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, 193 insertions, 0 deletions

diff --git a/net/ceph/decode.c b/net/ceph/decode.c
new file mode 100644
index 000000000..2f21af38c
--- /dev/null
+++ b/net/ceph/decode.c
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/ceph/ceph_debug.h>
+
+#include <linux/inet.h>
+
+#include <linux/ceph/decode.h>
+#include <linux/ceph/messenger.h>  /* for ceph_pr_addr() */
+
+static int
+ceph_decode_entity_addr_versioned(void **p, void *end,
+				  struct ceph_entity_addr *addr)
+{
+	int ret;
+	u8 struct_v;
+	u32 struct_len, addr_len;
+	void *struct_end;
+
+	ret = ceph_start_decoding(p, end, 1, "entity_addr_t", &struct_v,
+				  &struct_len);
+	if (ret)
+		goto bad;
+
+	ret = -EINVAL;
+	struct_end = *p + struct_len;
+
+	ceph_decode_copy_safe(p, end, &addr->type, sizeof(addr->type), bad);
+
+	ceph_decode_copy_safe(p, end, &addr->nonce, sizeof(addr->nonce), bad);
+
+	ceph_decode_32_safe(p, end, addr_len, bad);
+	if (addr_len > sizeof(addr->in_addr))
+		goto bad;
+
+	memset(&addr->in_addr, 0, sizeof(addr->in_addr));
+	if (addr_len) {
+		ceph_decode_copy_safe(p, end, &addr->in_addr, addr_len, bad);
+
+		addr->in_addr.ss_family =
+			le16_to_cpu((__force __le16)addr->in_addr.ss_family);
+	}
+
+	/* Advance past anything the client doesn't yet understand */
+	*p = struct_end;
+	ret = 0;
+bad:
+	return ret;
+}
+
+static int
+ceph_decode_entity_addr_legacy(void **p, void *end,
+			       struct ceph_entity_addr *addr)
+{
+	int ret = -EINVAL;
+
+	/* Skip rest of type field */
+	ceph_decode_skip_n(p, end, 3, bad);
+
+	/*
+	 * Clients that don't support ADDR2 always send TYPE_NONE, change it
+	 * to TYPE_LEGACY for forward compatibility.
+	 */
+	addr->type = CEPH_ENTITY_ADDR_TYPE_LEGACY;
+	ceph_decode_copy_safe(p, end, &addr->nonce, sizeof(addr->nonce), bad);
+	memset(&addr->in_addr, 0, sizeof(addr->in_addr));
+	ceph_decode_copy_safe(p, end, &addr->in_addr,
+			      sizeof(addr->in_addr), bad);
+	addr->in_addr.ss_family =
+			be16_to_cpu((__force __be16)addr->in_addr.ss_family);
+	ret = 0;
+bad:
+	return ret;
+}
+
+int
+ceph_decode_entity_addr(void **p, void *end, struct ceph_entity_addr *addr)
+{
+	u8 marker;
+
+	ceph_decode_8_safe(p, end, marker, bad);
+	if (marker == 1)
+		return ceph_decode_entity_addr_versioned(p, end, addr);
+	else if (marker == 0)
+		return ceph_decode_entity_addr_legacy(p, end, addr);
+bad:
+	return -EINVAL;
+}
+EXPORT_SYMBOL(ceph_decode_entity_addr);
+
+/*
+ * Return addr of desired type (MSGR2 or LEGACY) or error.  In case of
+ * multiple matches, use the first one for compatibility with userspace
+ * messenger.
+ *
+ * Assume encoding with MSG_ADDR2.
+ */
+int ceph_decode_entity_addrvec(void **p, void *end, bool msgr2,
+			       struct ceph_entity_addr *addr)
+{
+	__le32 my_type = msgr2 ? CEPH_ENTITY_ADDR_TYPE_MSGR2 :
+				 CEPH_ENTITY_ADDR_TYPE_LEGACY;
+	struct ceph_entity_addr tmp_addr;
+	int addr_cnt;
+	bool found;
+	u8 marker;
+	int ret;
+	int i;
+
+	ceph_decode_8_safe(p, end, marker, e_inval);
+	if (marker != 2) {
+		pr_err("bad addrvec marker %d\n", marker);
+		return -EINVAL;
+	}
+
+	ceph_decode_32_safe(p, end, addr_cnt, e_inval);
+	dout("%s addr_cnt %d\n", __func__, addr_cnt);
+
+	found = false;
+	for (i = 0; i < addr_cnt; i++) {
+		ret = ceph_decode_entity_addr(p, end, &tmp_addr);
+		if (ret)
+			return ret;
+
+		dout("%s i %d addr %s\n", __func__, i, ceph_pr_addr(&tmp_addr));
+		if (tmp_addr.type == my_type) {
+			if (!found) {
+				memcpy(addr, &tmp_addr, sizeof(*addr));
+				found = true;
+			} else {
+				dout("%s skipping extra match of type %d in addrvec\n",
+				     __func__, le32_to_cpu(my_type));
+			}
+		}
+	}
+
+	if (found)
+		return 0;
+
+	if (!addr_cnt)
+		return 0;  /* normal -- e.g. unused OSD id/slot */
+
+	if (addr_cnt == 1 && !memchr_inv(&tmp_addr, 0, sizeof(tmp_addr)))
+		return 0;  /* weird but effectively the same as !addr_cnt */
+
+	pr_err("no match of type %d in addrvec\n", le32_to_cpu(my_type));
+	return -ENOENT;
+
+e_inval:
+	return -EINVAL;
+}
+EXPORT_SYMBOL(ceph_decode_entity_addrvec);
+
+static int get_sockaddr_encoding_len(sa_family_t family)
+{
+	union {
+		struct sockaddr sa;
+		struct sockaddr_in sin;
+		struct sockaddr_in6 sin6;
+	} u;
+
+	switch (family) {
+	case AF_INET:
+		return sizeof(u.sin);
+	case AF_INET6:
+		return sizeof(u.sin6);
+	default:
+		return sizeof(u);
+	}
+}
+
+int ceph_entity_addr_encoding_len(const struct ceph_entity_addr *addr)
+{
+	sa_family_t family = get_unaligned(&addr->in_addr.ss_family);
+	int addr_len = get_sockaddr_encoding_len(family);
+
+	return 1 + CEPH_ENCODING_START_BLK_LEN + 4 + 4 + 4 + addr_len;
+}
+
+void ceph_encode_entity_addr(void **p, const struct ceph_entity_addr *addr)
+{
+	sa_family_t family = get_unaligned(&addr->in_addr.ss_family);
+	int addr_len = get_sockaddr_encoding_len(family);
+
+	ceph_encode_8(p, 1);  /* marker */
+	ceph_start_encoding(p, 1, 1, sizeof(addr->type) +
+				     sizeof(addr->nonce) +
+				     sizeof(u32) + addr_len);
+	ceph_encode_copy(p, &addr->type, sizeof(addr->type));
+	ceph_encode_copy(p, &addr->nonce, sizeof(addr->nonce));
+
+	ceph_encode_32(p, addr_len);
+	ceph_encode_16(p, family);
+	ceph_encode_copy(p, addr->in_addr.__data, addr_len - sizeof(family));
+}