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From: Will Drewry on 2 Aug 2010 22:50
efi_partition_walk provides a generic mechanism for iterating over a partition
table using a callback over the GPT entry data. However, it avoids exposing
too many internals while still providing less specialized access than the
previous patch.

The same questions apply - any and all feedback is truly appreciated.

I'll post an updated version of the original with feedback from Joe Perches and
David Miller shortly.

Signed-off-by: Will Drewry <wad(a)chromium.org>
---
fs/partitions/efi.c | 123 ++++++++++++++++++++++++++++++++++++++-------------
include/linux/efi.h | 9 ++++
2 files changed, 101 insertions(+), 31 deletions(-)

diff --git a/fs/partitions/efi.c b/fs/partitions/efi.c
index 9efb2cf..cfb52ac 100644
--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -580,56 +580,117 @@ static int find_valid_gpt(struct parsed_partitions *state, gpt_header **gpt,
}

/**
- * efi_partition(struct parsed_partitions *state)
- * @state
+ * efi_partition_walk
+ * @bdev: Whole block device to scan for a GPT.
+ * @walk_arg: Opaque data to pass to the walker
+ * @walk: Function to walk valid GPT entries
*
- * Description: called from check.c, if the disk contains GPT
- * partitions, sets up partition entries in the kernel.
+ * If walk() returns non-zero, then the walk will terminate early.
*
- * If the first block on the disk is a legacy MBR,
- * it will get handled by msdos_partition().
- * If it's a Protective MBR, we'll handle it here.
+ * We ignore the GPT entry so the first number refers to the first
+ * data partition.
*
- * We do not create a Linux partition for GPT, but
- * only for the actual data partitions.
* Returns:
- * -1 if unable to read the partition table
- * 0 if this isn't our partition table
- * 1 if successful
+ * -1 if an error occurred or unable to read
+ * 0 if there is no gpt entry
+ * 1 if traversal occurred (even if terminated early)
*
*/
-int efi_partition(struct parsed_partitions *state)
+int efi_partition_walk(struct block_device *bdev, void *walk_arg,
+ efi_partition_callback_t walk)
{
gpt_header *gpt = NULL;
gpt_entry *ptes = NULL;
+ struct parsed_partitions *state = NULL;
+ unsigned ssz = 0;
u32 i;
- unsigned ssz = bdev_logical_block_size(state->bdev) / 512;

- if (!find_valid_gpt(state, &gpt, &ptes) || !gpt || !ptes) {
+ if (!bdev || !walk)
+ return -1;
+
+ ssz = bdev_logical_block_size(bdev) / 512;
+
+ state = kzalloc(sizeof(struct parsed_partitions), GFP_KERNEL);
+ if (!state)
+ return -1;
+ state->limit = disk_max_parts(bdev->bd_disk);
+ state->bdev = bdev;
+
+ pr_debug(KERN_WARNING "efi_find_partition looking for gpt\n");
+ if (!find_valid_gpt(state, &gpt, &ptes) || !gpt || !ptes) {
+ pr_debug(KERN_WARNING "efi_find_partition no GPT\n");
kfree(gpt);
kfree(ptes);
+ kfree(state);
return 0;
}

- pr_debug("GUID Partition Table is valid! Yea!\n");
-
- for (i = 0; i < le32_to_cpu(gpt->num_partition_entries) && i < state->limit-1; i++) {
- u64 start = le64_to_cpu(ptes[i].starting_lba);
- u64 size = le64_to_cpu(ptes[i].ending_lba) -
- le64_to_cpu(ptes[i].starting_lba) + 1ULL;
-
- if (!is_pte_valid(&ptes[i], last_lba(state->bdev)))
+ pr_debug(KERN_WARNING "efi_find_partition: 0 -> %d (limit:%d)\n",
+ le32_to_cpu(gpt->num_partition_entries),
+ state->limit);
+ for (i = 0; i < le32_to_cpu(gpt->num_partition_entries) &&
+ i < state->limit-1; i++) {
+ /* Convert start and size to sectors from lbas */
+ sector_t start = le64_to_cpu(ptes[i].starting_lba) * ssz;
+ sector_t size = ssz * (le64_to_cpu(ptes[i].ending_lba) -
+ le64_to_cpu(ptes[i].starting_lba) + 1ULL);
+ if (!is_pte_valid(&ptes[i], last_lba(bdev)))
continue;
-
- put_partition(state, i+1, start * ssz, size * ssz);
-
- /* If this is a RAID volume, tell md */
- if (!efi_guidcmp(ptes[i].partition_type_guid,
- PARTITION_LINUX_RAID_GUID))
- state->parts[i + 1].flags = ADDPART_FLAG_RAID;
+ if (walk(i+1,
+ &ptes[i].partition_type_guid,
+ &ptes[i].unique_partition_guid,
+ start, size, walk_arg) != 0)
+ break;
}
kfree(ptes);
kfree(gpt);
- printk("\n");
+ kfree(state);
return 1;
}
+
+/**
+ * efi_partition_add
+ * @num: current partition number
+ * @entry: gpt_entry
+ * @arg: void * to a struct parsed_partition *
+ *
+ * Callback for efi_partition().
+ */
+static int efi_partition_add(int num, efi_guid_t *partition_type_guid,
+ efi_guid_t *unique_partition_guid, sector_t start, sector_t size,
+ void *arg)
+{
+ struct parsed_partitions *state = arg;
+
+ put_partition(state, num, start, size);
+
+ /* If this is a RAID volume, tell md */
+ if (!efi_guidcmp(*partition_type_guid, PARTITION_LINUX_RAID_GUID))
+ state->parts[num].flags = 1;
+ return 0;
+}
+
+
+/**
+ * efi_partition(struct parsed_partitions *state)
+ * @state
+ *
+ * Description: called from check.c, if the disk contains GPT
+ * partitions, sets up partition entries in the kernel.
+ *
+ * If the first block on the disk is a legacy MBR,
+ * it will get handled by msdos_partition().
+ * If it's a Protective MBR, we'll handle it here.
+ *
+ * We do not create a Linux partition for GPT, but
+ * only for the actual data partitions.
+ * Returns:
+ * -1 if unable to read the partition table
+ * 0 if this isn't our partition table
+ * 1 if successful
+ *
+ */
+int efi_partition(struct parsed_partitions *state)
+{
+ return efi_partition_walk(state->bdev, state, efi_partition_add);
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index fb737bc..15165bc 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -301,6 +301,15 @@ extern unsigned long efi_get_time(void);
extern int efi_set_rtc_mmss(unsigned long nowtime);
extern struct efi_memory_map memmap;

+#ifdef CONFIG_EFI_PARTITION
+typedef int (*efi_partition_callback_t) (int num,
+ efi_guid_t *partition_type_guid, efi_guid_t *unique_partition_guid,
+ sector_t start, sector_t size, void *arg);
+struct block_device;
+int efi_partition_walk(struct block_device *bdev, void *walk_arg,
+ efi_partition_callback_t walk);
+#endif
+
/**
* efi_range_is_wc - check the WC bit on an address range
* @start: starting kvirt address
--
1.7.0.4

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Prev: linux-next: Fix AppArmor build warnings after merge of the security-testing tree
Next: [PATCH v2 RFC] efi: add and expose efi_partition_by_guid