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, 317 insertions, 0 deletions

diff --git a/lib/logic_pio.c b/lib/logic_pio.c
new file mode 100644
index 000000000..e29496a38
--- /dev/null
+++ b/lib/logic_pio.c
@@ -0,0 +1,317 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 HiSilicon Limited, All Rights Reserved.
+ * Author: Gabriele Paoloni <gabriele.paoloni@huawei.com>
+ * Author: Zhichang Yuan <yuanzhichang@hisilicon.com>
+ * Author: John Garry <john.garry@huawei.com>
+ */
+
+#define pr_fmt(fmt)	"LOGIC PIO: " fmt
+
+#include <linux/of.h>
+#include <linux/io.h>
+#include <linux/logic_pio.h>
+#include <linux/mm.h>
+#include <linux/rculist.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+
+/* The unique hardware address list */
+static LIST_HEAD(io_range_list);
+static DEFINE_MUTEX(io_range_mutex);
+
+/**
+ * logic_pio_register_range - register logical PIO range for a host
+ * @new_range: pointer to the IO range to be registered.
+ *
+ * Returns 0 on success, the error code in case of failure.
+ * If the range already exists, -EEXIST will be returned, which should be
+ * considered a success.
+ *
+ * Register a new IO range node in the IO range list.
+ */
+int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
+{
+	struct logic_pio_hwaddr *range;
+	resource_size_t start;
+	resource_size_t end;
+	resource_size_t mmio_end = 0;
+	resource_size_t iio_sz = MMIO_UPPER_LIMIT;
+	int ret = 0;
+
+	if (!new_range || !new_range->fwnode || !new_range->size ||
+	    (new_range->flags == LOGIC_PIO_INDIRECT && !new_range->ops))
+		return -EINVAL;
+
+	start = new_range->hw_start;
+	end = new_range->hw_start + new_range->size;
+
+	mutex_lock(&io_range_mutex);
+	list_for_each_entry(range, &io_range_list, list) {
+		if (range->fwnode == new_range->fwnode) {
+			/* range already there */
+			ret = -EEXIST;
+			goto end_register;
+		}
+		if (range->flags == LOGIC_PIO_CPU_MMIO &&
+		    new_range->flags == LOGIC_PIO_CPU_MMIO) {
+			/* for MMIO ranges we need to check for overlap */
+			if (start >= range->hw_start + range->size ||
+			    end < range->hw_start) {
+				mmio_end = range->io_start + range->size;
+			} else {
+				ret = -EFAULT;
+				goto end_register;
+			}
+		} else if (range->flags == LOGIC_PIO_INDIRECT &&
+			   new_range->flags == LOGIC_PIO_INDIRECT) {
+			iio_sz += range->size;
+		}
+	}
+
+	/* range not registered yet, check for available space */
+	if (new_range->flags == LOGIC_PIO_CPU_MMIO) {
+		if (mmio_end + new_range->size - 1 > MMIO_UPPER_LIMIT) {
+			/* if it's too big check if 64K space can be reserved */
+			if (mmio_end + SZ_64K - 1 > MMIO_UPPER_LIMIT) {
+				ret = -E2BIG;
+				goto end_register;
+			}
+			new_range->size = SZ_64K;
+			pr_warn("Requested IO range too big, new size set to 64K\n");
+		}
+		new_range->io_start = mmio_end;
+	} else if (new_range->flags == LOGIC_PIO_INDIRECT) {
+		if (iio_sz + new_range->size - 1 > IO_SPACE_LIMIT) {
+			ret = -E2BIG;
+			goto end_register;
+		}
+		new_range->io_start = iio_sz;
+	} else {
+		/* invalid flag */
+		ret = -EINVAL;
+		goto end_register;
+	}
+
+	list_add_tail_rcu(&new_range->list, &io_range_list);
+
+end_register:
+	mutex_unlock(&io_range_mutex);
+	return ret;
+}
+
+/**
+ * logic_pio_unregister_range - unregister a logical PIO range for a host
+ * @range: pointer to the IO range which has been already registered.
+ *
+ * Unregister a previously-registered IO range node.
+ */
+void logic_pio_unregister_range(struct logic_pio_hwaddr *range)
+{
+	mutex_lock(&io_range_mutex);
+	list_del_rcu(&range->list);
+	mutex_unlock(&io_range_mutex);
+	synchronize_rcu();
+}
+
+/**
+ * find_io_range_by_fwnode - find logical PIO range for given FW node
+ * @fwnode: FW node handle associated with logical PIO range
+ *
+ * Returns pointer to node on success, NULL otherwise.
+ *
+ * Traverse the io_range_list to find the registered node for @fwnode.
+ */
+struct logic_pio_hwaddr *find_io_range_by_fwnode(const struct fwnode_handle *fwnode)
+{
+	struct logic_pio_hwaddr *range, *found_range = NULL;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (range->fwnode == fwnode) {
+			found_range = range;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return found_range;
+}
+
+/* Return a registered range given an input PIO token */
+static struct logic_pio_hwaddr *find_io_range(unsigned long pio)
+{
+	struct logic_pio_hwaddr *range, *found_range = NULL;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (in_range(pio, range->io_start, range->size)) {
+			found_range = range;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!found_range)
+		pr_err("PIO entry token 0x%lx invalid\n", pio);
+
+	return found_range;
+}
+
+/**
+ * logic_pio_to_hwaddr - translate logical PIO to HW address
+ * @pio: logical PIO value
+ *
+ * Returns HW address if valid, ~0 otherwise.
+ *
+ * Translate the input logical PIO to the corresponding hardware address.
+ * The input PIO should be unique in the whole logical PIO space.
+ */
+resource_size_t logic_pio_to_hwaddr(unsigned long pio)
+{
+	struct logic_pio_hwaddr *range;
+
+	range = find_io_range(pio);
+	if (range)
+		return range->hw_start + pio - range->io_start;
+
+	return (resource_size_t)~0;
+}
+
+/**
+ * logic_pio_trans_hwaddr - translate HW address to logical PIO
+ * @fwnode: FW node reference for the host
+ * @addr: Host-relative HW address
+ * @size: size to translate
+ *
+ * Returns Logical PIO value if successful, ~0UL otherwise
+ */
+unsigned long logic_pio_trans_hwaddr(const struct fwnode_handle *fwnode,
+				     resource_size_t addr, resource_size_t size)
+{
+	struct logic_pio_hwaddr *range;
+
+	range = find_io_range_by_fwnode(fwnode);
+	if (!range || range->flags == LOGIC_PIO_CPU_MMIO) {
+		pr_err("IO range not found or invalid\n");
+		return ~0UL;
+	}
+	if (range->size < size) {
+		pr_err("resource size %pa cannot fit in IO range size %pa\n",
+		       &size, &range->size);
+		return ~0UL;
+	}
+	return addr - range->hw_start + range->io_start;
+}
+
+unsigned long logic_pio_trans_cpuaddr(resource_size_t addr)
+{
+	struct logic_pio_hwaddr *range;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (range->flags != LOGIC_PIO_CPU_MMIO)
+			continue;
+		if (in_range(addr, range->hw_start, range->size)) {
+			unsigned long cpuaddr;
+
+			cpuaddr = addr - range->hw_start + range->io_start;
+
+			rcu_read_unlock();
+			return cpuaddr;
+		}
+	}
+	rcu_read_unlock();
+
+	pr_err("addr %pa not registered in io_range_list\n", &addr);
+
+	return ~0UL;
+}
+
+#if defined(CONFIG_INDIRECT_PIO) && defined(PCI_IOBASE)
+#define BUILD_LOGIC_IO(bwl, type)					\
+type logic_in##bwl(unsigned long addr)					\
+{									\
+	type ret = (type)~0;						\
+									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		ret = _in##bwl(addr);					\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) { \
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			ret = entry->ops->in(entry->hostdata,		\
+					addr, sizeof(type));		\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+	return ret;							\
+}									\
+									\
+void logic_out##bwl(type value, unsigned long addr)			\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		_out##bwl(value, addr);				\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->out(entry->hostdata,		\
+					addr, value, sizeof(type));	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+}									\
+									\
+void logic_ins##bwl(unsigned long addr, void *buffer,			\
+		    unsigned int count)					\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		reads##bwl(PCI_IOBASE + addr, buffer, count);		\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->ins(entry->hostdata,		\
+				addr, buffer, sizeof(type), count);	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+									\
+}									\
+									\
+void logic_outs##bwl(unsigned long addr, const void *buffer,		\
+		     unsigned int count)				\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		writes##bwl(PCI_IOBASE + addr, buffer, count);		\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->outs(entry->hostdata,		\
+				addr, buffer, sizeof(type), count);	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+}
+
+BUILD_LOGIC_IO(b, u8)
+EXPORT_SYMBOL(logic_inb);
+EXPORT_SYMBOL(logic_insb);
+EXPORT_SYMBOL(logic_outb);
+EXPORT_SYMBOL(logic_outsb);
+
+BUILD_LOGIC_IO(w, u16)
+EXPORT_SYMBOL(logic_inw);
+EXPORT_SYMBOL(logic_insw);
+EXPORT_SYMBOL(logic_outw);
+EXPORT_SYMBOL(logic_outsw);
+
+BUILD_LOGIC_IO(l, u32)
+EXPORT_SYMBOL(logic_inl);
+EXPORT_SYMBOL(logic_insl);
+EXPORT_SYMBOL(logic_outl);
+EXPORT_SYMBOL(logic_outsl);
+
+#endif /* CONFIG_INDIRECT_PIO && PCI_IOBASE */