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, 141 insertions, 0 deletions

diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c
new file mode 100644
index 000000000..c07b6e8fd
--- /dev/null
+++ b/security/apparmor/procattr.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor /proc/<pid>/attr/ interface functions
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ */
+
+#include "include/apparmor.h"
+#include "include/cred.h"
+#include "include/policy.h"
+#include "include/policy_ns.h"
+#include "include/domain.h"
+#include "include/procattr.h"
+
+
+/**
+ * aa_getprocattr - Return the label information for @label
+ * @label: the label to print label info about  (NOT NULL)
+ * @string: Returns - string containing the label info (NOT NULL)
+ * @newline: indicates that a newline should be added
+ *
+ * Requires: label != NULL && string != NULL
+ *
+ * Creates a string containing the label information for @label.
+ *
+ * Returns: size of string placed in @string else error code on failure
+ */
+int aa_getprocattr(struct aa_label *label, char **string, bool newline)
+{
+	struct aa_ns *ns = labels_ns(label);
+	struct aa_ns *current_ns = aa_get_current_ns();
+	int len;
+
+	if (!aa_ns_visible(current_ns, ns, true)) {
+		aa_put_ns(current_ns);
+		return -EACCES;
+	}
+
+	len = aa_label_snxprint(NULL, 0, current_ns, label,
+				FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
+				FLAG_HIDDEN_UNCONFINED);
+	AA_BUG(len < 0);
+
+	*string = kmalloc(len + 2, GFP_KERNEL);
+	if (!*string) {
+		aa_put_ns(current_ns);
+		return -ENOMEM;
+	}
+
+	len = aa_label_snxprint(*string, len + 2, current_ns, label,
+				FLAG_SHOW_MODE | FLAG_VIEW_SUBNS |
+				FLAG_HIDDEN_UNCONFINED);
+	if (len < 0) {
+		kfree(*string);
+		*string = NULL;
+		aa_put_ns(current_ns);
+		return len;
+	}
+
+	if (newline)
+		(*string)[len++] = '\n';
+	(*string)[len] = 0;
+
+	aa_put_ns(current_ns);
+	return len;
+}
+
+/**
+ * split_token_from_name - separate a string of form  <token>^<name>
+ * @op: operation being checked
+ * @args: string to parse  (NOT NULL)
+ * @token: stores returned parsed token value  (NOT NULL)
+ *
+ * Returns: start position of name after token else NULL on failure
+ */
+static char *split_token_from_name(const char *op, char *args, u64 *token)
+{
+	char *name;
+
+	*token = simple_strtoull(args, &name, 16);
+	if ((name == args) || *name != '^') {
+		AA_ERROR("%s: Invalid input '%s'", op, args);
+		return ERR_PTR(-EINVAL);
+	}
+
+	name++;			/* skip ^ */
+	if (!*name)
+		name = NULL;
+	return name;
+}
+
+/**
+ * aa_setprocattr_changehat - handle procattr interface to change_hat
+ * @args: args received from writing to /proc/<pid>/attr/current (NOT NULL)
+ * @size: size of the args
+ * @flags: set of flags governing behavior
+ *
+ * Returns: %0 or error code if change_hat fails
+ */
+int aa_setprocattr_changehat(char *args, size_t size, int flags)
+{
+	char *hat;
+	u64 token;
+	const char *hats[16];		/* current hard limit on # of names */
+	int count = 0;
+
+	hat = split_token_from_name(OP_CHANGE_HAT, args, &token);
+	if (IS_ERR(hat))
+		return PTR_ERR(hat);
+
+	if (!hat && !token) {
+		AA_ERROR("change_hat: Invalid input, NULL hat and NULL magic");
+		return -EINVAL;
+	}
+
+	if (hat) {
+		/* set up hat name vector, args guaranteed null terminated
+		 * at args[size] by setprocattr.
+		 *
+		 * If there are multiple hat names in the buffer each is
+		 * separated by a \0.  Ie. userspace writes them pre tokenized
+		 */
+		char *end = args + size;
+		for (count = 0; (hat < end) && count < 16; ++count) {
+			char *next = hat + strlen(hat) + 1;
+			hats[count] = hat;
+			AA_DEBUG(DEBUG_DOMAIN,
+				 "%s: (pid %d) Magic 0x%llx count %d hat '%s'\n"
+				 , __func__, current->pid, token, count, hat);
+			hat = next;
+		}
+	} else
+		AA_DEBUG(DEBUG_DOMAIN,
+			 "%s: (pid %d) Magic 0x%llx count %d Hat '%s'\n",
+			 __func__, current->pid, token, count, "<NULL>");
+
+	return aa_change_hat(hats, count, token, flags);
+}