From d02b74a5dcfed4bfc8f2f8e545bca4d2afabb296 Mon Sep 17 00:00:00 2001
From: Googler <noreply@google.com>
Date: Fri, 27 Apr 2018 10:37:02 -0700
Subject: Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463
---
 pkg/sentry/mm/proc_pid_maps.go | 105 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 pkg/sentry/mm/proc_pid_maps.go

(limited to 'pkg/sentry/mm/proc_pid_maps.go')

diff --git a/pkg/sentry/mm/proc_pid_maps.go b/pkg/sentry/mm/proc_pid_maps.go
new file mode 100644
index 000000000..5840b257c
--- /dev/null
+++ b/pkg/sentry/mm/proc_pid_maps.go
@@ -0,0 +1,105 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"bytes"
+	"fmt"
+	"strings"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/seqfile"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+const (
+	// devMinorBits is the number of minor bits in a device number. Linux:
+	// include/linux/kdev_t.h:MINORBITS
+	devMinorBits = 20
+)
+
+// NeedsUpdate implements seqfile.SeqSource.NeedsUpdate.
+func (mm *MemoryManager) NeedsUpdate(generation int64) bool {
+	return true
+}
+
+// ReadSeqFileData is called by fs/proc.mapsData.ReadSeqFileData.
+func (mm *MemoryManager) ReadSeqFileData(ctx context.Context, handle seqfile.SeqHandle) ([]seqfile.SeqData, int64) {
+	mm.mappingMu.RLock()
+	defer mm.mappingMu.RUnlock()
+	var data []seqfile.SeqData
+	var start usermem.Addr
+	if handle != nil {
+		start = *handle.(*usermem.Addr)
+	}
+	for vseg := mm.vmas.LowerBoundSegment(start); vseg.Ok(); vseg = vseg.NextSegment() {
+		// FIXME: If we use a usermem.Addr for the handle, we get
+		// "panic: autosave error: type usermem.Addr is not registered".
+		vmaAddr := vseg.End()
+		data = append(data, seqfile.SeqData{
+			Buf:    mm.vmaMapsEntryLocked(ctx, vseg),
+			Handle: &vmaAddr,
+		})
+	}
+	return data, 1
+}
+
+// vmaMapsEntryLocked returns a /proc/[pid]/maps entry for the vma iterated by
+// vseg, including the trailing newline.
+//
+// Preconditions: mm.mappingMu must be locked.
+func (mm *MemoryManager) vmaMapsEntryLocked(ctx context.Context, vseg vmaIterator) []byte {
+	vma := vseg.ValuePtr()
+	private := "p"
+	if !vma.private {
+		private = "s"
+	}
+
+	var dev, ino uint64
+	if vma.id != nil {
+		dev = vma.id.DeviceID()
+		ino = vma.id.InodeID()
+	}
+	devMajor := uint32(dev >> devMinorBits)
+	devMinor := uint32(dev & ((1 << devMinorBits) - 1))
+
+	var b bytes.Buffer
+	// Do not include the guard page: fs/proc/task_mmu.c:show_map_vma() =>
+	// stack_guard_page_start().
+	fmt.Fprintf(&b, "%08x-%08x %s%s %08x %02x:%02x %d ",
+		vseg.Start(), vseg.End(), vma.realPerms, private, vma.off, devMajor, devMinor, ino)
+
+	// Figure out our filename or hint.
+	var s string
+	if vma.hint != "" {
+		s = vma.hint
+	} else if vma.id != nil {
+		// FIXME: We are holding mm.mappingMu here, which is
+		// consistent with Linux's holding mmap_sem in
+		// fs/proc/task_mmu.c:show_map_vma() => fs/seq_file.c:seq_file_path().
+		// However, it's not clear that fs.File.MappedName() is actually
+		// consistent with this lock order.
+		s = vma.id.MappedName(ctx)
+	}
+	if s != "" {
+		// Per linux, we pad until the 74th character.
+		if pad := 73 - b.Len(); pad > 0 {
+			b.WriteString(strings.Repeat(" ", pad))
+		}
+		b.WriteString(s)
+	}
+	b.WriteString("\n")
+	return b.Bytes()
+}
-- 
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