[PATCH v4] commands/search: Add support to search by PARTUUID

[Vitaly Kuzmichev]

Improve 'search' grub-shell command with functionality to search for
a partition by PARTUUID string. This is useful for embedded systems
where FSUUID is not guaranteed to be constant, e.g. it is not preserved
between system updates, and modifying grub.cfg is undesired.

V2:
This patch is based on Michael Grzeschik version from 27 May 2019 [1]
with the following changes:

1. Addressed review feedback from Daniel Kiper [2] and Nick Vinson [3].

2. Added support for GPT PARTUUID.

3. Moved MBR disk signature reading from partmap/msdos.c to
commands/search.c to read it only when it is needed.

[1] https://lists.gnu.org/archive/html/grub-devel/2019-05/msg00124.html
[2] https://lists.gnu.org/archive/html/grub-devel/2019-05/msg00131.html
[3] https://lists.gnu.org/archive/html/grub-devel/2019-05/msg00134.html

V3, V4:
Coding style and spelling fixes.

Signed-off-by: Vitaly Kuzmichev <vkuzmichev@dev.rtsoft.ru>
---
 grub-core/Makefile.core.def          |  5 ++
 grub-core/commands/search.c          | 80 +++++++++++++++++++++++++++-
 grub-core/commands/search_partuuid.c |  5 ++
 grub-core/commands/search_wrap.c     | 10 +++-
 include/grub/search.h                |  2 +
 5 files changed, 98 insertions(+), 4 deletions(-)
 create mode 100644 grub-core/commands/search_partuuid.c

diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 8022e1c0a..4568943e3 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -1063,6 +1063,11 @@ module = {
   common = commands/search_file.c;
 };
 
+module = {
+  name = search_partuuid;
+  common = commands/search_partuuid.c;
+};
+
 module = {
   name = search_fs_uuid;
   common = commands/search_uuid.c;
diff --git a/grub-core/commands/search.c b/grub-core/commands/search.c
index ed090b3af..9b690ba85 100644
--- a/grub-core/commands/search.c
+++ b/grub-core/commands/search.c
@@ -54,6 +54,28 @@ struct search_ctx
   int is_cache;
 };
 
+#ifdef DO_SEARCH_PARTUUID
+#include <grub/gpt_partition.h>
+#include <grub/i386/pc/boot.h>
+
+/* Helper for iterate_device. */
+static char *
+convert_gpt_guid_to_str (grub_gpt_part_guid_t *gpt_guid)
+{
+  /* Convert mixed-endian UUID from bytes to string */
+  return
+    grub_xasprintf (
+      "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+       grub_le_to_cpu32 (gpt_guid->data1),
+       grub_le_to_cpu16 (gpt_guid->data2),
+       grub_le_to_cpu16 (gpt_guid->data3),
+       gpt_guid->data4[0], gpt_guid->data4[1],
+       gpt_guid->data4[2], gpt_guid->data4[3],
+       gpt_guid->data4[4], gpt_guid->data4[5],
+       gpt_guid->data4[6], gpt_guid->data4[7]);
+}
+#endif
+
 /* Helper for FUNC_NAME.  */
 static int
 iterate_device (const char *name, void *data)
@@ -66,13 +88,63 @@ iterate_device (const char *name, void *data)
       name[0] == 'f' && name[1] == 'd' && name[2] >= '0' && name[2] <= '9')
     return 1;
 
-#ifdef DO_SEARCH_FS_UUID
+#if defined (DO_SEARCH_FS_UUID) || defined (DO_SEARCH_PARTUUID)
 #define compare_fn grub_strcasecmp
 #else
 #define compare_fn grub_strcmp
 #endif
 
-#ifdef DO_SEARCH_FILE
+#ifdef DO_SEARCH_PARTUUID
+    {
+      struct grub_gpt_partentry gptdata;
+      grub_uint32_t disk_sig;
+      grub_disk_t ptdisk;
+      grub_disk_t disk;
+      char *part_uuid;
+
+      ptdisk = grub_disk_open (name);
+      if (ptdisk && ptdisk->partition && ptdisk->partition->partmap)
+       {
+         if (grub_strcmp (ptdisk->partition->partmap->name, "gpt") == 0)
+           {
+             disk = grub_disk_open (ptdisk->name);
+             if (disk && grub_disk_read (disk, ptdisk->partition->offset,
+                                         ptdisk->partition->index,
+                                         sizeof (gptdata), &gptdata) == 0)
+               {
+                 part_uuid = convert_gpt_guid_to_str (&gptdata.guid);
+
+                 if (part_uuid && compare_fn (part_uuid, ctx->key) == 0)
+                   found = 1;
+                 if (part_uuid)
+                   grub_free (part_uuid);
+               }
+             if (disk)
+               grub_disk_close (disk);
+           }
+         else if (grub_strcmp (ptdisk->partition->partmap->name, "msdos") == 0)
+           {
+             disk = grub_disk_open (ptdisk->name);
+             if (disk && grub_disk_read (disk, 0,
+                                         GRUB_BOOT_MACHINE_WINDOWS_NT_MAGIC,
+                                         sizeof (disk_sig), &disk_sig) == 0)
+               {
+                 part_uuid = grub_xasprintf ("%08x-%02x",
+                                             grub_le_to_cpu32 (disk_sig),
+                                             ptdisk->partition->index + 1);
+                 if (part_uuid && compare_fn (part_uuid, ctx->key) == 0)
+                   found = 1;
+                 if (part_uuid)
+                   grub_free (part_uuid);
+               }
+             if (disk)
+               grub_disk_close (disk);
+           }
+       }
+      if (ptdisk)
+       grub_disk_close (ptdisk);
+    }
+#elif defined (DO_SEARCH_FILE)
     {
       char *buf;
       grub_file_t file;
@@ -313,6 +385,8 @@ static grub_command_t cmd;
 
 #ifdef DO_SEARCH_FILE
 GRUB_MOD_INIT(search_fs_file)
+#elif defined (DO_SEARCH_PARTUUID)
+GRUB_MOD_INIT(search_partuuid)
 #elif defined (DO_SEARCH_FS_UUID)
 GRUB_MOD_INIT(search_fs_uuid)
 #else
@@ -327,6 +401,8 @@ GRUB_MOD_INIT(search_label)
 
 #ifdef DO_SEARCH_FILE
 GRUB_MOD_FINI(search_fs_file)
+#elif defined (DO_SEARCH_PARTUUID)
+GRUB_MOD_FINI(search_partuuid)
 #elif defined (DO_SEARCH_FS_UUID)
 GRUB_MOD_FINI(search_fs_uuid)
 #else
diff --git a/grub-core/commands/search_partuuid.c 
b/grub-core/commands/search_partuuid.c
new file mode 100644
index 000000000..e4aa20b5f
--- /dev/null
+++ b/grub-core/commands/search_partuuid.c
@@ -0,0 +1,5 @@
+#define DO_SEARCH_PARTUUID 1
+#define FUNC_NAME grub_search_partuuid
+#define COMMAND_NAME "search.partuuid"
+#define HELP_MESSAGE N_("Search devices by PARTUUID. If VARIABLE is specified, 
the first device found is set to a variable.")
+#include "search.c"
diff --git a/grub-core/commands/search_wrap.c b/grub-core/commands/search_wrap.c
index 47fc8eb99..f516b584e 100644
--- a/grub-core/commands/search_wrap.c
+++ b/grub-core/commands/search_wrap.c
@@ -36,6 +36,8 @@ static const struct grub_arg_option options[] =
      0, 0},
     {"fs-uuid",                'u', 0, N_("Search devices by a filesystem 
UUID."),
      0, 0},
+    {"partuuid",       'p', 0, N_("Search devices by a PARTUUID."),
+     0, 0},
     {"set",            's', GRUB_ARG_OPTION_OPTIONAL,
      N_("Set a variable to the first device found."), N_("VARNAME"),
      ARG_TYPE_STRING},
@@ -71,6 +73,7 @@ enum options
     SEARCH_FILE,
     SEARCH_LABEL,
     SEARCH_FS_UUID,
+    SEARCH_PARTUUID,
     SEARCH_SET,
     SEARCH_NO_FLOPPY,
     SEARCH_HINT,
@@ -186,6 +189,9 @@ grub_cmd_search (grub_extcmd_context_t ctxt, int argc, char 
**args)
   else if (state[SEARCH_FS_UUID].set)
     grub_search_fs_uuid (id, var, state[SEARCH_NO_FLOPPY].set,
                         hints, nhints);
+  else if (state[SEARCH_PARTUUID].set)
+    grub_search_partuuid (id, var, state[SEARCH_NO_FLOPPY].set,
+                         hints, nhints);
   else if (state[SEARCH_FILE].set)
     grub_search_fs_file (id, var, state[SEARCH_NO_FLOPPY].set, 
                         hints, nhints);
@@ -206,8 +212,8 @@ GRUB_MOD_INIT(search)
                          GRUB_COMMAND_FLAG_EXTRACTOR | 
GRUB_COMMAND_ACCEPT_DASH,
                          N_("[-f|-l|-u|-s|-n] [--hint HINT [--hint HINT] ...]"
                             " NAME"),
-                         N_("Search devices by file, filesystem label"
-                            " or filesystem UUID."
+                         N_("Search devices by file, filesystem label,"
+                            " PARTUUID or filesystem UUID."
                             " If --set is specified, the first device found is"
                             " set to a variable. If no variable name is"
                             " specified, `root' is used."),
diff --git a/include/grub/search.h b/include/grub/search.h
index d80347df3..7755645f6 100644
--- a/include/grub/search.h
+++ b/include/grub/search.h
@@ -25,5 +25,7 @@ void grub_search_fs_uuid (const char *key, const char *var, 
int no_floppy,
                          char **hints, unsigned nhints);
 void grub_search_label (const char *key, const char *var, int no_floppy,
                        char **hints, unsigned nhints);
+void grub_search_partuuid (const char *key, const char *var, int no_floppy,
+                          char **hints, unsigned nhints);
 
 #endif
-- 
2.25.1