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, 261 insertions, 0 deletions

diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
new file mode 100644
index 000000000..36c9c06e9
--- /dev/null
+++ b/fs/gfs2/main.c
@@ -0,0 +1,261 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/gfs2_ondisk.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist_bl.h>
+#include <linux/atomic.h>
+#include <linux/mempool.h>
+
+#include "gfs2.h"
+#include "incore.h"
+#include "super.h"
+#include "sys.h"
+#include "util.h"
+#include "glock.h"
+#include "quota.h"
+#include "recovery.h"
+#include "dir.h"
+#include "glops.h"
+
+struct workqueue_struct *gfs2_control_wq;
+
+static void gfs2_init_inode_once(void *foo)
+{
+	struct gfs2_inode *ip = foo;
+
+	inode_init_once(&ip->i_inode);
+	atomic_set(&ip->i_sizehint, 0);
+	init_rwsem(&ip->i_rw_mutex);
+	INIT_LIST_HEAD(&ip->i_ordered);
+	ip->i_qadata = NULL;
+	gfs2_holder_mark_uninitialized(&ip->i_rgd_gh);
+	memset(&ip->i_res, 0, sizeof(ip->i_res));
+	RB_CLEAR_NODE(&ip->i_res.rs_node);
+	ip->i_hash_cache = NULL;
+	gfs2_holder_mark_uninitialized(&ip->i_iopen_gh);
+}
+
+static void gfs2_init_glock_once(void *foo)
+{
+	struct gfs2_glock *gl = foo;
+
+	INIT_LIST_HEAD(&gl->gl_holders);
+	INIT_LIST_HEAD(&gl->gl_ail_list);
+	atomic_set(&gl->gl_ail_count, 0);
+	atomic_set(&gl->gl_revokes, 0);
+}
+
+static void gfs2_init_gl_aspace_once(void *foo)
+{
+	struct gfs2_glock_aspace *gla = foo;
+
+	gfs2_init_glock_once(&gla->glock);
+	address_space_init_once(&gla->mapping);
+}
+
+/**
+ * init_gfs2_fs - Register GFS2 as a filesystem
+ *
+ * Returns: 0 on success, error code on failure
+ */
+
+static int __init init_gfs2_fs(void)
+{
+	int error;
+
+	gfs2_str2qstr(&gfs2_qdot, ".");
+	gfs2_str2qstr(&gfs2_qdotdot, "..");
+	gfs2_quota_hash_init();
+
+	error = gfs2_sys_init();
+	if (error)
+		return error;
+
+	error = list_lru_init(&gfs2_qd_lru);
+	if (error)
+		goto fail_lru;
+
+	error = gfs2_glock_init();
+	if (error)
+		goto fail_glock;
+
+	error = -ENOMEM;
+	gfs2_glock_cachep = kmem_cache_create("gfs2_glock",
+					      sizeof(struct gfs2_glock),
+					      0, SLAB_RECLAIM_ACCOUNT,
+					      gfs2_init_glock_once);
+	if (!gfs2_glock_cachep)
+		goto fail_cachep1;
+
+	gfs2_glock_aspace_cachep = kmem_cache_create("gfs2_glock(aspace)",
+					sizeof(struct gfs2_glock_aspace),
+					0, 0, gfs2_init_gl_aspace_once);
+
+	if (!gfs2_glock_aspace_cachep)
+		goto fail_cachep2;
+
+	gfs2_inode_cachep = kmem_cache_create("gfs2_inode",
+					      sizeof(struct gfs2_inode),
+					      0,  SLAB_RECLAIM_ACCOUNT|
+						  SLAB_ACCOUNT,
+					      gfs2_init_inode_once);
+	if (!gfs2_inode_cachep)
+		goto fail_cachep3;
+
+	gfs2_bufdata_cachep = kmem_cache_create("gfs2_bufdata",
+						sizeof(struct gfs2_bufdata),
+					        0, 0, NULL);
+	if (!gfs2_bufdata_cachep)
+		goto fail_cachep4;
+
+	gfs2_rgrpd_cachep = kmem_cache_create("gfs2_rgrpd",
+					      sizeof(struct gfs2_rgrpd),
+					      0, 0, NULL);
+	if (!gfs2_rgrpd_cachep)
+		goto fail_cachep5;
+
+	gfs2_quotad_cachep = kmem_cache_create("gfs2_quotad",
+					       sizeof(struct gfs2_quota_data),
+					       0, SLAB_RECLAIM_ACCOUNT, NULL);
+	if (!gfs2_quotad_cachep)
+		goto fail_cachep6;
+
+	gfs2_qadata_cachep = kmem_cache_create("gfs2_qadata",
+					       sizeof(struct gfs2_qadata),
+					       0, 0, NULL);
+	if (!gfs2_qadata_cachep)
+		goto fail_cachep7;
+
+	gfs2_trans_cachep = kmem_cache_create("gfs2_trans",
+					       sizeof(struct gfs2_trans),
+					       0, 0, NULL);
+	if (!gfs2_trans_cachep)
+		goto fail_cachep8;
+
+	error = gfs2_qd_shrinker_init();
+	if (error)
+		goto fail_shrinker;
+
+	error = -ENOMEM;
+	gfs2_recovery_wq = alloc_workqueue("gfs2_recovery",
+					  WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU,
+					  0);
+	if (!gfs2_recovery_wq)
+		goto fail_wq1;
+
+	gfs2_control_wq = alloc_workqueue("gfs2_control",
+					  WQ_UNBOUND | WQ_FREEZABLE, 0);
+	if (!gfs2_control_wq)
+		goto fail_wq2;
+
+	gfs2_freeze_wq = alloc_workqueue("gfs2_freeze", WQ_PERCPU, 0);
+
+	if (!gfs2_freeze_wq)
+		goto fail_wq3;
+
+	gfs2_page_pool = mempool_create_page_pool(64, 0);
+	if (!gfs2_page_pool)
+		goto fail_mempool;
+
+	gfs2_register_debugfs();
+	error = register_filesystem(&gfs2_fs_type);
+	if (error)
+		goto fail_fs1;
+
+	error = register_filesystem(&gfs2meta_fs_type);
+	if (error)
+		goto fail_fs2;
+
+
+	pr_info("GFS2 installed\n");
+
+	return 0;
+
+fail_fs2:
+	unregister_filesystem(&gfs2_fs_type);
+fail_fs1:
+	mempool_destroy(gfs2_page_pool);
+fail_mempool:
+	destroy_workqueue(gfs2_freeze_wq);
+fail_wq3:
+	destroy_workqueue(gfs2_control_wq);
+fail_wq2:
+	destroy_workqueue(gfs2_recovery_wq);
+fail_wq1:
+	gfs2_qd_shrinker_exit();
+fail_shrinker:
+	kmem_cache_destroy(gfs2_trans_cachep);
+fail_cachep8:
+	kmem_cache_destroy(gfs2_qadata_cachep);
+fail_cachep7:
+	kmem_cache_destroy(gfs2_quotad_cachep);
+fail_cachep6:
+	kmem_cache_destroy(gfs2_rgrpd_cachep);
+fail_cachep5:
+	kmem_cache_destroy(gfs2_bufdata_cachep);
+fail_cachep4:
+	kmem_cache_destroy(gfs2_inode_cachep);
+fail_cachep3:
+	kmem_cache_destroy(gfs2_glock_aspace_cachep);
+fail_cachep2:
+	kmem_cache_destroy(gfs2_glock_cachep);
+fail_cachep1:
+	gfs2_glock_exit();
+fail_glock:
+	list_lru_destroy(&gfs2_qd_lru);
+fail_lru:
+	gfs2_sys_uninit();
+	return error;
+}
+
+/**
+ * exit_gfs2_fs - Unregister the file system
+ *
+ */
+
+static void __exit exit_gfs2_fs(void)
+{
+	gfs2_qd_shrinker_exit();
+	gfs2_glock_exit();
+	gfs2_unregister_debugfs();
+	unregister_filesystem(&gfs2_fs_type);
+	unregister_filesystem(&gfs2meta_fs_type);
+	destroy_workqueue(gfs2_recovery_wq);
+	destroy_workqueue(gfs2_control_wq);
+	destroy_workqueue(gfs2_freeze_wq);
+	list_lru_destroy(&gfs2_qd_lru);
+
+	rcu_barrier();
+
+	mempool_destroy(gfs2_page_pool);
+	kmem_cache_destroy(gfs2_trans_cachep);
+	kmem_cache_destroy(gfs2_qadata_cachep);
+	kmem_cache_destroy(gfs2_quotad_cachep);
+	kmem_cache_destroy(gfs2_rgrpd_cachep);
+	kmem_cache_destroy(gfs2_bufdata_cachep);
+	kmem_cache_destroy(gfs2_inode_cachep);
+	kmem_cache_destroy(gfs2_glock_aspace_cachep);
+	kmem_cache_destroy(gfs2_glock_cachep);
+
+	gfs2_sys_uninit();
+}
+
+MODULE_DESCRIPTION("Global File System");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+module_init(init_gfs2_fs);
+module_exit(exit_gfs2_fs);
+