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, 307 insertions, 0 deletions

diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
new file mode 100644
index 000000000..adb93003b
--- /dev/null
+++ b/security/selinux/netnode.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Network node table
+ *
+ * SELinux must keep a mapping of network nodes to labels/SIDs.  This
+ * mapping is maintained as part of the normal policy but a fast cache is
+ * needed to reduce the lookup overhead since most of these queries happen on
+ * a per-packet basis.
+ *
+ * Author: Paul Moore <paul@paul-moore.com>
+ *
+ * This code is heavily based on the "netif" concept originally developed by
+ * James Morris <jmorris@redhat.com>
+ *   (see security/selinux/netif.c for more information)
+ */
+
+/*
+ * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
+ */
+
+#include <linux/types.h>
+#include <linux/rcupdate.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+
+#include "initcalls.h"
+#include "netnode.h"
+#include "objsec.h"
+
+#define SEL_NETNODE_HASH_SIZE       256
+#define SEL_NETNODE_HASH_BKT_LIMIT   16
+
+struct sel_netnode_bkt {
+	unsigned int size;
+	struct list_head list;
+};
+
+struct sel_netnode {
+	struct netnode_security_struct nsec;
+
+	struct list_head list;
+	struct rcu_head rcu;
+};
+
+/* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
+ * for this is that I suspect most users will not make heavy use of both
+ * address families at the same time so one table will usually end up wasted,
+ * if this becomes a problem we can always add a hash table for each address
+ * family later */
+
+static DEFINE_SPINLOCK(sel_netnode_lock);
+static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
+
+/**
+ * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
+ * @addr: IPv4 address
+ *
+ * Description:
+ * This is the IPv4 hashing function for the node interface table, it returns
+ * the bucket number for the given IP address.
+ *
+ */
+static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
+{
+	/* at some point we should determine if the mismatch in byte order
+	 * affects the hash function dramatically */
+	return (addr & (SEL_NETNODE_HASH_SIZE - 1));
+}
+
+/**
+ * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
+ * @addr: IPv6 address
+ *
+ * Description:
+ * This is the IPv6 hashing function for the node interface table, it returns
+ * the bucket number for the given IP address.
+ *
+ */
+static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
+{
+	/* just hash the least significant 32 bits to keep things fast (they
+	 * are the most likely to be different anyway), we can revisit this
+	 * later if needed */
+	return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
+}
+
+/**
+ * sel_netnode_find - Search for a node record
+ * @addr: IP address
+ * @family: address family
+ *
+ * Description:
+ * Search the network node table and return the record matching @addr.  If an
+ * entry can not be found in the table return NULL.
+ *
+ */
+static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
+{
+	unsigned int idx;
+	struct sel_netnode *node;
+
+	switch (family) {
+	case PF_INET:
+		idx = sel_netnode_hashfn_ipv4(*(const __be32 *)addr);
+		break;
+	case PF_INET6:
+		idx = sel_netnode_hashfn_ipv6(addr);
+		break;
+	default:
+		BUG();
+		return NULL;
+	}
+
+	list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
+		if (node->nsec.family == family)
+			switch (family) {
+			case PF_INET:
+				if (node->nsec.addr.ipv4 == *(const __be32 *)addr)
+					return node;
+				break;
+			case PF_INET6:
+				if (ipv6_addr_equal(&node->nsec.addr.ipv6,
+						    addr))
+					return node;
+				break;
+			}
+
+	return NULL;
+}
+
+/**
+ * sel_netnode_insert - Insert a new node into the table
+ * @node: the new node record
+ *
+ * Description:
+ * Add a new node record to the network address hash table.
+ *
+ */
+static void sel_netnode_insert(struct sel_netnode *node)
+{
+	unsigned int idx;
+
+	switch (node->nsec.family) {
+	case PF_INET:
+		idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
+		break;
+	case PF_INET6:
+		idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
+		break;
+	default:
+		BUG();
+		return;
+	}
+
+	/* we need to impose a limit on the growth of the hash table so check
+	 * this bucket to make sure it is within the specified bounds */
+	list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
+	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
+		struct sel_netnode *tail;
+		tail = list_entry(
+			rcu_dereference_protected(
+				list_tail_rcu(&sel_netnode_hash[idx].list),
+				lockdep_is_held(&sel_netnode_lock)),
+			struct sel_netnode, list);
+		list_del_rcu(&tail->list);
+		kfree_rcu(tail, rcu);
+	} else
+		sel_netnode_hash[idx].size++;
+}
+
+/**
+ * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
+ * @addr: the IP address
+ * @family: the address family
+ * @sid: node SID
+ *
+ * Description:
+ * This function determines the SID of a network address by querying the
+ * security policy.  The result is added to the network address table to
+ * speedup future queries.  Returns zero on success, negative values on
+ * failure.
+ *
+ */
+static int sel_netnode_sid_slow(const void *addr, u16 family, u32 *sid)
+{
+	int ret;
+	struct sel_netnode *node;
+	struct sel_netnode *new;
+
+	spin_lock_bh(&sel_netnode_lock);
+	node = sel_netnode_find(addr, family);
+	if (node != NULL) {
+		*sid = node->nsec.sid;
+		spin_unlock_bh(&sel_netnode_lock);
+		return 0;
+	}
+
+	/* If this memory allocation fails still return 0. The SID
+	 * is valid, it just won't be added to the cache.
+	 */
+	new = kmalloc_obj(*new, GFP_ATOMIC);
+	switch (family) {
+	case PF_INET:
+		ret = security_node_sid(PF_INET,
+					addr, sizeof(struct in_addr), sid);
+		if (new)
+			new->nsec.addr.ipv4 = *(const __be32 *)addr;
+		break;
+	case PF_INET6:
+		ret = security_node_sid(PF_INET6,
+					addr, sizeof(struct in6_addr), sid);
+		if (new)
+			new->nsec.addr.ipv6 = *(const struct in6_addr *)addr;
+		break;
+	default:
+		BUG();
+		ret = -EINVAL;
+	}
+	if (ret == 0 && new) {
+		new->nsec.family = family;
+		new->nsec.sid = *sid;
+		sel_netnode_insert(new);
+	} else
+		kfree(new);
+
+	spin_unlock_bh(&sel_netnode_lock);
+	if (unlikely(ret))
+		pr_warn("SELinux: failure in %s(), unable to determine network node label\n",
+			__func__);
+	return ret;
+}
+
+/**
+ * sel_netnode_sid - Lookup the SID of a network address
+ * @addr: the IP address
+ * @family: the address family
+ * @sid: node SID
+ *
+ * Description:
+ * This function determines the SID of a network address using the fastest
+ * method possible.  First the address table is queried, but if an entry
+ * can't be found then the policy is queried and the result is added to the
+ * table to speedup future queries.  Returns zero on success, negative values
+ * on failure.
+ *
+ */
+int sel_netnode_sid(const void *addr, u16 family, u32 *sid)
+{
+	struct sel_netnode *node;
+
+	rcu_read_lock();
+	node = sel_netnode_find(addr, family);
+	if (likely(node != NULL)) {
+		*sid = node->nsec.sid;
+		rcu_read_unlock();
+		return 0;
+	}
+	rcu_read_unlock();
+
+	return sel_netnode_sid_slow(addr, family, sid);
+}
+
+/**
+ * sel_netnode_flush - Flush the entire network address table
+ *
+ * Description:
+ * Remove all entries from the network address table.
+ *
+ */
+void sel_netnode_flush(void)
+{
+	unsigned int idx;
+	struct sel_netnode *node, *node_tmp;
+
+	spin_lock_bh(&sel_netnode_lock);
+	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
+		list_for_each_entry_safe(node, node_tmp,
+					 &sel_netnode_hash[idx].list, list) {
+				list_del_rcu(&node->list);
+				kfree_rcu(node, rcu);
+		}
+		sel_netnode_hash[idx].size = 0;
+	}
+	spin_unlock_bh(&sel_netnode_lock);
+}
+
+int __init sel_netnode_init(void)
+{
+	int iter;
+
+	if (!selinux_enabled_boot)
+		return 0;
+
+	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
+		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
+		sel_netnode_hash[iter].size = 0;
+	}
+
+	return 0;
+}