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, 504 insertions, 0 deletions

diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
new file mode 100644
index 000000000..e8b6ae75f
--- /dev/null
+++ b/crypto/crypto_user.c
@@ -0,0 +1,504 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Crypto user configuration API.
+ *
+ * Copyright (C) 2011 secunet Security Networks AG
+ * Copyright (C) 2011 Steffen Klassert <steffen.klassert@secunet.com>
+ */
+
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/cryptouser.h>
+#include <linux/sched.h>
+#include <linux/security.h>
+#include <net/netlink.h>
+#include <net/net_namespace.h>
+#include <net/sock.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/internal/rng.h>
+#include <crypto/akcipher.h>
+#include <crypto/kpp.h>
+
+#include "internal.h"
+
+#define null_terminated(x)	(strnlen(x, sizeof(x)) < sizeof(x))
+
+static DEFINE_MUTEX(crypto_cfg_mutex);
+
+struct crypto_dump_info {
+	struct sk_buff *in_skb;
+	struct sk_buff *out_skb;
+	u32 nlmsg_seq;
+	u16 nlmsg_flags;
+};
+
+static struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact)
+{
+	struct crypto_alg *q, *alg = NULL;
+
+	down_read(&crypto_alg_sem);
+
+	list_for_each_entry(q, &crypto_alg_list, cra_list) {
+		int match = 0;
+
+		if (crypto_is_larval(q))
+			continue;
+
+		if ((q->cra_flags ^ p->cru_type) & p->cru_mask)
+			continue;
+
+		if (strlen(p->cru_driver_name))
+			match = !strcmp(q->cra_driver_name,
+					p->cru_driver_name);
+		else if (!exact)
+			match = !strcmp(q->cra_name, p->cru_name);
+
+		if (!match)
+			continue;
+
+		if (unlikely(!crypto_mod_get(q)))
+			continue;
+
+		alg = q;
+		break;
+	}
+
+	up_read(&crypto_alg_sem);
+
+	return alg;
+}
+
+static int crypto_report_cipher(struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct crypto_report_cipher rcipher = {
+		.type = "cipher",
+	};
+
+	rcipher.blocksize = alg->cra_blocksize;
+	rcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
+	rcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_CIPHER,
+		       sizeof(rcipher), &rcipher);
+}
+
+static int crypto_report_one(struct crypto_alg *alg,
+			     struct crypto_user_alg *ualg, struct sk_buff *skb)
+{
+	memset(ualg, 0, sizeof(*ualg));
+
+	strscpy(ualg->cru_name, alg->cra_name, sizeof(ualg->cru_name));
+	strscpy(ualg->cru_driver_name, alg->cra_driver_name,
+		sizeof(ualg->cru_driver_name));
+	strscpy(ualg->cru_module_name, module_name(alg->cra_module),
+		sizeof(ualg->cru_module_name));
+
+	ualg->cru_type = 0;
+	ualg->cru_mask = 0;
+	ualg->cru_flags = alg->cra_flags;
+	ualg->cru_refcnt = refcount_read(&alg->cra_refcnt);
+
+	if (nla_put_u32(skb, CRYPTOCFGA_PRIORITY_VAL, alg->cra_priority))
+		goto nla_put_failure;
+	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
+		struct crypto_report_larval rl = {
+			.type = "larval",
+		};
+
+		if (nla_put(skb, CRYPTOCFGA_REPORT_LARVAL, sizeof(rl), &rl))
+			goto nla_put_failure;
+		goto out;
+	}
+
+	if (alg->cra_type && alg->cra_type->report) {
+		if (alg->cra_type->report(skb, alg))
+			goto nla_put_failure;
+
+		goto out;
+	}
+
+	switch (alg->cra_flags & (CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_LARVAL)) {
+	case CRYPTO_ALG_TYPE_CIPHER:
+		if (crypto_report_cipher(skb, alg))
+			goto nla_put_failure;
+
+		break;
+	}
+
+out:
+	return 0;
+
+nla_put_failure:
+	return -EMSGSIZE;
+}
+
+static int crypto_report_alg(struct crypto_alg *alg,
+			     struct crypto_dump_info *info)
+{
+	struct sk_buff *in_skb = info->in_skb;
+	struct sk_buff *skb = info->out_skb;
+	struct nlmsghdr *nlh;
+	struct crypto_user_alg *ualg;
+	int err = 0;
+
+	nlh = nlmsg_put(skb, NETLINK_CB(in_skb).portid, info->nlmsg_seq,
+			CRYPTO_MSG_GETALG, sizeof(*ualg), info->nlmsg_flags);
+	if (!nlh) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	ualg = nlmsg_data(nlh);
+
+	err = crypto_report_one(alg, ualg, skb);
+	if (err) {
+		nlmsg_cancel(skb, nlh);
+		goto out;
+	}
+
+	nlmsg_end(skb, nlh);
+
+out:
+	return err;
+}
+
+static int crypto_report(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
+			 struct nlattr **attrs)
+{
+	struct net *net = sock_net(in_skb->sk);
+	struct crypto_user_alg *p = nlmsg_data(in_nlh);
+	struct crypto_alg *alg;
+	struct sk_buff *skb;
+	struct crypto_dump_info info;
+	int err;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 0);
+	if (!alg)
+		return -ENOENT;
+
+	err = -ENOMEM;
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!skb)
+		goto drop_alg;
+
+	info.in_skb = in_skb;
+	info.out_skb = skb;
+	info.nlmsg_seq = in_nlh->nlmsg_seq;
+	info.nlmsg_flags = 0;
+
+	err = crypto_report_alg(alg, &info);
+
+drop_alg:
+	crypto_mod_put(alg);
+
+	if (err) {
+		kfree_skb(skb);
+		return err;
+	}
+
+	return nlmsg_unicast(net->crypto_nlsk, skb, NETLINK_CB(in_skb).portid);
+}
+
+static int crypto_dump_report(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	const size_t start_pos = cb->args[0];
+	size_t pos = 0;
+	struct crypto_dump_info info;
+	struct crypto_alg *alg;
+	int res;
+
+	info.in_skb = cb->skb;
+	info.out_skb = skb;
+	info.nlmsg_seq = cb->nlh->nlmsg_seq;
+	info.nlmsg_flags = NLM_F_MULTI;
+
+	down_read(&crypto_alg_sem);
+	list_for_each_entry(alg, &crypto_alg_list, cra_list) {
+		if (pos >= start_pos) {
+			res = crypto_report_alg(alg, &info);
+			if (res == -EMSGSIZE)
+				break;
+			if (res)
+				goto out;
+		}
+		pos++;
+	}
+	cb->args[0] = pos;
+	res = skb->len;
+out:
+	up_read(&crypto_alg_sem);
+	return res;
+}
+
+static int crypto_dump_report_done(struct netlink_callback *cb)
+{
+	return 0;
+}
+
+static int crypto_update_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			     struct nlattr **attrs)
+{
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	struct nlattr *priority = attrs[CRYPTOCFGA_PRIORITY_VAL];
+	LIST_HEAD(list);
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	if (priority && !strlen(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 1);
+	if (!alg)
+		return -ENOENT;
+
+	down_write(&crypto_alg_sem);
+
+	crypto_remove_spawns(alg, &list, NULL);
+
+	if (priority)
+		alg->cra_priority = nla_get_u32(priority);
+
+	up_write(&crypto_alg_sem);
+
+	crypto_mod_put(alg);
+	crypto_remove_final(&list);
+
+	return 0;
+}
+
+static int crypto_del_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	int err;
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, 1);
+	if (!alg)
+		return -ENOENT;
+
+	/* We can not unregister core algorithms such as aes.
+	 * We would loose the reference in the crypto_alg_list to this algorithm
+	 * if we try to unregister. Unregistering such an algorithm without
+	 * removing the module is not possible, so we restrict to crypto
+	 * instances that are build from templates. */
+	err = -EINVAL;
+	if (!(alg->cra_flags & CRYPTO_ALG_INSTANCE))
+		goto drop_alg;
+
+	err = -EBUSY;
+	if (refcount_read(&alg->cra_refcnt) > 2)
+		goto drop_alg;
+
+	crypto_unregister_instance((struct crypto_instance *)alg);
+	err = 0;
+
+drop_alg:
+	crypto_mod_put(alg);
+	return err;
+}
+
+static int crypto_add_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	int exact = 0;
+	const char *name;
+	struct crypto_alg *alg;
+	struct crypto_user_alg *p = nlmsg_data(nlh);
+	struct nlattr *priority = attrs[CRYPTOCFGA_PRIORITY_VAL];
+
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!null_terminated(p->cru_name) || !null_terminated(p->cru_driver_name))
+		return -EINVAL;
+
+	if (strlen(p->cru_driver_name))
+		exact = 1;
+
+	if (priority && !exact)
+		return -EINVAL;
+
+	alg = crypto_alg_match(p, exact);
+	if (alg) {
+		crypto_mod_put(alg);
+		return -EEXIST;
+	}
+
+	if (strlen(p->cru_driver_name))
+		name = p->cru_driver_name;
+	else
+		name = p->cru_name;
+
+	alg = crypto_alg_mod_lookup(name, p->cru_type, p->cru_mask);
+	if (IS_ERR(alg))
+		return PTR_ERR(alg);
+
+	down_write(&crypto_alg_sem);
+
+	if (priority)
+		alg->cra_priority = nla_get_u32(priority);
+
+	up_write(&crypto_alg_sem);
+
+	crypto_mod_put(alg);
+
+	return 0;
+}
+
+static int crypto_del_rng(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attrs)
+{
+	if (!netlink_capable(skb, CAP_NET_ADMIN))
+		return -EPERM;
+	return crypto_del_default_rng();
+}
+
+static int crypto_reportstat(struct sk_buff *in_skb, struct nlmsghdr *in_nlh,
+			     struct nlattr **attrs)
+{
+	/* No longer supported */
+	return -ENOTSUPP;
+}
+
+#define MSGSIZE(type) sizeof(struct type)
+
+static const int crypto_msg_min[CRYPTO_NR_MSGTYPES] = {
+	[CRYPTO_MSG_NEWALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_DELALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_UPDATEALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_GETALG	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = 0,
+	[CRYPTO_MSG_GETSTAT	- CRYPTO_MSG_BASE] = MSGSIZE(crypto_user_alg),
+};
+
+static const struct nla_policy crypto_policy[CRYPTOCFGA_MAX+1] = {
+	[CRYPTOCFGA_PRIORITY_VAL]   = { .type = NLA_U32},
+};
+
+#undef MSGSIZE
+
+static const struct crypto_link {
+	int (*doit)(struct sk_buff *, struct nlmsghdr *, struct nlattr **);
+	int (*dump)(struct sk_buff *, struct netlink_callback *);
+	int (*done)(struct netlink_callback *);
+} crypto_dispatch[CRYPTO_NR_MSGTYPES] = {
+	[CRYPTO_MSG_NEWALG	- CRYPTO_MSG_BASE] = { .doit = crypto_add_alg},
+	[CRYPTO_MSG_DELALG	- CRYPTO_MSG_BASE] = { .doit = crypto_del_alg},
+	[CRYPTO_MSG_UPDATEALG	- CRYPTO_MSG_BASE] = { .doit = crypto_update_alg},
+	[CRYPTO_MSG_GETALG	- CRYPTO_MSG_BASE] = { .doit = crypto_report,
+						       .dump = crypto_dump_report,
+						       .done = crypto_dump_report_done},
+	[CRYPTO_MSG_DELRNG	- CRYPTO_MSG_BASE] = { .doit = crypto_del_rng },
+	[CRYPTO_MSG_GETSTAT	- CRYPTO_MSG_BASE] = { .doit = crypto_reportstat},
+};
+
+static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
+			       struct netlink_ext_ack *extack)
+{
+	struct net *net = sock_net(skb->sk);
+	struct nlattr *attrs[CRYPTOCFGA_MAX+1];
+	const struct crypto_link *link;
+	int type, err;
+
+	type = nlh->nlmsg_type;
+	if (type > CRYPTO_MSG_MAX)
+		return -EINVAL;
+
+	type -= CRYPTO_MSG_BASE;
+	link = &crypto_dispatch[type];
+
+	if ((type == (CRYPTO_MSG_GETALG - CRYPTO_MSG_BASE) &&
+	    (nlh->nlmsg_flags & NLM_F_DUMP))) {
+		struct crypto_alg *alg;
+		unsigned long dump_alloc = 0;
+
+		if (link->dump == NULL)
+			return -EINVAL;
+
+		down_read(&crypto_alg_sem);
+		list_for_each_entry(alg, &crypto_alg_list, cra_list)
+			dump_alloc += CRYPTO_REPORT_MAXSIZE;
+		up_read(&crypto_alg_sem);
+
+		{
+			struct netlink_dump_control c = {
+				.dump = link->dump,
+				.done = link->done,
+				.min_dump_alloc = min(dump_alloc, 65535UL),
+			};
+			err = netlink_dump_start(net->crypto_nlsk, skb, nlh, &c);
+		}
+
+		return err;
+	}
+
+	err = nlmsg_parse_deprecated(nlh, crypto_msg_min[type], attrs,
+				     CRYPTOCFGA_MAX, crypto_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (link->doit == NULL)
+		return -EINVAL;
+
+	return link->doit(skb, nlh, attrs);
+}
+
+static void crypto_netlink_rcv(struct sk_buff *skb)
+{
+	mutex_lock(&crypto_cfg_mutex);
+	netlink_rcv_skb(skb, &crypto_user_rcv_msg);
+	mutex_unlock(&crypto_cfg_mutex);
+}
+
+static int __net_init crypto_netlink_init(struct net *net)
+{
+	struct netlink_kernel_cfg cfg = {
+		.input	= crypto_netlink_rcv,
+	};
+
+	net->crypto_nlsk = netlink_kernel_create(net, NETLINK_CRYPTO, &cfg);
+	return net->crypto_nlsk == NULL ? -ENOMEM : 0;
+}
+
+static void __net_exit crypto_netlink_exit(struct net *net)
+{
+	netlink_kernel_release(net->crypto_nlsk);
+	net->crypto_nlsk = NULL;
+}
+
+static struct pernet_operations crypto_netlink_net_ops = {
+	.init = crypto_netlink_init,
+	.exit = crypto_netlink_exit,
+};
+
+static int __init crypto_user_init(void)
+{
+	return register_pernet_subsys(&crypto_netlink_net_ops);
+}
+
+static void __exit crypto_user_exit(void)
+{
+	unregister_pernet_subsys(&crypto_netlink_net_ops);
+}
+
+module_init(crypto_user_init);
+module_exit(crypto_user_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
+MODULE_DESCRIPTION("Crypto userspace configuration API");
+MODULE_ALIAS("net-pf-16-proto-21");