From f95f0f95cfb7f180ed7571d4915432d5098df7ec Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 14 May 2020 12:49:02 +0200 Subject: xdp: Add frame size to xdp_buff MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit XDP have evolved to support several frame sizes, but xdp_buff was not updated with this information. The frame size (frame_sz) member of xdp_buff is introduced to know the real size of the memory the frame is delivered in. When introducing this also make it clear that some tailroom is reserved/required when creating SKBs using build_skb(). It would also have been an option to introduce a pointer to data_hard_end (with reserved offset). The advantage with frame_sz is that (like rxq) drivers only need to setup/assign this value once per NAPI cycle. Due to XDP-generic (and some drivers) it's not possible to store frame_sz inside xdp_rxq_info, because it's varies per packet as it can be based/depend on packet length. V2: nitpick: deduct -> deduce Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov Acked-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/bpf/158945334261.97035.555255657490688547.stgit@firesoul --- include/net/xdp.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include') diff --git a/include/net/xdp.h b/include/net/xdp.h index 3cc6d5d84aa4..a764af4ae0ea 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -6,6 +6,8 @@ #ifndef __LINUX_NET_XDP_H__ #define __LINUX_NET_XDP_H__ +#include /* skb_shared_info */ + /** * DOC: XDP RX-queue information * @@ -70,8 +72,19 @@ struct xdp_buff { void *data_hard_start; unsigned long handle; struct xdp_rxq_info *rxq; + u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/ }; +/* Reserve memory area at end-of data area. + * + * This macro reserves tailroom in the XDP buffer by limiting the + * XDP/BPF data access to data_hard_end. Notice same area (and size) + * is used for XDP_PASS, when constructing the SKB via build_skb(). + */ +#define xdp_data_hard_end(xdp) \ + ((xdp)->data_hard_start + (xdp)->frame_sz - \ + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) + struct xdp_frame { void *data; u16 len; -- cgit v1.2.3 From 34cc0b338a61de3eee3a2bfcaf4f9d6e9fae091a Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 14 May 2020 12:49:33 +0200 Subject: xdp: Xdp_frame add member frame_sz and handle in convert_to_xdp_frame MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Use hole in struct xdp_frame, when adding member frame_sz, which keeps same sizeof struct (32 bytes) Drivers ixgbe and sfc had bug cases where the necessary/expected tailroom was not reserved. This can lead to some hard to catch memory corruption issues. Having the drivers frame_sz this can be detected when packet length/end via xdp->data_end exceed the xdp_data_hard_end pointer, which accounts for the reserved the tailroom. When detecting this driver issue, simply fail the conversion with NULL, which results in feedback to driver (failing xdp_do_redirect()) causing driver to drop packet. Given the lack of consistent XDP stats, this can be hard to troubleshoot. And given this is a driver bug, we want to generate some more noise in form of a WARN stack dump (to ID the driver code that inlined convert_to_xdp_frame). Inlining the WARN macro is problematic, because it adds an asm instruction (on Intel CPUs ud2) what influence instruction cache prefetching. Thus, introduce xdp_warn and macro XDP_WARN, to avoid this and at the same time make identifying the function and line of this inlined function easier. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov Acked-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/bpf/158945337313.97035.10015729316710496600.stgit@firesoul --- include/net/xdp.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/net/xdp.h b/include/net/xdp.h index a764af4ae0ea..3094fccf5a88 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -89,7 +89,8 @@ struct xdp_frame { void *data; u16 len; u16 headroom; - u16 metasize; + u32 metasize:8; + u32 frame_sz:24; /* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time, * while mem info is valid on remote CPU. */ @@ -104,6 +105,10 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame) frame->dev_rx = NULL; } +/* Avoids inlining WARN macro in fast-path */ +void xdp_warn(const char *msg, const char *func, const int line); +#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__) + struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp); /* Convert xdp_buff to xdp_frame */ @@ -124,6 +129,12 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp) if (unlikely((headroom - metasize) < sizeof(*xdp_frame))) return NULL; + /* Catch if driver didn't reserve tailroom for skb_shared_info */ + if (unlikely(xdp->data_end > xdp_data_hard_end(xdp))) { + XDP_WARN("Driver BUG: missing reserved tailroom"); + return NULL; + } + /* Store info in top of packet */ xdp_frame = xdp->data_hard_start; @@ -131,6 +142,7 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp) xdp_frame->len = xdp->data_end - xdp->data; xdp_frame->headroom = headroom - sizeof(*xdp_frame); xdp_frame->metasize = metasize; + xdp_frame->frame_sz = xdp->frame_sz; /* rxq only valid until napi_schedule ends, convert to xdp_mem_info */ xdp_frame->mem = xdp->rxq->mem; -- cgit v1.2.3 From 2a637c5b1aaf3b21418fadffad7e56ff27cee6f7 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 14 May 2020 12:51:15 +0200 Subject: xdp: For Intel AF_XDP drivers add XDP frame_sz MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Intel drivers implement native AF_XDP zerocopy in separate C-files, that have its own invocation of bpf_prog_run_xdp(). The setup of xdp_buff is also handled in separately from normal code path. This patch update XDP frame_sz for AF_XDP zerocopy drivers i40e, ice and ixgbe, as the code changes needed are very similar. Introduce a helper function xsk_umem_xdp_frame_sz() for calculating frame size. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov Acked-by: Björn Töpel Cc: intel-wired-lan@lists.osuosl.org Cc: Magnus Karlsson Link: https://lore.kernel.org/bpf/158945347511.97035.8536753731329475655.stgit@firesoul --- include/net/xdp_sock.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include') diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h index 67191ccaab85..abd72de25fa4 100644 --- a/include/net/xdp_sock.h +++ b/include/net/xdp_sock.h @@ -236,6 +236,12 @@ static inline u64 xsk_umem_adjust_offset(struct xdp_umem *umem, u64 address, else return address + offset; } + +static inline u32 xsk_umem_xdp_frame_sz(struct xdp_umem *umem) +{ + return umem->chunk_size_nohr + umem->headroom; +} + #else static inline int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp) { @@ -366,6 +372,11 @@ static inline u64 xsk_umem_adjust_offset(struct xdp_umem *umem, u64 handle, return 0; } +static inline u32 xsk_umem_xdp_frame_sz(struct xdp_umem *umem) +{ + return 0; +} + static inline int __xsk_map_redirect(struct xdp_sock *xs, struct xdp_buff *xdp) { return -EOPNOTSUPP; -- cgit v1.2.3 From c8741e2bfe872425ea6f10bb6f7dc1d67bc60c3a Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 14 May 2020 12:51:25 +0200 Subject: xdp: Allow bpf_xdp_adjust_tail() to grow packet size Finally, after all drivers have a frame size, allow BPF-helper bpf_xdp_adjust_tail() to grow or extend packet size at frame tail. Remember that helper/macro xdp_data_hard_end have reserved some tailroom. Thus, this helper makes sure that the BPF-prog don't have access to this tailroom area. V2: Remove one chicken check and use WARN_ONCE for other Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/158945348530.97035.12577148209134239291.stgit@firesoul --- include/uapi/linux/bpf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 32cbf36c7729..b9b8a0f63b91 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2015,8 +2015,8 @@ union bpf_attr { * int bpf_xdp_adjust_tail(struct xdp_buff *xdp_md, int delta) * Description * Adjust (move) *xdp_md*\ **->data_end** by *delta* bytes. It is - * only possible to shrink the packet as of this writing, - * therefore *delta* must be a negative integer. + * possible to both shrink and grow the packet tail. + * Shrink done via *delta* being a negative integer. * * A call to this helper is susceptible to change the underlying * packet buffer. Therefore, at load time, all checks on pointers -- cgit v1.2.3