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, 101 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/c3-isp.rst b/Documentation/admin-guide/media/c3-isp.rst
new file mode 100644
index 000000000..ac508b8c6
--- /dev/null
+++ b/Documentation/admin-guide/media/c3-isp.rst
@@ -0,0 +1,101 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR MIT)
+
+.. include:: <isonum.txt>
+
+=================================================
+Amlogic C3 Image Signal Processing (C3ISP) driver
+=================================================
+
+Introduction
+============
+
+This file documents the Amlogic C3ISP driver located under
+drivers/media/platform/amlogic/c3/isp.
+
+The current version of the driver supports the C3ISP found on
+Amlogic C308L processor.
+
+The driver implements V4L2, Media controller and V4L2 subdev interfaces.
+Camera sensor using V4L2 subdev interface in the kernel is supported.
+
+The driver has been tested on AW419-C308L-Socket platform.
+
+Amlogic C3 ISP
+==============
+
+The Camera hardware found on C308L processors and supported by
+the driver consists of:
+
+- 1 MIPI-CSI-2 module: handles the physical layer of the MIPI CSI-2 receiver and
+  receives data from the connected camera sensor.
+- 1 MIPI-ADAPTER module: organizes MIPI data to meet ISP input requirements and
+  send MIPI data to ISP.
+- 1 ISP (Image Signal Processing) module: contains a pipeline of image processing
+  hardware blocks. The ISP pipeline contains three resizers at the end each of
+  them connected to a DMA interface which writes the output data to memory.
+
+A high-level functional view of the C3 ISP is presented below.::
+
+                                                                   +----------+    +-------+
+                                                                   | Resizer  |--->| WRMIF |
+  +---------+    +------------+    +--------------+    +-------+   |----------+    +-------+
+  | Sensor  |--->| MIPI CSI-2 |--->| MIPI ADAPTER |--->|  ISP  |---|----------+    +-------+
+  +---------+    +------------+    +--------------+    +-------+   | Resizer  |--->| WRMIF |
+                                                                   +----------+    +-------+
+                                                                   |----------+    +-------+
+                                                                   | Resizer  |--->| WRMIF |
+                                                                   +----------+    +-------+
+
+Driver architecture and design
+==============================
+
+With the goal to model the hardware links between the modules and to expose a
+clean, logical and usable interface, the driver registers the following V4L2
+sub-devices:
+
+- 1 `c3-mipi-csi2` sub-device - the MIPI CSI-2 receiver
+- 1 `c3-mipi-adapter` sub-device - the MIPI adapter
+- 1 `c3-isp-core` sub-device - the ISP core
+- 3 `c3-isp-resizer` sub-devices - the ISP resizers
+
+The `c3-isp-core` sub-device is linked to 2 video device nodes for statistics
+capture and parameters programming:
+
+- the `c3-isp-stats` capture video device node for statistics capture
+- the `c3-isp-params` output video device for parameters programming
+
+Each `c3-isp-resizer` sub-device is linked to a capture video device node where
+frames are captured from:
+
+- `c3-isp-resizer0` is linked to the `c3-isp-cap0` capture video device
+- `c3-isp-resizer1` is linked to the `c3-isp-cap1` capture video device
+- `c3-isp-resizer2` is linked to the `c3-isp-cap2` capture video device
+
+The media controller pipeline graph is as follows (with connected a
+IMX290 camera sensor):
+
+.. _isp_topology_graph:
+
+.. kernel-figure:: c3-isp.dot
+    :alt:   c3-isp.dot
+    :align: center
+
+    Media pipeline topology
+
+Implementation
+==============
+
+Runtime configuration of the ISP hardware is performed on the `c3-isp-params`
+video device node using the :ref:`V4L2_META_FMT_C3ISP_PARAMS
+<v4l2-meta-fmt-c3isp-params>` as data format. The buffer structure is defined by
+:c:type:`c3_isp_params_cfg`.
+
+Statistics are captured from the `c3-isp-stats` video device node using the
+:ref:`V4L2_META_FMT_C3ISP_STATS <v4l2-meta-fmt-c3isp-stats>` data format.
+
+The final picture size and format is configured using the V4L2 video
+capture interface on the `c3-isp-cap[0, 2]` video device nodes.
+
+The Amlogic C3 ISP is supported by `libcamera <https://libcamera.org>`_ with a
+dedicated pipeline handler and algorithms that perform run-time image correction
+and enhancement.