[Libguestfs] [PATCH 5/7] hivex: Add offset-&-length function for long value data
This patch adds value_data_cell_offset to the hivex ABI, to report the
hive space used for long value data.
Signed-off-by: Alex Nelson <ajnelson(a)cs.ucsc.edu>
---
generator/generator.ml | 11 +++++++++++
lib/hivex.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 0 deletions(-)
diff --git a/generator/generator.ml b/generator/generator.ml
index 5a71930..b607421 100755
--- a/generator/generator.ml
+++ b/generator/generator.ml
@@ -276,6 +276,17 @@ and sets errno on error.";
Return the length of the value data structure. Returns 0
and sets errno on error.";
+ "value_data_cell_offset", (RLenValue, [AHive; AValue "val"]),
+ "return the offset and length of a value data cell",
+ "\
+Return the offset and length of the value's data cell, not value cell.
+E.g. if the value were \"foobar\" then the length would be 6, and the
+offset would be to a value data cell, which is the data prefixed with
+4 bytes describing the size. If the length is not greater than 4,
+then 0 is returned, as the data are inline in the value.
+
+Returns 0 and sets errno on error.";
+
"value_value", (RLenTypeVal, [AHive; AValue "val"]),
"return data length, data type and data of a value",
"\
diff --git a/lib/hivex.c b/lib/hivex.c
index d8ffa63..04ceed3 100644
--- a/lib/hivex.c
+++ b/lib/hivex.c
@@ -1294,6 +1294,51 @@ hivex_value_type (hive_h *h, hive_value_h value, hive_type *t,
size_t *len)
return 0;
}
+hive_value_h
+hivex_value_data_cell_offset (hive_h *h, hive_value_h value, size_t *len)
+{
+ if (!IS_VALID_BLOCK (h, value) || !BLOCK_ID_EQ (h, value, "vk")) {
+ errno = EINVAL;
+ return 0;
+ }
+
+ struct ntreg_vk_record *vk = (struct ntreg_vk_record *) (h->addr + value);
+
+ size_t data_len;
+ int is_inline;
+
+ data_len = le32toh (vk->data_len);
+ is_inline = !!(data_len & 0x80000000);
+ data_len &= 0x7fffffff;
+
+ if (is_inline && data_len > 4) {
+ errno = ENOTSUP;
+ return 0;
+ }
+
+ if (is_inline) {
+ /* There is no other location for the value data. */
+ if (len)
+ *len = 0;
+ return 0;
+ } else {
+ if (len)
+ *len = data_len + 4; /* Include 4 header length bytes */
+ }
+
+ size_t data_offset = le32toh (vk->data_offset);
+ data_offset += 0x1000; /* Add 0x1000 because everything's off by 4KiB */
+ if (!IS_VALID_BLOCK (h, data_offset)) {
+ if (h->msglvl >= 2)
+ fprintf (stderr, "hivex_value_data_cell_offset: returning EFAULT because data
"
+ "offset is not a valid block (0x%zx)\n",
+ data_offset);
+ errno = EFAULT;
+ return 0;
+ }
+ return data_offset;
+}
+
char *
hivex_value_value (hive_h *h, hive_value_h value,
hive_type *t_rtn, size_t *len_rtn)
--
1.7.6