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 --- Documentation/ABI/testing/sysfs-class-powercap | 152 +++++++++++++++++++++++++ 1 file changed, 152 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-powercap (limited to 'Documentation/ABI/testing/sysfs-class-powercap') diff --git a/Documentation/ABI/testing/sysfs-class-powercap b/Documentation/ABI/testing/sysfs-class-powercap new file mode 100644 index 000000000..ca491ec4e --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-powercap @@ -0,0 +1,152 @@ +What: /sys/class/powercap/ +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + The powercap/ class sub directory belongs to the power cap + subsystem. Refer to + Documentation/power/powercap/powercap.rst for details. + +What: /sys/class/powercap/ +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + A is a unique name under /sys/class/powercap. + Here determines how the power is going to be + controlled. A can contain multiple power zones. + +What: /sys/class/powercap//enabled +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + This allows to enable/disable power capping for a "control type". + This status affects every power zone using this "control_type. + +What: /sys/class/powercap// +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + A power zone is a single or a collection of devices, which can + be independently monitored and controlled. A power zone sysfs + entry is qualified with the name of the . + E.g. intel-rapl:0:1:1. + +What: /sys/class/powercap/// +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Power zones may be organized in a hierarchy in which child + power zones provide monitoring and control for a subset of + devices under the parent. For example, if there is a parent + power zone for a whole CPU package, each CPU core in it can + be a child power zone. + +What: /sys/class/powercap/...//name +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Specifies the name of this power zone. + +What: /sys/class/powercap/...//energy_uj +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Current energy counter in micro-joules. Write "0" to reset. + If the counter can not be reset, then this attribute is + read-only. + +What: /sys/class/powercap/...//max_energy_range_uj +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Range of the above energy counter in micro-joules. + + +What: /sys/class/powercap/...//power_uw +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Current power in micro-watts. + +What: /sys/class/powercap/...//max_power_range_uw +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Range of the above power value in micro-watts. + +What: /sys/class/powercap/...//constraint_X_name +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Each power zone can define one or more constraints. Each + constraint can have an optional name. Here "X" can have values + from 0 to max integer. + +What: /sys/class/powercap/...//constraint_X_power_limit_uw +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Power limit in micro-watts should be applicable for + the time window specified by "constraint_X_time_window_us". + Here "X" can have values from 0 to max integer. + +What: /sys/class/powercap/...//constraint_X_time_window_us +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Time window in micro seconds. This is used along with + constraint_X_power_limit_uw to define a power constraint. + Here "X" can have values from 0 to max integer. + + +What: /sys/class/powercap//.../constraint_X_max_power_uw +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Maximum allowed power in micro watts for this constraint. + Here "X" can have values from 0 to max integer. + +What: /sys/class/powercap//.../constraint_X_min_power_uw +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Minimum allowed power in micro watts for this constraint. + Here "X" can have values from 0 to max integer. + +What: /sys/class/powercap/...//constraint_X_max_time_window_us +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Maximum allowed time window in micro seconds for this + constraint. Here "X" can have values from 0 to max integer. + +What: /sys/class/powercap/...//constraint_X_min_time_window_us +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + Minimum allowed time window in micro seconds for this + constraint. Here "X" can have values from 0 to max integer. + +What: /sys/class/powercap/...//enabled +Date: September 2013 +KernelVersion: 3.13 +Contact: linux-pm@vger.kernel.org +Description: + This allows to enable/disable power capping at power zone level. + This applies to current power zone and its children. -- cgit v1.3.1