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, 257 insertions, 0 deletions

diff --git a/drivers/ata/libata-trace.c b/drivers/ata/libata-trace.c
new file mode 100644
index 000000000..9b5363fd0
--- /dev/null
+++ b/drivers/ata/libata-trace.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * libata-trace.c - trace functions for libata
+ *
+ * Copyright 2015 Hannes Reinecke
+ * Copyright 2015 SUSE Linux GmbH
+ */
+
+#include <linux/kernel.h>
+#include <linux/trace_seq.h>
+#include <trace/events/libata.h>
+
+const char *
+libata_trace_parse_status(struct trace_seq *p, unsigned char status)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "{ ");
+	if (status & ATA_BUSY)
+		trace_seq_printf(p, "BUSY ");
+	if (status & ATA_DRDY)
+		trace_seq_printf(p, "DRDY ");
+	if (status & ATA_DF)
+		trace_seq_printf(p, "DF ");
+	if (status & ATA_DSC)
+		trace_seq_printf(p, "DSC ");
+	if (status & ATA_DRQ)
+		trace_seq_printf(p, "DRQ ");
+	if (status & ATA_CORR)
+		trace_seq_printf(p, "CORR ");
+	if (status & ATA_SENSE)
+		trace_seq_printf(p, "SENSE ");
+	if (status & ATA_ERR)
+		trace_seq_printf(p, "ERR ");
+	trace_seq_putc(p, '}');
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_host_stat(struct trace_seq *p, unsigned char host_stat)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "{ ");
+	if (host_stat & ATA_DMA_INTR)
+		trace_seq_printf(p, "INTR ");
+	if (host_stat & ATA_DMA_ERR)
+		trace_seq_printf(p, "ERR ");
+	if (host_stat & ATA_DMA_ACTIVE)
+		trace_seq_printf(p, "ACTIVE ");
+	trace_seq_putc(p, '}');
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_eh_action(struct trace_seq *p, unsigned int eh_action)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "%x", eh_action);
+	if (eh_action) {
+		trace_seq_printf(p, "{ ");
+		if (eh_action & ATA_EH_REVALIDATE)
+			trace_seq_printf(p, "REVALIDATE ");
+		if (eh_action & (ATA_EH_SOFTRESET | ATA_EH_HARDRESET))
+			trace_seq_printf(p, "RESET ");
+		else if (eh_action & ATA_EH_SOFTRESET)
+			trace_seq_printf(p, "SOFTRESET ");
+		else if (eh_action & ATA_EH_HARDRESET)
+			trace_seq_printf(p, "HARDRESET ");
+		if (eh_action & ATA_EH_ENABLE_LINK)
+			trace_seq_printf(p, "ENABLE_LINK ");
+		if (eh_action & ATA_EH_PARK)
+			trace_seq_printf(p, "PARK ");
+		trace_seq_putc(p, '}');
+	}
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_eh_err_mask(struct trace_seq *p, unsigned int eh_err_mask)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "%x", eh_err_mask);
+	if (eh_err_mask) {
+		trace_seq_printf(p, "{ ");
+		if (eh_err_mask & AC_ERR_DEV)
+			trace_seq_printf(p, "DEV ");
+		if (eh_err_mask & AC_ERR_HSM)
+			trace_seq_printf(p, "HSM ");
+		if (eh_err_mask & AC_ERR_TIMEOUT)
+			trace_seq_printf(p, "TIMEOUT ");
+		if (eh_err_mask & AC_ERR_MEDIA)
+			trace_seq_printf(p, "MEDIA ");
+		if (eh_err_mask & AC_ERR_ATA_BUS)
+			trace_seq_printf(p, "ATA_BUS ");
+		if (eh_err_mask & AC_ERR_HOST_BUS)
+			trace_seq_printf(p, "HOST_BUS ");
+		if (eh_err_mask & AC_ERR_SYSTEM)
+			trace_seq_printf(p, "SYSTEM ");
+		if (eh_err_mask & AC_ERR_INVALID)
+			trace_seq_printf(p, "INVALID ");
+		if (eh_err_mask & AC_ERR_OTHER)
+			trace_seq_printf(p, "OTHER ");
+		if (eh_err_mask & AC_ERR_NODEV_HINT)
+			trace_seq_printf(p, "NODEV_HINT ");
+		if (eh_err_mask & AC_ERR_NCQ)
+			trace_seq_printf(p, "NCQ ");
+		trace_seq_putc(p, '}');
+	}
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_qc_flags(struct trace_seq *p, unsigned int qc_flags)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "%x", qc_flags);
+	if (qc_flags) {
+		trace_seq_printf(p, "{ ");
+		if (qc_flags & ATA_QCFLAG_ACTIVE)
+			trace_seq_printf(p, "ACTIVE ");
+		if (qc_flags & ATA_QCFLAG_DMAMAP)
+			trace_seq_printf(p, "DMAMAP ");
+		if (qc_flags & ATA_QCFLAG_IO)
+			trace_seq_printf(p, "IO ");
+		if (qc_flags & ATA_QCFLAG_RESULT_TF)
+			trace_seq_printf(p, "RESULT_TF ");
+		if (qc_flags & ATA_QCFLAG_CLEAR_EXCL)
+			trace_seq_printf(p, "CLEAR_EXCL ");
+		if (qc_flags & ATA_QCFLAG_QUIET)
+			trace_seq_printf(p, "QUIET ");
+		if (qc_flags & ATA_QCFLAG_RETRY)
+			trace_seq_printf(p, "RETRY ");
+		if (qc_flags & ATA_QCFLAG_EH)
+			trace_seq_printf(p, "FAILED ");
+		if (qc_flags & ATA_QCFLAG_SENSE_VALID)
+			trace_seq_printf(p, "SENSE_VALID ");
+		if (qc_flags & ATA_QCFLAG_EH_SCHEDULED)
+			trace_seq_printf(p, "EH_SCHEDULED ");
+		trace_seq_putc(p, '}');
+	}
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_tf_flags(struct trace_seq *p, unsigned int tf_flags)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	trace_seq_printf(p, "%x", tf_flags);
+	if (tf_flags) {
+		trace_seq_printf(p, "{ ");
+		if (tf_flags & ATA_TFLAG_LBA48)
+			trace_seq_printf(p, "LBA48 ");
+		if (tf_flags & ATA_TFLAG_ISADDR)
+			trace_seq_printf(p, "ISADDR ");
+		if (tf_flags & ATA_TFLAG_DEVICE)
+			trace_seq_printf(p, "DEV ");
+		if (tf_flags & ATA_TFLAG_WRITE)
+			trace_seq_printf(p, "WRITE ");
+		if (tf_flags & ATA_TFLAG_LBA)
+			trace_seq_printf(p, "LBA ");
+		if (tf_flags & ATA_TFLAG_FUA)
+			trace_seq_printf(p, "FUA ");
+		if (tf_flags & ATA_TFLAG_POLLING)
+			trace_seq_printf(p, "POLL ");
+		trace_seq_putc(p, '}');
+	}
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+const char *
+libata_trace_parse_subcmd(struct trace_seq *p, unsigned char cmd,
+			  unsigned char feature, unsigned char hob_nsect)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	switch (cmd) {
+	case ATA_CMD_FPDMA_RECV:
+		switch (hob_nsect & 0x5f) {
+		case ATA_SUBCMD_FPDMA_RECV_RD_LOG_DMA_EXT:
+			trace_seq_printf(p, " READ_LOG_DMA_EXT");
+			break;
+		case ATA_SUBCMD_FPDMA_RECV_ZAC_MGMT_IN:
+			trace_seq_printf(p, " ZAC_MGMT_IN");
+			break;
+		}
+		break;
+	case ATA_CMD_FPDMA_SEND:
+		switch (hob_nsect & 0x5f) {
+		case ATA_SUBCMD_FPDMA_SEND_WR_LOG_DMA_EXT:
+			trace_seq_printf(p, " WRITE_LOG_DMA_EXT");
+			break;
+		case ATA_SUBCMD_FPDMA_SEND_DSM:
+			trace_seq_printf(p, " DATASET_MANAGEMENT");
+			break;
+		}
+		break;
+	case ATA_CMD_NCQ_NON_DATA:
+		switch (feature) {
+		case ATA_SUBCMD_NCQ_NON_DATA_ABORT_QUEUE:
+			trace_seq_printf(p, " ABORT_QUEUE");
+			break;
+		case ATA_SUBCMD_NCQ_NON_DATA_SET_FEATURES:
+			trace_seq_printf(p, " SET_FEATURES");
+			break;
+		case ATA_SUBCMD_NCQ_NON_DATA_ZERO_EXT:
+			trace_seq_printf(p, " ZERO_EXT");
+			break;
+		case ATA_SUBCMD_NCQ_NON_DATA_ZAC_MGMT_OUT:
+			trace_seq_printf(p, " ZAC_MGMT_OUT");
+			break;
+		}
+		break;
+	case ATA_CMD_ZAC_MGMT_IN:
+		switch (feature) {
+		case ATA_SUBCMD_ZAC_MGMT_IN_REPORT_ZONES:
+			trace_seq_printf(p, " REPORT_ZONES");
+			break;
+		}
+		break;
+	case ATA_CMD_ZAC_MGMT_OUT:
+		switch (feature) {
+		case ATA_SUBCMD_ZAC_MGMT_OUT_CLOSE_ZONE:
+			trace_seq_printf(p, " CLOSE_ZONE");
+			break;
+		case ATA_SUBCMD_ZAC_MGMT_OUT_FINISH_ZONE:
+			trace_seq_printf(p, " FINISH_ZONE");
+			break;
+		case ATA_SUBCMD_ZAC_MGMT_OUT_OPEN_ZONE:
+			trace_seq_printf(p, " OPEN_ZONE");
+			break;
+		case ATA_SUBCMD_ZAC_MGMT_OUT_RESET_WRITE_POINTER:
+			trace_seq_printf(p, " RESET_WRITE_POINTER");
+			break;
+		}
+		break;
+	}
+	trace_seq_putc(p, 0);
+
+	return ret;
+}