From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/clocksource/timer-keystone.c | 226 +++++++++++++++++++++++++++++++++++ 1 file changed, 226 insertions(+) create mode 100644 drivers/clocksource/timer-keystone.c (limited to 'drivers/clocksource/timer-keystone.c') diff --git a/drivers/clocksource/timer-keystone.c b/drivers/clocksource/timer-keystone.c new file mode 100644 index 000000000..fea8a4f85 --- /dev/null +++ b/drivers/clocksource/timer-keystone.c @@ -0,0 +1,226 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Keystone broadcast clock-event + * + * Copyright 2013 Texas Instruments, Inc. + * + * Author: Ivan Khoronzhuk + */ + +#include +#include +#include +#include +#include +#include + +#define TIMER_NAME "timer-keystone" + +/* Timer register offsets */ +#define TIM12 0x10 +#define TIM34 0x14 +#define PRD12 0x18 +#define PRD34 0x1c +#define TCR 0x20 +#define TGCR 0x24 +#define INTCTLSTAT 0x44 + +/* Timer register bitfields */ +#define TCR_ENAMODE_MASK 0xC0 +#define TCR_ENAMODE_ONESHOT_MASK 0x40 +#define TCR_ENAMODE_PERIODIC_MASK 0x80 + +#define TGCR_TIM_UNRESET_MASK 0x03 +#define INTCTLSTAT_ENINT_MASK 0x01 + +/** + * struct keystone_timer: holds timer's data + * @base: timer memory base address + * @hz_period: cycles per HZ period + * @event_dev: event device based on timer + */ +static struct keystone_timer { + void __iomem *base; + unsigned long hz_period; + struct clock_event_device event_dev; +} timer; + +static inline u32 keystone_timer_readl(unsigned long rg) +{ + return readl_relaxed(timer.base + rg); +} + +static inline void keystone_timer_writel(u32 val, unsigned long rg) +{ + writel_relaxed(val, timer.base + rg); +} + +/** + * keystone_timer_barrier: write memory barrier + * use explicit barrier to avoid using readl/writel non relaxed function + * variants, because in our case non relaxed variants hide the true places + * where barrier is needed. + */ +static inline void keystone_timer_barrier(void) +{ + __iowmb(); +} + +/** + * keystone_timer_config: configures timer to work in oneshot/periodic modes. + * @ mask: mask of the mode to configure + * @ period: cycles number to configure for + */ +static int keystone_timer_config(u64 period, int mask) +{ + u32 tcr; + u32 off; + + tcr = keystone_timer_readl(TCR); + off = tcr & ~(TCR_ENAMODE_MASK); + + /* set enable mode */ + tcr |= mask; + + /* disable timer */ + keystone_timer_writel(off, TCR); + /* here we have to be sure the timer has been disabled */ + keystone_timer_barrier(); + + /* reset counter to zero, set new period */ + keystone_timer_writel(0, TIM12); + keystone_timer_writel(0, TIM34); + keystone_timer_writel(period & 0xffffffff, PRD12); + keystone_timer_writel(period >> 32, PRD34); + + /* + * enable timer + * here we have to be sure that CNTLO, CNTHI, PRDLO, PRDHI registers + * have been written. + */ + keystone_timer_barrier(); + keystone_timer_writel(tcr, TCR); + return 0; +} + +static void keystone_timer_disable(void) +{ + u32 tcr; + + tcr = keystone_timer_readl(TCR); + + /* disable timer */ + tcr &= ~(TCR_ENAMODE_MASK); + keystone_timer_writel(tcr, TCR); +} + +static irqreturn_t keystone_timer_interrupt(int irq, void *dev_id) +{ + struct clock_event_device *evt = dev_id; + + evt->event_handler(evt); + return IRQ_HANDLED; +} + +static int keystone_set_next_event(unsigned long cycles, + struct clock_event_device *evt) +{ + return keystone_timer_config(cycles, TCR_ENAMODE_ONESHOT_MASK); +} + +static int keystone_shutdown(struct clock_event_device *evt) +{ + keystone_timer_disable(); + return 0; +} + +static int keystone_set_periodic(struct clock_event_device *evt) +{ + keystone_timer_config(timer.hz_period, TCR_ENAMODE_PERIODIC_MASK); + return 0; +} + +static int __init keystone_timer_init(struct device_node *np) +{ + struct clock_event_device *event_dev = &timer.event_dev; + unsigned long rate; + struct clk *clk; + int irq, error; + + irq = irq_of_parse_and_map(np, 0); + if (!irq) { + pr_err("%s: failed to map interrupts\n", __func__); + return -EINVAL; + } + + timer.base = of_iomap(np, 0); + if (!timer.base) { + pr_err("%s: failed to map registers\n", __func__); + return -ENXIO; + } + + clk = of_clk_get(np, 0); + if (IS_ERR(clk)) { + pr_err("%s: failed to get clock\n", __func__); + iounmap(timer.base); + return PTR_ERR(clk); + } + + error = clk_prepare_enable(clk); + if (error) { + pr_err("%s: failed to enable clock\n", __func__); + goto err; + } + + rate = clk_get_rate(clk); + + /* disable, use internal clock source */ + keystone_timer_writel(0, TCR); + /* here we have to be sure the timer has been disabled */ + keystone_timer_barrier(); + + /* reset timer as 64-bit, no pre-scaler, plus features are disabled */ + keystone_timer_writel(0, TGCR); + + /* unreset timer */ + keystone_timer_writel(TGCR_TIM_UNRESET_MASK, TGCR); + + /* init counter to zero */ + keystone_timer_writel(0, TIM12); + keystone_timer_writel(0, TIM34); + + timer.hz_period = DIV_ROUND_UP(rate, HZ); + + /* enable timer interrupts */ + keystone_timer_writel(INTCTLSTAT_ENINT_MASK, INTCTLSTAT); + + error = request_irq(irq, keystone_timer_interrupt, IRQF_TIMER, + TIMER_NAME, event_dev); + if (error) { + pr_err("%s: failed to setup irq\n", __func__); + goto err; + } + + /* setup clockevent */ + event_dev->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; + event_dev->set_next_event = keystone_set_next_event; + event_dev->set_state_shutdown = keystone_shutdown; + event_dev->set_state_periodic = keystone_set_periodic; + event_dev->set_state_oneshot = keystone_shutdown; + event_dev->cpumask = cpu_possible_mask; + event_dev->owner = THIS_MODULE; + event_dev->name = TIMER_NAME; + event_dev->irq = irq; + + clockevents_config_and_register(event_dev, rate, 1, ULONG_MAX); + + pr_info("keystone timer clock @%lu Hz\n", rate); + return 0; +err: + clk_put(clk); + iounmap(timer.base); + return error; +} + +TIMER_OF_DECLARE(keystone_timer, "ti,keystone-timer", + keystone_timer_init); -- cgit v1.3.1