From 294635a8165a31408a8b3a24f9c74849ca3d8701 Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 24 Feb 2023 17:36:07 +0100 Subject: bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit &xdp_buff and &xdp_frame are bound in a way that xdp_buff->data_hard_start == xdp_frame It's always the case and e.g. xdp_convert_buff_to_frame() relies on this. IOW, the following: for (u32 i = 0; i < 0xdead; i++) { xdpf = xdp_convert_buff_to_frame(&xdp); xdp_convert_frame_to_buff(xdpf, &xdp); } shouldn't ever modify @xdpf's contents or the pointer itself. However, "live packet" code wrongly treats &xdp_frame as part of its context placed *before* the data_hard_start. With such flow, data_hard_start is sizeof(*xdpf) off to the right and no longer points to the XDP frame. Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several places and praying that there are no more miscalcs left somewhere in the code, unionize ::frm with ::data in a flex array, so that both starts pointing to the actual data_hard_start and the XDP frame actually starts being a part of it, i.e. a part of the headroom, not the context. A nice side effect is that the maximum frame size for this mode gets increased by 40 bytes, as xdp_buff::frame_sz includes everything from data_hard_start (-> includes xdpf already) to the end of XDP/skb shared info. Also update %MAX_PKT_SIZE accordingly in the selftests code. Leave it hardcoded for 64 bit && 4k pages, it can be made more flexible later on. Minor: align `&head->data` with how `head->frm` is assigned for consistency. Minor #2: rename 'frm' to 'frame' in &xdp_page_head while at it for clarity. (was found while testing XDP traffic generator on ice, which calls xdp_convert_frame_to_buff() for each XDP frame) Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN") Acked-by: Toke Høiland-Jørgensen Signed-off-by: Alexander Lobakin Link: https://lore.kernel.org/r/20230224163607.2994755-1-aleksander.lobakin@intel.com Signed-off-by: Martin KaFai Lau --- net/bpf/test_run.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) (limited to 'net/bpf') diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 6f3d654b3339..f81b24320a36 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -97,8 +97,11 @@ reset: struct xdp_page_head { struct xdp_buff orig_ctx; struct xdp_buff ctx; - struct xdp_frame frm; - u8 data[]; + union { + /* ::data_hard_start starts here */ + DECLARE_FLEX_ARRAY(struct xdp_frame, frame); + DECLARE_FLEX_ARRAY(u8, data); + }; }; struct xdp_test_data { @@ -113,6 +116,10 @@ struct xdp_test_data { u32 frame_cnt; }; +/* tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c:%MAX_PKT_SIZE + * must be updated accordingly this gets changed, otherwise BPF selftests + * will fail. + */ #define TEST_XDP_FRAME_SIZE (PAGE_SIZE - sizeof(struct xdp_page_head)) #define TEST_XDP_MAX_BATCH 256 @@ -132,8 +139,8 @@ static void xdp_test_run_init_page(struct page *page, void *arg) headroom -= meta_len; new_ctx = &head->ctx; - frm = &head->frm; - data = &head->data; + frm = head->frame; + data = head->data; memcpy(data + headroom, orig_ctx->data_meta, frm_len); xdp_init_buff(new_ctx, TEST_XDP_FRAME_SIZE, &xdp->rxq); @@ -223,7 +230,7 @@ static void reset_ctx(struct xdp_page_head *head) head->ctx.data = head->orig_ctx.data; head->ctx.data_meta = head->orig_ctx.data_meta; head->ctx.data_end = head->orig_ctx.data_end; - xdp_update_frame_from_buff(&head->ctx, &head->frm); + xdp_update_frame_from_buff(&head->ctx, head->frame); } static int xdp_recv_frames(struct xdp_frame **frames, int nframes, @@ -285,7 +292,7 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog, head = phys_to_virt(page_to_phys(page)); reset_ctx(head); ctx = &head->ctx; - frm = &head->frm; + frm = head->frame; xdp->frame_cnt++; act = bpf_prog_run_xdp(prog, ctx); -- cgit v1.2.3