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, 211 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/utstring.c b/drivers/acpi/acpica/utstring.c
new file mode 100644
index 000000000..aae71b8c5
--- /dev/null
+++ b/drivers/acpi/acpica/utstring.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*******************************************************************************
+ *
+ * Module Name: utstring - Common functions for strings and characters
+ *
+ ******************************************************************************/
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acnamesp.h"
+
+#define _COMPONENT          ACPI_UTILITIES
+ACPI_MODULE_NAME("utstring")
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_print_string
+ *
+ * PARAMETERS:  string          - Null terminated ASCII string
+ *              max_length      - Maximum output length. Used to constrain the
+ *                                length of strings during debug output only.
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Dump an ASCII string with support for ACPI-defined escape
+ *              sequences.
+ *
+ ******************************************************************************/
+void acpi_ut_print_string(char *string, u16 max_length)
+{
+	u32 i;
+
+	if (!string) {
+		acpi_os_printf("<\"NULL STRING PTR\">");
+		return;
+	}
+
+	acpi_os_printf("\"");
+	for (i = 0; (i < max_length) && string[i]; i++) {
+
+		/* Escape sequences */
+
+		switch (string[i]) {
+		case 0x07:
+
+			acpi_os_printf("\\a");	/* BELL */
+			break;
+
+		case 0x08:
+
+			acpi_os_printf("\\b");	/* BACKSPACE */
+			break;
+
+		case 0x0C:
+
+			acpi_os_printf("\\f");	/* FORMFEED */
+			break;
+
+		case 0x0A:
+
+			acpi_os_printf("\\n");	/* LINEFEED */
+			break;
+
+		case 0x0D:
+
+			acpi_os_printf("\\r");	/* CARRIAGE RETURN */
+			break;
+
+		case 0x09:
+
+			acpi_os_printf("\\t");	/* HORIZONTAL TAB */
+			break;
+
+		case 0x0B:
+
+			acpi_os_printf("\\v");	/* VERTICAL TAB */
+			break;
+
+		case '\'':	/* Single Quote */
+		case '\"':	/* Double Quote */
+		case '\\':	/* Backslash */
+
+			acpi_os_printf("\\%c", (int)string[i]);
+			break;
+
+		default:
+
+			/* Check for printable character or hex escape */
+
+			if (isprint((int)string[i])) {
+				/* This is a normal character */
+
+				acpi_os_printf("%c", (int)string[i]);
+			} else {
+				/* All others will be Hex escapes */
+
+				acpi_os_printf("\\x%2.2X", (s32)string[i]);
+			}
+			break;
+		}
+	}
+
+	acpi_os_printf("\"");
+
+	if (i == max_length && string[i]) {
+		acpi_os_printf("...");
+	}
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_repair_name
+ *
+ * PARAMETERS:  name            - The ACPI name to be repaired
+ *
+ * RETURN:      Repaired version of the name
+ *
+ * DESCRIPTION: Repair an ACPI name: Change invalid characters to '*' and
+ *              return the new name. NOTE: the Name parameter must reside in
+ *              read/write memory, cannot be a const.
+ *
+ * An ACPI Name must consist of valid ACPI characters. We will repair the name
+ * if necessary because we don't want to abort because of this, but we want
+ * all namespace names to be printable. A warning message is appropriate.
+ *
+ * This issue came up because there are in fact machines that exhibit
+ * this problem, and we want to be able to enable ACPI support for them,
+ * even though there are a few bad names.
+ *
+ ******************************************************************************/
+
+void acpi_ut_repair_name(char *name)
+{
+	u32 i;
+	u8 found_bad_char = FALSE;
+	u32 original_name;
+
+	ACPI_FUNCTION_NAME(ut_repair_name);
+
+	/*
+	 * Special case for the root node. This can happen if we get an
+	 * error during the execution of module-level code.
+	 */
+	if (ACPI_COMPARE_NAMESEG(name, ACPI_ROOT_PATHNAME)) {
+		return;
+	}
+
+	ACPI_COPY_NAMESEG(&original_name, &name[0]);
+
+	/* Check each character in the name */
+
+	for (i = 0; i < ACPI_NAMESEG_SIZE; i++) {
+		if (acpi_ut_valid_name_char(name[i], i)) {
+			continue;
+		}
+
+		/*
+		 * Replace a bad character with something printable, yet technically
+		 * "odd". This prevents any collisions with existing "good"
+		 * names in the namespace.
+		 */
+		name[i] = '_';
+		found_bad_char = TRUE;
+	}
+
+	if (found_bad_char) {
+
+		/* Report warning only if in strict mode or debug mode */
+
+		if (!acpi_gbl_enable_interpreter_slack) {
+			ACPI_WARNING((AE_INFO,
+				      "Invalid character(s) in name (0x%.8X) %p, repaired: [%4.4s]",
+				      original_name, name, &name[0]));
+		} else {
+			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+					  "Invalid character(s) in name (0x%.8X), repaired: [%4.4s]",
+					  original_name, name));
+		}
+	}
+}
+
+#if defined ACPI_ASL_COMPILER || defined ACPI_EXEC_APP
+/*******************************************************************************
+ *
+ * FUNCTION:    ut_convert_backslashes
+ *
+ * PARAMETERS:  pathname        - File pathname string to be converted
+ *
+ * RETURN:      Modifies the input Pathname
+ *
+ * DESCRIPTION: Convert all backslashes (0x5C) to forward slashes (0x2F) within
+ *              the entire input file pathname string.
+ *
+ ******************************************************************************/
+
+void ut_convert_backslashes(char *pathname)
+{
+
+	if (!pathname) {
+		return;
+	}
+
+	while (*pathname) {
+		if (*pathname == '\\') {
+			*pathname = '/';
+		}
+
+		pathname++;
+	}
+}
+#endif