x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 459 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-fttmr010.c b/drivers/clocksource/timer-fttmr010.c
new file mode 100644
index 000000000..308f94bfb
--- /dev/null
+++ b/drivers/clocksource/timer-fttmr010.c
@@ -0,0 +1,459 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Faraday Technology FTTMR010 timer driver
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * Based on a rewrite of arch/arm/mach-gemini/timer.c:
+ * Copyright (C) 2001-2006 Storlink, Corp.
+ * Copyright (C) 2008-2009 Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
+ */
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
+#include <linux/clk.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+
+/*
+ * Register definitions common for all the timer variants.
+ */
+#define TIMER1_COUNT		(0x00)
+#define TIMER1_LOAD		(0x04)
+#define TIMER1_MATCH1		(0x08)
+#define TIMER1_MATCH2		(0x0c)
+#define TIMER2_COUNT		(0x10)
+#define TIMER2_LOAD		(0x14)
+#define TIMER2_MATCH1		(0x18)
+#define TIMER2_MATCH2		(0x1c)
+#define TIMER3_COUNT		(0x20)
+#define TIMER3_LOAD		(0x24)
+#define TIMER3_MATCH1		(0x28)
+#define TIMER3_MATCH2		(0x2c)
+#define TIMER_CR		(0x30)
+
+/*
+ * Control register set to clear for ast2600 only.
+ */
+#define AST2600_TIMER_CR_CLR	(0x3c)
+
+/*
+ * Control register (TMC30) bit fields for fttmr010/gemini/moxart timers.
+ */
+#define TIMER_1_CR_ENABLE	BIT(0)
+#define TIMER_1_CR_CLOCK	BIT(1)
+#define TIMER_1_CR_INT		BIT(2)
+#define TIMER_2_CR_ENABLE	BIT(3)
+#define TIMER_2_CR_CLOCK	BIT(4)
+#define TIMER_2_CR_INT		BIT(5)
+#define TIMER_3_CR_ENABLE	BIT(6)
+#define TIMER_3_CR_CLOCK	BIT(7)
+#define TIMER_3_CR_INT		BIT(8)
+#define TIMER_1_CR_UPDOWN	BIT(9)
+#define TIMER_2_CR_UPDOWN	BIT(10)
+#define TIMER_3_CR_UPDOWN	BIT(11)
+
+/*
+ * Control register (TMC30) bit fields for aspeed ast2400/ast2500 timers.
+ * The aspeed timers move bits around in the control register and lacks
+ * bits for setting the timer to count upwards.
+ */
+#define TIMER_1_CR_ASPEED_ENABLE	BIT(0)
+#define TIMER_1_CR_ASPEED_CLOCK		BIT(1)
+#define TIMER_1_CR_ASPEED_INT		BIT(2)
+#define TIMER_2_CR_ASPEED_ENABLE	BIT(4)
+#define TIMER_2_CR_ASPEED_CLOCK		BIT(5)
+#define TIMER_2_CR_ASPEED_INT		BIT(6)
+#define TIMER_3_CR_ASPEED_ENABLE	BIT(8)
+#define TIMER_3_CR_ASPEED_CLOCK		BIT(9)
+#define TIMER_3_CR_ASPEED_INT		BIT(10)
+
+/*
+ * Interrupt status/mask register definitions for fttmr010/gemini/moxart
+ * timers.
+ * The registers don't exist and they are not needed on aspeed timers
+ * because:
+ *   - aspeed timer overflow interrupt is controlled by bits in Control
+ *     Register (TMC30).
+ *   - aspeed timers always generate interrupt when either one of the
+ *     Match registers equals to Status register.
+ */
+#define TIMER_INTR_STATE	(0x34)
+#define TIMER_INTR_MASK		(0x38)
+#define TIMER_1_INT_MATCH1	BIT(0)
+#define TIMER_1_INT_MATCH2	BIT(1)
+#define TIMER_1_INT_OVERFLOW	BIT(2)
+#define TIMER_2_INT_MATCH1	BIT(3)
+#define TIMER_2_INT_MATCH2	BIT(4)
+#define TIMER_2_INT_OVERFLOW	BIT(5)
+#define TIMER_3_INT_MATCH1	BIT(6)
+#define TIMER_3_INT_MATCH2	BIT(7)
+#define TIMER_3_INT_OVERFLOW	BIT(8)
+#define TIMER_INT_ALL_MASK	0x1ff
+
+struct fttmr010 {
+	void __iomem *base;
+	unsigned int tick_rate;
+	bool is_aspeed;
+	u32 t1_enable_val;
+	struct clock_event_device clkevt;
+	int (*timer_shutdown)(struct clock_event_device *evt);
+#ifdef CONFIG_ARM
+	struct delay_timer delay_timer;
+#endif
+};
+
+/*
+ * A local singleton used by sched_clock and delay timer reads, which are
+ * fast and stateless
+ */
+static struct fttmr010 *local_fttmr;
+
+static inline struct fttmr010 *to_fttmr010(struct clock_event_device *evt)
+{
+	return container_of(evt, struct fttmr010, clkevt);
+}
+
+static unsigned long fttmr010_read_current_timer_up(void)
+{
+	return readl(local_fttmr->base + TIMER2_COUNT);
+}
+
+static unsigned long fttmr010_read_current_timer_down(void)
+{
+	return ~readl(local_fttmr->base + TIMER2_COUNT);
+}
+
+static u64 notrace fttmr010_read_sched_clock_up(void)
+{
+	return fttmr010_read_current_timer_up();
+}
+
+static u64 notrace fttmr010_read_sched_clock_down(void)
+{
+	return fttmr010_read_current_timer_down();
+}
+
+static int fttmr010_timer_set_next_event(unsigned long cycles,
+				       struct clock_event_device *evt)
+{
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+	u32 cr;
+
+	/* Stop */
+	fttmr010->timer_shutdown(evt);
+
+	if (fttmr010->is_aspeed) {
+		/*
+		 * ASPEED Timer Controller will load TIMER1_LOAD register
+		 * into TIMER1_COUNT register when the timer is re-enabled.
+		 */
+		writel(cycles, fttmr010->base + TIMER1_LOAD);
+	} else {
+		/* Setup the match register forward in time */
+		cr = readl(fttmr010->base + TIMER1_COUNT);
+		writel(cr + cycles, fttmr010->base + TIMER1_MATCH1);
+	}
+
+	/* Start */
+	cr = readl(fttmr010->base + TIMER_CR);
+	cr |= fttmr010->t1_enable_val;
+	writel(cr, fttmr010->base + TIMER_CR);
+
+	return 0;
+}
+
+static int ast2600_timer_shutdown(struct clock_event_device *evt)
+{
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+
+	/* Stop */
+	writel(fttmr010->t1_enable_val, fttmr010->base + AST2600_TIMER_CR_CLR);
+
+	return 0;
+}
+
+static int fttmr010_timer_shutdown(struct clock_event_device *evt)
+{
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+	u32 cr;
+
+	/* Stop */
+	cr = readl(fttmr010->base + TIMER_CR);
+	cr &= ~fttmr010->t1_enable_val;
+	writel(cr, fttmr010->base + TIMER_CR);
+
+	return 0;
+}
+
+static int fttmr010_timer_set_oneshot(struct clock_event_device *evt)
+{
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+	u32 cr;
+
+	/* Stop */
+	fttmr010->timer_shutdown(evt);
+
+	/* Setup counter start from 0 or ~0 */
+	writel(0, fttmr010->base + TIMER1_COUNT);
+	if (fttmr010->is_aspeed) {
+		writel(~0, fttmr010->base + TIMER1_LOAD);
+	} else {
+		writel(0, fttmr010->base + TIMER1_LOAD);
+
+		/* Enable interrupt */
+		cr = readl(fttmr010->base + TIMER_INTR_MASK);
+		cr &= ~(TIMER_1_INT_OVERFLOW | TIMER_1_INT_MATCH2);
+		cr |= TIMER_1_INT_MATCH1;
+		writel(cr, fttmr010->base + TIMER_INTR_MASK);
+	}
+
+	return 0;
+}
+
+static int fttmr010_timer_set_periodic(struct clock_event_device *evt)
+{
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+	u32 period = DIV_ROUND_CLOSEST(fttmr010->tick_rate, HZ);
+	u32 cr;
+
+	/* Stop */
+	fttmr010->timer_shutdown(evt);
+
+	/* Setup timer to fire at 1/HZ intervals. */
+	if (fttmr010->is_aspeed) {
+		writel(period, fttmr010->base + TIMER1_LOAD);
+	} else {
+		cr = 0xffffffff - (period - 1);
+		writel(cr, fttmr010->base + TIMER1_COUNT);
+		writel(cr, fttmr010->base + TIMER1_LOAD);
+
+		/* Enable interrupt on overflow */
+		cr = readl(fttmr010->base + TIMER_INTR_MASK);
+		cr &= ~(TIMER_1_INT_MATCH1 | TIMER_1_INT_MATCH2);
+		cr |= TIMER_1_INT_OVERFLOW;
+		writel(cr, fttmr010->base + TIMER_INTR_MASK);
+	}
+
+	/* Start the timer */
+	cr = readl(fttmr010->base + TIMER_CR);
+	cr |= fttmr010->t1_enable_val;
+	writel(cr, fttmr010->base + TIMER_CR);
+
+	return 0;
+}
+
+/*
+ * IRQ handler for the timer
+ */
+static irqreturn_t fttmr010_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	evt->event_handler(evt);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t ast2600_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+	struct fttmr010 *fttmr010 = to_fttmr010(evt);
+
+	writel(0x1, fttmr010->base + TIMER_INTR_STATE);
+
+	evt->event_handler(evt);
+	return IRQ_HANDLED;
+}
+
+static int __init fttmr010_common_init(struct device_node *np,
+				       bool is_aspeed, bool is_ast2600)
+{
+	struct fttmr010 *fttmr010;
+	int irq;
+	struct clk *clk;
+	int ret;
+	u32 val;
+
+	/*
+	 * These implementations require a clock reference.
+	 * FIXME: we currently only support clocking using PCLK
+	 * and using EXTCLK is not supported in the driver.
+	 */
+	clk = of_clk_get_by_name(np, "PCLK");
+	if (IS_ERR(clk)) {
+		pr_err("could not get PCLK\n");
+		return PTR_ERR(clk);
+	}
+	ret = clk_prepare_enable(clk);
+	if (ret) {
+		pr_err("failed to enable PCLK\n");
+		return ret;
+	}
+
+	fttmr010 = kzalloc_obj(*fttmr010);
+	if (!fttmr010) {
+		ret = -ENOMEM;
+		goto out_disable_clock;
+	}
+	fttmr010->tick_rate = clk_get_rate(clk);
+
+	fttmr010->base = of_iomap(np, 0);
+	if (!fttmr010->base) {
+		pr_err("Can't remap registers\n");
+		ret = -ENXIO;
+		goto out_free;
+	}
+	/* IRQ for timer 1 */
+	irq = irq_of_parse_and_map(np, 0);
+	if (irq <= 0) {
+		pr_err("Can't parse IRQ\n");
+		ret = -EINVAL;
+		goto out_unmap;
+	}
+
+	/*
+	 * The Aspeed timers move bits around in the control register.
+	 */
+	if (is_aspeed) {
+		fttmr010->t1_enable_val = TIMER_1_CR_ASPEED_ENABLE |
+			TIMER_1_CR_ASPEED_INT;
+		fttmr010->is_aspeed = true;
+	} else {
+		fttmr010->t1_enable_val = TIMER_1_CR_ENABLE | TIMER_1_CR_INT;
+
+		/*
+		 * Reset the interrupt mask and status
+		 */
+		writel(TIMER_INT_ALL_MASK, fttmr010->base + TIMER_INTR_MASK);
+		writel(0, fttmr010->base + TIMER_INTR_STATE);
+	}
+
+	/*
+	 * Enable timer 1 count up, timer 2 count up, except on Aspeed,
+	 * where everything just counts down.
+	 */
+	if (is_aspeed)
+		val = TIMER_2_CR_ASPEED_ENABLE;
+	else {
+		val = TIMER_2_CR_ENABLE | TIMER_1_CR_UPDOWN |
+			TIMER_2_CR_UPDOWN;
+	}
+	writel(val, fttmr010->base + TIMER_CR);
+
+	/*
+	 * Setup free-running clocksource timer (interrupts
+	 * disabled.)
+	 */
+	local_fttmr = fttmr010;
+	writel(0, fttmr010->base + TIMER2_COUNT);
+	writel(0, fttmr010->base + TIMER2_MATCH1);
+	writel(0, fttmr010->base + TIMER2_MATCH2);
+
+	if (fttmr010->is_aspeed) {
+		writel(~0, fttmr010->base + TIMER2_LOAD);
+		clocksource_mmio_init(fttmr010->base + TIMER2_COUNT,
+				      "FTTMR010-TIMER2",
+				      fttmr010->tick_rate,
+				      300, 32, clocksource_mmio_readl_down);
+		sched_clock_register(fttmr010_read_sched_clock_down, 32,
+				     fttmr010->tick_rate);
+	} else {
+		writel(0, fttmr010->base + TIMER2_LOAD);
+		clocksource_mmio_init(fttmr010->base + TIMER2_COUNT,
+				      "FTTMR010-TIMER2",
+				      fttmr010->tick_rate,
+				      300, 32, clocksource_mmio_readl_up);
+		sched_clock_register(fttmr010_read_sched_clock_up, 32,
+				     fttmr010->tick_rate);
+	}
+
+	/*
+	 * Setup clockevent timer (interrupt-driven) on timer 1.
+	 */
+	writel(0, fttmr010->base + TIMER1_COUNT);
+	writel(0, fttmr010->base + TIMER1_LOAD);
+	writel(0, fttmr010->base + TIMER1_MATCH1);
+	writel(0, fttmr010->base + TIMER1_MATCH2);
+
+	if (is_ast2600) {
+		fttmr010->timer_shutdown = ast2600_timer_shutdown;
+		ret = request_irq(irq, ast2600_timer_interrupt,
+				  IRQF_TIMER, "FTTMR010-TIMER1",
+				  &fttmr010->clkevt);
+	} else {
+		fttmr010->timer_shutdown = fttmr010_timer_shutdown;
+		ret = request_irq(irq, fttmr010_timer_interrupt,
+				  IRQF_TIMER, "FTTMR010-TIMER1",
+				  &fttmr010->clkevt);
+	}
+	if (ret) {
+		pr_err("FTTMR010-TIMER1 no IRQ\n");
+		goto out_unmap;
+	}
+
+	fttmr010->clkevt.name = "FTTMR010-TIMER1";
+	/* Reasonably fast and accurate clock event */
+	fttmr010->clkevt.rating = 300;
+	fttmr010->clkevt.features = CLOCK_EVT_FEAT_PERIODIC |
+		CLOCK_EVT_FEAT_ONESHOT;
+	fttmr010->clkevt.set_next_event = fttmr010_timer_set_next_event;
+	fttmr010->clkevt.set_state_shutdown = fttmr010->timer_shutdown;
+	fttmr010->clkevt.set_state_periodic = fttmr010_timer_set_periodic;
+	fttmr010->clkevt.set_state_oneshot = fttmr010_timer_set_oneshot;
+	fttmr010->clkevt.tick_resume = fttmr010->timer_shutdown;
+	fttmr010->clkevt.cpumask = cpumask_of(0);
+	fttmr010->clkevt.irq = irq;
+	clockevents_config_and_register(&fttmr010->clkevt,
+					fttmr010->tick_rate,
+					1, 0xffffffff);
+
+#ifdef CONFIG_ARM
+	/* Also use this timer for delays */
+	if (fttmr010->is_aspeed)
+		fttmr010->delay_timer.read_current_timer =
+			fttmr010_read_current_timer_down;
+	else
+		fttmr010->delay_timer.read_current_timer =
+			fttmr010_read_current_timer_up;
+	fttmr010->delay_timer.freq = fttmr010->tick_rate;
+	register_current_timer_delay(&fttmr010->delay_timer);
+#endif
+
+	return 0;
+
+out_unmap:
+	iounmap(fttmr010->base);
+out_free:
+	kfree(fttmr010);
+out_disable_clock:
+	clk_disable_unprepare(clk);
+
+	return ret;
+}
+
+static __init int ast2600_timer_init(struct device_node *np)
+{
+	return fttmr010_common_init(np, true, true);
+}
+
+static __init int aspeed_timer_init(struct device_node *np)
+{
+	return fttmr010_common_init(np, true, false);
+}
+
+static __init int fttmr010_timer_init(struct device_node *np)
+{
+	return fttmr010_common_init(np, false, false);
+}
+
+TIMER_OF_DECLARE(fttmr010, "faraday,fttmr010", fttmr010_timer_init);
+TIMER_OF_DECLARE(gemini, "cortina,gemini-timer", fttmr010_timer_init);
+TIMER_OF_DECLARE(moxart, "moxa,moxart-timer", fttmr010_timer_init);
+TIMER_OF_DECLARE(ast2400, "aspeed,ast2400-timer", aspeed_timer_init);
+TIMER_OF_DECLARE(ast2500, "aspeed,ast2500-timer", aspeed_timer_init);
+TIMER_OF_DECLARE(ast2600, "aspeed,ast2600-timer", ast2600_timer_init);