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, 482 insertions, 0 deletions

diff --git a/drivers/ssb/driver_gpio.c b/drivers/ssb/driver_gpio.c
new file mode 100644
index 000000000..905657c92
--- /dev/null
+++ b/drivers/ssb/driver_gpio.c
@@ -0,0 +1,482 @@
+/*
+ * Sonics Silicon Backplane
+ * GPIO driver
+ *
+ * Copyright 2011, Broadcom Corporation
+ * Copyright 2012, Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * Licensed under the GNU/GPL. See COPYING for details.
+ */
+
+#include "ssb_private.h"
+
+#include <linux/gpio/driver.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
+#include <linux/irqdomain.h>
+#include <linux/export.h>
+#include <linux/ssb/ssb.h>
+
+
+/**************************************************
+ * Shared
+ **************************************************/
+
+#if IS_ENABLED(CONFIG_SSB_EMBEDDED)
+static int ssb_gpio_to_irq(struct gpio_chip *chip, unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	if (bus->bustype == SSB_BUSTYPE_SSB)
+		return irq_find_mapping(bus->irq_domain, gpio);
+	else
+		return -EINVAL;
+}
+#endif
+
+/**************************************************
+ * ChipCommon
+ **************************************************/
+
+static int ssb_gpio_chipco_get_value(struct gpio_chip *chip, unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	return !!ssb_chipco_gpio_in(&bus->chipco, 1 << gpio);
+}
+
+static int ssb_gpio_chipco_set_value(struct gpio_chip *chip, unsigned int gpio,
+				     int value)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_chipco_gpio_out(&bus->chipco, 1 << gpio, value ? 1 << gpio : 0);
+
+	return 0;
+}
+
+static int ssb_gpio_chipco_direction_input(struct gpio_chip *chip,
+					   unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_chipco_gpio_outen(&bus->chipco, 1 << gpio, 0);
+	return 0;
+}
+
+static int ssb_gpio_chipco_direction_output(struct gpio_chip *chip,
+					    unsigned int gpio, int value)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_chipco_gpio_outen(&bus->chipco, 1 << gpio, 1 << gpio);
+	ssb_chipco_gpio_out(&bus->chipco, 1 << gpio, value ? 1 << gpio : 0);
+	return 0;
+}
+
+static int ssb_gpio_chipco_request(struct gpio_chip *chip, unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_chipco_gpio_control(&bus->chipco, 1 << gpio, 0);
+	/* clear pulldown */
+	ssb_chipco_gpio_pulldown(&bus->chipco, 1 << gpio, 0);
+	/* Set pullup */
+	ssb_chipco_gpio_pullup(&bus->chipco, 1 << gpio, 1 << gpio);
+
+	return 0;
+}
+
+static void ssb_gpio_chipco_free(struct gpio_chip *chip, unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	/* clear pullup */
+	ssb_chipco_gpio_pullup(&bus->chipco, 1 << gpio, 0);
+}
+
+#if IS_ENABLED(CONFIG_SSB_EMBEDDED)
+static void ssb_gpio_irq_chipco_mask(struct irq_data *d)
+{
+	struct ssb_bus *bus = irq_data_get_irq_chip_data(d);
+	int gpio = irqd_to_hwirq(d);
+
+	ssb_chipco_gpio_intmask(&bus->chipco, BIT(gpio), 0);
+}
+
+static void ssb_gpio_irq_chipco_unmask(struct irq_data *d)
+{
+	struct ssb_bus *bus = irq_data_get_irq_chip_data(d);
+	int gpio = irqd_to_hwirq(d);
+	u32 val = ssb_chipco_gpio_in(&bus->chipco, BIT(gpio));
+
+	ssb_chipco_gpio_polarity(&bus->chipco, BIT(gpio), val);
+	ssb_chipco_gpio_intmask(&bus->chipco, BIT(gpio), BIT(gpio));
+}
+
+static struct irq_chip ssb_gpio_irq_chipco_chip = {
+	.name		= "SSB-GPIO-CC",
+	.irq_mask	= ssb_gpio_irq_chipco_mask,
+	.irq_unmask	= ssb_gpio_irq_chipco_unmask,
+};
+
+static irqreturn_t ssb_gpio_irq_chipco_handler(int irq, void *dev_id)
+{
+	struct ssb_bus *bus = dev_id;
+	struct ssb_chipcommon *chipco = &bus->chipco;
+	u32 val = chipco_read32(chipco, SSB_CHIPCO_GPIOIN);
+	u32 mask = chipco_read32(chipco, SSB_CHIPCO_GPIOIRQ);
+	u32 pol = chipco_read32(chipco, SSB_CHIPCO_GPIOPOL);
+	unsigned long irqs = (val ^ pol) & mask;
+	int gpio;
+
+	if (!irqs)
+		return IRQ_NONE;
+
+	for_each_set_bit(gpio, &irqs, bus->gpio.ngpio)
+		generic_handle_domain_irq_safe(bus->irq_domain, gpio);
+
+	ssb_chipco_gpio_polarity(chipco, irqs, val & irqs);
+
+	return IRQ_HANDLED;
+}
+
+static int ssb_gpio_irq_chipco_domain_init(struct ssb_bus *bus)
+{
+	struct ssb_chipcommon *chipco = &bus->chipco;
+	struct gpio_chip *chip = &bus->gpio;
+	int gpio, hwirq, err;
+
+	if (bus->bustype != SSB_BUSTYPE_SSB)
+		return 0;
+
+	bus->irq_domain = irq_domain_create_linear(NULL, chip->ngpio, &irq_domain_simple_ops,
+						   chipco);
+	if (!bus->irq_domain) {
+		err = -ENODEV;
+		goto err_irq_domain;
+	}
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_create_mapping(bus->irq_domain, gpio);
+
+		irq_set_chip_data(irq, bus);
+		irq_set_chip_and_handler(irq, &ssb_gpio_irq_chipco_chip,
+					 handle_simple_irq);
+	}
+
+	hwirq = ssb_mips_irq(bus->chipco.dev) + 2;
+	err = request_irq(hwirq, ssb_gpio_irq_chipco_handler, IRQF_SHARED,
+			  "gpio", bus);
+	if (err)
+		goto err_req_irq;
+
+	ssb_chipco_gpio_intmask(&bus->chipco, ~0, 0);
+	chipco_set32(chipco, SSB_CHIPCO_IRQMASK, SSB_CHIPCO_IRQ_GPIO);
+
+	return 0;
+
+err_req_irq:
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_find_mapping(bus->irq_domain, gpio);
+
+		irq_dispose_mapping(irq);
+	}
+	irq_domain_remove(bus->irq_domain);
+err_irq_domain:
+	return err;
+}
+
+static void ssb_gpio_irq_chipco_domain_exit(struct ssb_bus *bus)
+{
+	struct ssb_chipcommon *chipco = &bus->chipco;
+	struct gpio_chip *chip = &bus->gpio;
+	int gpio;
+
+	if (bus->bustype != SSB_BUSTYPE_SSB)
+		return;
+
+	chipco_mask32(chipco, SSB_CHIPCO_IRQMASK, ~SSB_CHIPCO_IRQ_GPIO);
+	free_irq(ssb_mips_irq(bus->chipco.dev) + 2, chipco);
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_find_mapping(bus->irq_domain, gpio);
+
+		irq_dispose_mapping(irq);
+	}
+	irq_domain_remove(bus->irq_domain);
+}
+#else
+static int ssb_gpio_irq_chipco_domain_init(struct ssb_bus *bus)
+{
+	return 0;
+}
+
+static void ssb_gpio_irq_chipco_domain_exit(struct ssb_bus *bus)
+{
+}
+#endif
+
+static int ssb_gpio_chipco_init(struct ssb_bus *bus)
+{
+	struct gpio_chip *chip = &bus->gpio;
+	int err;
+
+	chip->label		= "ssb_chipco_gpio";
+	chip->owner		= THIS_MODULE;
+	chip->request		= ssb_gpio_chipco_request;
+	chip->free		= ssb_gpio_chipco_free;
+	chip->get		= ssb_gpio_chipco_get_value;
+	chip->set		= ssb_gpio_chipco_set_value;
+	chip->direction_input	= ssb_gpio_chipco_direction_input;
+	chip->direction_output	= ssb_gpio_chipco_direction_output;
+#if IS_ENABLED(CONFIG_SSB_EMBEDDED)
+	chip->to_irq		= ssb_gpio_to_irq;
+#endif
+	chip->ngpio		= 16;
+	/* There is just one SoC in one device and its GPIO addresses should be
+	 * deterministic to address them more easily. The other buses could get
+	 * a random base number.
+	 */
+	if (bus->bustype == SSB_BUSTYPE_SSB)
+		chip->base		= 0;
+	else
+		chip->base		= -1;
+
+	err = ssb_gpio_irq_chipco_domain_init(bus);
+	if (err)
+		return err;
+
+	err = gpiochip_add_data(chip, bus);
+	if (err) {
+		ssb_gpio_irq_chipco_domain_exit(bus);
+		return err;
+	}
+
+	return 0;
+}
+
+/**************************************************
+ * EXTIF
+ **************************************************/
+
+#ifdef CONFIG_SSB_DRIVER_EXTIF
+
+static int ssb_gpio_extif_get_value(struct gpio_chip *chip, unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	return !!ssb_extif_gpio_in(&bus->extif, 1 << gpio);
+}
+
+static int ssb_gpio_extif_set_value(struct gpio_chip *chip, unsigned int gpio,
+				    int value)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_extif_gpio_out(&bus->extif, 1 << gpio, value ? 1 << gpio : 0);
+
+	return 0;
+}
+
+static int ssb_gpio_extif_direction_input(struct gpio_chip *chip,
+					  unsigned int gpio)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_extif_gpio_outen(&bus->extif, 1 << gpio, 0);
+	return 0;
+}
+
+static int ssb_gpio_extif_direction_output(struct gpio_chip *chip,
+					   unsigned int gpio, int value)
+{
+	struct ssb_bus *bus = gpiochip_get_data(chip);
+
+	ssb_extif_gpio_outen(&bus->extif, 1 << gpio, 1 << gpio);
+	ssb_extif_gpio_out(&bus->extif, 1 << gpio, value ? 1 << gpio : 0);
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_SSB_EMBEDDED)
+static void ssb_gpio_irq_extif_mask(struct irq_data *d)
+{
+	struct ssb_bus *bus = irq_data_get_irq_chip_data(d);
+	int gpio = irqd_to_hwirq(d);
+
+	ssb_extif_gpio_intmask(&bus->extif, BIT(gpio), 0);
+}
+
+static void ssb_gpio_irq_extif_unmask(struct irq_data *d)
+{
+	struct ssb_bus *bus = irq_data_get_irq_chip_data(d);
+	int gpio = irqd_to_hwirq(d);
+	u32 val = ssb_extif_gpio_in(&bus->extif, BIT(gpio));
+
+	ssb_extif_gpio_polarity(&bus->extif, BIT(gpio), val);
+	ssb_extif_gpio_intmask(&bus->extif, BIT(gpio), BIT(gpio));
+}
+
+static struct irq_chip ssb_gpio_irq_extif_chip = {
+	.name		= "SSB-GPIO-EXTIF",
+	.irq_mask	= ssb_gpio_irq_extif_mask,
+	.irq_unmask	= ssb_gpio_irq_extif_unmask,
+};
+
+static irqreturn_t ssb_gpio_irq_extif_handler(int irq, void *dev_id)
+{
+	struct ssb_bus *bus = dev_id;
+	struct ssb_extif *extif = &bus->extif;
+	u32 val = ssb_read32(extif->dev, SSB_EXTIF_GPIO_IN);
+	u32 mask = ssb_read32(extif->dev, SSB_EXTIF_GPIO_INTMASK);
+	u32 pol = ssb_read32(extif->dev, SSB_EXTIF_GPIO_INTPOL);
+	unsigned long irqs = (val ^ pol) & mask;
+	int gpio;
+
+	if (!irqs)
+		return IRQ_NONE;
+
+	for_each_set_bit(gpio, &irqs, bus->gpio.ngpio)
+		generic_handle_domain_irq_safe(bus->irq_domain, gpio);
+
+	ssb_extif_gpio_polarity(extif, irqs, val & irqs);
+
+	return IRQ_HANDLED;
+}
+
+static int ssb_gpio_irq_extif_domain_init(struct ssb_bus *bus)
+{
+	struct ssb_extif *extif = &bus->extif;
+	struct gpio_chip *chip = &bus->gpio;
+	int gpio, hwirq, err;
+
+	if (bus->bustype != SSB_BUSTYPE_SSB)
+		return 0;
+
+	bus->irq_domain = irq_domain_create_linear(NULL, chip->ngpio, &irq_domain_simple_ops,
+						   extif);
+	if (!bus->irq_domain) {
+		err = -ENODEV;
+		goto err_irq_domain;
+	}
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_create_mapping(bus->irq_domain, gpio);
+
+		irq_set_chip_data(irq, bus);
+		irq_set_chip_and_handler(irq, &ssb_gpio_irq_extif_chip,
+					 handle_simple_irq);
+	}
+
+	hwirq = ssb_mips_irq(bus->extif.dev) + 2;
+	err = request_irq(hwirq, ssb_gpio_irq_extif_handler, IRQF_SHARED,
+			  "gpio", bus);
+	if (err)
+		goto err_req_irq;
+
+	ssb_extif_gpio_intmask(&bus->extif, ~0, 0);
+
+	return 0;
+
+err_req_irq:
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_find_mapping(bus->irq_domain, gpio);
+
+		irq_dispose_mapping(irq);
+	}
+	irq_domain_remove(bus->irq_domain);
+err_irq_domain:
+	return err;
+}
+
+static void ssb_gpio_irq_extif_domain_exit(struct ssb_bus *bus)
+{
+	struct ssb_extif *extif = &bus->extif;
+	struct gpio_chip *chip = &bus->gpio;
+	int gpio;
+
+	if (bus->bustype != SSB_BUSTYPE_SSB)
+		return;
+
+	free_irq(ssb_mips_irq(bus->extif.dev) + 2, extif);
+	for (gpio = 0; gpio < chip->ngpio; gpio++) {
+		int irq = irq_find_mapping(bus->irq_domain, gpio);
+
+		irq_dispose_mapping(irq);
+	}
+	irq_domain_remove(bus->irq_domain);
+}
+#else
+static int ssb_gpio_irq_extif_domain_init(struct ssb_bus *bus)
+{
+	return 0;
+}
+
+static void ssb_gpio_irq_extif_domain_exit(struct ssb_bus *bus)
+{
+}
+#endif
+
+static int ssb_gpio_extif_init(struct ssb_bus *bus)
+{
+	struct gpio_chip *chip = &bus->gpio;
+	int err;
+
+	chip->label		= "ssb_extif_gpio";
+	chip->owner		= THIS_MODULE;
+	chip->get		= ssb_gpio_extif_get_value;
+	chip->set		= ssb_gpio_extif_set_value;
+	chip->direction_input	= ssb_gpio_extif_direction_input;
+	chip->direction_output	= ssb_gpio_extif_direction_output;
+#if IS_ENABLED(CONFIG_SSB_EMBEDDED)
+	chip->to_irq		= ssb_gpio_to_irq;
+#endif
+	chip->ngpio		= 5;
+	/* There is just one SoC in one device and its GPIO addresses should be
+	 * deterministic to address them more easily. The other buses could get
+	 * a random base number.
+	 */
+	if (bus->bustype == SSB_BUSTYPE_SSB)
+		chip->base		= 0;
+	else
+		chip->base		= -1;
+
+	err = ssb_gpio_irq_extif_domain_init(bus);
+	if (err)
+		return err;
+
+	err = gpiochip_add_data(chip, bus);
+	if (err) {
+		ssb_gpio_irq_extif_domain_exit(bus);
+		return err;
+	}
+
+	return 0;
+}
+
+#else
+static int ssb_gpio_extif_init(struct ssb_bus *bus)
+{
+	return -ENOTSUPP;
+}
+#endif
+
+/**************************************************
+ * Init
+ **************************************************/
+
+int ssb_gpio_init(struct ssb_bus *bus)
+{
+	if (ssb_chipco_available(&bus->chipco))
+		return ssb_gpio_chipco_init(bus);
+	else if (ssb_extif_available(&bus->extif))
+		return ssb_gpio_extif_init(bus);
+	return -1;
+}
+
+int ssb_gpio_unregister(struct ssb_bus *bus)
+{
+	if (ssb_chipco_available(&bus->chipco) ||
+	    ssb_extif_available(&bus->extif)) {
+		gpiochip_remove(&bus->gpio);
+		return 0;
+	}
+	return -1;
+}