kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

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 <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 314 insertions, 0 deletions

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
new file mode 100644
index 000000000..813013ca4
--- /dev/null
+++ b/net/ipv6/proc.c
@@ -0,0 +1,314 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		This file implements the various access functions for the
+ *		PROC file system.  This is very similar to the IPv4 version,
+ *		except it reports the sockets in the INET6 address family.
+ *
+ * Authors:	David S. Miller (davem@caip.rutgers.edu)
+ *		YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
+ */
+#include <linux/socket.h>
+#include <linux/net.h>
+#include <linux/ipv6.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/stddef.h>
+#include <linux/export.h>
+#include <net/net_namespace.h>
+#include <net/ip.h>
+#include <net/sock.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+#include <net/transp_v6.h>
+#include <net/ipv6.h>
+
+#define MAX4(a, b, c, d) \
+	MAX_T(u32, MAX_T(u32, a, b), MAX_T(u32, c, d))
+#define SNMP_MIB_MAX MAX4(UDP_MIB_MAX, TCP_MIB_MAX, \
+			IPSTATS_MIB_MAX, ICMP_MIB_MAX)
+
+static int sockstat6_seq_show(struct seq_file *seq, void *v)
+{
+	struct net *net = seq->private;
+
+	seq_printf(seq, "TCP6: inuse %d\n",
+		       sock_prot_inuse_get(net, &tcpv6_prot));
+	seq_printf(seq, "UDP6: inuse %d\n",
+		       sock_prot_inuse_get(net, &udpv6_prot));
+	seq_printf(seq, "RAW6: inuse %d\n",
+		       sock_prot_inuse_get(net, &rawv6_prot));
+	seq_printf(seq, "FRAG6: inuse %u memory %lu\n",
+		   atomic_read(&net->ipv6.fqdir->rhashtable.nelems),
+		   frag_mem_limit(net->ipv6.fqdir));
+	return 0;
+}
+
+static const struct snmp_mib snmp6_ipstats_list[] = {
+/* ipv6 mib according to RFC 2465 */
+	SNMP_MIB_ITEM("Ip6InReceives", IPSTATS_MIB_INPKTS),
+	SNMP_MIB_ITEM("Ip6InHdrErrors", IPSTATS_MIB_INHDRERRORS),
+	SNMP_MIB_ITEM("Ip6InTooBigErrors", IPSTATS_MIB_INTOOBIGERRORS),
+	SNMP_MIB_ITEM("Ip6InNoRoutes", IPSTATS_MIB_INNOROUTES),
+	SNMP_MIB_ITEM("Ip6InAddrErrors", IPSTATS_MIB_INADDRERRORS),
+	SNMP_MIB_ITEM("Ip6InUnknownProtos", IPSTATS_MIB_INUNKNOWNPROTOS),
+	SNMP_MIB_ITEM("Ip6InTruncatedPkts", IPSTATS_MIB_INTRUNCATEDPKTS),
+	SNMP_MIB_ITEM("Ip6InDiscards", IPSTATS_MIB_INDISCARDS),
+	SNMP_MIB_ITEM("Ip6InDelivers", IPSTATS_MIB_INDELIVERS),
+	SNMP_MIB_ITEM("Ip6OutForwDatagrams", IPSTATS_MIB_OUTFORWDATAGRAMS),
+	SNMP_MIB_ITEM("Ip6OutRequests", IPSTATS_MIB_OUTREQUESTS),
+	SNMP_MIB_ITEM("Ip6OutDiscards", IPSTATS_MIB_OUTDISCARDS),
+	SNMP_MIB_ITEM("Ip6OutNoRoutes", IPSTATS_MIB_OUTNOROUTES),
+	SNMP_MIB_ITEM("Ip6ReasmTimeout", IPSTATS_MIB_REASMTIMEOUT),
+	SNMP_MIB_ITEM("Ip6ReasmReqds", IPSTATS_MIB_REASMREQDS),
+	SNMP_MIB_ITEM("Ip6ReasmOKs", IPSTATS_MIB_REASMOKS),
+	SNMP_MIB_ITEM("Ip6ReasmFails", IPSTATS_MIB_REASMFAILS),
+	SNMP_MIB_ITEM("Ip6FragOKs", IPSTATS_MIB_FRAGOKS),
+	SNMP_MIB_ITEM("Ip6FragFails", IPSTATS_MIB_FRAGFAILS),
+	SNMP_MIB_ITEM("Ip6FragCreates", IPSTATS_MIB_FRAGCREATES),
+	SNMP_MIB_ITEM("Ip6InMcastPkts", IPSTATS_MIB_INMCASTPKTS),
+	SNMP_MIB_ITEM("Ip6OutMcastPkts", IPSTATS_MIB_OUTMCASTPKTS),
+	SNMP_MIB_ITEM("Ip6InOctets", IPSTATS_MIB_INOCTETS),
+	SNMP_MIB_ITEM("Ip6OutOctets", IPSTATS_MIB_OUTOCTETS),
+	SNMP_MIB_ITEM("Ip6InMcastOctets", IPSTATS_MIB_INMCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
+	/* IPSTATS_MIB_CSUMERRORS is not relevant in IPv6 (no checksum) */
+	SNMP_MIB_ITEM("Ip6InNoECTPkts", IPSTATS_MIB_NOECTPKTS),
+	SNMP_MIB_ITEM("Ip6InECT1Pkts", IPSTATS_MIB_ECT1PKTS),
+	SNMP_MIB_ITEM("Ip6InECT0Pkts", IPSTATS_MIB_ECT0PKTS),
+	SNMP_MIB_ITEM("Ip6InCEPkts", IPSTATS_MIB_CEPKTS),
+	SNMP_MIB_ITEM("Ip6OutTransmits", IPSTATS_MIB_OUTPKTS),
+};
+
+static const struct snmp_mib snmp6_icmp6_list[] = {
+/* icmpv6 mib according to RFC 2466 */
+	SNMP_MIB_ITEM("Icmp6InMsgs", ICMP6_MIB_INMSGS),
+	SNMP_MIB_ITEM("Icmp6InErrors", ICMP6_MIB_INERRORS),
+	SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
+	SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
+	SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
+/* ICMP6_MIB_RATELIMITHOST needs to be last, see snmp6_dev_seq_show(). */
+	SNMP_MIB_ITEM("Icmp6OutRateLimitHost", ICMP6_MIB_RATELIMITHOST),
+};
+
+static const struct snmp_mib snmp6_udp6_list[] = {
+	SNMP_MIB_ITEM("Udp6InDatagrams", UDP_MIB_INDATAGRAMS),
+	SNMP_MIB_ITEM("Udp6NoPorts", UDP_MIB_NOPORTS),
+	SNMP_MIB_ITEM("Udp6InErrors", UDP_MIB_INERRORS),
+	SNMP_MIB_ITEM("Udp6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
+	SNMP_MIB_ITEM("Udp6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
+	SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
+	SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
+	SNMP_MIB_ITEM("Udp6IgnoredMulti", UDP_MIB_IGNOREDMULTI),
+	SNMP_MIB_ITEM("Udp6MemErrors", UDP_MIB_MEMERRORS),
+};
+
+static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, atomic_long_t *smib)
+{
+	char name[32];
+	int i;
+
+	/* print by name -- deprecated items */
+	for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
+		const char *p = NULL;
+		int icmptype;
+
+#define CASE(TYP, STR) case TYP: p = STR; break;
+
+		icmptype = i & 0xff;
+		switch (icmptype) {
+/* RFC 4293 v6 ICMPMsgStatsTable; named items for RFC 2466 compatibility */
+		CASE(ICMPV6_DEST_UNREACH,	"DestUnreachs")
+		CASE(ICMPV6_PKT_TOOBIG,		"PktTooBigs")
+		CASE(ICMPV6_TIME_EXCEED,	"TimeExcds")
+		CASE(ICMPV6_PARAMPROB,		"ParmProblems")
+		CASE(ICMPV6_ECHO_REQUEST,	"Echos")
+		CASE(ICMPV6_ECHO_REPLY,		"EchoReplies")
+		CASE(ICMPV6_MGM_QUERY,		"GroupMembQueries")
+		CASE(ICMPV6_MGM_REPORT,		"GroupMembResponses")
+		CASE(ICMPV6_MGM_REDUCTION,	"GroupMembReductions")
+		CASE(ICMPV6_MLD2_REPORT,	"MLDv2Reports")
+		CASE(NDISC_ROUTER_ADVERTISEMENT, "RouterAdvertisements")
+		CASE(NDISC_ROUTER_SOLICITATION, "RouterSolicits")
+		CASE(NDISC_NEIGHBOUR_ADVERTISEMENT, "NeighborAdvertisements")
+		CASE(NDISC_NEIGHBOUR_SOLICITATION, "NeighborSolicits")
+		CASE(NDISC_REDIRECT,		"Redirects")
+		}
+#undef CASE
+		if (!p)	/* don't print un-named types here */
+			continue;
+		snprintf(name, sizeof(name), "Icmp6%s%s",
+			i & 0x100 ? "Out" : "In", p);
+		seq_printf(seq, "%-32s\t%lu\n", name,
+			   atomic_long_read(smib + i));
+	}
+
+	/* print by number (nonzero only) - ICMPMsgStat format */
+	for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
+		unsigned long val;
+
+		val = atomic_long_read(smib + i);
+		if (!val)
+			continue;
+		snprintf(name, sizeof(name), "Icmp6%sType%u",
+			i & 0x100 ?  "Out" : "In", i & 0xff);
+		seq_printf(seq, "%-32s\t%lu\n", name, val);
+	}
+}
+
+/* can be called either with percpu mib (pcpumib != NULL),
+ * or shared one (smib != NULL)
+ */
+static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,
+				atomic_long_t *smib,
+				const struct snmp_mib *itemlist,
+				int cnt)
+{
+	unsigned long buff[SNMP_MIB_MAX];
+	int i;
+
+	if (pcpumib) {
+		memset(buff, 0, sizeof(unsigned long) * cnt);
+
+		snmp_get_cpu_field_batch_cnt(buff, itemlist, cnt, pcpumib);
+		for (i = 0; i < cnt; i++)
+			seq_printf(seq, "%-32s\t%lu\n",
+				   itemlist[i].name, buff[i]);
+	} else {
+		for (i = 0; i < cnt; i++)
+			seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name,
+				   atomic_long_read(smib + itemlist[i].entry));
+	}
+}
+
+static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,
+				  const struct snmp_mib *itemlist,
+				  int cnt, size_t syncpoff)
+{
+	u64 buff64[SNMP_MIB_MAX];
+	int i;
+
+	memset(buff64, 0, sizeof(u64) * cnt);
+
+	snmp_get_cpu_field64_batch_cnt(buff64, itemlist, cnt, mib, syncpoff);
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, "%-32s\t%llu\n", itemlist[i].name, buff64[i]);
+}
+
+static int snmp6_seq_show(struct seq_file *seq, void *v)
+{
+	struct net *net = (struct net *)seq->private;
+
+	snmp6_seq_show_item64(seq, net->mib.ipv6_statistics,
+			      snmp6_ipstats_list,
+			      ARRAY_SIZE(snmp6_ipstats_list),
+			      offsetof(struct ipstats_mib, syncp));
+	snmp6_seq_show_item(seq, net->mib.icmpv6_statistics,
+			    NULL, snmp6_icmp6_list,
+			    ARRAY_SIZE(snmp6_icmp6_list));
+	snmp6_seq_show_icmpv6msg(seq, net->mib.icmpv6msg_statistics->mibs);
+	snmp6_seq_show_item(seq, net->mib.udp_stats_in6,
+			    NULL, snmp6_udp6_list,
+			    ARRAY_SIZE(snmp6_udp6_list));
+	return 0;
+}
+
+static int snmp6_dev_seq_show(struct seq_file *seq, void *v)
+{
+	struct inet6_dev *idev = (struct inet6_dev *)seq->private;
+
+	seq_printf(seq, "%-32s\t%u\n", "ifIndex", idev->dev->ifindex);
+	snmp6_seq_show_item64(seq, idev->stats.ipv6,
+			      snmp6_ipstats_list,
+			      ARRAY_SIZE(snmp6_ipstats_list),
+			      offsetof(struct ipstats_mib, syncp));
+
+	/* Per idev icmp stats do not have ICMP6_MIB_RATELIMITHOST */
+	snmp6_seq_show_item(seq, NULL, idev->stats.icmpv6dev->mibs,
+			    snmp6_icmp6_list, ARRAY_SIZE(snmp6_icmp6_list) - 1);
+
+	snmp6_seq_show_icmpv6msg(seq, idev->stats.icmpv6msgdev->mibs);
+	return 0;
+}
+
+int snmp6_register_dev(struct inet6_dev *idev)
+{
+	struct proc_dir_entry *p;
+	struct net *net;
+
+	if (!idev || !idev->dev)
+		return -EINVAL;
+
+	net = dev_net(idev->dev);
+	if (!net->mib.proc_net_devsnmp6)
+		return -ENOENT;
+
+	p = proc_create_single_data(idev->dev->name, 0444,
+			net->mib.proc_net_devsnmp6, snmp6_dev_seq_show, idev);
+	if (!p)
+		return -ENOMEM;
+
+	idev->stats.proc_dir_entry = p;
+	return 0;
+}
+
+int snmp6_unregister_dev(struct inet6_dev *idev)
+{
+	struct net *net = dev_net(idev->dev);
+	if (!net->mib.proc_net_devsnmp6)
+		return -ENOENT;
+	if (!idev->stats.proc_dir_entry)
+		return -EINVAL;
+	proc_remove(idev->stats.proc_dir_entry);
+	idev->stats.proc_dir_entry = NULL;
+	return 0;
+}
+
+static int __net_init ipv6_proc_init_net(struct net *net)
+{
+	if (!proc_create_net_single("sockstat6", 0444, net->proc_net,
+			sockstat6_seq_show, NULL))
+		return -ENOMEM;
+
+	if (!proc_create_net_single("snmp6", 0444, net->proc_net,
+			snmp6_seq_show, NULL))
+		goto proc_snmp6_fail;
+
+	net->mib.proc_net_devsnmp6 = proc_mkdir("dev_snmp6", net->proc_net);
+	if (!net->mib.proc_net_devsnmp6)
+		goto proc_dev_snmp6_fail;
+	return 0;
+
+proc_dev_snmp6_fail:
+	remove_proc_entry("snmp6", net->proc_net);
+proc_snmp6_fail:
+	remove_proc_entry("sockstat6", net->proc_net);
+	return -ENOMEM;
+}
+
+static void __net_exit ipv6_proc_exit_net(struct net *net)
+{
+	remove_proc_entry("sockstat6", net->proc_net);
+	remove_proc_entry("dev_snmp6", net->proc_net);
+	remove_proc_entry("snmp6", net->proc_net);
+}
+
+static struct pernet_operations ipv6_proc_ops = {
+	.init = ipv6_proc_init_net,
+	.exit = ipv6_proc_exit_net,
+};
+
+int __init ipv6_misc_proc_init(void)
+{
+	return register_pernet_subsys(&ipv6_proc_ops);
+}
+
+void ipv6_misc_proc_exit(void)
+{
+	unregister_pernet_subsys(&ipv6_proc_ops);
+}