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-sp.h | 63 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 drivers/clocksource/timer-sp.h (limited to 'drivers/clocksource/timer-sp.h') diff --git a/drivers/clocksource/timer-sp.h b/drivers/clocksource/timer-sp.h new file mode 100644 index 000000000..811f840be --- /dev/null +++ b/drivers/clocksource/timer-sp.h @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * ARM timer implementation, found in Integrator, Versatile and Realview + * platforms. Not all platforms support all registers and bits in these + * registers, so we mark them with A for Integrator AP, C for Integrator + * CP, V for Versatile and R for Realview. + * + * Integrator AP has 16-bit timers, Integrator CP, Versatile and Realview + * can have 16-bit or 32-bit selectable via a bit in the control register. + * + * Every SP804 contains two identical timers. + */ +#define NR_TIMERS 2 +#define TIMER_1_BASE 0x00 +#define TIMER_2_BASE 0x20 + +#define TIMER_LOAD 0x00 /* ACVR rw */ +#define TIMER_VALUE 0x04 /* ACVR ro */ +#define TIMER_CTRL 0x08 /* ACVR rw */ +#define TIMER_CTRL_ONESHOT (1 << 0) /* CVR */ +#define TIMER_CTRL_32BIT (1 << 1) /* CVR */ +#define TIMER_CTRL_DIV1 (0 << 2) /* ACVR */ +#define TIMER_CTRL_DIV16 (1 << 2) /* ACVR */ +#define TIMER_CTRL_DIV256 (2 << 2) /* ACVR */ +#define TIMER_CTRL_IE (1 << 5) /* VR */ +#define TIMER_CTRL_PERIODIC (1 << 6) /* ACVR */ +#define TIMER_CTRL_ENABLE (1 << 7) /* ACVR */ + +#define TIMER_INTCLR 0x0c /* ACVR wo */ +#define TIMER_RIS 0x10 /* CVR ro */ +#define TIMER_MIS 0x14 /* CVR ro */ +#define TIMER_BGLOAD 0x18 /* CVR rw */ + +struct sp804_timer { + int load; + int load_h; + int value; + int value_h; + int ctrl; + int intclr; + int ris; + int mis; + int bgload; + int bgload_h; + int timer_base[NR_TIMERS]; + int width; +}; + +struct sp804_clkevt { + void __iomem *base; + void __iomem *load; + void __iomem *load_h; + void __iomem *value; + void __iomem *value_h; + void __iomem *ctrl; + void __iomem *intclr; + void __iomem *ris; + void __iomem *mis; + void __iomem *bgload; + void __iomem *bgload_h; + unsigned long reload; + int width; +}; -- cgit v1.3.1