Per the comment for vfs.GenericProxyDeviceConfigureMMap(), this ensures that if
invalid arguments are provided to application mmap() for a proxy device file,
then an error is returned immediately (from host mmap()) rather than when
demand paging causes host mmap() to be invoked.
PiperOrigin-RevId: 680733678
memmap.Mappable.Translate() is passed a hostarch.AccessType indicating what
permissions are *immediately* required; it returns permissions in
memmap.Translation.Perms that are granted *to MM* until invalidation. MM
ensures that the permissions granted to the application are the intersection of
those granted by Translate, and those granted by VMA permissions; see
determination of pma.effectivePerms in
mm.MemoryManager.getPMAsInternalLocked(). This mechanism is used to avoid
marking pages dirty in the sentry's page cache for gofer-backed files until
PROT_WRITE pages are actually written to; see gofer.dentry.Translate(). In most
other cases, granting all supported permissions (to MM) up-front avoids a
redundant page fault for pages that are touched first for reading, and later
for writing.
Also:
- Prevent PROT_WRITE mappings of erofs files at mmap()/mprotect() time, rather
than raising SIGBUS when writing to such mappings.
- Map nvproxy.frontendFD with PlatformEffectPopulate. This is the original goal
of this CL; however, before this rest of this CL, MM.MMap() =>
MM.populateVMAAndUnlock() => MM.getPMAsLocked(at=hostarch.NoAccess) =>
MM.getPMAsInternalLocked(at=hostarch.NoAccess) =>
nvproxy.frontendFD.Translate(at=hostarch.NoAccess) returns Translations with
no permissions, causing MM.mapASLocked() to no-op.
PiperOrigin-RevId: 679360594
These support the relatively common use case of removing all segments in a
given range (unconditionally) but doing something with them before they're
removed. This is always more compact, and may be slightly faster in some cases
(every replaced loop calls Isolate per iteration, while RemoveRangeWith avoids
redundant split checks between segments), at the cost of a direct function
call.
Also slightly optimize Set.LowerBoundSegmentSplitBefore() and
Set.UpperBoundSegmentSplitAfter() by inlining LowerBoundSegment and
UpperBoundSegment respectively; in the cases where Find() returns a
GapIterator, the segment that is returned doesn't need to be split since it
doesn't contain min/max respectively.
PiperOrigin-RevId: 675824581
Ubuntu TPU images do not have the vfio-dev directories that COS images do,
so we need a more robust way of setting up the sandbox chroot to handle this
case. This change implements a way to get devices and minor numbers into the
sandbox with minimal support from the host filesystem and cleans up a few
methods to reflect their current usage.
Addresses #10795
PiperOrigin-RevId: 674363342
Jamie LiuandgVisor bot
Lucas ManningandgVisor bot