Add PARTUUID detection support

Add PARTUUID detection support grub-probe for MBR and GPT partition schemes.

Signed-off-by Nicholas Vinson <[email protected]>

---
 util/grub-probe.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

util/grub-probe.c +3 -0

index 21cb80fbe..48ef1e2ec 100644
@@ -28,6 +28,7 @@
 #include <grub/partition.h>
 #include <grub/msdos_partition.h>
 #include <grub/gpt_partition.h>
+#include <grub/i386/pc/boot.h>
 #include <grub/emu/hostdisk.h>
 #include <grub/emu/getroot.h>
 #include <grub/term.h>

@@ -62,6 +63,7 @@ enum {
   PRINT_DRIVE,
   PRINT_DEVICE,
   PRINT_PARTMAP,
+  PRINT_PARTUUID,
   PRINT_ABSTRACTION,
   PRINT_CRYPTODISK_UUID,
   PRINT_HINT_STR,

@@ -85,6 +87,7 @@ static const char *targets[] =
     [PRINT_DRIVE]              = "drive",
     [PRINT_DEVICE]             = "device",
     [PRINT_PARTMAP]            = "partmap",
+    [PRINT_PARTUUID]           = "partuuid",
     [PRINT_ABSTRACTION]        = "abstraction",
     [PRINT_CRYPTODISK_UUID]    = "cryptodisk_uuid",
     [PRINT_HINT_STR]           = "hints_string",

util/grub-probe.c +8 -0

+  /*
+   * Nested partitions not supported for now.
+   * Non-nested partitions must have disk->partition->parent == NULL
+   */
+  if (disk->partition && disk->partition->parent == NULL)
+    {
+      if (strcmp(disk->partition->partmap->name, "msdos") == 0)
+	{

Hello,

This is a request to add PARTUUID detection support grub-probe for MBR and GPT partition schemes. The Linux kernel supports mounting the root filesystem by Linux device name or by the Partition [GU]UID. GRUB's mkconfig, however, currently only supports specifying the rootfs in the kernel command-line by Linux device name unless an initramfs is also present. When an initramfs is present GRUB's mkconfig will set the kernel's root parameter value to either the Linux device name or to the filesystem [GU]UID.

Therefore, the only way to protect a Linux system from failing to boot when its Linux storage device names change is to either manually edit grub.cfg or /etc/default/grub and append root=PARTUUID=xxx to the command-line or create an initramfs that understands how to mount devices by filesystem [G]UID and let grub-mkconfig pass the filesystem [GU]UID to the initramfs.

The goal of this patch set is to enable root=PARTUUID=xxx support in grub-mkconfig, so that users don't have to manually edit /etc/default/grub or grub.cfg, or create an initramfs for the sole purpose of having a robust bootloader configuration for Linux.

Quoted 40 lines · Nicholas Vinson

Add PARTUUID detection support grub-probe for MBR and GPT partition schemes.

Signed-off-by Nicholas Vinson <[email protected]>

---
 util/grub-probe.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

util/grub-probe.c +3 -0

index 21cb80fbe..48ef1e2ec 100644
@@ -28,6 +28,7 @@
 #include <grub/partition.h>
 #include <grub/msdos_partition.h>
 #include <grub/gpt_partition.h>
+#include <grub/i386/pc/boot.h>
 #include <grub/emu/hostdisk.h>
 #include <grub/emu/getroot.h>
 #include <grub/term.h>

@@ -62,6 +63,7 @@ enum {
   PRINT_DRIVE,
   PRINT_DEVICE,
   PRINT_PARTMAP,
+  PRINT_PARTUUID,
   PRINT_ABSTRACTION,
   PRINT_CRYPTODISK_UUID,
   PRINT_HINT_STR,

@@ -85,6 +87,7 @@ static const char *targets[] =
     [PRINT_DRIVE]              = "drive",
     [PRINT_DEVICE]             = "device",
     [PRINT_PARTMAP]            = "partmap",
+    [PRINT_PARTUUID]           = "partuuid",
     [PRINT_ABSTRACTION]        = "abstraction",
     [PRINT_CRYPTODISK_UUID]    = "cryptodisk_uuid",
     [PRINT_HINT_STR]           = "hints_string",

@@ -181,6 +184,45 @@ probe_partmap (grub_disk_t disk, char delim)
     }
 }
 

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 190

Quoted 4 lines

util/grub-probe.c +4 -0

+static void
+probe_partuuid (grub_disk_t disk, char delim)
+{
+  grub_partition_t p = disk->partition;

Lack of empty line.

Quoted 13 lines

util/grub-probe.c +12 -0

+  /*
+   * Nested partitions not supported for now.
+   * Non-nested partitions must have disk->partition->parent == NULL
+   */
+  if (disk->partition && disk->partition->parent == NULL)
+    {
+      if (strcmp(disk->partition->partmap->name, "msdos") == 0)
+	{
+	    /*
+	     * The partition GUID for MSDOS is the partition number (starting
+	     * with 1) prepended with the NT disk signature.
+	     */

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 208

Quoted 6 lines

util/grub-probe.c +6 -0

+	    grub_uint32_t nt_disk_sig;
+	    disk->partition = p->parent;
+
+	    if (grub_disk_read (disk, 0, GRUB_BOOT_MACHINE_WINDOWS_NT_MAGIC,
+				sizeof(nt_disk_sig), &nt_disk_sig) == 0)
+

Redundant empty line.

Quoted 4 lines

util/grub-probe.c +3 -0

+		grub_printf ("%08x-%02x",
+			     grub_le_to_cpu32(nt_disk_sig), 1 + p->number);
+	}

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 221

Quoted 10 lines

util/grub-probe.c +10 -0

+      else if (strcmp(disk->partition->partmap->name, "gpt") == 0)
+	{
+	  struct grub_gpt_partentry gptdata;
+
+	  disk->partition = p->parent;
+
+	  if (grub_disk_read (disk, p->offset, p->index,
+			      sizeof(gptdata), &gptdata) == 0)
+	    print_gpt_guid(gptdata.guid);
+	}

Why "disk->partition = p;" is not here? Because compiler complains if it is here?

Anyway, if I know the reason for above I can fix earlier ntipicks myself before commiting this patch.> Well, "disk->partition = p->parent;" can be before "if (strcmp(disk->partition->partmap->name, "msdos") == 0)". Am I right?

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 225

Quoted 4 lines

util/grub-probe.c +4 -0

+    }
+  disk->partition = p;
+}
+

Daniel

Quoted 41 lines · Daniel Kiper

Quoted 40 lines · Nicholas Vinson

Add PARTUUID detection support grub-probe for MBR and GPT partition schemes.

Signed-off-by Nicholas Vinson <[email protected]>

---
 util/grub-probe.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

util/grub-probe.c +3 -0

index 21cb80fbe..48ef1e2ec 100644
@@ -28,6 +28,7 @@
 #include <grub/partition.h>
 #include <grub/msdos_partition.h>
 #include <grub/gpt_partition.h>
+#include <grub/i386/pc/boot.h>
 #include <grub/emu/hostdisk.h>
 #include <grub/emu/getroot.h>
 #include <grub/term.h>

@@ -62,6 +63,7 @@ enum {
   PRINT_DRIVE,
   PRINT_DEVICE,
   PRINT_PARTMAP,
+  PRINT_PARTUUID,
   PRINT_ABSTRACTION,
   PRINT_CRYPTODISK_UUID,
   PRINT_HINT_STR,

@@ -85,6 +87,7 @@ static const char *targets[] =
     [PRINT_DRIVE]              = "drive",
     [PRINT_DEVICE]             = "device",
     [PRINT_PARTMAP]            = "partmap",
+    [PRINT_PARTUUID]           = "partuuid",
     [PRINT_ABSTRACTION]        = "abstraction",
     [PRINT_CRYPTODISK_UUID]    = "cryptodisk_uuid",
     [PRINT_HINT_STR]           = "hints_string",

@@ -181,6 +184,45 @@ probe_partmap (grub_disk_t disk, char delim)
     }
 }
 

Quoted 6 lines

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 190

Quoted 4 lines

util/grub-probe.c +4 -0

+static void
+probe_partuuid (grub_disk_t disk, char delim)
+{
+  grub_partition_t p = disk->partition;

Lack of empty line.

added an empty line.

Quoted 13 lines

Quoted 13 lines

util/grub-probe.c +12 -0

+  /*
+   * Nested partitions not supported for now.
+   * Non-nested partitions must have disk->partition->parent == NULL
+   */
+  if (disk->partition && disk->partition->parent == NULL)
+    {
+      if (strcmp(disk->partition->partmap->name, "msdos") == 0)
+	{
+	    /*
+	     * The partition GUID for MSDOS is the partition number (starting
+	     * with 1) prepended with the NT disk signature.
+	     */

Quoted 8 lines

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 208

Quoted 6 lines

util/grub-probe.c +6 -0

+	    grub_uint32_t nt_disk_sig;
+	    disk->partition = p->parent;
+
+	    if (grub_disk_read (disk, 0, GRUB_BOOT_MACHINE_WINDOWS_NT_MAGIC,
+				sizeof(nt_disk_sig), &nt_disk_sig) == 0)
+

Redundant empty line.

removed the empty line.

Quoted 17 lines

Quoted 4 lines

util/grub-probe.c +3 -0

+		grub_printf ("%08x-%02x",
+			     grub_le_to_cpu32(nt_disk_sig), 1 + p->number);
+	}

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 221

Quoted 10 lines

util/grub-probe.c +10 -0

+      else if (strcmp(disk->partition->partmap->name, "gpt") == 0)
+	{
+	  struct grub_gpt_partentry gptdata;
+
+	  disk->partition = p->parent;
+
+	  if (grub_disk_read (disk, p->offset, p->index,
+			      sizeof(gptdata), &gptdata) == 0)
+	    print_gpt_guid(gptdata.guid);
+	}

Why "disk->partition = p;" is not here? Because compiler complains if it is here?

I misread my own diff and thought you had asked for me to put it below instead of here. Either location works, so it's not too critical where it's put.

Quoted 5 lines

Anyway, if I know the reason for above I can fix earlier ntipicks myself before commiting this patch.> Well, "disk->partition = p->parent;" can be before "if (strcmp(disk->partition->partmap->name, "msdos") == 0)". Am I right?

Yes, but it'll require some changes to the checks to make such a change work. For example, "disk->partition->partmap->name" would have to be changed to "p->partmap->name"

I'll send a second email with an updated patch for this commit. If you would like me to regenerate the entire patch set, please let me know.