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, 406 insertions, 0 deletions

diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
new file mode 100644
index 000000000..7ad3b3601
--- /dev/null
+++ b/drivers/acpi/acpi_extlog.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Extended Error Log driver
+ *
+ * Copyright (C) 2013 Intel Corp.
+ * Author: Chen, Gong <gong.chen@intel.com>
+ */
+
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/cper.h>
+#include <linux/ratelimit.h>
+#include <linux/edac.h>
+#include <linux/ras.h>
+#include <cxl/event.h>
+#include <acpi/ghes.h>
+#include <asm/cpu.h>
+#include <asm/mce.h>
+#include <asm/msr.h>
+
+#include "apei/apei-internal.h"
+#include <ras/ras_event.h>
+
+#define EXT_ELOG_ENTRY_MASK	GENMASK_ULL(51, 0) /* elog entry address mask */
+
+#define EXTLOG_DSM_REV		0x0
+#define	EXTLOG_FN_ADDR		0x1
+
+#define FLAG_OS_OPTIN		BIT(0)
+#define ELOG_ENTRY_VALID	(1ULL<<63)
+#define ELOG_ENTRY_LEN		0x1000
+
+#define EMCA_BUG \
+	"Can not request iomem region <0x%016llx-0x%016llx> - eMCA disabled\n"
+
+struct extlog_l1_head {
+	u32 ver;	/* Header Version */
+	u32 hdr_len;	/* Header Length */
+	u64 total_len;	/* entire L1 Directory length including this header */
+	u64 elog_base;	/* MCA Error Log Directory base address */
+	u64 elog_len;	/* MCA Error Log Directory length */
+	u32 flags;	/* bit 0 - OS/VMM Opt-in */
+	u8  rev0[12];
+	u32 entries;	/* Valid L1 Directory entries per logical processor */
+	u8  rev1[12];
+};
+
+static u8 extlog_dsm_uuid[] __initdata = "663E35AF-CC10-41A4-88EA-5470AF055295";
+
+/* L1 table related physical address */
+static u64 elog_base;
+static size_t elog_size;
+static u64 l1_dirbase;
+static size_t l1_size;
+
+/* L1 table related virtual address */
+static void __iomem *extlog_l1_addr;
+static void __iomem *elog_addr;
+
+static void *elog_buf;
+
+static u64 *l1_entry_base;
+static u32 l1_percpu_entry;
+
+#define ELOG_IDX(cpu, bank) \
+	(cpu_physical_id(cpu) * l1_percpu_entry + (bank))
+
+#define ELOG_ENTRY_DATA(idx) \
+	(*(l1_entry_base + (idx)))
+
+#define ELOG_ENTRY_ADDR(phyaddr) \
+	(phyaddr - elog_base + (u8 *)elog_addr)
+
+static struct acpi_hest_generic_status *extlog_elog_entry_check(int cpu, int bank)
+{
+	int idx;
+	u64 data;
+	struct acpi_hest_generic_status *estatus;
+
+	WARN_ON(cpu < 0);
+	idx = ELOG_IDX(cpu, bank);
+	data = ELOG_ENTRY_DATA(idx);
+	if ((data & ELOG_ENTRY_VALID) == 0)
+		return NULL;
+
+	data &= EXT_ELOG_ENTRY_MASK;
+	estatus = (struct acpi_hest_generic_status *)ELOG_ENTRY_ADDR(data);
+
+	/* if no valid data in elog entry, just return */
+	if (estatus->block_status == 0)
+		return NULL;
+
+	return estatus;
+}
+
+static void __print_extlog_rcd(const char *pfx,
+			       struct acpi_hest_generic_status *estatus, int cpu)
+{
+	static atomic_t seqno;
+	unsigned int curr_seqno;
+	char pfx_seq[64];
+
+	if (!pfx) {
+		if (estatus->error_severity <= CPER_SEV_CORRECTED)
+			pfx = KERN_INFO;
+		else
+			pfx = KERN_ERR;
+	}
+	curr_seqno = atomic_inc_return(&seqno);
+	snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}", pfx, curr_seqno);
+	printk("%s""Hardware error detected on CPU%d\n", pfx_seq, cpu);
+	cper_estatus_print(pfx_seq, estatus);
+}
+
+static int print_extlog_rcd(const char *pfx,
+			    struct acpi_hest_generic_status *estatus, int cpu)
+{
+	/* Not more than 2 messages every 5 seconds */
+	static DEFINE_RATELIMIT_STATE(ratelimit_corrected, 5*HZ, 2);
+	static DEFINE_RATELIMIT_STATE(ratelimit_uncorrected, 5*HZ, 2);
+	struct ratelimit_state *ratelimit;
+
+	if (estatus->error_severity == CPER_SEV_CORRECTED ||
+	    (estatus->error_severity == CPER_SEV_INFORMATIONAL))
+		ratelimit = &ratelimit_corrected;
+	else
+		ratelimit = &ratelimit_uncorrected;
+	if (__ratelimit(ratelimit)) {
+		__print_extlog_rcd(pfx, estatus, cpu);
+		return 0;
+	}
+
+	return 1;
+}
+
+static void extlog_print_pcie(struct cper_sec_pcie *pcie_err,
+			      int severity)
+{
+#ifdef ACPI_APEI_PCIEAER
+	struct aer_capability_regs *aer;
+	struct pci_dev *pdev;
+	unsigned int devfn;
+	unsigned int bus;
+	int aer_severity;
+	int domain;
+
+	if (!(pcie_err->validation_bits & CPER_PCIE_VALID_DEVICE_ID &&
+	      pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO))
+		return;
+
+	aer_severity = cper_severity_to_aer(severity);
+	aer = (struct aer_capability_regs *)pcie_err->aer_info;
+	domain = pcie_err->device_id.segment;
+	bus = pcie_err->device_id.bus;
+	devfn = PCI_DEVFN(pcie_err->device_id.device,
+			  pcie_err->device_id.function);
+	pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
+	if (!pdev)
+		return;
+
+	pci_print_aer(pdev, aer_severity, aer);
+	pci_dev_put(pdev);
+#endif
+}
+
+static void
+extlog_cxl_cper_handle_prot_err(struct cxl_cper_sec_prot_err *prot_err,
+				int severity)
+{
+#ifdef ACPI_APEI_PCIEAER
+	struct cxl_cper_prot_err_work_data wd;
+
+	if (cxl_cper_sec_prot_err_valid(prot_err))
+		return;
+
+	if (cxl_cper_setup_prot_err_work_data(&wd, prot_err, severity))
+		return;
+
+	cxl_cper_handle_prot_err(&wd);
+#endif
+}
+
+static int extlog_print(struct notifier_block *nb, unsigned long val,
+			void *data)
+{
+	struct mce *mce = (struct mce *)data;
+	int	bank = mce->bank;
+	int	cpu = mce->extcpu;
+	struct acpi_hest_generic_status *estatus, *tmp;
+	struct acpi_hest_generic_data *gdata;
+	const guid_t *fru_id;
+	char *fru_text;
+	guid_t *sec_type;
+	static u32 err_seq;
+
+	estatus = extlog_elog_entry_check(cpu, bank);
+	if (!estatus)
+		return NOTIFY_DONE;
+
+	if (mce->kflags & MCE_HANDLED_CEC) {
+		estatus->block_status = 0;
+		return NOTIFY_DONE;
+	}
+
+	memcpy(elog_buf, (void *)estatus, ELOG_ENTRY_LEN);
+	/* clear record status to enable BIOS to update it again */
+	estatus->block_status = 0;
+
+	tmp = (struct acpi_hest_generic_status *)elog_buf;
+
+	if (!ras_userspace_consumers()) {
+		print_extlog_rcd(NULL, tmp, cpu);
+		goto out;
+	}
+
+	/* log event via trace */
+	err_seq++;
+	apei_estatus_for_each_section(tmp, gdata) {
+		if (gdata->validation_bits & CPER_SEC_VALID_FRU_ID)
+			fru_id = (guid_t *)gdata->fru_id;
+		else
+			fru_id = &guid_null;
+		if (gdata->validation_bits & CPER_SEC_VALID_FRU_TEXT)
+			fru_text = gdata->fru_text;
+		else
+			fru_text = "";
+		sec_type = (guid_t *)gdata->section_type;
+		if (guid_equal(sec_type, &CPER_SEC_PLATFORM_MEM)) {
+			struct cper_sec_mem_err *mem = acpi_hest_get_payload(gdata);
+
+			if (gdata->error_data_length >= sizeof(*mem))
+				trace_extlog_mem_event(mem, err_seq, fru_id, fru_text,
+						       (u8)gdata->error_severity);
+		} else if (guid_equal(sec_type, &CPER_SEC_CXL_PROT_ERR)) {
+			struct cxl_cper_sec_prot_err *prot_err =
+				acpi_hest_get_payload(gdata);
+
+			extlog_cxl_cper_handle_prot_err(prot_err,
+							gdata->error_severity);
+		} else if (guid_equal(sec_type, &CPER_SEC_PCIE)) {
+			struct cper_sec_pcie *pcie_err = acpi_hest_get_payload(gdata);
+
+			extlog_print_pcie(pcie_err, gdata->error_severity);
+		} else {
+			void *err = acpi_hest_get_payload(gdata);
+
+			log_non_standard_event(sec_type, fru_id, fru_text,
+					       gdata->error_severity, err,
+					       gdata->error_data_length);
+		}
+	}
+
+out:
+	mce->kflags |= MCE_HANDLED_EXTLOG;
+	return NOTIFY_OK;
+}
+
+static bool __init extlog_get_l1addr(void)
+{
+	guid_t guid;
+	acpi_handle handle;
+	union acpi_object *obj;
+
+	if (guid_parse(extlog_dsm_uuid, &guid))
+		return false;
+	if (ACPI_FAILURE(acpi_get_handle(NULL, "\\_SB", &handle)))
+		return false;
+	if (!acpi_check_dsm(handle, &guid, EXTLOG_DSM_REV, 1 << EXTLOG_FN_ADDR))
+		return false;
+	obj = acpi_evaluate_dsm_typed(handle, &guid, EXTLOG_DSM_REV,
+				      EXTLOG_FN_ADDR, NULL, ACPI_TYPE_INTEGER);
+	if (!obj) {
+		return false;
+	} else {
+		l1_dirbase = obj->integer.value;
+		ACPI_FREE(obj);
+	}
+
+	/* Spec says L1 directory must be 4K aligned, bail out if it isn't */
+	if (l1_dirbase & ((1 << 12) - 1)) {
+		pr_warn(FW_BUG "L1 Directory is invalid at physical %llx\n",
+			l1_dirbase);
+		return false;
+	}
+
+	return true;
+}
+static struct notifier_block extlog_mce_dec = {
+	.notifier_call	= extlog_print,
+	.priority	= MCE_PRIO_EXTLOG,
+};
+
+static int __init extlog_init(void)
+{
+	struct extlog_l1_head *l1_head;
+	void __iomem *extlog_l1_hdr;
+	size_t l1_hdr_size;
+	struct resource *r;
+	u64 cap;
+	int rc;
+
+	if (rdmsrq_safe(MSR_IA32_MCG_CAP, &cap) ||
+	    !(cap & MCG_ELOG_P) ||
+	    !extlog_get_l1addr())
+		return -ENODEV;
+
+	rc = -EINVAL;
+	/* get L1 header to fetch necessary information */
+	l1_hdr_size = sizeof(struct extlog_l1_head);
+	r = request_mem_region(l1_dirbase, l1_hdr_size, "L1 DIR HDR");
+	if (!r) {
+		pr_warn(FW_BUG EMCA_BUG,
+			(unsigned long long)l1_dirbase,
+			(unsigned long long)l1_dirbase + l1_hdr_size);
+		goto err;
+	}
+
+	extlog_l1_hdr = acpi_os_map_iomem(l1_dirbase, l1_hdr_size);
+	if (!extlog_l1_hdr) {
+		rc = -ENOMEM;
+		goto err_release_l1_hdr;
+	}
+	l1_head = (struct extlog_l1_head *)extlog_l1_hdr;
+	l1_size = l1_head->total_len;
+	l1_percpu_entry = l1_head->entries;
+	elog_base = l1_head->elog_base;
+	elog_size = l1_head->elog_len;
+	acpi_os_unmap_iomem(extlog_l1_hdr, l1_hdr_size);
+	release_mem_region(l1_dirbase, l1_hdr_size);
+
+	/* remap L1 header again based on completed information */
+	r = request_mem_region(l1_dirbase, l1_size, "L1 Table");
+	if (!r) {
+		pr_warn(FW_BUG EMCA_BUG,
+			(unsigned long long)l1_dirbase,
+			(unsigned long long)l1_dirbase + l1_size);
+		goto err;
+	}
+	extlog_l1_addr = acpi_os_map_iomem(l1_dirbase, l1_size);
+	if (!extlog_l1_addr) {
+		rc = -ENOMEM;
+		goto err_release_l1_dir;
+	}
+	l1_entry_base = (u64 *)((u8 *)extlog_l1_addr + l1_hdr_size);
+
+	/* remap elog table */
+	r = request_mem_region(elog_base, elog_size, "Elog Table");
+	if (!r) {
+		pr_warn(FW_BUG EMCA_BUG,
+			(unsigned long long)elog_base,
+			(unsigned long long)elog_base + elog_size);
+		goto err_release_l1_dir;
+	}
+	elog_addr = acpi_os_map_iomem(elog_base, elog_size);
+	if (!elog_addr) {
+		rc = -ENOMEM;
+		goto err_release_elog;
+	}
+
+	rc = -ENOMEM;
+	/* allocate buffer to save elog record */
+	elog_buf = kmalloc(ELOG_ENTRY_LEN, GFP_KERNEL);
+	if (elog_buf == NULL)
+		goto err_release_elog;
+
+	mce_register_decode_chain(&extlog_mce_dec);
+	/* enable OS to be involved to take over management from BIOS */
+	((struct extlog_l1_head *)extlog_l1_addr)->flags |= FLAG_OS_OPTIN;
+
+	return 0;
+
+err_release_elog:
+	if (elog_addr)
+		acpi_os_unmap_iomem(elog_addr, elog_size);
+	release_mem_region(elog_base, elog_size);
+err_release_l1_dir:
+	if (extlog_l1_addr)
+		acpi_os_unmap_iomem(extlog_l1_addr, l1_size);
+	release_mem_region(l1_dirbase, l1_size);
+err_release_l1_hdr:
+	release_mem_region(l1_dirbase, l1_hdr_size);
+err:
+	pr_warn(FW_BUG "Extended error log disabled because of problems parsing f/w tables\n");
+	return rc;
+}
+
+static void __exit extlog_exit(void)
+{
+	mce_unregister_decode_chain(&extlog_mce_dec);
+	if (extlog_l1_addr) {
+		((struct extlog_l1_head *)extlog_l1_addr)->flags &= ~FLAG_OS_OPTIN;
+		acpi_os_unmap_iomem(extlog_l1_addr, l1_size);
+	}
+	if (elog_addr)
+		acpi_os_unmap_iomem(elog_addr, elog_size);
+	release_mem_region(elog_base, elog_size);
+	release_mem_region(l1_dirbase, l1_size);
+	kfree(elog_buf);
+}
+
+module_init(extlog_init);
+module_exit(extlog_exit);
+
+MODULE_AUTHOR("Chen, Gong <gong.chen@intel.com>");
+MODULE_DESCRIPTION("Extended MCA Error Log Driver");
+MODULE_LICENSE("GPL");