From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- net/ipv4/gre_offload.c | 287 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 287 insertions(+) create mode 100644 net/ipv4/gre_offload.c (limited to 'net/ipv4/gre_offload.c') diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c new file mode 100644 index 000000000..5028c72d4 --- /dev/null +++ b/net/ipv4/gre_offload.c @@ -0,0 +1,287 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * IPV4 GSO/GRO offload support + * Linux INET implementation + * + * GRE GSO support + */ + +#include +#include +#include +#include +#include +#include + +static struct sk_buff *gre_gso_segment(struct sk_buff *skb, + netdev_features_t features) +{ + int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb); + bool need_csum, offload_csum, gso_partial, need_ipsec; + struct sk_buff *segs = ERR_PTR(-EINVAL); + u16 mac_offset = skb->mac_header; + __be16 protocol = skb->protocol; + u16 mac_len = skb->mac_len; + int gre_offset, outer_hlen; + + if (!skb->encapsulation) + goto out; + + if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr))) + goto out; + + if (unlikely(!pskb_may_pull(skb, tnl_hlen))) + goto out; + + /* setup inner skb. */ + skb->encapsulation = 0; + SKB_GSO_CB(skb)->encap_level = 0; + __skb_pull(skb, tnl_hlen); + skb_reset_mac_header(skb); + skb_set_network_header(skb, skb_inner_network_offset(skb)); + skb->mac_len = skb_inner_network_offset(skb); + skb->protocol = skb->inner_protocol; + + need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM); + skb->encap_hdr_csum = need_csum; + + features &= skb->dev->hw_enc_features; + if (need_csum) + features &= ~NETIF_F_SCTP_CRC; + + need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb)); + /* Try to offload checksum if possible */ + offload_csum = !!(need_csum && !need_ipsec && + (skb->dev->features & NETIF_F_HW_CSUM)); + + /* segment inner packet. */ + segs = skb_mac_gso_segment(skb, features); + if (IS_ERR_OR_NULL(segs)) { + skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset, + mac_len); + goto out; + } + + gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL); + + outer_hlen = skb_tnl_header_len(skb); + gre_offset = outer_hlen - tnl_hlen; + skb = segs; + do { + struct gre_base_hdr *greh; + __sum16 *pcsum; + + /* Set up inner headers if we are offloading inner checksum */ + if (skb->ip_summed == CHECKSUM_PARTIAL) { + skb_reset_inner_headers(skb); + skb->encapsulation = 1; + } + + skb->mac_len = mac_len; + skb->protocol = protocol; + + __skb_push(skb, outer_hlen); + skb_reset_mac_header(skb); + skb_set_network_header(skb, mac_len); + skb_set_transport_header(skb, gre_offset); + + if (!need_csum) + continue; + + greh = (struct gre_base_hdr *)skb_transport_header(skb); + pcsum = (__sum16 *)(greh + 1); + + if (gso_partial && skb_is_gso(skb)) { + unsigned int partial_adj; + + /* Adjust checksum to account for the fact that + * the partial checksum is based on actual size + * whereas headers should be based on MSS size. + */ + partial_adj = skb->len + skb_headroom(skb) - + SKB_GSO_CB(skb)->data_offset - + skb_shinfo(skb)->gso_size; + *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj)); + } else { + *pcsum = 0; + } + + *(pcsum + 1) = 0; + if (skb->encapsulation || !offload_csum) { + *pcsum = gso_make_checksum(skb, 0); + } else { + skb->ip_summed = CHECKSUM_PARTIAL; + skb->csum_start = skb_transport_header(skb) - skb->head; + skb->csum_offset = sizeof(*greh); + } + } while ((skb = skb->next)); +out: + return segs; +} + +static struct sk_buff *gre_gro_receive(struct list_head *head, + struct sk_buff *skb) +{ + struct sk_buff *pp = NULL; + struct sk_buff *p; + const struct gre_base_hdr *greh; + unsigned int hlen, grehlen; + unsigned int off; + int flush = 1; + struct packet_offload *ptype; + __be16 type; + + if (NAPI_GRO_CB(skb)->encap_mark) + goto out; + + NAPI_GRO_CB(skb)->encap_mark = 1; + + off = skb_gro_offset(skb); + hlen = off + sizeof(*greh); + greh = skb_gro_header(skb, hlen, off); + if (unlikely(!greh)) + goto out; + + /* Only support version 0 and K (key), C (csum) flags. Note that + * although the support for the S (seq#) flag can be added easily + * for GRO, this is problematic for GSO hence can not be enabled + * here because a GRO pkt may end up in the forwarding path, thus + * requiring GSO support to break it up correctly. + */ + if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0) + goto out; + + /* We can only support GRE_CSUM if we can track the location of + * the GRE header. In the case of FOU/GUE we cannot because the + * outer UDP header displaces the GRE header leaving us in a state + * of limbo. + */ + if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou) + goto out; + + type = greh->protocol; + + ptype = gro_find_receive_by_type(type); + if (!ptype) + goto out; + + grehlen = GRE_HEADER_SECTION; + + if (greh->flags & GRE_KEY) + grehlen += GRE_HEADER_SECTION; + + if (greh->flags & GRE_CSUM) + grehlen += GRE_HEADER_SECTION; + + hlen = off + grehlen; + if (!skb_gro_may_pull(skb, hlen)) { + greh = skb_gro_header_slow(skb, hlen, off); + if (unlikely(!greh)) + goto out; + } + + /* Don't bother verifying checksum if we're going to flush anyway. */ + if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) { + if (skb_gro_checksum_simple_validate(skb)) + goto out; + + skb_gro_checksum_try_convert(skb, IPPROTO_GRE, + null_compute_pseudo); + } + + list_for_each_entry(p, head, list) { + const struct gre_base_hdr *greh2; + + if (!NAPI_GRO_CB(p)->same_flow) + continue; + + /* The following checks are needed to ensure only pkts + * from the same tunnel are considered for aggregation. + * The criteria for "the same tunnel" includes: + * 1) same version (we only support version 0 here) + * 2) same protocol (we only support ETH_P_IP for now) + * 3) same set of flags + * 4) same key if the key field is present. + */ + greh2 = (struct gre_base_hdr *)(p->data + off); + + if (greh2->flags != greh->flags || + greh2->protocol != greh->protocol) { + NAPI_GRO_CB(p)->same_flow = 0; + continue; + } + if (greh->flags & GRE_KEY) { + /* compare keys */ + if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) { + NAPI_GRO_CB(p)->same_flow = 0; + continue; + } + } + } + + skb_gro_pull(skb, grehlen); + + /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/ + skb_gro_postpull_rcsum(skb, greh, grehlen); + + pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb); + flush = 0; + +out: + skb_gro_flush_final(skb, pp, flush); + + return pp; +} + +static int gre_gro_complete(struct sk_buff *skb, int nhoff) +{ + struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff); + struct packet_offload *ptype; + unsigned int grehlen = sizeof(*greh); + int err = -ENOENT; + __be16 type; + + skb->encapsulation = 1; + skb_shinfo(skb)->gso_type = SKB_GSO_GRE; + + type = greh->protocol; + if (greh->flags & GRE_KEY) + grehlen += GRE_HEADER_SECTION; + + if (greh->flags & GRE_CSUM) + grehlen += GRE_HEADER_SECTION; + + ptype = gro_find_complete_by_type(type); + if (ptype) + err = ptype->callbacks.gro_complete(skb, nhoff + grehlen); + + skb_set_inner_mac_header(skb, nhoff + grehlen); + + return err; +} + +static const struct net_offload gre_offload = { + .callbacks = { + .gso_segment = gre_gso_segment, + .gro_receive = gre_gro_receive, + .gro_complete = gre_gro_complete, + }, +}; + +static int __init gre_offload_init(void) +{ + int err; + + err = inet_add_offload(&gre_offload, IPPROTO_GRE); +#if IS_ENABLED(CONFIG_IPV6) + if (err) + return err; + + err = inet6_add_offload(&gre_offload, IPPROTO_GRE); + if (err) + inet_del_offload(&gre_offload, IPPROTO_GRE); +#endif + + return err; +} +device_initcall(gre_offload_init); -- cgit v1.3.1