update_engine: use librootdev
Rewrote BootDevice() to call rootdev() with full resolution
enabled. BootDevice() was crawling /proc/cmdline while rootdev()
uses /sys. We should have both /proc and /sys normally so hopefully
this is a minor change to get us to a working updater over dm-verity.
TEST=none yet.
BUG=chromium-os:5938
Change-Id: I7ee654d5b429d67d65e9729210ef839c58fa1d34
Review URL: http://codereview.chromium.org/3232004
diff --git a/SConstruct b/SConstruct
index b5c2c70..4df1395 100644
--- a/SConstruct
+++ b/SConstruct
@@ -165,6 +165,7 @@
metrics
protobuf
pthread
+ rootdev
ssl
xml2
z""")
diff --git a/utils.cc b/utils.cc
index 246bfaa..1d1cb7d 100644
--- a/utils.cc
+++ b/utils.cc
@@ -18,11 +18,13 @@
#include <algorithm>
-#include "base/file_path.h"
-#include "base/file_util.h"
-#include "base/rand_util.h"
-#include "base/string_util.h"
-#include "base/logging.h"
+#include <base/file_path.h>
+#include <base/file_util.h>
+#include <base/rand_util.h>
+#include <base/string_util.h>
+#include <base/logging.h>
+#include <rootdev/rootdev.h>
+
#include "update_engine/file_writer.h"
#include "update_engine/omaha_request_params.h"
#include "update_engine/subprocess.h"
@@ -363,31 +365,21 @@
return 0 == str.compare(0, prefix.size(), prefix);
}
-const string BootDevice() {
- string proc_cmdline;
- if (!ReadFileToString("/proc/cmdline", &proc_cmdline))
- return "";
- // look for "root=" in the command line
- string::size_type pos = 0;
- if (!StringHasPrefix(proc_cmdline, "root=")) {
- pos = proc_cmdline.find(" root=") + 1;
- }
- if (pos == string::npos) {
- // can't find root=
+const std::string BootDevice() {
+ char boot_path[PATH_MAX];
+ // Resolve the boot device path fully, including dereferencing
+ // through dm-verity.
+ int ret = rootdev(boot_path, sizeof(boot_path), true, false);
+
+ if (ret < 0) {
+ LOG(ERROR) << "rootdev failed to find the root device";
return "";
}
- // at this point, pos is the point in the string where "root=" starts
- string ret;
- pos += strlen("root="); // advance to the device name itself
- while (pos < proc_cmdline.size()) {
- char c = proc_cmdline[pos];
- if (c == ' ')
- break;
- ret += c;
- pos++;
- }
- return ret;
- // TODO(adlr): use findfs to figure out UUID= or LABEL= filesystems
+ LOG_IF(WARNING, ret > 0) << "rootdev found a device name with no device node";
+
+ // This local variable is used to construct the return string and is not
+ // passed around after use.
+ return boot_path;
}
const string BootKernelDevice(const std::string& boot_device) {
