diff options
Diffstat (limited to 'pkg/sentry/mm/pma.go')
| -rw-r--r-- | pkg/sentry/mm/pma.go | 47 |
1 files changed, 32 insertions, 15 deletions
diff --git a/pkg/sentry/mm/pma.go b/pkg/sentry/mm/pma.go index 5583f62b2..05cdcd8ae 100644 --- a/pkg/sentry/mm/pma.go +++ b/pkg/sentry/mm/pma.go @@ -18,12 +18,12 @@ import ( "fmt" "gvisor.dev/gvisor/pkg/context" + "gvisor.dev/gvisor/pkg/errors/linuxerr" "gvisor.dev/gvisor/pkg/hostarch" "gvisor.dev/gvisor/pkg/safecopy" "gvisor.dev/gvisor/pkg/safemem" "gvisor.dev/gvisor/pkg/sentry/memmap" "gvisor.dev/gvisor/pkg/sentry/usage" - "gvisor.dev/gvisor/pkg/syserror" ) // existingPMAsLocked checks that pmas exist for all addresses in ar, and @@ -116,7 +116,7 @@ func (mm *MemoryManager) getPMAsLocked(ctx context.Context, vseg vmaIterator, ar var alignerr error if !ok { end = ar.End.RoundDown() - alignerr = syserror.EFAULT + alignerr = linuxerr.EFAULT } ar = hostarch.AddrRange{ar.Start.RoundDown(), end} @@ -162,7 +162,7 @@ func (mm *MemoryManager) getVecPMAsLocked(ctx context.Context, ars hostarch.Addr var alignerr error if !ok { end = ar.End.RoundDown() - alignerr = syserror.EFAULT + alignerr = linuxerr.EFAULT } ar = hostarch.AddrRange{ar.Start.RoundDown(), end} @@ -324,20 +324,37 @@ func (mm *MemoryManager) getPMAsInternalLocked(ctx context.Context, vseg vmaIter 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 hostarch.AddrRange - if vseg.ValuePtr().effectivePerms.Execute { + if vma := vseg.ValuePtr(); vma.effectivePerms.Execute { + // 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. copyAR = pseg.Range().Intersect(ar) + } else if vma.growsDown { + // In most cases, the new process will not use most of + // its stack before exiting or invoking execve(); it is + // especially unlikely to return very far down its call + // stack, since async-signal-safety concerns in + // multithreaded programs prevent the new process from + // being able to do much. So only copy up to one page + // before and after the pages required. + stackMaskAR := ar + if newStart := stackMaskAR.Start - hostarch.PageSize; newStart < stackMaskAR.Start { + stackMaskAR.Start = newStart + } + if newEnd := stackMaskAR.End + hostarch.PageSize; newEnd > stackMaskAR.End { + stackMaskAR.End = newEnd + } + copyAR = pseg.Range().Intersect(stackMaskAR) } else { copyAR = pseg.Range().Intersect(maskAR) } |