github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/mm/debug.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package mm
    16  
    17  import (
    18  	"bytes"
    19  	"fmt"
    20  
    21  	"github.com/SagerNet/gvisor/pkg/context"
    22  )
    23  
    24  const (
    25  	// If checkInvariants is true, perform runtime checks for invariants
    26  	// expected by the mm package. This is normally disabled since MM is a
    27  	// significant hot path in general, and some such checks (notably
    28  	// memmap.CheckTranslateResult) are very expensive.
    29  	checkInvariants = false
    30  
    31  	// If logIOErrors is true, log I/O errors that originate from MM before
    32  	// converting them to EFAULT.
    33  	logIOErrors = false
    34  )
    35  
    36  // String implements fmt.Stringer.String.
    37  func (mm *MemoryManager) String() string {
    38  	return mm.DebugString(context.Background())
    39  }
    40  
    41  // DebugString returns a string containing information about mm for debugging.
    42  func (mm *MemoryManager) DebugString(ctx context.Context) string {
    43  	mm.mappingMu.RLock()
    44  	defer mm.mappingMu.RUnlock()
    45  	mm.activeMu.RLock()
    46  	defer mm.activeMu.RUnlock()
    47  	return mm.debugStringLocked(ctx)
    48  }
    49  
    50  // Preconditions: mm.mappingMu and mm.activeMu must be locked.
    51  func (mm *MemoryManager) debugStringLocked(ctx context.Context) string {
    52  	var b bytes.Buffer
    53  	b.WriteString("VMAs:\n")
    54  	for vseg := mm.vmas.FirstSegment(); vseg.Ok(); vseg = vseg.NextSegment() {
    55  		b.Write(mm.vmaMapsEntryLocked(ctx, vseg))
    56  	}
    57  	b.WriteString("PMAs:\n")
    58  	for pseg := mm.pmas.FirstSegment(); pseg.Ok(); pseg = pseg.NextSegment() {
    59  		b.Write(pseg.debugStringEntryLocked())
    60  	}
    61  	return string(b.Bytes())
    62  }
    63  
    64  // Preconditions: mm.activeMu must be locked.
    65  func (pseg pmaIterator) debugStringEntryLocked() []byte {
    66  	var b bytes.Buffer
    67  
    68  	fmt.Fprintf(&b, "%08x-%08x ", pseg.Start(), pseg.End())
    69  
    70  	pma := pseg.ValuePtr()
    71  	if pma.effectivePerms.Read {
    72  		b.WriteByte('r')
    73  	} else {
    74  		b.WriteByte('-')
    75  	}
    76  	if pma.effectivePerms.Write {
    77  		if pma.needCOW {
    78  			b.WriteByte('c')
    79  		} else {
    80  			b.WriteByte('w')
    81  		}
    82  	} else {
    83  		b.WriteByte('-')
    84  	}
    85  	if pma.effectivePerms.Execute {
    86  		b.WriteByte('x')
    87  	} else {
    88  		b.WriteByte('-')
    89  	}
    90  	if pma.private {
    91  		b.WriteByte('p')
    92  	} else {
    93  		b.WriteByte('s')
    94  	}
    95  
    96  	fmt.Fprintf(&b, " %08x %T\n", pma.off, pma.file)
    97  	return b.Bytes()
    98  }