IdStorage

See also [1].

Description

Region of the PSVita eMMC where perconsole info is stored.

Location

Idstorage data is stored at first raw partition (code 0x1). Use [2] to extract.

Structure

The IdStorage partition is divided in two parts: the mapping table and the leaves.

Mapping table

The mapping table is located at the start of the partition. It's an array of 16-bit leaf IDs that serves as a leaf ID->index mapping table. The mapping table must be at least one-sector wide but may be bigger.

There are two leaf IDs reserved for usage in the mapping table: all entries corresponding to the mapping table (i.e. the first M entries for an M sectors sized table) must hold the value 0xFFF5, and all unallocated leaves hold the value 0xFFFF.

To lookup a leaf index based on its ID, use the following algorithm:

#define M /* implementation defined */

#define NUM_TABLE_ITEMS ((M * SECTOR_SIZE) / sizeof(uint16_t))
uint16_t g_mappingTable[NUM_TABLE_ITEMS];

int leafIndexFromId(unsigned id) {
   if (id >= 0xFFF0)
       return /* ERROR: invalid leaf ID */;

   for (int i = 0; i < NUM_TABLE_ITEMS; i++) {
      if (g_mappingTable[i] == id)
         return i;
   }
   return /* ERROR: leaf ID is not in mapping table */;
}

Leaves

Leaves are used to store arbitrary data. On Vita, leaves are all 512-bytes sized (one sector).

To read a leaf's data, obtain the leaf index (this can be known directly, or obtained from a leaf ID using the previously mentioned algorithm) then read 512 bytes starting at offset 512 * leafIndex in the IdStorage partition.

Limits

The number of leaves that can be stored in an IdStorage partition is limited by three factors: the size of the partition, the size of the mapping table and the size of leaf IDs.

• An M sectors wide mapping table can hold up to 255 * M leaves
  • This is because a single-sector mapping table can hold SECTOR_SIZE/sizeof(u16) - 1 = 255 leaves (- 1 is needed because the table uses an entry for itself)
• A P sectors wide partition can hold up to P - M leaves
  • This is because leaves are sector-sized, and the mapping table consumes M sectors
• There are 65520 leaf IDs available
  • While an unsigned 16-bit variable can hold 65536 values, IDs superior or equal to 0xFFF0 are reserved and cannot be used

From this, we can conclude that an IdStorage partition of P sectors with an M sectors mapping table can hold up to min(255*M, P-M, 65520) leaves. We can also deduce an IdStorage partition is optimally shaped (no space is non-allocatable) when P = 256 * N.

On Vita, the IdStorage partition is 512KiB and 32 sectors are reserved for the indexing table (P = 1024, M = 32, a non-optimal choice), which means the console's partition can hold up to 992 IdStorage leaves.

Content

Table of leaves

Leaf Index	Empty?	Unique?	Notes
0x00->0x07	No	No	SceIdStoragePspCertificates
0x08->0x1F	Yes	No
0x20->0x27	Yes	No	This is equal to SceIdStoragePspCertificates from leaf 0x00 to 0x07.
0x28->0x3F	Yes	No
0x40->0x47	No	Yes	SceIdStoragePsp2Certificates
0x48->0x4F	No	Yes	It looks like a cert, but it may actually be useless data.
0x50->0x7D	Yes	No
0x7E	No	Yes
0x7F	Yes	No
0x80	No	Yes	Special leaf with "SMI" header. SMI data: factory firmware encrypted and signed. Contains minver at offset 0x08 (size 4 bytes).
0x100	No	Yes	Build data strings.
0x102	No	Yes	Like idstorage mgmt data, Some strings, Like some flags, And like mac address, Maybe more?
0x103	No	Yes	Hw info, Syscon version (include DL verstion), Production date, Mac address, Mac address (USB), some strings, and more.
0x110	No	Yes	Manufacturing flags (3 byte) + 0xFF padding.
0x111	No	Yes	Mac address (6 byte) + 0xFF padding.
0x112	No	Yes	Serial number wide strings.
0x113	No	Yes	0xFFed.
0x114	No	Yes	some data (0x40 byte) + 0xFF padding.
0x115	No	Yes	Model strings + 0xFF padding.