diff mbox series

[bpf-next,v2,1/3] bpf: support input xdp_md context in BPF_PROG_TEST_RUN

Message ID 20210527201341.7128-2-zeffron@riotgames.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: support input xdp_md context in BPF_PROG_TEST_RUN | expand

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netdev/build_32bit fail Errors and warnings before: 10043 this patch: 10045
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Commit Message

Zvi Effron May 27, 2021, 8:13 p.m. UTC 
Support passing a xdp_md via ctx_in/ctx_out in bpf_attr for
BPF_PROG_TEST_RUN.

The intended use case is to pass some XDP meta data to the test runs of
XDP programs that are used as tail calls.

For programs that use bpf_prog_test_run_xdp, support xdp_md input and
output. Unlike with an actual xdp_md during a non-test run, data_meta must
be 0 because it must point to the start of the provided user data. From
the initial xdp_md, use data and data_end to adjust the pointers in the
generated xdp_buff. All other non-zero fields are prohibited (with
EINVAL). If the user has set ctx_out/ctx_size_out, copy the (potentially
different) xdp_md back to the userspace.

We require all fields of input xdp_md except the ones we explicitly
support to be set to zero. The expectation is that in the future we might
add support for more fields and we want to fail explicitly if the user
runs the program on the kernel where we don't yet support them.

Co-developed-by: Cody Haas <chaas@riotgames.com>
Signed-off-by: Cody Haas <chaas@riotgames.com>
Co-developed-by: Lisa Watanabe <lwatanabe@riotgames.com>
Signed-off-by: Lisa Watanabe <lwatanabe@riotgames.com>
Signed-off-by: Zvi Effron <zeffron@riotgames.com>
---
 include/uapi/linux/bpf.h |  3 --
 net/bpf/test_run.c       | 84 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 77 insertions(+), 10 deletions(-)

Comments

Fijalkowski, Maciej May 28, 2021, 9:30 a.m. UTC | #1 
On Thu, May 27, 2021 at 08:13:39PM +0000, Zvi Effron wrote:
> Support passing a xdp_md via ctx_in/ctx_out in bpf_attr for
> BPF_PROG_TEST_RUN.
> 
> The intended use case is to pass some XDP meta data to the test runs of
> XDP programs that are used as tail calls.

How about providing an actual selftests that will showcase the above so
reviewers could get in an easier way a grasp of what this set is about?

> 
> For programs that use bpf_prog_test_run_xdp, support xdp_md input and
> output. Unlike with an actual xdp_md during a non-test run, data_meta must
> be 0 because it must point to the start of the provided user data. From
> the initial xdp_md, use data and data_end to adjust the pointers in the
> generated xdp_buff. All other non-zero fields are prohibited (with
> EINVAL). If the user has set ctx_out/ctx_size_out, copy the (potentially
> different) xdp_md back to the userspace.
> 
> We require all fields of input xdp_md except the ones we explicitly
> support to be set to zero. The expectation is that in the future we might
> add support for more fields and we want to fail explicitly if the user
> runs the program on the kernel where we don't yet support them.
> 
> Co-developed-by: Cody Haas <chaas@riotgames.com>
> Signed-off-by: Cody Haas <chaas@riotgames.com>
> Co-developed-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Zvi Effron <zeffron@riotgames.com>
> ---
>  include/uapi/linux/bpf.h |  3 --
>  net/bpf/test_run.c       | 84 ++++++++++++++++++++++++++++++++++++----
>  2 files changed, 77 insertions(+), 10 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 2c1ba70abbf1..a9dcf3d8c85a 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -324,9 +324,6 @@ union bpf_iter_link_info {
>   *		**BPF_PROG_TYPE_SK_LOOKUP**
>   *			*data_in* and *data_out* must be NULL.
>   *
> - *		**BPF_PROG_TYPE_XDP**
> - *			*ctx_in* and *ctx_out* must be NULL.
> - *
>   *		**BPF_PROG_TYPE_RAW_TRACEPOINT**,
>   *		**BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE**
>   *
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index aa47af349ba8..3718c8a331dc 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -687,6 +687,45 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
>  	return ret;
>  }
>  
> +static int convert_xdpmd_to_xdpb(struct xdp_buff *xdp, struct xdp_md *xdp_md)

Maybe xdp_convert_md_to_buff ?

> +{
> +	void *data;
> +	u32 metalen;
> +	struct net_device *device;
> +	struct netdev_rx_queue *rxqueue;

rxqueue is unused in here, maybe it with 2nd patch?

> +
> +	if (!xdp_md)
> +		return 0;
> +
> +	if (xdp_md->egress_ifindex != 0)
> +		return -EINVAL;
> +
> +	metalen = xdp_md->data - xdp_md->data_meta;
> +	data = xdp->data_meta + metalen;
> +	if (data > xdp->data_end)
> +		return -EINVAL;
> +	xdp->data = data;
> +
> +	if (xdp_md->data_end - xdp_md->data != xdp->data_end - xdp->data)
> +		return -EINVAL;
> +
> +	if (xdp_md->ingress_ifindex != 0 || xdp_md->rx_queue_index != 0)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static void convert_xdpb_to_xdpmd(struct xdp_buff *xdp, struct xdp_md *xdp_md)
> +{
> +	if (!xdp_md)
> +		return;
> +
> +	/* xdp_md->data_meta must always point to the start of the out buffer */
> +	xdp_md->data_meta = 0;
> +	xdp_md->data = xdp->data - xdp->data_meta;
> +	xdp_md->data_end = xdp->data_end - xdp->data_meta;
> +}
> +
>  int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
>  			  union bpf_attr __user *uattr)
>  {
> @@ -696,36 +735,68 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
>  	u32 repeat = kattr->test.repeat;
>  	struct netdev_rx_queue *rxqueue;
>  	struct xdp_buff xdp = {};
> +	struct xdp_md *ctx = NULL;
>  	u32 retval, duration;
>  	u32 max_data_sz;
> +	u32 metalen;
>  	void *data;
>  	int ret;
>  
> -	if (kattr->test.ctx_in || kattr->test.ctx_out)
> -		return -EINVAL;
> +	ctx = bpf_ctx_init(kattr, sizeof(struct xdp_md));
> +	if (IS_ERR(ctx))
> +		return PTR_ERR(ctx);
> +
> +	/* There can't be user provided data before the metadata */
> +	if (ctx) {
> +		if (ctx->data_meta != 0)
> +			return -EINVAL;
> +		metalen = ctx->data - ctx->data_meta;
> +		if (unlikely((metalen & (sizeof(__u32) - 1)) ||
> +			     metalen > 32))
> +			return -EINVAL;
> +		/* Metadata is allocated from the headroom */
> +		headroom -= metalen;
> +	}
>  
>  	/* XDP have extra tailroom as (most) drivers use full page */
>  	max_data_sz = 4096 - headroom - tailroom;
>  
>  	data = bpf_test_init(kattr, max_data_sz, headroom, tailroom);
> -	if (IS_ERR(data))
> +	if (IS_ERR(data)) {
> +		kfree(ctx);
>  		return PTR_ERR(data);
> +	}
>  
>  	rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
>  	xdp_init_buff(&xdp, headroom + max_data_sz + tailroom,
>  		      &rxqueue->xdp_rxq);
>  	xdp_prepare_buff(&xdp, data, headroom, size, true);
>  
> +	ret = convert_xdpmd_to_xdpb(&xdp, ctx);
> +	if (ret) {
> +		kfree(data);
> +		kfree(ctx);
> +		return ret;
> +	}
> +
>  	bpf_prog_change_xdp(NULL, prog);
>  	ret = bpf_test_run(prog, &xdp, repeat, &retval, &duration, true);
>  	if (ret)
>  		goto out;
> -	if (xdp.data != data + headroom || xdp.data_end != xdp.data + size)
> -		size = xdp.data_end - xdp.data;
> -	ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
> +
> +	if (xdp.data_meta != data + headroom || xdp.data_end != xdp.data_meta + size)
> +		size = xdp.data_end - xdp.data_meta;
> +
> +	convert_xdpb_to_xdpmd(&xdp, ctx);
> +
> +	ret = bpf_test_finish(kattr, uattr, xdp.data_meta, size, retval, duration);
> +	if (!ret)
> +		ret = bpf_ctx_finish(kattr, uattr, ctx,
> +				     sizeof(struct xdp_md));
>  out:
>  	bpf_prog_change_xdp(prog, NULL);
>  	kfree(data);
> +	kfree(ctx);
>  	return ret;
>  }
>  
> @@ -809,7 +880,6 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
>  	if (!ret)
>  		ret = bpf_ctx_finish(kattr, uattr, user_ctx,
>  				     sizeof(struct bpf_flow_keys));
> -
>  out:
>  	kfree(user_ctx);
>  	kfree(data);
> -- 
> 2.31.1
>
Zvi Effron May 28, 2021, 6:40 p.m. UTC | #2 
On Fri, May 28, 2021 at 2:43 AM Maciej Fijalkowski
<maciej.fijalkowski@intel.com> wrote:
>
> On Thu, May 27, 2021 at 08:13:39PM +0000, Zvi Effron wrote:
> > Support passing a xdp_md via ctx_in/ctx_out in bpf_attr for
> > BPF_PROG_TEST_RUN.
> >
> > The intended use case is to pass some XDP meta data to the test runs of
> > XDP programs that are used as tail calls.
>
> How about providing an actual selftests that will showcase the above so
> reviewers could get in an easier way a grasp of what this set is about?
>

The very first test case in the added selftests (patch 3) does exactly
that. The return code is passed via XDP meta data to the tested
program (a program that normally would be invoked via tail call). This
is the exact use case we have that prompted this patch set.
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2c1ba70abbf1..a9dcf3d8c85a 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -324,9 +324,6 @@  union bpf_iter_link_info {
  *		**BPF_PROG_TYPE_SK_LOOKUP**
  *			*data_in* and *data_out* must be NULL.
  *
- *		**BPF_PROG_TYPE_XDP**
- *			*ctx_in* and *ctx_out* must be NULL.
- *
  *		**BPF_PROG_TYPE_RAW_TRACEPOINT**,
  *		**BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE**
  *
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index aa47af349ba8..3718c8a331dc 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -687,6 +687,45 @@  int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
 	return ret;
 }
 
+static int convert_xdpmd_to_xdpb(struct xdp_buff *xdp, struct xdp_md *xdp_md)
+{
+	void *data;
+	u32 metalen;
+	struct net_device *device;
+	struct netdev_rx_queue *rxqueue;
+
+	if (!xdp_md)
+		return 0;
+
+	if (xdp_md->egress_ifindex != 0)
+		return -EINVAL;
+
+	metalen = xdp_md->data - xdp_md->data_meta;
+	data = xdp->data_meta + metalen;
+	if (data > xdp->data_end)
+		return -EINVAL;
+	xdp->data = data;
+
+	if (xdp_md->data_end - xdp_md->data != xdp->data_end - xdp->data)
+		return -EINVAL;
+
+	if (xdp_md->ingress_ifindex != 0 || xdp_md->rx_queue_index != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+static void convert_xdpb_to_xdpmd(struct xdp_buff *xdp, struct xdp_md *xdp_md)
+{
+	if (!xdp_md)
+		return;
+
+	/* xdp_md->data_meta must always point to the start of the out buffer */
+	xdp_md->data_meta = 0;
+	xdp_md->data = xdp->data - xdp->data_meta;
+	xdp_md->data_end = xdp->data_end - xdp->data_meta;
+}
+
 int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 			  union bpf_attr __user *uattr)
 {
@@ -696,36 +735,68 @@  int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 	u32 repeat = kattr->test.repeat;
 	struct netdev_rx_queue *rxqueue;
 	struct xdp_buff xdp = {};
+	struct xdp_md *ctx = NULL;
 	u32 retval, duration;
 	u32 max_data_sz;
+	u32 metalen;
 	void *data;
 	int ret;
 
-	if (kattr->test.ctx_in || kattr->test.ctx_out)
-		return -EINVAL;
+	ctx = bpf_ctx_init(kattr, sizeof(struct xdp_md));
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+
+	/* There can't be user provided data before the metadata */
+	if (ctx) {
+		if (ctx->data_meta != 0)
+			return -EINVAL;
+		metalen = ctx->data - ctx->data_meta;
+		if (unlikely((metalen & (sizeof(__u32) - 1)) ||
+			     metalen > 32))
+			return -EINVAL;
+		/* Metadata is allocated from the headroom */
+		headroom -= metalen;
+	}
 
 	/* XDP have extra tailroom as (most) drivers use full page */
 	max_data_sz = 4096 - headroom - tailroom;
 
 	data = bpf_test_init(kattr, max_data_sz, headroom, tailroom);
-	if (IS_ERR(data))
+	if (IS_ERR(data)) {
+		kfree(ctx);
 		return PTR_ERR(data);
+	}
 
 	rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
 	xdp_init_buff(&xdp, headroom + max_data_sz + tailroom,
 		      &rxqueue->xdp_rxq);
 	xdp_prepare_buff(&xdp, data, headroom, size, true);
 
+	ret = convert_xdpmd_to_xdpb(&xdp, ctx);
+	if (ret) {
+		kfree(data);
+		kfree(ctx);
+		return ret;
+	}
+
 	bpf_prog_change_xdp(NULL, prog);
 	ret = bpf_test_run(prog, &xdp, repeat, &retval, &duration, true);
 	if (ret)
 		goto out;
-	if (xdp.data != data + headroom || xdp.data_end != xdp.data + size)
-		size = xdp.data_end - xdp.data;
-	ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
+
+	if (xdp.data_meta != data + headroom || xdp.data_end != xdp.data_meta + size)
+		size = xdp.data_end - xdp.data_meta;
+
+	convert_xdpb_to_xdpmd(&xdp, ctx);
+
+	ret = bpf_test_finish(kattr, uattr, xdp.data_meta, size, retval, duration);
+	if (!ret)
+		ret = bpf_ctx_finish(kattr, uattr, ctx,
+				     sizeof(struct xdp_md));
 out:
 	bpf_prog_change_xdp(prog, NULL);
 	kfree(data);
+	kfree(ctx);
 	return ret;
 }
 
@@ -809,7 +880,6 @@  int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 	if (!ret)
 		ret = bpf_ctx_finish(kattr, uattr, user_ctx,
 				     sizeof(struct bpf_flow_keys));
-
 out:
 	kfree(user_ctx);
 	kfree(data);