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, 303 insertions, 0 deletions

diff --git a/drivers/edac/pasemi_edac.c b/drivers/edac/pasemi_edac.c
new file mode 100644
index 000000000..1a1c3296c
--- /dev/null
+++ b/drivers/edac/pasemi_edac.c
@@ -0,0 +1,303 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2006-2007 PA Semi, Inc
+ *
+ * Author: Egor Martovetsky <egor@pasemi.com>
+ * Maintained by: Olof Johansson <olof@lixom.net>
+ *
+ * Driver for the PWRficient onchip memory controllers
+ */
+
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+#include <linux/pci_ids.h>
+#include <linux/edac.h>
+#include "edac_module.h"
+
+#define MODULE_NAME "pasemi_edac"
+
+#define MCCFG_MCEN				0x300
+#define   MCCFG_MCEN_MMC_EN			0x00000001
+#define MCCFG_ERRCOR				0x388
+#define   MCCFG_ERRCOR_RNK_FAIL_DET_EN		0x00000100
+#define   MCCFG_ERRCOR_ECC_GEN_EN		0x00000010
+#define   MCCFG_ERRCOR_ECC_CRR_EN		0x00000001
+#define MCCFG_SCRUB				0x384
+#define   MCCFG_SCRUB_RGLR_SCRB_EN		0x00000001
+#define MCDEBUG_ERRCTL1				0x728
+#define   MCDEBUG_ERRCTL1_RFL_LOG_EN		0x00080000
+#define   MCDEBUG_ERRCTL1_MBE_LOG_EN		0x00040000
+#define   MCDEBUG_ERRCTL1_SBE_LOG_EN		0x00020000
+#define MCDEBUG_ERRSTA				0x730
+#define   MCDEBUG_ERRSTA_RFL_STATUS		0x00000004
+#define   MCDEBUG_ERRSTA_MBE_STATUS		0x00000002
+#define   MCDEBUG_ERRSTA_SBE_STATUS		0x00000001
+#define MCDEBUG_ERRCNT1				0x734
+#define   MCDEBUG_ERRCNT1_SBE_CNT_OVRFLO	0x00000080
+#define MCDEBUG_ERRLOG1A			0x738
+#define   MCDEBUG_ERRLOG1A_MERR_TYPE_M		0x30000000
+#define   MCDEBUG_ERRLOG1A_MERR_TYPE_NONE	0x00000000
+#define   MCDEBUG_ERRLOG1A_MERR_TYPE_SBE	0x10000000
+#define   MCDEBUG_ERRLOG1A_MERR_TYPE_MBE	0x20000000
+#define   MCDEBUG_ERRLOG1A_MERR_TYPE_RFL	0x30000000
+#define   MCDEBUG_ERRLOG1A_MERR_BA_M		0x00700000
+#define   MCDEBUG_ERRLOG1A_MERR_BA_S		20
+#define   MCDEBUG_ERRLOG1A_MERR_CS_M		0x00070000
+#define   MCDEBUG_ERRLOG1A_MERR_CS_S		16
+#define   MCDEBUG_ERRLOG1A_SYNDROME_M		0x0000ffff
+#define MCDRAM_RANKCFG				0x114
+#define   MCDRAM_RANKCFG_EN			0x00000001
+#define   MCDRAM_RANKCFG_TYPE_SIZE_M		0x000001c0
+#define   MCDRAM_RANKCFG_TYPE_SIZE_S		6
+
+#define PASEMI_EDAC_NR_CSROWS			8
+#define PASEMI_EDAC_NR_CHANS			1
+#define PASEMI_EDAC_ERROR_GRAIN			64
+
+static int last_page_in_mmc;
+static int system_mmc_id;
+
+
+static u32 pasemi_edac_get_error_info(struct mem_ctl_info *mci)
+{
+	struct pci_dev *pdev = to_pci_dev(mci->pdev);
+	u32 tmp;
+
+	pci_read_config_dword(pdev, MCDEBUG_ERRSTA,
+			      &tmp);
+
+	tmp &= (MCDEBUG_ERRSTA_RFL_STATUS | MCDEBUG_ERRSTA_MBE_STATUS
+		| MCDEBUG_ERRSTA_SBE_STATUS);
+
+	if (tmp) {
+		if (tmp & MCDEBUG_ERRSTA_SBE_STATUS)
+			pci_write_config_dword(pdev, MCDEBUG_ERRCNT1,
+					       MCDEBUG_ERRCNT1_SBE_CNT_OVRFLO);
+		pci_write_config_dword(pdev, MCDEBUG_ERRSTA, tmp);
+	}
+
+	return tmp;
+}
+
+static void pasemi_edac_process_error_info(struct mem_ctl_info *mci, u32 errsta)
+{
+	struct pci_dev *pdev = to_pci_dev(mci->pdev);
+	u32 errlog1a;
+	u32 cs;
+
+	if (!errsta)
+		return;
+
+	pci_read_config_dword(pdev, MCDEBUG_ERRLOG1A, &errlog1a);
+
+	cs = (errlog1a & MCDEBUG_ERRLOG1A_MERR_CS_M) >>
+		MCDEBUG_ERRLOG1A_MERR_CS_S;
+
+	/* uncorrectable/multi-bit errors */
+	if (errsta & (MCDEBUG_ERRSTA_MBE_STATUS |
+		      MCDEBUG_ERRSTA_RFL_STATUS)) {
+		edac_mc_handle_error(HW_EVENT_ERR_UNCORRECTED, mci, 1,
+				     mci->csrows[cs]->first_page, 0, 0,
+				     cs, 0, -1, mci->ctl_name, "");
+	}
+
+	/* correctable/single-bit errors */
+	if (errsta & MCDEBUG_ERRSTA_SBE_STATUS)
+		edac_mc_handle_error(HW_EVENT_ERR_CORRECTED, mci, 1,
+				     mci->csrows[cs]->first_page, 0, 0,
+				     cs, 0, -1, mci->ctl_name, "");
+}
+
+static void pasemi_edac_check(struct mem_ctl_info *mci)
+{
+	u32 errsta;
+
+	errsta = pasemi_edac_get_error_info(mci);
+	if (errsta)
+		pasemi_edac_process_error_info(mci, errsta);
+}
+
+static int pasemi_edac_init_csrows(struct mem_ctl_info *mci,
+				   struct pci_dev *pdev,
+				   enum edac_type edac_mode)
+{
+	struct csrow_info *csrow;
+	struct dimm_info *dimm;
+	u32 rankcfg;
+	int index;
+
+	for (index = 0; index < mci->nr_csrows; index++) {
+		csrow = mci->csrows[index];
+		dimm = csrow->channels[0]->dimm;
+
+		pci_read_config_dword(pdev,
+				      MCDRAM_RANKCFG + (index * 12),
+				      &rankcfg);
+
+		if (!(rankcfg & MCDRAM_RANKCFG_EN))
+			continue;
+
+		switch ((rankcfg & MCDRAM_RANKCFG_TYPE_SIZE_M) >>
+			MCDRAM_RANKCFG_TYPE_SIZE_S) {
+		case 0:
+			dimm->nr_pages = 128 << (20 - PAGE_SHIFT);
+			break;
+		case 1:
+			dimm->nr_pages = 256 << (20 - PAGE_SHIFT);
+			break;
+		case 2:
+		case 3:
+			dimm->nr_pages = 512 << (20 - PAGE_SHIFT);
+			break;
+		case 4:
+			dimm->nr_pages = 1024 << (20 - PAGE_SHIFT);
+			break;
+		case 5:
+			dimm->nr_pages = 2048 << (20 - PAGE_SHIFT);
+			break;
+		default:
+			edac_mc_printk(mci, KERN_ERR,
+				"Unrecognized Rank Config. rankcfg=%u\n",
+				rankcfg);
+			return -EINVAL;
+		}
+
+		csrow->first_page = last_page_in_mmc;
+		csrow->last_page = csrow->first_page + dimm->nr_pages - 1;
+		last_page_in_mmc += dimm->nr_pages;
+		csrow->page_mask = 0;
+		dimm->grain = PASEMI_EDAC_ERROR_GRAIN;
+		dimm->mtype = MEM_DDR;
+		dimm->dtype = DEV_UNKNOWN;
+		dimm->edac_mode = edac_mode;
+	}
+	return 0;
+}
+
+static int pasemi_edac_probe(struct pci_dev *pdev,
+			     const struct pci_device_id *ent)
+{
+	struct mem_ctl_info *mci = NULL;
+	struct edac_mc_layer layers[2];
+	u32 errctl1, errcor, scrub, mcen;
+
+	pci_read_config_dword(pdev, MCCFG_MCEN, &mcen);
+	if (!(mcen & MCCFG_MCEN_MMC_EN))
+		return -ENODEV;
+
+	/*
+	 * We should think about enabling other error detection later on
+	 */
+
+	pci_read_config_dword(pdev, MCDEBUG_ERRCTL1, &errctl1);
+	errctl1 |= MCDEBUG_ERRCTL1_SBE_LOG_EN |
+		MCDEBUG_ERRCTL1_MBE_LOG_EN |
+		MCDEBUG_ERRCTL1_RFL_LOG_EN;
+	pci_write_config_dword(pdev, MCDEBUG_ERRCTL1, errctl1);
+
+	layers[0].type = EDAC_MC_LAYER_CHIP_SELECT;
+	layers[0].size = PASEMI_EDAC_NR_CSROWS;
+	layers[0].is_virt_csrow = true;
+	layers[1].type = EDAC_MC_LAYER_CHANNEL;
+	layers[1].size = PASEMI_EDAC_NR_CHANS;
+	layers[1].is_virt_csrow = false;
+	mci = edac_mc_alloc(system_mmc_id++, ARRAY_SIZE(layers), layers,
+			    0);
+	if (mci == NULL)
+		return -ENOMEM;
+
+	pci_read_config_dword(pdev, MCCFG_ERRCOR, &errcor);
+	errcor |= MCCFG_ERRCOR_RNK_FAIL_DET_EN |
+		MCCFG_ERRCOR_ECC_GEN_EN |
+		MCCFG_ERRCOR_ECC_CRR_EN;
+
+	mci->pdev = &pdev->dev;
+	mci->mtype_cap = MEM_FLAG_DDR | MEM_FLAG_RDDR;
+	mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_EC | EDAC_FLAG_SECDED;
+	mci->edac_cap = (errcor & MCCFG_ERRCOR_ECC_GEN_EN) ?
+		((errcor & MCCFG_ERRCOR_ECC_CRR_EN) ?
+		 (EDAC_FLAG_EC | EDAC_FLAG_SECDED) : EDAC_FLAG_EC) :
+		EDAC_FLAG_NONE;
+	mci->mod_name = MODULE_NAME;
+	mci->dev_name = pci_name(pdev);
+	mci->ctl_name = "pasemi,pwrficient-mc";
+	mci->edac_check = pasemi_edac_check;
+	mci->ctl_page_to_phys = NULL;
+	pci_read_config_dword(pdev, MCCFG_SCRUB, &scrub);
+	mci->scrub_cap = SCRUB_FLAG_HW_PROG | SCRUB_FLAG_HW_SRC;
+	mci->scrub_mode =
+		((errcor & MCCFG_ERRCOR_ECC_CRR_EN) ? SCRUB_FLAG_HW_SRC : 0) |
+		((scrub & MCCFG_SCRUB_RGLR_SCRB_EN) ? SCRUB_FLAG_HW_PROG : 0);
+
+	if (pasemi_edac_init_csrows(mci, pdev,
+				    (mci->edac_cap & EDAC_FLAG_SECDED) ?
+				    EDAC_SECDED :
+				    ((mci->edac_cap & EDAC_FLAG_EC) ?
+				     EDAC_EC : EDAC_NONE)))
+		goto fail;
+
+	/*
+	 * Clear status
+	 */
+	pasemi_edac_get_error_info(mci);
+
+	if (edac_mc_add_mc(mci))
+		goto fail;
+
+	/* get this far and it's successful */
+	return 0;
+
+fail:
+	edac_mc_free(mci);
+	return -ENODEV;
+}
+
+static void pasemi_edac_remove(struct pci_dev *pdev)
+{
+	struct mem_ctl_info *mci = edac_mc_del_mc(&pdev->dev);
+
+	if (!mci)
+		return;
+
+	edac_mc_free(mci);
+}
+
+
+static const struct pci_device_id pasemi_edac_pci_tbl[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_PASEMI, 0xa00a) },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(pci, pasemi_edac_pci_tbl);
+
+static struct pci_driver pasemi_edac_driver = {
+	.name = MODULE_NAME,
+	.probe = pasemi_edac_probe,
+	.remove = pasemi_edac_remove,
+	.id_table = pasemi_edac_pci_tbl,
+};
+
+static int __init pasemi_edac_init(void)
+{
+       /* Ensure that the OPSTATE is set correctly for POLL or NMI */
+       opstate_init();
+
+	return pci_register_driver(&pasemi_edac_driver);
+}
+
+static void __exit pasemi_edac_exit(void)
+{
+	pci_unregister_driver(&pasemi_edac_driver);
+}
+
+module_init(pasemi_edac_init);
+module_exit(pasemi_edac_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
+MODULE_DESCRIPTION("MC support for PA Semi PWRficient memory controller");
+module_param(edac_op_state, int, 0444);
+MODULE_PARM_DESC(edac_op_state, "EDAC Error Reporting state: 0=Poll,1=NMI");
+