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, 86 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
new file mode 100644
index 000000000..b1cd556bb
--- /dev/null
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) interface driver
+ *
+ * Copyright (C) 2017-2019 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ */
+
+#ifndef __SEV_DEV_H__
+#define __SEV_DEV_H__
+
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/dmapool.h>
+#include <linux/hw_random.h>
+#include <linux/bitops.h>
+#include <linux/interrupt.h>
+#include <linux/irqreturn.h>
+#include <linux/dmaengine.h>
+#include <linux/psp-sev.h>
+#include <linux/miscdevice.h>
+#include <linux/capability.h>
+
+#define SEV_CMDRESP_CMD			GENMASK(26, 16)
+#define SEV_CMD_COMPLETE		BIT(1)
+#define SEV_CMDRESP_IOC			BIT(0)
+
+struct sev_misc_dev {
+	struct kref refcount;
+	struct miscdevice misc;
+};
+
+struct sev_tio_status;
+
+struct sev_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	void __iomem *io_regs;
+
+	struct sev_vdata *vdata;
+
+	unsigned int int_rcvd;
+	wait_queue_head_t int_queue;
+	struct sev_misc_dev *misc;
+
+	u8 api_major;
+	u8 api_minor;
+	u8 build;
+
+	void *cmd_buf;
+	void *cmd_buf_backup;
+	bool cmd_buf_active;
+	bool cmd_buf_backup_active;
+
+	bool snp_initialized;
+
+	struct sev_user_data_status sev_plat_status;
+
+	struct sev_user_data_snp_status snp_plat_status;
+	struct snp_feature_info snp_feat_info_0;
+
+	struct tsm_dev *tsmdev;
+	struct sev_tio_status *tio_status;
+};
+
+int sev_dev_init(struct psp_device *psp);
+void sev_dev_destroy(struct psp_device *psp);
+
+int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret);
+
+void sev_pci_init(void);
+void sev_pci_exit(void);
+
+struct page *snp_alloc_hv_fixed_pages(unsigned int num_2mb_pages);
+void snp_free_hv_fixed_pages(struct page *page);
+
+void sev_tsm_init_locked(struct sev_device *sev, void *tio_status_page);
+void sev_tsm_uninit(struct sev_device *sev);
+int sev_tio_cmd_buffer_len(int cmd);
+
+#endif /* __SEV_DEV_H */