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, 108 insertions, 0 deletions

diff --git a/Documentation/gpu/vc4.rst b/Documentation/gpu/vc4.rst
new file mode 100644
index 000000000..5e5e92e40
--- /dev/null
+++ b/Documentation/gpu/vc4.rst
@@ -0,0 +1,108 @@
+=====================================
+ drm/vc4 Broadcom VC4 Graphics Driver
+=====================================
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_drv.c
+   :doc: Broadcom VC4 Graphics Driver
+
+Display Hardware Handling
+=========================
+
+This section covers everything related to the display hardware including
+the mode setting infrastructure, plane, sprite and cursor handling and
+display, output probing and related topics.
+
+Pixel Valve (DRM CRTC)
+----------------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_crtc.c
+   :doc: VC4 CRTC module
+
+HVS
+---
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_hvs.c
+   :doc: VC4 HVS module.
+
+HVS planes
+----------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_plane.c
+   :doc: VC4 plane module
+
+HDMI encoder
+------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_hdmi.c
+   :doc: VC4 Falcon HDMI module
+
+DSI encoder
+-----------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_dsi.c
+   :doc: VC4 DSI0/DSI1 module
+
+DPI encoder
+-----------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_dpi.c
+   :doc: VC4 DPI module
+
+VEC (Composite TV out) encoder
+------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_vec.c
+   :doc: VC4 SDTV module
+
+KUnit Tests
+===========
+
+The VC4 Driver uses KUnit to perform driver-specific unit and
+integration tests.
+
+These tests are using a mock driver and can be ran using the
+command below, on either arm or arm64 architectures,
+
+.. code-block:: bash
+
+	$ ./tools/testing/kunit/kunit.py run \
+		--kunitconfig=drivers/gpu/drm/vc4/tests/.kunitconfig \
+		--cross_compile aarch64-linux-gnu- --arch arm64
+
+Parts of the driver that are currently covered by tests are:
+ * The HVS to PixelValve dynamic FIFO assignment, for the BCM2835-7
+   and BCM2711.
+
+Memory Management and 3D Command Submission
+===========================================
+
+This section covers the GEM implementation in the vc4 driver.
+
+GPU buffer object (BO) management
+---------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_bo.c
+   :doc: VC4 GEM BO management support
+
+V3D binner command list (BCL) validation
+----------------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_validate.c
+   :doc: Command list validator for VC4.
+
+V3D render command list (RCL) generation
+----------------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_render_cl.c
+   :doc: Render command list generation
+
+Shader validator for VC4
+---------------------------
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_validate_shaders.c
+   :doc: Shader validator for VC4.
+
+V3D Interrupts
+--------------
+
+.. kernel-doc:: drivers/gpu/drm/vc4/vc4_irq.c
+   :doc: Interrupt management for the V3D engine