From: Fam Zheng <famzheng@amazon.com>
null-co:// has a read-zeroes=off default, when used to in security
analysis, this can cause false positives because the driver doesn't
write to the read buffer.
null-co:// has the highest possible performance as a block driver, so
let's keep it that way. This patch introduces zero-co:// and
zero-aio://, largely similar with null-*://, but have read-zeroes=on by
default, so it's more suitable in cases than null-co://.
Signed-off-by: Fam Zheng <fam@euphon.net>
---
block/null.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 91 insertions(+)
diff --git a/block/null.c b/block/null.c
index cc9b1d4ea7..5de97e8fda 100644
--- a/block/null.c
+++ b/block/null.c
@@ -76,6 +76,30 @@ static void null_aio_parse_filename(const char *filename,
QDict *options,
}
}
+static void zero_co_parse_filename(const char *filename, QDict *options,
+ Error **errp)
+{
+ /* This functions only exists so that a zero-co:// filename is accepted
+ * with the zero-co driver. */
+ if (strcmp(filename, "zero-co://")) {
+ error_setg(errp, "The only allowed filename for this driver is "
+ "'zero-co://'");
+ return;
+ }
+}
+
+static void zero_aio_parse_filename(const char *filename, QDict *options,
+ Error **errp)
+{
+ /* This functions only exists so that a zero-aio:// filename is accepted
+ * with the zero-aio driver. */
+ if (strcmp(filename, "zero-aio://")) {
+ error_setg(errp, "The only allowed filename for this driver is "
+ "'zero-aio://'");
+ return;
+ }
+}
+
static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
@@ -99,6 +123,29 @@ static int null_file_open(BlockDriverState *bs, QDict
*options, int flags,
return ret;
}
+static int zero_file_open(BlockDriverState *bs, QDict *options, int flags,
+ Error **errp)
+{
+ QemuOpts *opts;
+ BDRVNullState *s = bs->opaque;
+ int ret = 0;
+
+ opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+ qemu_opts_absorb_qdict(opts, options, &error_abort);
+ s->length =
+ qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
+ s->latency_ns =
+ qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
+ if (s->latency_ns < 0) {
+ error_setg(errp, "latency-ns is invalid");
+ ret = -EINVAL;
+ }
+ s->read_zeroes = true;
+ qemu_opts_del(opts);
+ bs->supported_write_flags = BDRV_REQ_FUA;
+ return ret;
+}
+
static int64_t null_getlength(BlockDriverState *bs)
{
BDRVNullState *s = bs->opaque;
@@ -316,10 +363,54 @@ static BlockDriver bdrv_null_aio = {
.strong_runtime_opts = null_strong_runtime_opts,
};
+static BlockDriver bdrv_zero_co = {
+ .format_name = "zero-co",
+ .protocol_name = "zero-co",
+ .instance_size = sizeof(BDRVNullState),
+
+ .bdrv_file_open = zero_file_open,
+ .bdrv_parse_filename = zero_co_parse_filename,
+ .bdrv_getlength = null_getlength,
+ .bdrv_get_allocated_file_size = null_allocated_file_size,
+
+ .bdrv_co_preadv = null_co_preadv,
+ .bdrv_co_pwritev = null_co_pwritev,
+ .bdrv_co_flush_to_disk = null_co_flush,
+ .bdrv_reopen_prepare = null_reopen_prepare,
+
+ .bdrv_co_block_status = null_co_block_status,
+
+ .bdrv_refresh_filename = null_refresh_filename,
+ .strong_runtime_opts = null_strong_runtime_opts,
+};
+
+static BlockDriver bdrv_zero_aio = {
+ .format_name = "zero-aio",
+ .protocol_name = "zero-aio",
+ .instance_size = sizeof(BDRVNullState),
+
+ .bdrv_file_open = zero_file_open,
+ .bdrv_parse_filename = zero_aio_parse_filename,
+ .bdrv_getlength = null_getlength,
+ .bdrv_get_allocated_file_size = null_allocated_file_size,
+
+ .bdrv_aio_preadv = null_aio_preadv,
+ .bdrv_aio_pwritev = null_aio_pwritev,
+ .bdrv_aio_flush = null_aio_flush,
+ .bdrv_reopen_prepare = null_reopen_prepare,
+
+ .bdrv_co_block_status = null_co_block_status,
+
+ .bdrv_refresh_filename = null_refresh_filename,
+ .strong_runtime_opts = null_strong_runtime_opts,
+};