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, 158 insertions, 0 deletions

diff --git a/net/ethtool/wol.c b/net/ethtool/wol.c
new file mode 100644
index 000000000..60f9a1d85
--- /dev/null
+++ b/net/ethtool/wol.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "bitset.h"
+#include "common.h"
+#include "netlink.h"
+
+struct wol_req_info {
+	struct ethnl_req_info		base;
+};
+
+struct wol_reply_data {
+	struct ethnl_reply_data		base;
+	struct ethtool_wolinfo		wol;
+	bool				show_sopass;
+};
+
+#define WOL_REPDATA(__reply_base) \
+	container_of(__reply_base, struct wol_reply_data, base)
+
+const struct nla_policy ethnl_wol_get_policy[] = {
+	[ETHTOOL_A_WOL_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+};
+
+static int wol_prepare_data(const struct ethnl_req_info *req_base,
+			    struct ethnl_reply_data *reply_base,
+			    const struct genl_info *info)
+{
+	struct wol_reply_data *data = WOL_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	int ret;
+
+	if (!dev->ethtool_ops->get_wol)
+		return -EOPNOTSUPP;
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+	dev->ethtool_ops->get_wol(dev, &data->wol);
+	ethnl_ops_complete(dev);
+	/* do not include password in notifications */
+	data->show_sopass = !genl_info_is_ntf(info) &&
+		(data->wol.supported & WAKE_MAGICSECURE);
+
+	return 0;
+}
+
+static int wol_reply_size(const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct wol_reply_data *data = WOL_REPDATA(reply_base);
+	int len;
+
+	len = ethnl_bitset32_size(&data->wol.wolopts, &data->wol.supported,
+				  WOL_MODE_COUNT, wol_mode_names, compact);
+	if (len < 0)
+		return len;
+	if (data->show_sopass)
+		len += nla_total_size(sizeof(data->wol.sopass));
+
+	return len;
+}
+
+static int wol_fill_reply(struct sk_buff *skb,
+			  const struct ethnl_req_info *req_base,
+			  const struct ethnl_reply_data *reply_base)
+{
+	bool compact = req_base->flags & ETHTOOL_FLAG_COMPACT_BITSETS;
+	const struct wol_reply_data *data = WOL_REPDATA(reply_base);
+	int ret;
+
+	ret = ethnl_put_bitset32(skb, ETHTOOL_A_WOL_MODES, &data->wol.wolopts,
+				 &data->wol.supported, WOL_MODE_COUNT,
+				 wol_mode_names, compact);
+	if (ret < 0)
+		return ret;
+	if (data->show_sopass &&
+	    nla_put(skb, ETHTOOL_A_WOL_SOPASS, sizeof(data->wol.sopass),
+		    data->wol.sopass))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+/* WOL_SET */
+
+const struct nla_policy ethnl_wol_set_policy[] = {
+	[ETHTOOL_A_WOL_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy),
+	[ETHTOOL_A_WOL_MODES]		= { .type = NLA_NESTED },
+	[ETHTOOL_A_WOL_SOPASS]		= { .type = NLA_BINARY,
+					    .len = SOPASS_MAX },
+};
+
+static int
+ethnl_set_wol_validate(struct ethnl_req_info *req_info, struct genl_info *info)
+{
+	const struct ethtool_ops *ops = req_info->dev->ethtool_ops;
+
+	return ops->get_wol && ops->set_wol ? 1 : -EOPNOTSUPP;
+}
+
+static int
+ethnl_set_wol(struct ethnl_req_info *req_info, struct genl_info *info)
+{
+	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
+	struct net_device *dev = req_info->dev;
+	struct nlattr **tb = info->attrs;
+	bool mod = false;
+	int ret;
+
+	dev->ethtool_ops->get_wol(dev, &wol);
+	ret = ethnl_update_bitset32(&wol.wolopts, WOL_MODE_COUNT,
+				    tb[ETHTOOL_A_WOL_MODES], wol_mode_names,
+				    info->extack, &mod);
+	if (ret < 0)
+		return ret;
+	if (wol.wolopts & ~wol.supported) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[ETHTOOL_A_WOL_MODES],
+				    "cannot enable unsupported WoL mode");
+		return -EINVAL;
+	}
+	if (tb[ETHTOOL_A_WOL_SOPASS]) {
+		if (!(wol.supported & WAKE_MAGICSECURE)) {
+			NL_SET_ERR_MSG_ATTR(info->extack,
+					    tb[ETHTOOL_A_WOL_SOPASS],
+					    "magicsecure not supported, cannot set password");
+			return -EINVAL;
+		}
+		ethnl_update_binary(wol.sopass, sizeof(wol.sopass),
+				    tb[ETHTOOL_A_WOL_SOPASS], &mod);
+	}
+
+	if (!mod)
+		return 0;
+	ret = dev->ethtool_ops->set_wol(dev, &wol);
+	if (ret)
+		return ret;
+	dev->ethtool->wol_enabled = !!wol.wolopts;
+	return 1;
+}
+
+const struct ethnl_request_ops ethnl_wol_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_WOL_GET,
+	.reply_cmd		= ETHTOOL_MSG_WOL_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_WOL_HEADER,
+	.req_info_size		= sizeof(struct wol_req_info),
+	.reply_data_size	= sizeof(struct wol_reply_data),
+
+	.prepare_data		= wol_prepare_data,
+	.reply_size		= wol_reply_size,
+	.fill_reply		= wol_fill_reply,
+
+	.set_validate		= ethnl_set_wol_validate,
+	.set			= ethnl_set_wol,
+	.set_ntf_cmd		= ETHTOOL_MSG_WOL_NTF,
+};