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, 228 insertions, 0 deletions

diff --git a/drivers/ata/sata_uli.c b/drivers/ata/sata_uli.c
new file mode 100644
index 000000000..122133199
--- /dev/null
+++ b/drivers/ata/sata_uli.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  sata_uli.c - ULi Electronics SATA
+ *
+ *  libata documentation is available via 'make {ps|pdf}docs',
+ *  as Documentation/driver-api/libata.rst
+ *
+ *  Hardware documentation available under NDA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/gfp.h>
+#include <linux/pci.h>
+#include <linux/blkdev.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <scsi/scsi_host.h>
+#include <linux/libata.h>
+
+#define DRV_NAME	"sata_uli"
+#define DRV_VERSION	"1.3"
+
+enum {
+	uli_5289		= 0,
+	uli_5287		= 1,
+	uli_5281		= 2,
+
+	uli_max_ports		= 4,
+
+	/* PCI configuration registers */
+	ULI5287_BASE		= 0x90, /* sata0 phy SCR registers */
+	ULI5287_OFFS		= 0x10, /* offset from sata0->sata1 phy regs */
+	ULI5281_BASE		= 0x60, /* sata0 phy SCR  registers */
+	ULI5281_OFFS		= 0x60, /* offset from sata0->sata1 phy regs */
+};
+
+struct uli_priv {
+	unsigned int		scr_cfg_addr[uli_max_ports];
+};
+
+static int uli_init_one(struct pci_dev *pdev, const struct pci_device_id *ent);
+static int uli_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val);
+static int uli_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val);
+
+static const struct pci_device_id uli_pci_tbl[] = {
+	{ PCI_VDEVICE(AL, 0x5289), .driver_data = uli_5289 },
+	{ PCI_VDEVICE(AL, 0x5287), .driver_data = uli_5287 },
+	{ PCI_VDEVICE(AL, 0x5281), .driver_data = uli_5281 },
+	{ }	/* terminate list */
+};
+
+static struct pci_driver uli_pci_driver = {
+	.name			= DRV_NAME,
+	.id_table		= uli_pci_tbl,
+	.probe			= uli_init_one,
+	.remove			= ata_pci_remove_one,
+};
+
+static const struct scsi_host_template uli_sht = {
+	ATA_BMDMA_SHT(DRV_NAME),
+};
+
+static struct ata_port_operations uli_ops = {
+	.inherits		= &ata_bmdma_port_ops,
+	.scr_read		= uli_scr_read,
+	.scr_write		= uli_scr_write,
+	.reset.hardreset	= ATA_OP_NULL,
+};
+
+static const struct ata_port_info uli_port_info = {
+	.flags		= ATA_FLAG_SATA | ATA_FLAG_IGN_SIMPLEX,
+	.pio_mask       = ATA_PIO4,
+	.udma_mask      = ATA_UDMA6,
+	.port_ops       = &uli_ops,
+};
+
+
+MODULE_AUTHOR("Peer Chen");
+MODULE_DESCRIPTION("low-level driver for ULi Electronics SATA controller");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(pci, uli_pci_tbl);
+MODULE_VERSION(DRV_VERSION);
+
+static unsigned int get_scr_cfg_addr(struct ata_port *ap, unsigned int sc_reg)
+{
+	struct uli_priv *hpriv = ap->host->private_data;
+	return hpriv->scr_cfg_addr[ap->port_no] + (4 * sc_reg);
+}
+
+static u32 uli_scr_cfg_read(struct ata_link *link, unsigned int sc_reg)
+{
+	struct pci_dev *pdev = to_pci_dev(link->ap->host->dev);
+	unsigned int cfg_addr = get_scr_cfg_addr(link->ap, sc_reg);
+	u32 val;
+
+	pci_read_config_dword(pdev, cfg_addr, &val);
+	return val;
+}
+
+static void uli_scr_cfg_write(struct ata_link *link, unsigned int scr, u32 val)
+{
+	struct pci_dev *pdev = to_pci_dev(link->ap->host->dev);
+	unsigned int cfg_addr = get_scr_cfg_addr(link->ap, scr);
+
+	pci_write_config_dword(pdev, cfg_addr, val);
+}
+
+static int uli_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val)
+{
+	if (sc_reg > SCR_CONTROL)
+		return -EINVAL;
+
+	*val = uli_scr_cfg_read(link, sc_reg);
+	return 0;
+}
+
+static int uli_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val)
+{
+	if (sc_reg > SCR_CONTROL) //SCR_CONTROL=2, SCR_ERROR=1, SCR_STATUS=0
+		return -EINVAL;
+
+	uli_scr_cfg_write(link, sc_reg, val);
+	return 0;
+}
+
+static int uli_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
+{
+	const struct ata_port_info *ppi[] = { &uli_port_info, NULL };
+	unsigned int board_idx = (unsigned int) ent->driver_data;
+	struct ata_host *host;
+	struct uli_priv *hpriv;
+	void __iomem * const *iomap;
+	struct ata_ioports *ioaddr;
+	int n_ports, rc;
+
+	ata_print_version_once(&pdev->dev, DRV_VERSION);
+
+	rc = pcim_enable_device(pdev);
+	if (rc)
+		return rc;
+
+	n_ports = 2;
+	if (board_idx == uli_5287)
+		n_ports = 4;
+
+	/* allocate the host */
+	host = ata_host_alloc_pinfo(&pdev->dev, ppi, n_ports);
+	if (!host)
+		return -ENOMEM;
+
+	hpriv = devm_kzalloc(&pdev->dev, sizeof(*hpriv), GFP_KERNEL);
+	if (!hpriv)
+		return -ENOMEM;
+	host->private_data = hpriv;
+
+	/* the first two ports are standard SFF */
+	rc = ata_pci_sff_init_host(host);
+	if (rc)
+		return rc;
+
+	ata_pci_bmdma_init(host);
+
+	iomap = host->iomap;
+
+	switch (board_idx) {
+	case uli_5287:
+		/* If there are four, the last two live right after
+		 * the standard SFF ports.
+		 */
+		hpriv->scr_cfg_addr[0] = ULI5287_BASE;
+		hpriv->scr_cfg_addr[1] = ULI5287_BASE + ULI5287_OFFS;
+
+		ioaddr = &host->ports[2]->ioaddr;
+		ioaddr->cmd_addr = iomap[0] + 8;
+		ioaddr->altstatus_addr =
+		ioaddr->ctl_addr = (void __iomem *)
+			((unsigned long)iomap[1] | ATA_PCI_CTL_OFS) + 4;
+		ioaddr->bmdma_addr = iomap[4] + 16;
+		hpriv->scr_cfg_addr[2] = ULI5287_BASE + ULI5287_OFFS*4;
+		ata_sff_std_ports(ioaddr);
+
+		ata_port_desc(host->ports[2],
+			"cmd 0x%llx ctl 0x%llx bmdma 0x%llx",
+			(unsigned long long)pci_resource_start(pdev, 0) + 8,
+			((unsigned long long)pci_resource_start(pdev, 1) | ATA_PCI_CTL_OFS) + 4,
+			(unsigned long long)pci_resource_start(pdev, 4) + 16);
+
+		ioaddr = &host->ports[3]->ioaddr;
+		ioaddr->cmd_addr = iomap[2] + 8;
+		ioaddr->altstatus_addr =
+		ioaddr->ctl_addr = (void __iomem *)
+			((unsigned long)iomap[3] | ATA_PCI_CTL_OFS) + 4;
+		ioaddr->bmdma_addr = iomap[4] + 24;
+		hpriv->scr_cfg_addr[3] = ULI5287_BASE + ULI5287_OFFS*5;
+		ata_sff_std_ports(ioaddr);
+
+		ata_port_desc(host->ports[2],
+			"cmd 0x%llx ctl 0x%llx bmdma 0x%llx",
+			(unsigned long long)pci_resource_start(pdev, 2) + 9,
+			((unsigned long long)pci_resource_start(pdev, 3) | ATA_PCI_CTL_OFS) + 4,
+			(unsigned long long)pci_resource_start(pdev, 4) + 24);
+
+		break;
+
+	case uli_5289:
+		hpriv->scr_cfg_addr[0] = ULI5287_BASE;
+		hpriv->scr_cfg_addr[1] = ULI5287_BASE + ULI5287_OFFS;
+		break;
+
+	case uli_5281:
+		hpriv->scr_cfg_addr[0] = ULI5281_BASE;
+		hpriv->scr_cfg_addr[1] = ULI5281_BASE + ULI5281_OFFS;
+		break;
+
+	default:
+		BUG();
+		break;
+	}
+
+	pci_set_master(pdev);
+	pcim_intx(pdev, 1);
+	return ata_host_activate(host, pdev->irq, ata_bmdma_interrupt,
+				 IRQF_SHARED, &uli_sht);
+}
+
+module_pci_driver(uli_pci_driver);