Add PARTUUID detection support

To help clean the code and simplify the code in util/grub-probe.c, this patch renames grub_gpt_part_type to grub_gpt_part_guid and updates grub_gpt_partentry to use this type for both the partition type GUID string and the partition GUID string entries.

This patch also moves the GUID printing logic in util/grub-probe.c to a separate function. This change allows the partuuid logic in the next commit to use the same printing logic without having to completely duplicate it.

Quoted 5 lines · Nicholas Vinson

To help clean the code and simplify the code in util/grub-probe.c, this patch renames grub_gpt_part_type to grub_gpt_part_guid and updates grub_gpt_partentry to use this type for both the partition type GUID string and the partition GUID string entries.

Quoted 4 lines

This patch also moves the GUID printing logic in util/grub-probe.c to a separate function. This change allows the partuuid logic in the next commit to use the same printing logic without having to completely duplicate it.

One logical change per patch please...

And please add your SOB next time.

Daniel

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 specifing 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.

---
 util/grub-probe.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

util/grub-probe.c +9 -0

index 21cb80fbe..3656e32e8 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 +184,48 @@ probe_partmap (grub_disk_t disk, char delim)
     }
 }
 
+static void
+probe_partuuid (grub_disk_t disk, char delim)
+{
+  /*
+   * Nested partitions not supported for now.
+   * Non-nested partitions must have disk->partition->parent == NULL

Quoted 62 lines · Nicholas Vinson

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 specifing 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.

---
 util/grub-probe.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

util/grub-probe.c +9 -0

index 21cb80fbe..3656e32e8 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 +184,48 @@ probe_partmap (grub_disk_t disk, char delim)
     }
 }
 
+static void
+probe_partuuid (grub_disk_t disk, char delim)
+{
+  /*
+   * Nested partitions not supported for now.
+   * Non-nested partitions must have disk->partition->parent == NULL

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 202

Quoted 10 lines

util/grub-probe.c +10 -0

+   */
+  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.
+	     */
+            grub_uint32_t nt_disk_sig;

Here you use spaces...

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 203

Quoted 1 line

util/grub-probe.c +1 -0

+	    grub_partition_t p = disk->partition;

...and here tab and spaces. I prefer the latter.
Please fix this.

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 211

Quoted 8 lines

util/grub-probe.c +8 -0

+	    disk->partition = p->parent;
+
+	    if (grub_disk_read (disk, 0, GRUB_BOOT_MACHINE_WINDOWS_NT_MAGIC,
+				sizeof(nt_disk_sig), &nt_disk_sig) == 0)
+	      {
+		grub_printf ("%08x-%02x",
+			     grub_le_to_cpu32(nt_disk_sig), 1 + p->number);
+	      }

These curly brackets are not needed. Please remove them and leave empty line before next instruction.

Quoted 6 lines

util/grub-probe.c +6 -0

+	    disk->partition = p;
+	}
+      else if (strcmp(disk->partition->partmap->name, "gpt") == 0)
+	{
+	  grub_partition_t p = disk->partition;
+	  struct grub_gpt_partentry gptdata;

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 223

Quoted 6 lines

util/grub-probe.c +6 -0

+
+	  disk->partition = p->parent;
+
+	  if (grub_disk_read (disk, p->offset, p->index,
+			      sizeof(gptdata), &gptdata) == 0)
+	    print_gpt_guid(gptdata.guid);

Please add empty line here.

util/grub-probe.c probe_partmap (grub_disk_t disk, char delim) · line 228

Quoted 5 lines

util/grub-probe.c +5 -0

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

Otherwise patch LGMT.

Daniel

Update grub-mkconfig.in and 10_linux.in to support grub-probe's new partuuid target. Update grub.texi documenation.

Quoted 2 lines · Nicholas Vinson

Update grub-mkconfig.in and 10_linux.in to support grub-probe's new partuuid target. Update grub.texi documenation.

As earlier lack of SOB. Otherwise LGTM.

Daniel