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, 421 insertions, 0 deletions

diff --git a/drivers/bcma/driver_chipcommon.c b/drivers/bcma/driver_chipcommon.c
new file mode 100644
index 000000000..fd91a39f0
--- /dev/null
+++ b/drivers/bcma/driver_chipcommon.c
@@ -0,0 +1,421 @@
+/*
+ * Broadcom specific AMBA
+ * ChipCommon core driver
+ *
+ * Copyright 2005, Broadcom Corporation
+ * Copyright 2006, 2007, Michael Buesch <m@bues.ch>
+ * Copyright 2012, Hauke Mehrtens <hauke@hauke-m.de>
+ *
+ * Licensed under the GNU/GPL. See COPYING for details.
+ */
+
+#include "bcma_private.h"
+#include <linux/bcm47xx_wdt.h>
+#include <linux/export.h>
+#include <linux/platform_device.h>
+#include <linux/bcma/bcma.h>
+
+static inline u32 bcma_cc_write32_masked(struct bcma_drv_cc *cc, u16 offset,
+					 u32 mask, u32 value)
+{
+	value &= mask;
+	value |= bcma_cc_read32(cc, offset) & ~mask;
+	bcma_cc_write32(cc, offset, value);
+
+	return value;
+}
+
+u32 bcma_chipco_get_alp_clock(struct bcma_drv_cc *cc)
+{
+	if (cc->capabilities & BCMA_CC_CAP_PMU)
+		return bcma_pmu_get_alp_clock(cc);
+
+	return 20000000;
+}
+EXPORT_SYMBOL_GPL(bcma_chipco_get_alp_clock);
+
+static bool bcma_core_cc_has_pmu_watchdog(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+
+	if (cc->capabilities & BCMA_CC_CAP_PMU) {
+		if (bus->chipinfo.id == BCMA_CHIP_ID_BCM53573) {
+			WARN(bus->chipinfo.rev <= 1, "No watchdog available\n");
+			/* 53573B0 and 53573B1 have bugged PMU watchdog. It can
+			 * be enabled but timer can't be bumped. Use CC one
+			 * instead.
+			 */
+			return false;
+		}
+		return true;
+	} else {
+		return false;
+	}
+}
+
+static u32 bcma_chipco_watchdog_get_max_timer(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+	u32 nb;
+
+	if (bcma_core_cc_has_pmu_watchdog(cc)) {
+		if (bus->chipinfo.id == BCMA_CHIP_ID_BCM4706)
+			nb = 32;
+		else if (cc->core->id.rev < 26)
+			nb = 16;
+		else
+			nb = (cc->core->id.rev >= 37) ? 32 : 24;
+	} else {
+		nb = 28;
+	}
+	if (nb == 32)
+		return 0xffffffff;
+	else
+		return (1 << nb) - 1;
+}
+
+static u32 bcma_chipco_watchdog_timer_set_wdt(struct bcm47xx_wdt *wdt,
+					      u32 ticks)
+{
+	struct bcma_drv_cc *cc = bcm47xx_wdt_get_drvdata(wdt);
+
+	return bcma_chipco_watchdog_timer_set(cc, ticks);
+}
+
+static u32 bcma_chipco_watchdog_timer_set_ms_wdt(struct bcm47xx_wdt *wdt,
+						 u32 ms)
+{
+	struct bcma_drv_cc *cc = bcm47xx_wdt_get_drvdata(wdt);
+	u32 ticks;
+
+	ticks = bcma_chipco_watchdog_timer_set(cc, cc->ticks_per_ms * ms);
+	return ticks / cc->ticks_per_ms;
+}
+
+static int bcma_chipco_watchdog_ticks_per_ms(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+
+	if (cc->capabilities & BCMA_CC_CAP_PMU) {
+		if (bus->chipinfo.id == BCMA_CHIP_ID_BCM4706)
+			/* 4706 CC and PMU watchdogs are clocked at 1/4 of ALP
+			 * clock
+			 */
+			return bcma_chipco_get_alp_clock(cc) / 4000;
+		else
+			/* based on 32KHz ILP clock */
+			return 32;
+	} else {
+		return bcma_chipco_get_alp_clock(cc) / 1000;
+	}
+}
+
+int bcma_chipco_watchdog_register(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+	struct bcm47xx_wdt wdt = {};
+	struct platform_device *pdev;
+
+	if (bus->chipinfo.id == BCMA_CHIP_ID_BCM53573 &&
+	    bus->chipinfo.rev <= 1) {
+		pr_debug("No watchdog on 53573A0 / 53573A1\n");
+		return 0;
+	}
+
+	wdt.driver_data = cc;
+	wdt.timer_set = bcma_chipco_watchdog_timer_set_wdt;
+	wdt.timer_set_ms = bcma_chipco_watchdog_timer_set_ms_wdt;
+	wdt.max_timer_ms =
+		bcma_chipco_watchdog_get_max_timer(cc) / cc->ticks_per_ms;
+
+	pdev = platform_device_register_data(NULL, "bcm47xx-wdt",
+					     bus->num, &wdt,
+					     sizeof(wdt));
+	if (IS_ERR(pdev))
+		return PTR_ERR(pdev);
+
+	cc->watchdog = pdev;
+
+	return 0;
+}
+
+static void bcma_core_chipcommon_flash_detect(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+
+	switch (cc->capabilities & BCMA_CC_CAP_FLASHT) {
+	case BCMA_CC_FLASHT_STSER:
+	case BCMA_CC_FLASHT_ATSER:
+		bcma_debug(bus, "Found serial flash\n");
+		bcma_sflash_init(cc);
+		break;
+	case BCMA_CC_FLASHT_PARA:
+		bcma_debug(bus, "Found parallel flash\n");
+		bcma_pflash_init(cc);
+		break;
+	default:
+		bcma_err(bus, "Flash type not supported\n");
+	}
+
+	if (cc->core->id.rev == 38 ||
+	    bus->chipinfo.id == BCMA_CHIP_ID_BCM4706) {
+		if (cc->capabilities & BCMA_CC_CAP_NFLASH) {
+			bcma_debug(bus, "Found NAND flash\n");
+			bcma_nflash_init(cc);
+		}
+	}
+}
+
+void bcma_core_chipcommon_early_init(struct bcma_drv_cc *cc)
+{
+	struct bcma_bus *bus = cc->core->bus;
+
+	if (cc->early_setup_done)
+		return;
+
+	spin_lock_init(&cc->gpio_lock);
+
+	if (cc->core->id.rev >= 11)
+		cc->status = bcma_cc_read32(cc, BCMA_CC_CHIPSTAT);
+	cc->capabilities = bcma_cc_read32(cc, BCMA_CC_CAP);
+	if (cc->core->id.rev >= 35)
+		cc->capabilities_ext = bcma_cc_read32(cc, BCMA_CC_CAP_EXT);
+
+	if (cc->capabilities & BCMA_CC_CAP_PMU)
+		bcma_pmu_early_init(cc);
+
+	if (bus->hosttype == BCMA_HOSTTYPE_SOC)
+		bcma_core_chipcommon_flash_detect(cc);
+
+	cc->early_setup_done = true;
+}
+
+void bcma_core_chipcommon_init(struct bcma_drv_cc *cc)
+{
+	u32 leddc_on = 10;
+	u32 leddc_off = 90;
+
+	if (cc->setup_done)
+		return;
+
+	bcma_core_chipcommon_early_init(cc);
+
+	if (cc->core->id.rev >= 20) {
+		u32 pullup = 0, pulldown = 0;
+
+		if (cc->core->bus->chipinfo.id == BCMA_CHIP_ID_BCM43142) {
+			pullup = 0x402e0;
+			pulldown = 0x20500;
+		}
+
+		bcma_cc_write32(cc, BCMA_CC_GPIOPULLUP, pullup);
+		bcma_cc_write32(cc, BCMA_CC_GPIOPULLDOWN, pulldown);
+	}
+
+	if (cc->capabilities & BCMA_CC_CAP_PMU)
+		bcma_pmu_init(cc);
+	if (cc->capabilities & BCMA_CC_CAP_PCTL)
+		bcma_err(cc->core->bus, "Power control not implemented!\n");
+
+	if (cc->core->id.rev >= 16) {
+		if (cc->core->bus->sprom.leddc_on_time &&
+		    cc->core->bus->sprom.leddc_off_time) {
+			leddc_on = cc->core->bus->sprom.leddc_on_time;
+			leddc_off = cc->core->bus->sprom.leddc_off_time;
+		}
+		bcma_cc_write32(cc, BCMA_CC_GPIOTIMER,
+			((leddc_on << BCMA_CC_GPIOTIMER_ONTIME_SHIFT) |
+			 (leddc_off << BCMA_CC_GPIOTIMER_OFFTIME_SHIFT)));
+	}
+	cc->ticks_per_ms = bcma_chipco_watchdog_ticks_per_ms(cc);
+
+	cc->setup_done = true;
+}
+
+/* Set chip watchdog reset timer to fire in 'ticks' backplane cycles */
+u32 bcma_chipco_watchdog_timer_set(struct bcma_drv_cc *cc, u32 ticks)
+{
+	u32 maxt;
+
+	maxt = bcma_chipco_watchdog_get_max_timer(cc);
+	if (bcma_core_cc_has_pmu_watchdog(cc)) {
+		if (ticks == 1)
+			ticks = 2;
+		else if (ticks > maxt)
+			ticks = maxt;
+		bcma_pmu_write32(cc, BCMA_CC_PMU_WATCHDOG, ticks);
+	} else {
+		struct bcma_bus *bus = cc->core->bus;
+
+		if (bus->chipinfo.id != BCMA_CHIP_ID_BCM4707 &&
+		    bus->chipinfo.id != BCMA_CHIP_ID_BCM47094 &&
+		    bus->chipinfo.id != BCMA_CHIP_ID_BCM53018)
+			bcma_core_set_clockmode(cc->core,
+						ticks ? BCMA_CLKMODE_FAST : BCMA_CLKMODE_DYNAMIC);
+
+		if (ticks > maxt)
+			ticks = maxt;
+		/* instant NMI */
+		bcma_cc_write32(cc, BCMA_CC_WATCHDOG, ticks);
+	}
+	return ticks;
+}
+
+void bcma_chipco_irq_mask(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	bcma_cc_write32_masked(cc, BCMA_CC_IRQMASK, mask, value);
+}
+
+u32 bcma_chipco_irq_status(struct bcma_drv_cc *cc, u32 mask)
+{
+	return bcma_cc_read32(cc, BCMA_CC_IRQSTAT) & mask;
+}
+
+u32 bcma_chipco_gpio_in(struct bcma_drv_cc *cc, u32 mask)
+{
+	return bcma_cc_read32(cc, BCMA_CC_GPIOIN) & mask;
+}
+
+u32 bcma_chipco_gpio_out(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOOUT, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(bcma_chipco_gpio_out);
+
+u32 bcma_chipco_gpio_outen(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOOUTEN, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(bcma_chipco_gpio_outen);
+
+/*
+ * If the bit is set to 0, chipcommon controls this GPIO,
+ * if the bit is set to 1, it is used by some part of the chip and not our code.
+ */
+u32 bcma_chipco_gpio_control(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOCTL, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(bcma_chipco_gpio_control);
+
+u32 bcma_chipco_gpio_intmask(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOIRQ, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+
+u32 bcma_chipco_gpio_polarity(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOPOL, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+
+u32 bcma_chipco_gpio_pullup(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	if (cc->core->id.rev < 20)
+		return 0;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOPULLUP, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+
+u32 bcma_chipco_gpio_pulldown(struct bcma_drv_cc *cc, u32 mask, u32 value)
+{
+	unsigned long flags;
+	u32 res;
+
+	if (cc->core->id.rev < 20)
+		return 0;
+
+	spin_lock_irqsave(&cc->gpio_lock, flags);
+	res = bcma_cc_write32_masked(cc, BCMA_CC_GPIOPULLDOWN, mask, value);
+	spin_unlock_irqrestore(&cc->gpio_lock, flags);
+
+	return res;
+}
+
+#ifdef CONFIG_BCMA_DRIVER_MIPS
+void bcma_chipco_serial_init(struct bcma_drv_cc *cc)
+{
+	unsigned int irq;
+	u32 baud_base;
+	u32 i;
+	unsigned int ccrev = cc->core->id.rev;
+	struct bcma_serial_port *ports = cc->serial_ports;
+
+	if (ccrev >= 11 && ccrev != 15) {
+		baud_base = bcma_chipco_get_alp_clock(cc);
+		if (ccrev >= 21) {
+			/* Turn off UART clock before switching clocksource. */
+			bcma_cc_write32(cc, BCMA_CC_CORECTL,
+				       bcma_cc_read32(cc, BCMA_CC_CORECTL)
+				       & ~BCMA_CC_CORECTL_UARTCLKEN);
+		}
+		/* Set the override bit so we don't divide it */
+		bcma_cc_write32(cc, BCMA_CC_CORECTL,
+			       bcma_cc_read32(cc, BCMA_CC_CORECTL)
+			       | BCMA_CC_CORECTL_UARTCLK0);
+		if (ccrev >= 21) {
+			/* Re-enable the UART clock. */
+			bcma_cc_write32(cc, BCMA_CC_CORECTL,
+				       bcma_cc_read32(cc, BCMA_CC_CORECTL)
+				       | BCMA_CC_CORECTL_UARTCLKEN);
+		}
+	} else {
+		bcma_err(cc->core->bus, "serial not supported on this device ccrev: 0x%x\n",
+			 ccrev);
+		return;
+	}
+
+	irq = bcma_core_irq(cc->core, 0);
+
+	/* Determine the registers of the UARTs */
+	cc->nr_serial_ports = (cc->capabilities & BCMA_CC_CAP_NRUART);
+	for (i = 0; i < cc->nr_serial_ports; i++) {
+		ports[i].regs = cc->core->io_addr + BCMA_CC_UART0_DATA +
+				(i * 256);
+		ports[i].irq = irq;
+		ports[i].baud_base = baud_base;
+		ports[i].reg_shift = 0;
+	}
+}
+#endif /* CONFIG_BCMA_DRIVER_MIPS */