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, 273 insertions, 0 deletions

diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
new file mode 100644
index 000000000..521531738
--- /dev/null
+++ b/drivers/misc/ibmasm/remote.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IBM ASM Service Processor Device Driver
+ *
+ * Copyright (C) IBM Corporation, 2004
+ *
+ * Authors: Max Asböck <amax@us.ibm.com>
+ *          Vernon Mauery <vernux@us.ibm.com>
+ */
+
+/* Remote mouse and keyboard event handling functions */
+
+#include <linux/pci.h>
+#include "ibmasm.h"
+#include "remote.h"
+
+#define MOUSE_X_MAX	1600
+#define MOUSE_Y_MAX	1200
+
+static const unsigned short xlate_high[XLATE_SIZE] = {
+	[KEY_SYM_ENTER & 0xff] = KEY_ENTER,
+	[KEY_SYM_KPSLASH & 0xff] = KEY_KPSLASH,
+	[KEY_SYM_KPSTAR & 0xff] = KEY_KPASTERISK,
+	[KEY_SYM_KPMINUS & 0xff] = KEY_KPMINUS,
+	[KEY_SYM_KPDOT & 0xff] = KEY_KPDOT,
+	[KEY_SYM_KPPLUS & 0xff] = KEY_KPPLUS,
+	[KEY_SYM_KP0 & 0xff] = KEY_KP0,
+	[KEY_SYM_KP1 & 0xff] = KEY_KP1,
+	[KEY_SYM_KP2 & 0xff] = KEY_KP2, [KEY_SYM_KPDOWN & 0xff] = KEY_KP2,
+	[KEY_SYM_KP3 & 0xff] = KEY_KP3,
+	[KEY_SYM_KP4 & 0xff] = KEY_KP4, [KEY_SYM_KPLEFT & 0xff] = KEY_KP4,
+	[KEY_SYM_KP5 & 0xff] = KEY_KP5,
+	[KEY_SYM_KP6 & 0xff] = KEY_KP6, [KEY_SYM_KPRIGHT & 0xff] = KEY_KP6,
+	[KEY_SYM_KP7 & 0xff] = KEY_KP7,
+	[KEY_SYM_KP8 & 0xff] = KEY_KP8, [KEY_SYM_KPUP & 0xff] = KEY_KP8,
+	[KEY_SYM_KP9 & 0xff] = KEY_KP9,
+	[KEY_SYM_BK_SPC & 0xff] = KEY_BACKSPACE,
+	[KEY_SYM_TAB & 0xff] = KEY_TAB,
+	[KEY_SYM_CTRL & 0xff] = KEY_LEFTCTRL,
+	[KEY_SYM_ALT & 0xff] = KEY_LEFTALT,
+	[KEY_SYM_INSERT & 0xff] = KEY_INSERT,
+	[KEY_SYM_DELETE & 0xff] = KEY_DELETE,
+	[KEY_SYM_SHIFT & 0xff] = KEY_LEFTSHIFT,
+	[KEY_SYM_UARROW & 0xff] = KEY_UP,
+	[KEY_SYM_DARROW & 0xff] = KEY_DOWN,
+	[KEY_SYM_LARROW & 0xff] = KEY_LEFT,
+	[KEY_SYM_RARROW & 0xff] = KEY_RIGHT,
+	[KEY_SYM_ESCAPE & 0xff] = KEY_ESC,
+        [KEY_SYM_PAGEUP & 0xff] = KEY_PAGEUP,
+        [KEY_SYM_PAGEDOWN & 0xff] = KEY_PAGEDOWN,
+        [KEY_SYM_HOME & 0xff] = KEY_HOME,
+        [KEY_SYM_END & 0xff] = KEY_END,
+	[KEY_SYM_F1 & 0xff] = KEY_F1,
+	[KEY_SYM_F2 & 0xff] = KEY_F2,
+	[KEY_SYM_F3 & 0xff] = KEY_F3,
+	[KEY_SYM_F4 & 0xff] = KEY_F4,
+	[KEY_SYM_F5 & 0xff] = KEY_F5,
+	[KEY_SYM_F6 & 0xff] = KEY_F6,
+	[KEY_SYM_F7 & 0xff] = KEY_F7,
+	[KEY_SYM_F8 & 0xff] = KEY_F8,
+	[KEY_SYM_F9 & 0xff] = KEY_F9,
+	[KEY_SYM_F10 & 0xff] = KEY_F10,
+	[KEY_SYM_F11 & 0xff] = KEY_F11,
+	[KEY_SYM_F12 & 0xff] = KEY_F12,
+	[KEY_SYM_CAP_LOCK & 0xff] = KEY_CAPSLOCK,
+	[KEY_SYM_NUM_LOCK & 0xff] = KEY_NUMLOCK,
+	[KEY_SYM_SCR_LOCK & 0xff] = KEY_SCROLLLOCK,
+};
+
+static const unsigned short xlate[XLATE_SIZE] = {
+	[NO_KEYCODE] = KEY_RESERVED,
+	[KEY_SYM_SPACE] = KEY_SPACE,
+	[KEY_SYM_TILDE] = KEY_GRAVE,        [KEY_SYM_BKTIC] = KEY_GRAVE,
+	[KEY_SYM_ONE] = KEY_1,              [KEY_SYM_BANG] = KEY_1,
+	[KEY_SYM_TWO] = KEY_2,              [KEY_SYM_AT] = KEY_2,
+	[KEY_SYM_THREE] = KEY_3,            [KEY_SYM_POUND] = KEY_3,
+	[KEY_SYM_FOUR] = KEY_4,             [KEY_SYM_DOLLAR] = KEY_4,
+	[KEY_SYM_FIVE] = KEY_5,             [KEY_SYM_PERCENT] = KEY_5,
+	[KEY_SYM_SIX] = KEY_6,              [KEY_SYM_CARAT] = KEY_6,
+	[KEY_SYM_SEVEN] = KEY_7,            [KEY_SYM_AMPER] = KEY_7,
+	[KEY_SYM_EIGHT] = KEY_8,            [KEY_SYM_STAR] = KEY_8,
+	[KEY_SYM_NINE] = KEY_9,             [KEY_SYM_LPAREN] = KEY_9,
+	[KEY_SYM_ZERO] = KEY_0,             [KEY_SYM_RPAREN] = KEY_0,
+	[KEY_SYM_MINUS] = KEY_MINUS,        [KEY_SYM_USCORE] = KEY_MINUS,
+	[KEY_SYM_EQUAL] = KEY_EQUAL,        [KEY_SYM_PLUS] = KEY_EQUAL,
+	[KEY_SYM_LBRKT] = KEY_LEFTBRACE,    [KEY_SYM_LCURLY] = KEY_LEFTBRACE,
+	[KEY_SYM_RBRKT] = KEY_RIGHTBRACE,   [KEY_SYM_RCURLY] = KEY_RIGHTBRACE,
+	[KEY_SYM_SLASH] = KEY_BACKSLASH,    [KEY_SYM_PIPE] = KEY_BACKSLASH,
+	[KEY_SYM_TIC] = KEY_APOSTROPHE,     [KEY_SYM_QUOTE] = KEY_APOSTROPHE,
+	[KEY_SYM_SEMIC] = KEY_SEMICOLON,    [KEY_SYM_COLON] = KEY_SEMICOLON,
+	[KEY_SYM_COMMA] = KEY_COMMA,        [KEY_SYM_LT] = KEY_COMMA,
+	[KEY_SYM_PERIOD] = KEY_DOT,         [KEY_SYM_GT] = KEY_DOT,
+	[KEY_SYM_BSLASH] = KEY_SLASH,       [KEY_SYM_QMARK] = KEY_SLASH,
+	[KEY_SYM_A] = KEY_A,                [KEY_SYM_a] = KEY_A,
+	[KEY_SYM_B] = KEY_B,                [KEY_SYM_b] = KEY_B,
+	[KEY_SYM_C] = KEY_C,                [KEY_SYM_c] = KEY_C,
+	[KEY_SYM_D] = KEY_D,                [KEY_SYM_d] = KEY_D,
+	[KEY_SYM_E] = KEY_E,                [KEY_SYM_e] = KEY_E,
+	[KEY_SYM_F] = KEY_F,                [KEY_SYM_f] = KEY_F,
+	[KEY_SYM_G] = KEY_G,                [KEY_SYM_g] = KEY_G,
+	[KEY_SYM_H] = KEY_H,                [KEY_SYM_h] = KEY_H,
+	[KEY_SYM_I] = KEY_I,                [KEY_SYM_i] = KEY_I,
+	[KEY_SYM_J] = KEY_J,                [KEY_SYM_j] = KEY_J,
+	[KEY_SYM_K] = KEY_K,                [KEY_SYM_k] = KEY_K,
+	[KEY_SYM_L] = KEY_L,                [KEY_SYM_l] = KEY_L,
+	[KEY_SYM_M] = KEY_M,                [KEY_SYM_m] = KEY_M,
+	[KEY_SYM_N] = KEY_N,                [KEY_SYM_n] = KEY_N,
+	[KEY_SYM_O] = KEY_O,                [KEY_SYM_o] = KEY_O,
+	[KEY_SYM_P] = KEY_P,                [KEY_SYM_p] = KEY_P,
+	[KEY_SYM_Q] = KEY_Q,                [KEY_SYM_q] = KEY_Q,
+	[KEY_SYM_R] = KEY_R,                [KEY_SYM_r] = KEY_R,
+	[KEY_SYM_S] = KEY_S,                [KEY_SYM_s] = KEY_S,
+	[KEY_SYM_T] = KEY_T,                [KEY_SYM_t] = KEY_T,
+	[KEY_SYM_U] = KEY_U,                [KEY_SYM_u] = KEY_U,
+	[KEY_SYM_V] = KEY_V,                [KEY_SYM_v] = KEY_V,
+	[KEY_SYM_W] = KEY_W,                [KEY_SYM_w] = KEY_W,
+	[KEY_SYM_X] = KEY_X,                [KEY_SYM_x] = KEY_X,
+	[KEY_SYM_Y] = KEY_Y,                [KEY_SYM_y] = KEY_Y,
+	[KEY_SYM_Z] = KEY_Z,                [KEY_SYM_z] = KEY_Z,
+};
+
+static void print_input(struct remote_input *input)
+{
+	if (input->type == INPUT_TYPE_MOUSE) {
+		unsigned char buttons = input->mouse_buttons;
+		dbg("remote mouse movement: (x,y)=(%d,%d)%s%s%s%s\n",
+			input->data.mouse.x, input->data.mouse.y,
+			(buttons) ? " -- buttons:" : "",
+			(buttons & REMOTE_BUTTON_LEFT) ? "left " : "",
+			(buttons & REMOTE_BUTTON_MIDDLE) ? "middle " : "",
+			(buttons & REMOTE_BUTTON_RIGHT) ? "right" : ""
+		      );
+	} else {
+		dbg("remote keypress (code, flag, down):"
+			   "%d (0x%x) [0x%x] [0x%x]\n",
+				input->data.keyboard.key_code,
+				input->data.keyboard.key_code,
+				input->data.keyboard.key_flag,
+				input->data.keyboard.key_down
+		      );
+	}
+}
+
+static void send_mouse_event(struct input_dev *dev, struct remote_input *input)
+{
+	unsigned char buttons = input->mouse_buttons;
+
+	input_report_abs(dev, ABS_X, input->data.mouse.x);
+	input_report_abs(dev, ABS_Y, input->data.mouse.y);
+	input_report_key(dev, BTN_LEFT, buttons & REMOTE_BUTTON_LEFT);
+	input_report_key(dev, BTN_MIDDLE, buttons & REMOTE_BUTTON_MIDDLE);
+	input_report_key(dev, BTN_RIGHT, buttons & REMOTE_BUTTON_RIGHT);
+	input_sync(dev);
+}
+
+static void send_keyboard_event(struct input_dev *dev,
+		struct remote_input *input)
+{
+	unsigned int key;
+	unsigned short code = input->data.keyboard.key_code;
+
+	if (code & 0xff00)
+		key = xlate_high[code & 0xff];
+	else
+		key = xlate[code];
+	input_report_key(dev, key, input->data.keyboard.key_down);
+	input_sync(dev);
+}
+
+void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
+{
+	unsigned long reader;
+	unsigned long writer;
+	struct remote_input input;
+
+	reader = get_queue_reader(sp);
+	writer = get_queue_writer(sp);
+
+	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
+		memcpy_fromio(&input, get_queue_entry(sp, reader),
+				sizeof(struct remote_input));
+
+		print_input(&input);
+		if (input.type == INPUT_TYPE_MOUSE) {
+			send_mouse_event(sp->remote.mouse_dev, &input);
+		} else if (input.type == INPUT_TYPE_KEYBOARD) {
+			send_keyboard_event(sp->remote.keybd_dev, &input);
+		} else
+			break;
+
+		reader = advance_queue_reader(sp, reader);
+		writer = get_queue_writer(sp);
+	}
+}
+
+int ibmasm_init_remote_input_dev(struct service_processor *sp)
+{
+	/* set up the mouse input device */
+	struct input_dev *mouse_dev, *keybd_dev;
+	struct pci_dev *pdev = to_pci_dev(sp->dev);
+	int error = -ENOMEM;
+	int i;
+
+	sp->remote.mouse_dev = mouse_dev = input_allocate_device();
+	sp->remote.keybd_dev = keybd_dev = input_allocate_device();
+
+	if (!mouse_dev || !keybd_dev)
+		goto err_free_devices;
+
+	mouse_dev->id.bustype = BUS_PCI;
+	mouse_dev->id.vendor = pdev->vendor;
+	mouse_dev->id.product = pdev->device;
+	mouse_dev->id.version = 1;
+	mouse_dev->dev.parent = sp->dev;
+	mouse_dev->evbit[0]  = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	mouse_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_RIGHT) | BIT_MASK(BTN_MIDDLE);
+	set_bit(BTN_TOUCH, mouse_dev->keybit);
+	mouse_dev->name = "ibmasm RSA I remote mouse";
+	input_set_abs_params(mouse_dev, ABS_X, 0, MOUSE_X_MAX, 0, 0);
+	input_set_abs_params(mouse_dev, ABS_Y, 0, MOUSE_Y_MAX, 0, 0);
+
+	keybd_dev->id.bustype = BUS_PCI;
+	keybd_dev->id.vendor = pdev->vendor;
+	keybd_dev->id.product = pdev->device;
+	keybd_dev->id.version = 2;
+	keybd_dev->dev.parent = sp->dev;
+	keybd_dev->evbit[0]  = BIT_MASK(EV_KEY);
+	keybd_dev->name = "ibmasm RSA I remote keyboard";
+
+	for (i = 0; i < XLATE_SIZE; i++) {
+		if (xlate_high[i])
+			set_bit(xlate_high[i], keybd_dev->keybit);
+		if (xlate[i])
+			set_bit(xlate[i], keybd_dev->keybit);
+	}
+
+	error = input_register_device(mouse_dev);
+	if (error)
+		goto err_free_devices;
+
+	error = input_register_device(keybd_dev);
+	if (error)
+		goto err_unregister_mouse_dev;
+
+	enable_mouse_interrupts(sp);
+
+	printk(KERN_INFO "ibmasm remote responding to events on RSA card %d\n", sp->number);
+
+	return 0;
+
+ err_unregister_mouse_dev:
+	input_unregister_device(mouse_dev);
+	mouse_dev = NULL; /* so we don't try to free it again below */
+ err_free_devices:
+	input_free_device(mouse_dev);
+	input_free_device(keybd_dev);
+
+	return error;
+}
+
+void ibmasm_free_remote_input_dev(struct service_processor *sp)
+{
+	disable_mouse_interrupts(sp);
+	input_unregister_device(sp->remote.mouse_dev);
+	input_unregister_device(sp->remote.keybd_dev);
+}
+