On 9/30/22 12:27 AM, Anuj Gupta wrote:
> Add IORING_URING_CMD_FIXED flag that is to be used for sending io_uring
> command with previously registered buffers. User-space passes the buffer
> index in sqe->buf_index, same as done in read/write variants that uses
> fixed buffers.
>
> Signed-off-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
> Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> ---
> include/linux/io_uring.h | 2 +-
> include/uapi/linux/io_uring.h | 9 +++++++++
> io_uring/uring_cmd.c | 18 +++++++++++++++++-
> 3 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index 1dbf51115c30..e10c5cc81082 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -28,7 +28,7 @@ struct io_uring_cmd {
> void *cookie;
> };
> u32 cmd_op;
> - u32 pad;
> + u32 flags;
> u8 pdu[32]; /* available inline for free use */
> };
>
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 92f29d9505a6..ab7458033ee3 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -56,6 +56,7 @@ struct io_uring_sqe {
> __u32 hardlink_flags;
> __u32 xattr_flags;
> __u32 msg_ring_flags;
> + __u32 uring_cmd_flags;
> };
> __u64 user_data; /* data to be passed back at completion time */
> /* pack this to avoid bogus arm OABI complaints */
> @@ -219,6 +220,14 @@ enum io_uring_op {
> IORING_OP_LAST,
> };
>
> +/*
> + * sqe->uring_cmd_flags
> + * IORING_URING_CMD_FIXED use registered buffer; pass thig flag
> + * along with setting sqe->buf_index.
> + */
> +#define IORING_URING_CMD_FIXED (1U << 0)
> +
> +
> /*
> * sqe->fsync_flags
> */
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index 6a6d69523d75..05e8ad8cef87 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -4,6 +4,7 @@
> #include <linux/file.h>
> #include <linux/io_uring.h>
> #include <linux/security.h>
> +#include <linux/nospec.h>
>
> #include <uapi/linux/io_uring.h>
>
> @@ -77,7 +78,22 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> {
> struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
>
> - if (sqe->rw_flags || sqe->__pad1)
> + if (sqe->__pad1)
> + return -EINVAL;
> +
> + ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
> + if (ioucmd->flags & IORING_URING_CMD_FIXED) {
> + struct io_ring_ctx *ctx = req->ctx;
> + u16 index;
> +
> + req->buf_index = READ_ONCE(sqe->buf_index);
> + if (unlikely(req->buf_index >= ctx->nr_user_bufs))
> + return -EFAULT;
> + index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
> + req->imu = ctx->user_bufs[index];
> + io_req_set_rsrc_node(req, ctx, 0);
> + }
> + if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
> return -EINVAL;
Not that it _really_ matters, but why isn't this check the first thing
that is done after reading the flags? No need to respin, I can just move
it myself.
--
Jens Axboe
