Handle Photon's "/dev/root" mount point when doing disk device mapping

Photon EFI boot VMs have the root disc mounted long before the various
PCI controllers are initialized and the attached devices enumerated.
When looking through the /proc/mounts, the root filesystem mounted
at '/' is displayed as if on device /dev/root/  But there is no "root"
device in /dev, nor in the PCI device tree at /sys/class/block.  Later
Photon builds fabricate a block device at "/dev/root" but again nothing
in the /sys/class/block PCI tree.

For this situation, it is necessary to use the pseudo device's major and
minor number to access the PCI device tree through /sys/dev/block.
The major and minor device number can be extracted from the contents of
/proc/self/mountinfo.

19 0 8:2 / / rw,relatime shared:1 - ext4 /dev/root rw

The 3rd field is the major:minor number and the 9th or 10th, depending
on Linux release, is the pseudo device in this case.

diff --git a/open-vm-tools/services/plugins/guestInfo/diskInfo.c b/open-vm-tools/services/plugins/guestInfo/diskInfo.c
index 032c09285113cf0cfded609a0c2fbc9cf7951912..c203c159984e3af0bec6e9f4710ce22c8617c6fe 100644 (file)
--- a/open-vm-tools/services/plugins/guestInfo/diskInfo.c
+++ b/open-vm-tools/services/plugins/guestInfo/diskInfo.c
@@ -1,5 +1,5 @@
 /*********************************************************
- * Copyright (C) 2014-2019 VMware, Inc. All rights reserved.
+ * Copyright (C) 2014-2020 VMware, Inc. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License as published
@@ -22,6 +22,7 @@
  *      Get disk information.
  */
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "vm_assert.h"
@@ -68,7 +69,9 @@
    # define PATH_MAX 1024
 #endif
 
-#define LINUX_SYS_BLOCK_DIR "/sys/class/block"
+#define LINUX_SYS_CLASS_BLOCK_DIR "/sys/class/block"
+#define LINUX_SYS_DEV_BLOCK_DIR "/sys/dev/block"
+#define LINUX_PROC_SELF_MOUNTINFO "/proc/self/mountinfo"
 
 #define PCI_IDE         0x010100
 #define PCI_SATA_AHCI_1 0x010601
@@ -577,11 +580,12 @@ finished:
  * @param[in]     devNum     The number of the DiskDevName to be updated.
  *                           The diskDevNames is numbered  1, 2, ... as opposed
  *                           to array indexes which start at 0.
+ * @return TRUE if the device name for the disk has been determined.
  *
  ******************************************************************************
  */
 
-static void
+static Bool
 GuestInfoLinuxBlockDevice(const char *startPath,
                           PartitionEntryInt *partEntry,
                           int devNum)
@@ -596,6 +600,7 @@ GuestInfoLinuxBlockDevice(const char *startPath,
    char *unit = NULL;
    unsigned int devClass;
    char devName[DISK_DEVICE_NAME_SIZE];
+   Bool devNameSet;
 
    ASSERT(startPath);
    ASSERT(partEntry);
@@ -690,8 +695,10 @@ finished:
    g_clear_error(&gErr);
    g_free(unit);
    free(realPath);
+   devNameSet = devName[0] != '\0';
    g_debug("%s: Filesystem of interest found on device \"%s\"\n",
-          __FUNCTION__, devName[0] == '\0' ? "** unknown **" : devName);
+           __FUNCTION__, devNameSet ? devName : "** unknown **");
+   return devNameSet;
 }
 
 
@@ -736,7 +743,7 @@ GuestInfoIsLinuxLvmDevice(const char *fsName,
    if ((realPath = Posix_RealPath(fsName)) == NULL) {
       return FALSE;
    }
-   Str_Snprintf(slavesPath, PATH_MAX, "%s/%s/slaves", LINUX_SYS_BLOCK_DIR,
+   Str_Snprintf(slavesPath, PATH_MAX, "%s/%s/slaves", LINUX_SYS_CLASS_BLOCK_DIR,
                 strrchr(realPath, '/') + 1);
    free(realPath);
    if (!File_IsDirectory(slavesPath)) {
@@ -778,6 +785,70 @@ GuestInfoIsLinuxLvmDevice(const char *fsName,
    return TRUE;
 }
 
+
+/*
+ ******************************************************************************
+ * GuestInfoCheckDevRoot --
+ *
+ * Disks mounted on /dev/root are setup at boot time before the OS enumerates
+ * the PCI devices in /sys/class/block.  The device for /dev/root does not
+ * appear there.   Instead the PCI device info needs to be accessed through
+ * /sys/dev/block and the major and minor device number.  That can be extracted
+ * from the contents of /proc/self/mountinfo.
+ *
+ * The format of the lines in /proc/self/mountinfo can vary between Linux
+ * versions.
+ *
+ *    Field
+ *    -----
+ *      3     The major and minor number of the device in "m:n" format.
+ *   9 or 10  The fsName for this specific entry.
+ *
+ * @param[in]  fsName       Name of the filesystem device - i.e. /dev/root
+ * @param[in]  pathLen      Maximum size including terminating NUL character
+ *                          for the starting search path.
+ * @param[out] blockDevPath Starting path to begin the search for the "device"
+ *                          file if the major and minor number can be found.
+ * @return TRUE if the device major and minor numbers have been located and
+ *         blockDevPath has been filled in.
+ *
+ ******************************************************************************
+ */
+
+static Bool
+GuestInfoCheckDevRoot(const char *fsName,
+                      int pathLen,
+                      char *blockDevPath)
+{
+   FILE *mountinfo;
+   char buffer[BUFSIZ];
+   char pattern[128];
+
+   if ((mountinfo = fopen(LINUX_PROC_SELF_MOUNTINFO, "r")) == NULL) {
+      g_debug("%s: unable to open \"" LINUX_PROC_SELF_MOUNTINFO
+              "\": (%d) %s\n", __FUNCTION__, errno, strerror(errno));
+      return FALSE;
+   }
+   snprintf(pattern, sizeof pattern, " %s ", fsName);
+   /* Locate the "/dev/root" entry in /proc/self/mountinfo. */
+   while ((fgets(buffer, sizeof buffer, mountinfo)) != NULL) {
+      if (strstr(buffer, pattern) != NULL) {
+         char *savedPtr = NULL;
+         const char *majMinNo;
+
+         (void) strtok_r(buffer, " ", &savedPtr);
+         (void) strtok_r(NULL, " ", &savedPtr);
+         majMinNo = strtok_r(NULL, " ", &savedPtr);
+         Str_Snprintf(blockDevPath, pathLen, "%s/%s", LINUX_SYS_DEV_BLOCK_DIR,
+                      majMinNo);
+         fclose(mountinfo);
+         return TRUE;
+      }
+   }
+   fclose(mountinfo);
+   return FALSE;
+}
+
 #endif /* __linux__ */
 
 /*
@@ -833,10 +904,24 @@ GuestInfoGetDiskDevice(const char *fsName,
        * lookup; avoid at this time.
        */
       if (baseDevName != NULL && strcmp(partEntry->fsType, "zfs") != 0) {
-         Str_Snprintf(blockDevPath, PATH_MAX,  "%s/%s", LINUX_SYS_BLOCK_DIR,
-                      baseDevName + 1);
-         /* First and only disk device. */
-         GuestInfoLinuxBlockDevice(blockDevPath, partEntry, 1);
+         /*
+          * Have a single disk device associated with this mount point.  The
+          * majority of these will be handled by the basic Linux block device
+          * lookup.
+          */
+         Str_Snprintf(blockDevPath, sizeof blockDevPath,  "%s/%s",
+                      LINUX_SYS_CLASS_BLOCK_DIR, baseDevName + 1);
+         if (!GuestInfoLinuxBlockDevice(blockDevPath, partEntry, 1)) {
+            /*
+             * No device name was located.  This may be a pseudo device
+             * such as Photon's /dev/root.  Try a lookup based on the device
+             * major and minor number.
+             */
+            if (GuestInfoCheckDevRoot(fsName, sizeof blockDevPath,
+                                      blockDevPath)) {
+               GuestInfoLinuxBlockDevice(blockDevPath, partEntry, 1);
+            }
+         }
       }
    }