From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- drivers/clocksource/bcm2835_timer.c | 137 ++++++++++++++++++++++++++++++++++++ 1 file changed, 137 insertions(+) create mode 100644 drivers/clocksource/bcm2835_timer.c (limited to 'drivers/clocksource/bcm2835_timer.c') diff --git a/drivers/clocksource/bcm2835_timer.c b/drivers/clocksource/bcm2835_timer.c new file mode 100644 index 000000000..d7662301b --- /dev/null +++ b/drivers/clocksource/bcm2835_timer.c @@ -0,0 +1,137 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright 2012 Simon Arlott + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#define REG_CONTROL 0x00 +#define REG_COUNTER_LO 0x04 +#define REG_COUNTER_HI 0x08 +#define REG_COMPARE(n) (0x0c + (n) * 4) +#define MAX_TIMER 3 +#define DEFAULT_TIMER 3 + +struct bcm2835_timer { + void __iomem *control; + void __iomem *compare; + int match_mask; + struct clock_event_device evt; +}; + +static void __iomem *system_clock __read_mostly; + +static u64 notrace bcm2835_sched_read(void) +{ + return readl_relaxed(system_clock); +} + +static int bcm2835_time_set_next_event(unsigned long event, + struct clock_event_device *evt_dev) +{ + struct bcm2835_timer *timer = container_of(evt_dev, + struct bcm2835_timer, evt); + writel_relaxed(readl_relaxed(system_clock) + event, + timer->compare); + return 0; +} + +static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id) +{ + struct bcm2835_timer *timer = dev_id; + void (*event_handler)(struct clock_event_device *); + if (readl_relaxed(timer->control) & timer->match_mask) { + writel_relaxed(timer->match_mask, timer->control); + + event_handler = READ_ONCE(timer->evt.event_handler); + if (event_handler) + event_handler(&timer->evt); + return IRQ_HANDLED; + } else { + return IRQ_NONE; + } +} + +static int __init bcm2835_timer_init(struct device_node *node) +{ + void __iomem *base; + u32 freq; + int irq, ret; + struct bcm2835_timer *timer; + + base = of_iomap(node, 0); + if (!base) { + pr_err("Can't remap registers\n"); + return -ENXIO; + } + + ret = of_property_read_u32(node, "clock-frequency", &freq); + if (ret) { + pr_err("Can't read clock-frequency\n"); + goto err_iounmap; + } + + system_clock = base + REG_COUNTER_LO; + sched_clock_register(bcm2835_sched_read, 32, freq); + + clocksource_mmio_init(base + REG_COUNTER_LO, node->name, + freq, 300, 32, clocksource_mmio_readl_up); + + irq = irq_of_parse_and_map(node, DEFAULT_TIMER); + if (irq <= 0) { + pr_err("Can't parse IRQ\n"); + ret = -EINVAL; + goto err_iounmap; + } + + timer = kzalloc_obj(*timer); + if (!timer) { + ret = -ENOMEM; + goto err_iounmap; + } + + timer->control = base + REG_CONTROL; + timer->compare = base + REG_COMPARE(DEFAULT_TIMER); + timer->match_mask = BIT(DEFAULT_TIMER); + timer->evt.name = node->name; + timer->evt.rating = 300; + timer->evt.features = CLOCK_EVT_FEAT_ONESHOT; + timer->evt.set_next_event = bcm2835_time_set_next_event; + timer->evt.cpumask = cpumask_of(0); + + ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED, + node->name, timer); + if (ret) { + pr_err("Can't set up timer IRQ\n"); + goto err_timer_free; + } + + clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff); + + pr_info("bcm2835: system timer (irq = %d)\n", irq); + + return 0; + +err_timer_free: + kfree(timer); + +err_iounmap: + iounmap(base); + return ret; +} +TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer", + bcm2835_timer_init); -- cgit v1.3.1