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, 502 insertions, 0 deletions

diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c
new file mode 100644
index 000000000..94c4718d3
--- /dev/null
+++ b/net/ethtool/strset.c
@@ -0,0 +1,502 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/ethtool.h>
+#include <linux/phy.h>
+
+#include "common.h"
+#include "netlink.h"
+
+struct strset_info {
+	bool per_dev;
+	bool free_strings;
+	unsigned int count;
+	const char (*strings)[ETH_GSTRING_LEN];
+};
+
+static const struct strset_info info_template[] = {
+	[ETH_SS_TEST] = {
+		.per_dev	= true,
+	},
+	[ETH_SS_STATS] = {
+		.per_dev	= true,
+	},
+	[ETH_SS_PRIV_FLAGS] = {
+		.per_dev	= true,
+	},
+	[ETH_SS_FEATURES] = {
+		.per_dev	= false,
+		.count		= ARRAY_SIZE(netdev_features_strings),
+		.strings	= netdev_features_strings,
+	},
+	[ETH_SS_RSS_HASH_FUNCS] = {
+		.per_dev	= false,
+		.count		= ARRAY_SIZE(rss_hash_func_strings),
+		.strings	= rss_hash_func_strings,
+	},
+	[ETH_SS_TUNABLES] = {
+		.per_dev	= false,
+		.count		= ARRAY_SIZE(tunable_strings),
+		.strings	= tunable_strings,
+	},
+	[ETH_SS_PHY_STATS] = {
+		.per_dev	= true,
+	},
+	[ETH_SS_PHY_TUNABLES] = {
+		.per_dev	= false,
+		.count		= ARRAY_SIZE(phy_tunable_strings),
+		.strings	= phy_tunable_strings,
+	},
+	[ETH_SS_LINK_MODES] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_LINK_MODE_MASK_NBITS,
+		.strings	= link_mode_names,
+	},
+	[ETH_SS_MSG_CLASSES] = {
+		.per_dev	= false,
+		.count		= NETIF_MSG_CLASS_COUNT,
+		.strings	= netif_msg_class_names,
+	},
+	[ETH_SS_WOL_MODES] = {
+		.per_dev	= false,
+		.count		= WOL_MODE_COUNT,
+		.strings	= wol_mode_names,
+	},
+	[ETH_SS_SOF_TIMESTAMPING] = {
+		.per_dev	= false,
+		.count		= __SOF_TIMESTAMPING_CNT,
+		.strings	= sof_timestamping_names,
+	},
+	[ETH_SS_TS_TX_TYPES] = {
+		.per_dev	= false,
+		.count		= __HWTSTAMP_TX_CNT,
+		.strings	= ts_tx_type_names,
+	},
+	[ETH_SS_TS_RX_FILTERS] = {
+		.per_dev	= false,
+		.count		= __HWTSTAMP_FILTER_CNT,
+		.strings	= ts_rx_filter_names,
+	},
+	[ETH_SS_TS_FLAGS] = {
+		.per_dev	= false,
+		.count		= __HWTSTAMP_FLAG_CNT,
+		.strings	= ts_flags_names,
+	},
+	[ETH_SS_UDP_TUNNEL_TYPES] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_UDP_TUNNEL_TYPE_CNT,
+		.strings	= udp_tunnel_type_names,
+	},
+	[ETH_SS_STATS_STD] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_STATS_CNT,
+		.strings	= stats_std_names,
+	},
+	[ETH_SS_STATS_ETH_PHY] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_A_STATS_ETH_PHY_CNT,
+		.strings	= stats_eth_phy_names,
+	},
+	[ETH_SS_STATS_ETH_MAC] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_A_STATS_ETH_MAC_CNT,
+		.strings	= stats_eth_mac_names,
+	},
+	[ETH_SS_STATS_ETH_CTRL] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_A_STATS_ETH_CTRL_CNT,
+		.strings	= stats_eth_ctrl_names,
+	},
+	[ETH_SS_STATS_RMON] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_A_STATS_RMON_CNT,
+		.strings	= stats_rmon_names,
+	},
+	[ETH_SS_STATS_PHY] = {
+		.per_dev	= false,
+		.count		= __ETHTOOL_A_STATS_PHY_CNT,
+		.strings	= stats_phy_names,
+	},
+};
+
+struct strset_req_info {
+	struct ethnl_req_info		base;
+	u32				req_ids;
+	bool				counts_only;
+};
+
+#define STRSET_REQINFO(__req_base) \
+	container_of(__req_base, struct strset_req_info, base)
+
+struct strset_reply_data {
+	struct ethnl_reply_data		base;
+	struct strset_info		sets[ETH_SS_COUNT];
+};
+
+#define STRSET_REPDATA(__reply_base) \
+	container_of(__reply_base, struct strset_reply_data, base)
+
+const struct nla_policy ethnl_strset_get_policy[] = {
+	[ETHTOOL_A_STRSET_HEADER]	=
+		NLA_POLICY_NESTED(ethnl_header_policy_phy),
+	[ETHTOOL_A_STRSET_STRINGSETS]	= { .type = NLA_NESTED },
+	[ETHTOOL_A_STRSET_COUNTS_ONLY]	= { .type = NLA_FLAG },
+};
+
+static const struct nla_policy get_stringset_policy[] = {
+	[ETHTOOL_A_STRINGSET_ID]	= { .type = NLA_U32 },
+};
+
+/**
+ * strset_include() - test if a string set should be included in reply
+ * @info: parsed client request
+ * @data: pointer to request data structure
+ * @id:   id of string set to check (ETH_SS_* constants)
+ */
+static bool strset_include(const struct strset_req_info *info,
+			   const struct strset_reply_data *data, u32 id)
+{
+	bool per_dev;
+
+	BUILD_BUG_ON(ETH_SS_COUNT >= BITS_PER_BYTE * sizeof(info->req_ids));
+
+	if (info->req_ids)
+		return info->req_ids & (1U << id);
+	per_dev = data->sets[id].per_dev;
+	if (!per_dev && !data->sets[id].strings)
+		return false;
+
+	return data->base.dev ? per_dev : !per_dev;
+}
+
+static int strset_get_id(const struct nlattr *nest, u32 *val,
+			 struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[ARRAY_SIZE(get_stringset_policy)];
+	int ret;
+
+	ret = nla_parse_nested(tb, ARRAY_SIZE(get_stringset_policy) - 1, nest,
+			       get_stringset_policy, extack);
+	if (ret < 0)
+		return ret;
+	if (NL_REQ_ATTR_CHECK(extack, nest, tb, ETHTOOL_A_STRINGSET_ID))
+		return -EINVAL;
+
+	*val = nla_get_u32(tb[ETHTOOL_A_STRINGSET_ID]);
+	return 0;
+}
+
+static const struct nla_policy strset_stringsets_policy[] = {
+	[ETHTOOL_A_STRINGSETS_STRINGSET]	= { .type = NLA_NESTED },
+};
+
+static int strset_parse_request(struct ethnl_req_info *req_base,
+				const struct genl_info *info,
+				struct nlattr **tb,
+				struct netlink_ext_ack *extack)
+{
+	struct strset_req_info *req_info = STRSET_REQINFO(req_base);
+	struct nlattr *nest = tb[ETHTOOL_A_STRSET_STRINGSETS];
+	struct nlattr *attr;
+	int rem, ret;
+
+	if (!nest)
+		return 0;
+	ret = nla_validate_nested(nest,
+				  ARRAY_SIZE(strset_stringsets_policy) - 1,
+				  strset_stringsets_policy, extack);
+	if (ret < 0)
+		return ret;
+
+	req_info->counts_only = tb[ETHTOOL_A_STRSET_COUNTS_ONLY];
+	nla_for_each_nested(attr, nest, rem) {
+		u32 id;
+
+		if (WARN_ONCE(nla_type(attr) != ETHTOOL_A_STRINGSETS_STRINGSET,
+			      "unexpected attrtype %u in ETHTOOL_A_STRSET_STRINGSETS\n",
+			      nla_type(attr)))
+			return -EINVAL;
+
+		ret = strset_get_id(attr, &id, extack);
+		if (ret < 0)
+			return ret;
+		if (id >= ETH_SS_COUNT) {
+			NL_SET_ERR_MSG_ATTR(extack, attr,
+					    "unknown string set id");
+			return -EOPNOTSUPP;
+		}
+
+		req_info->req_ids |= (1U << id);
+	}
+
+	return 0;
+}
+
+static void strset_cleanup_data(struct ethnl_reply_data *reply_base)
+{
+	struct strset_reply_data *data = STRSET_REPDATA(reply_base);
+	unsigned int i;
+
+	for (i = 0; i < ETH_SS_COUNT; i++)
+		if (data->sets[i].free_strings) {
+			kfree(data->sets[i].strings);
+			data->sets[i].strings = NULL;
+			data->sets[i].free_strings = false;
+		}
+}
+
+static int strset_prepare_set(struct strset_info *info, struct net_device *dev,
+			      struct phy_device *phydev, unsigned int id,
+			      bool counts_only)
+{
+	const struct ethtool_phy_ops *phy_ops = ethtool_phy_ops;
+	const struct ethtool_ops *ops = dev->ethtool_ops;
+	void *strings;
+	int count, ret;
+
+	if (id == ETH_SS_PHY_STATS && phydev &&
+	    !ops->get_ethtool_phy_stats && phy_ops &&
+	    phy_ops->get_sset_count)
+		ret = phy_ops->get_sset_count(phydev);
+	else if (ops->get_sset_count && ops->get_strings)
+		ret = ops->get_sset_count(dev, id);
+	else
+		ret = -EOPNOTSUPP;
+	if (ret <= 0) {
+		info->count = 0;
+		return 0;
+	}
+
+	count = ret;
+	if (!counts_only) {
+		strings = kcalloc(count, ETH_GSTRING_LEN, GFP_KERNEL);
+		if (!strings)
+			return -ENOMEM;
+		if (id == ETH_SS_PHY_STATS && phydev &&
+		    !ops->get_ethtool_phy_stats && phy_ops &&
+		    phy_ops->get_strings)
+			phy_ops->get_strings(phydev, strings);
+		else
+			ops->get_strings(dev, id, strings);
+		info->strings = strings;
+		info->free_strings = true;
+	}
+	info->count = count;
+
+	return 0;
+}
+
+static int strset_prepare_data(const struct ethnl_req_info *req_base,
+			       struct ethnl_reply_data *reply_base,
+			       const struct genl_info *info)
+{
+	const struct strset_req_info *req_info = STRSET_REQINFO(req_base);
+	struct strset_reply_data *data = STRSET_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	struct nlattr **tb = info->attrs;
+	struct phy_device *phydev;
+	unsigned int i;
+	int ret;
+
+	BUILD_BUG_ON(ARRAY_SIZE(info_template) != ETH_SS_COUNT);
+	memcpy(&data->sets, &info_template, sizeof(data->sets));
+
+	if (!dev) {
+		for (i = 0; i < ETH_SS_COUNT; i++) {
+			if ((req_info->req_ids & (1U << i)) &&
+			    data->sets[i].per_dev) {
+				GENL_SET_ERR_MSG(info, "requested per device strings without dev");
+				return -EINVAL;
+			}
+		}
+		return 0;
+	}
+
+	phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_STRSET_HEADER,
+				      info->extack);
+
+	/* phydev can be NULL, check for errors only */
+	if (IS_ERR(phydev))
+		return PTR_ERR(phydev);
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		goto err_strset;
+	for (i = 0; i < ETH_SS_COUNT; i++) {
+		if (!strset_include(req_info, data, i) ||
+		    !data->sets[i].per_dev)
+			continue;
+
+		ret = strset_prepare_set(&data->sets[i], dev, phydev, i,
+					 req_info->counts_only);
+		if (ret < 0)
+			goto err_ops;
+	}
+	ethnl_ops_complete(dev);
+
+	return 0;
+err_ops:
+	ethnl_ops_complete(dev);
+err_strset:
+	strset_cleanup_data(reply_base);
+	return ret;
+}
+
+/* calculate size of ETHTOOL_A_STRSET_STRINGSET nest for one string set */
+static int strset_set_size(const struct strset_info *info, bool counts_only)
+{
+	unsigned int len = 0;
+	unsigned int i;
+
+	if (info->count == 0)
+		return 0;
+	if (counts_only)
+		return nla_total_size(2 * nla_total_size(sizeof(u32)));
+
+	for (i = 0; i < info->count; i++) {
+		const char *str = info->strings[i];
+
+		/* ETHTOOL_A_STRING_INDEX, ETHTOOL_A_STRING_VALUE, nest */
+		len += nla_total_size(nla_total_size(sizeof(u32)) +
+				      ethnl_strz_size(str));
+	}
+	/* ETHTOOL_A_STRINGSET_ID, ETHTOOL_A_STRINGSET_COUNT */
+	len = 2 * nla_total_size(sizeof(u32)) + nla_total_size(len);
+
+	return nla_total_size(len);
+}
+
+static int strset_reply_size(const struct ethnl_req_info *req_base,
+			     const struct ethnl_reply_data *reply_base)
+{
+	const struct strset_req_info *req_info = STRSET_REQINFO(req_base);
+	const struct strset_reply_data *data = STRSET_REPDATA(reply_base);
+	unsigned int i;
+	int len = 0;
+	int ret;
+
+	len += nla_total_size(0); /* ETHTOOL_A_STRSET_STRINGSETS */
+
+	for (i = 0; i < ETH_SS_COUNT; i++) {
+		const struct strset_info *set_info = &data->sets[i];
+
+		if (!strset_include(req_info, data, i))
+			continue;
+
+		ret = strset_set_size(set_info, req_info->counts_only);
+		if (ret < 0)
+			return ret;
+		len += ret;
+	}
+
+	return len;
+}
+
+/* fill one string into reply */
+static int strset_fill_string(struct sk_buff *skb,
+			      const struct strset_info *set_info, u32 idx)
+{
+	struct nlattr *string_attr;
+	const char *value;
+
+	value = set_info->strings[idx];
+
+	string_attr = nla_nest_start(skb, ETHTOOL_A_STRINGS_STRING);
+	if (!string_attr)
+		return -EMSGSIZE;
+	if (nla_put_u32(skb, ETHTOOL_A_STRING_INDEX, idx) ||
+	    ethnl_put_strz(skb, ETHTOOL_A_STRING_VALUE, value))
+		goto nla_put_failure;
+	nla_nest_end(skb, string_attr);
+
+	return 0;
+nla_put_failure:
+	nla_nest_cancel(skb, string_attr);
+	return -EMSGSIZE;
+}
+
+/* fill one string set into reply */
+static int strset_fill_set(struct sk_buff *skb,
+			   const struct strset_info *set_info, u32 id,
+			   bool counts_only)
+{
+	struct nlattr *stringset_attr;
+	struct nlattr *strings_attr;
+	unsigned int i;
+
+	if (!set_info->per_dev && !set_info->strings)
+		return -EOPNOTSUPP;
+	if (set_info->count == 0)
+		return 0;
+	stringset_attr = nla_nest_start(skb, ETHTOOL_A_STRINGSETS_STRINGSET);
+	if (!stringset_attr)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, ETHTOOL_A_STRINGSET_ID, id) ||
+	    nla_put_u32(skb, ETHTOOL_A_STRINGSET_COUNT, set_info->count))
+		goto nla_put_failure;
+
+	if (!counts_only) {
+		strings_attr = nla_nest_start(skb, ETHTOOL_A_STRINGSET_STRINGS);
+		if (!strings_attr)
+			goto nla_put_failure;
+		for (i = 0; i < set_info->count; i++) {
+			if (strset_fill_string(skb, set_info, i) < 0)
+				goto nla_put_failure;
+		}
+		if (nla_nest_end_safe(skb, strings_attr) < 0)
+			goto nla_put_failure;
+	}
+
+	nla_nest_end(skb, stringset_attr);
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, stringset_attr);
+	return -EMSGSIZE;
+}
+
+static int strset_fill_reply(struct sk_buff *skb,
+			     const struct ethnl_req_info *req_base,
+			     const struct ethnl_reply_data *reply_base)
+{
+	const struct strset_req_info *req_info = STRSET_REQINFO(req_base);
+	const struct strset_reply_data *data = STRSET_REPDATA(reply_base);
+	struct nlattr *nest;
+	unsigned int i;
+	int ret;
+
+	nest = nla_nest_start(skb, ETHTOOL_A_STRSET_STRINGSETS);
+	if (!nest)
+		return -EMSGSIZE;
+
+	for (i = 0; i < ETH_SS_COUNT; i++) {
+		if (strset_include(req_info, data, i)) {
+			ret = strset_fill_set(skb, &data->sets[i], i,
+					      req_info->counts_only);
+			if (ret < 0)
+				goto nla_put_failure;
+		}
+	}
+
+	nla_nest_end(skb, nest);
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return ret;
+}
+
+const struct ethnl_request_ops ethnl_strset_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_STRSET_GET,
+	.reply_cmd		= ETHTOOL_MSG_STRSET_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_STRSET_HEADER,
+	.req_info_size		= sizeof(struct strset_req_info),
+	.reply_data_size	= sizeof(struct strset_reply_data),
+	.allow_nodev_do		= true,
+
+	.parse_request		= strset_parse_request,
+	.prepare_data		= strset_prepare_data,
+	.reply_size		= strset_reply_size,
+	.fill_reply		= strset_fill_reply,
+	.cleanup_data		= strset_cleanup_data,
+};