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, 208 insertions, 0 deletions

diff --git a/fs/afs/misc.c b/fs/afs/misc.c
new file mode 100644
index 000000000..c8a7f2660
--- /dev/null
+++ b/fs/afs/misc.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* miscellaneous bits
+ *
+ * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <crypto/krb5.h>
+#include "internal.h"
+#include "afs_fs.h"
+#include "protocol_uae.h"
+
+/*
+ * convert an AFS abort code to a Linux error number
+ */
+int afs_abort_to_error(u32 abort_code)
+{
+	switch (abort_code) {
+		/* Low errno codes inserted into abort namespace */
+	case 13:		return -EACCES;
+	case 27:		return -EFBIG;
+	case 30:		return -EROFS;
+
+		/* VICE "special error" codes; 101 - 111 */
+	case VSALVAGE:		return -EIO;
+	case VNOVNODE:		return -ENOENT;
+	case VNOVOL:		return -ENOMEDIUM;
+	case VVOLEXISTS:	return -EEXIST;
+	case VNOSERVICE:	return -EIO;
+	case VOFFLINE:		return -ENOENT;
+	case VONLINE:		return -EEXIST;
+	case VDISKFULL:		return -ENOSPC;
+	case VOVERQUOTA:	return -EDQUOT;
+	case VBUSY:		return -EBUSY;
+	case VMOVED:		return -ENXIO;
+
+		/* Volume Location server errors */
+	case AFSVL_IDEXIST:		return -EEXIST;
+	case AFSVL_IO:			return -EREMOTEIO;
+	case AFSVL_NAMEEXIST:		return -EEXIST;
+	case AFSVL_CREATEFAIL:		return -EREMOTEIO;
+	case AFSVL_NOENT:		return -ENOMEDIUM;
+	case AFSVL_EMPTY:		return -ENOMEDIUM;
+	case AFSVL_ENTDELETED:		return -ENOMEDIUM;
+	case AFSVL_BADNAME:		return -EINVAL;
+	case AFSVL_BADINDEX:		return -EINVAL;
+	case AFSVL_BADVOLTYPE:		return -EINVAL;
+	case AFSVL_BADSERVER:		return -EINVAL;
+	case AFSVL_BADPARTITION:	return -EINVAL;
+	case AFSVL_REPSFULL:		return -EFBIG;
+	case AFSVL_NOREPSERVER:		return -ENOENT;
+	case AFSVL_DUPREPSERVER:	return -EEXIST;
+	case AFSVL_RWNOTFOUND:		return -ENOENT;
+	case AFSVL_BADREFCOUNT:		return -EINVAL;
+	case AFSVL_SIZEEXCEEDED:	return -EINVAL;
+	case AFSVL_BADENTRY:		return -EINVAL;
+	case AFSVL_BADVOLIDBUMP:	return -EINVAL;
+	case AFSVL_IDALREADYHASHED:	return -EINVAL;
+	case AFSVL_ENTRYLOCKED:		return -EBUSY;
+	case AFSVL_BADVOLOPER:		return -EBADRQC;
+	case AFSVL_BADRELLOCKTYPE:	return -EINVAL;
+	case AFSVL_RERELEASE:		return -EREMOTEIO;
+	case AFSVL_BADSERVERFLAG:	return -EINVAL;
+	case AFSVL_PERM:		return -EACCES;
+	case AFSVL_NOMEM:		return -EREMOTEIO;
+
+		/* Unified AFS error table */
+	case UAEPERM:			return -EPERM;
+	case UAENOENT:			return -ENOENT;
+	case UAEAGAIN:			return -EAGAIN;
+	case UAEACCES:			return -EACCES;
+	case UAEBUSY:			return -EBUSY;
+	case UAEEXIST:			return -EEXIST;
+	case UAENOTDIR:			return -ENOTDIR;
+	case UAEISDIR:			return -EISDIR;
+	case UAEFBIG:			return -EFBIG;
+	case UAENOSPC:			return -ENOSPC;
+	case UAEROFS:			return -EROFS;
+	case UAEMLINK:			return -EMLINK;
+	case UAEDEADLK:			return -EDEADLK;
+	case UAENAMETOOLONG:		return -ENAMETOOLONG;
+	case UAENOLCK:			return -ENOLCK;
+	case UAENOTEMPTY:		return -ENOTEMPTY;
+	case UAELOOP:			return -ELOOP;
+	case UAEOVERFLOW:		return -EOVERFLOW;
+	case UAENOMEDIUM:		return -ENOMEDIUM;
+	case UAEDQUOT:			return -EDQUOT;
+
+		/* RXKAD abort codes; from include/rxrpc/packet.h.  ET "RXK" == 0x1260B00 */
+	case RXKADINCONSISTENCY: return -EPROTO;
+	case RXKADPACKETSHORT:	return -EPROTO;
+	case RXKADLEVELFAIL:	return -EKEYREJECTED;
+	case RXKADTICKETLEN:	return -EKEYREJECTED;
+	case RXKADOUTOFSEQUENCE: return -EPROTO;
+	case RXKADNOAUTH:	return -EKEYREJECTED;
+	case RXKADBADKEY:	return -EKEYREJECTED;
+	case RXKADBADTICKET:	return -EKEYREJECTED;
+	case RXKADUNKNOWNKEY:	return -EKEYREJECTED;
+	case RXKADEXPIRED:	return -EKEYEXPIRED;
+	case RXKADSEALEDINCON:	return -EKEYREJECTED;
+	case RXKADDATALEN:	return -EKEYREJECTED;
+	case RXKADILLEGALLEVEL:	return -EKEYREJECTED;
+
+	case RXGK_INCONSISTENCY:	return -EPROTO;
+	case RXGK_PACKETSHORT:		return -EPROTO;
+	case RXGK_BADCHALLENGE:		return -EPROTO;
+	case RXGK_SEALEDINCON:		return -EKEYREJECTED;
+	case RXGK_NOTAUTH:		return -EKEYREJECTED;
+	case RXGK_EXPIRED:		return -EKEYEXPIRED;
+	case RXGK_BADLEVEL:		return -EKEYREJECTED;
+	case RXGK_BADKEYNO:		return -EKEYREJECTED;
+	case RXGK_NOTRXGK:		return -EKEYREJECTED;
+	case RXGK_UNSUPPORTED:		return -EKEYREJECTED;
+	case RXGK_GSSERROR:		return -EKEYREJECTED;
+#ifdef RXGK_BADETYPE
+	case RXGK_BADETYPE:		return -ENOPKG;
+#endif
+#ifdef RXGK_BADTOKEN
+	case RXGK_BADTOKEN:		return -EKEYREJECTED;
+#endif
+#ifdef RXGK_BADETYPE
+	case RXGK_DATALEN:		return -EPROTO;
+#endif
+#ifdef RXGK_BADQOP
+	case RXGK_BADQOP:		return -EKEYREJECTED;
+#endif
+
+	case KRB5_PROG_KEYTYPE_NOSUPP:	return -ENOPKG;
+
+	case RXGEN_OPCODE:	return -ENOTSUPP;
+	case RX_INVALID_OPERATION:	return -ENOTSUPP;
+
+	default:		return -EREMOTEIO;
+	}
+}
+
+/*
+ * Select the error to report from a set of errors.
+ */
+void afs_prioritise_error(struct afs_error *e, int error, u32 abort_code)
+{
+	switch (error) {
+	case 0:
+		e->aborted = false;
+		e->error = 0;
+		return;
+	default:
+		if (e->error == -ETIMEDOUT ||
+		    e->error == -ETIME)
+			return;
+		fallthrough;
+	case -ETIMEDOUT:
+	case -ETIME:
+		if (e->error == -ENOMEM ||
+		    e->error == -ENONET)
+			return;
+		fallthrough;
+	case -ENOMEM:
+	case -ENONET:
+		if (e->error == -ERFKILL)
+			return;
+		fallthrough;
+	case -ERFKILL:
+		if (e->error == -EADDRNOTAVAIL)
+			return;
+		fallthrough;
+	case -EADDRNOTAVAIL:
+		if (e->error == -ENETUNREACH)
+			return;
+		fallthrough;
+	case -ENETUNREACH:
+		if (e->error == -EHOSTUNREACH)
+			return;
+		fallthrough;
+	case -EHOSTUNREACH:
+		if (e->error == -EHOSTDOWN)
+			return;
+		fallthrough;
+	case -EHOSTDOWN:
+		if (e->error == -ECONNREFUSED)
+			return;
+		fallthrough;
+	case -ECONNREFUSED:
+		if (e->error == -ECONNRESET)
+			return;
+		fallthrough;
+	case -ECONNRESET: /* Responded, but call expired. */
+		if (e->responded)
+			return;
+		e->error = error;
+		e->aborted = false;
+		return;
+
+	case -ECONNABORTED:
+		e->error = afs_abort_to_error(abort_code);
+		e->aborted = true;
+		e->responded = true;
+		return;
+	case -ENETRESET: /* Responded, but we seem to have changed address */
+		e->aborted = false;
+		e->responded = true;
+		e->error = error;
+		return;
+	}
+}