[PATCH v1 2/8] disk: efi: introduce {read,write}_disk_flags

[dmukhin at ford.com]

From: Denis Mukhin <dmukhin at ford.com> 

Introduce helper functions for updating top 16 bits of GUID partition
table entry attributes. The value can be used to store extra information
about bootflow, such as counters and status.

Signed-off-by: Denis Mukhin <dmukhin at ford.com>
---
 disk/part_efi.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/part.h  |  24 +++++++++
 2 files changed, 153 insertions(+)

diff --git a/disk/part_efi.c b/disk/part_efi.c
index d8b17ec2e91a..6d5520e53912 100644
--- a/disk/part_efi.c
+++ b/disk/part_efi.c
@@ -980,6 +980,135 @@ int write_mbr_and_gpt_partitions(struct blk_desc *desc, void *buf)
 
 	return 0;
 }
+
+int read_disk_flags(struct blk_desc *desc, int partnum, u16 *flags)
+{
+	ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_head, 1, desc->blksz);
+	gpt_entry *gpt_pte = NULL;
+	u64 attrs;
+
+	/* "part" argument must be at least 1 */
+	if (partnum < 1)
+		return -EINVAL;
+
+	gpt_repair_headers(desc);
+
+	/* This function validates AND fills in the GPT header and PTE */
+	if (find_valid_gpt(desc, gpt_head, &gpt_pte) != 1)
+		return -EINVAL;
+
+	if (partnum > le32_to_cpu(gpt_head->num_partition_entries) ||
+	    !is_pte_valid(&gpt_pte[partnum - 1])) {
+		free(gpt_pte);
+		return -EPERM;
+	}
+
+	attrs = le64_to_cpu(gpt_pte[partnum - 1].attributes.raw);
+	*flags = (attrs >> 48) & 0xFFFF;
+
+	free(gpt_pte);
+
+	return 0;
+}
+
+static int write_gpt_pte(struct blk_desc *desc, gpt_header *gpt_h, gpt_entry *gpt_e)
+{
+	const int cnt = BLOCK_CNT((le32_to_cpu(gpt_h->num_partition_entries)
+					   * sizeof(gpt_entry)), desc);
+	u32 crc32;
+	int rc;
+
+	crc32 = efi_crc32((const unsigned char *)gpt_e,
+			      le32_to_cpu(gpt_h->num_partition_entries) *
+			      le32_to_cpu(gpt_h->sizeof_partition_entry));
+	gpt_h->partition_entry_array_crc32 = cpu_to_le32(crc32);
+
+	gpt_h->header_crc32 = 0;
+	crc32 = efi_crc32((const unsigned char *)gpt_h,
+			      le32_to_cpu(gpt_h->header_size));
+	gpt_h->header_crc32 = cpu_to_le32(crc32);
+
+	rc = blk_dwrite(desc, le64_to_cpu(gpt_h->my_lba), 1, gpt_h);
+	if (rc != 1) {
+		pr_err("device %d: failed to update GPT header: %d\n",
+		       desc->devnum, rc);
+		return rc ?: -EIO;
+	}
+
+	rc = blk_dwrite(desc, le64_to_cpu(gpt_h->partition_entry_lba), cnt, gpt_e);
+	if (rc != cnt) {
+		pr_err("device %d: failed to update GPT PTE: %d\n",
+		       desc->devnum, rc);
+		return rc ?: -EIO;
+	}
+
+	return 0;
+}
+
+int write_disk_flags(struct blk_desc *desc, int partnum, u16 flags)
+{
+	ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_h1, 1, desc->blksz);
+	ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_h2, 1, desc->blksz);
+	gpt_entry *gpt_e1 = NULL, *gpt_e2 = NULL;
+	u64 attrs;
+	int rc;
+
+	/* "part" argument must be at least 1 */
+	if (partnum < 1)
+		return -EINVAL;
+
+	gpt_repair_headers(desc);
+
+	rc = is_gpt_valid(desc, GPT_PRIMARY_PARTITION_TABLE_LBA, gpt_h1, &gpt_e1);
+	if (!rc) {
+		rc = -EPERM;
+		goto out;
+	}
+	if (partnum > le32_to_cpu(gpt_h1->num_partition_entries) ||
+	    !is_pte_valid(&gpt_e1[partnum - 1])) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	attrs = le64_to_cpu(gpt_e1[partnum - 1].attributes.raw);
+	attrs &= ~(0xFFFFULL << 48);
+	attrs |= ((u64)flags << 48);
+	gpt_e1[partnum - 1].attributes.raw = cpu_to_le64(attrs);
+
+	rc = write_gpt_pte(desc, gpt_h1, gpt_e1);
+	if (rc < 0) {
+		pr_err("partnum %d: failed to update primary GPT PTE\n", partnum);
+		goto out;
+	}
+
+	rc = is_gpt_valid(desc, desc->lba - 1, gpt_h2, &gpt_e2);
+	if (!rc) {
+		rc = -EPERM;
+		goto out;
+	}
+	if (partnum > le32_to_cpu(gpt_h2->num_partition_entries) ||
+	    !is_pte_valid(&gpt_e2[partnum - 1])) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	attrs = le64_to_cpu(gpt_e2[partnum - 1].attributes.raw);
+	attrs &= ~(0xFFFFULL << 48);
+	attrs |= ((u64)flags << 48);
+	gpt_e2[partnum - 1].attributes.raw = cpu_to_le64(attrs);
+
+	rc = write_gpt_pte(desc, gpt_h2, gpt_e2);
+	if (rc < 0) {
+		pr_err("partnum %d: failed to update secondary GPT PTE\n", partnum);
+		goto out;
+	}
+
+out:
+	free(gpt_e1);
+	free(gpt_e2);
+
+	return rc;
+}
 #endif
 
 /*
diff --git a/include/part.h b/include/part.h
index 15daacd7faaa..4724e01c0a00 100644
--- a/include/part.h
+++ b/include/part.h
@@ -678,6 +678,30 @@ int get_disk_guid(struct blk_desc *desc, char *guid);
  */
 int part_get_gpt_pte(struct blk_desc *desc, int part, gpt_entry *gpt_e);
 
+/**
+ * write_disk_flags() - Write the top 16 bits of GPT partition table
+ *                      entry attributes.
+ *
+ * @desc:	block device descriptor
+ * @partnum:	GPT partition ID
+ * @flags:	attributes value
+ *
+ * Return:	zero on success, otherwise error
+ */
+int write_disk_flags(struct blk_desc *desc, int partnum, u16 flags);
+
+/**
+ * read_disk_flags() - Read the top 16 bits of GPT partition table
+ *                     entry attributes.
+ *
+ * @desc:	block device descriptor
+ * @partnum:	GPT partition ID
+ * @flags:	pointer to attributes value (cannot be NULL)
+ *
+ * Return:	zero on success, otherwise error
+ */
+int read_disk_flags(struct blk_desc *desc, int partnum, u16 *flags);
+
 #endif
 
 #if CONFIG_IS_ENABLED(DOS_PARTITION)
-- 
2.54.0