit bool) error {
 	var flags int
 	if precommit {
 		flags |= syscall.MAP_POPULATE