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, 235 insertions, 0 deletions

diff --git a/Documentation/gpu/afbc.rst b/Documentation/gpu/afbc.rst
new file mode 100644
index 000000000..4d38dc49d
--- /dev/null
+++ b/Documentation/gpu/afbc.rst
@@ -0,0 +1,235 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+===================================
+ Arm Framebuffer Compression (AFBC)
+===================================
+
+AFBC is a proprietary lossless image compression protocol and format.
+It provides fine-grained random access and minimizes the amount of
+data transferred between IP blocks.
+
+AFBC can be enabled on drivers which support it via use of the AFBC
+format modifiers defined in drm_fourcc.h. See DRM_FORMAT_MOD_ARM_AFBC(*).
+
+All users of the AFBC modifiers must follow the usage guidelines laid
+out in this document, to ensure compatibility across different AFBC
+producers and consumers.
+
+Components and Ordering
+=======================
+
+AFBC streams can contain several components - where a component
+corresponds to a color channel (i.e. R, G, B, X, A, Y, Cb, Cr).
+The assignment of input/output color channels must be consistent
+between the encoder and the decoder for correct operation, otherwise
+the consumer will interpret the decoded data incorrectly.
+
+Furthermore, when the lossless colorspace transform is used
+(AFBC_FORMAT_MOD_YTR, which should be enabled for RGB buffers for
+maximum compression efficiency), the component order must be:
+
+ * Component 0: R
+ * Component 1: G
+ * Component 2: B
+
+The component ordering is communicated via the fourcc code in the
+fourcc:modifier pair. In general, component '0' is considered to
+reside in the least-significant bits of the corresponding linear
+format. For example, COMP(bits):
+
+ * DRM_FORMAT_ABGR8888
+
+   * Component 0: R(8)
+   * Component 1: G(8)
+   * Component 2: B(8)
+   * Component 3: A(8)
+
+ * DRM_FORMAT_BGR888
+
+   * Component 0: R(8)
+   * Component 1: G(8)
+   * Component 2: B(8)
+
+ * DRM_FORMAT_YUYV
+
+   * Component 0: Y(8)
+   * Component 1: Cb(8, 2x1 subsampled)
+   * Component 2: Cr(8, 2x1 subsampled)
+
+In AFBC, 'X' components are not treated any differently from any other
+component. Therefore, an AFBC buffer with fourcc DRM_FORMAT_XBGR8888
+encodes with 4 components, like so:
+
+ * DRM_FORMAT_XBGR8888
+
+   * Component 0: R(8)
+   * Component 1: G(8)
+   * Component 2: B(8)
+   * Component 3: X(8)
+
+Please note, however, that the inclusion of a "wasted" 'X' channel is
+bad for compression efficiency, and so it's recommended to avoid
+formats containing 'X' bits. If a fourth component is
+required/expected by the encoder/decoder, then it is recommended to
+instead use an equivalent format with alpha, setting all alpha bits to
+'1'. If there is no requirement for a fourth component, then a format
+which doesn't include alpha can be used, e.g. DRM_FORMAT_BGR888.
+
+Number of Planes
+================
+
+Formats which are typically multi-planar in linear layouts (e.g. YUV
+420), can be encoded into one, or multiple, AFBC planes. As with
+component order, the encoder and decoder must agree about the number
+of planes in order to correctly decode the buffer. The fourcc code is
+used to determine the number of encoded planes in an AFBC buffer,
+matching the number of planes for the linear (unmodified) format.
+Within each plane, the component ordering also follows the fourcc
+code:
+
+For example:
+
+ * DRM_FORMAT_YUYV: nplanes = 1
+
+   * Plane 0:
+
+     * Component 0: Y(8)
+     * Component 1: Cb(8, 2x1 subsampled)
+     * Component 2: Cr(8, 2x1 subsampled)
+
+ * DRM_FORMAT_NV12: nplanes = 2
+
+   * Plane 0:
+
+     * Component 0: Y(8)
+
+   * Plane 1:
+
+     * Component 0: Cb(8, 2x1 subsampled)
+     * Component 1: Cr(8, 2x1 subsampled)
+
+Cross-device interoperability
+=============================
+
+For maximum compatibility across devices, the table below defines
+canonical formats for use between AFBC-enabled devices. Formats which
+are listed here must be used exactly as specified when using the AFBC
+modifiers. Formats which are not listed should be avoided.
+
+.. flat-table:: AFBC formats
+
+   * - Fourcc code
+     - Description
+     - Planes/Components
+
+   * - DRM_FORMAT_ABGR2101010
+     - 10-bit per component RGB, with 2-bit alpha
+     - Plane 0: 4 components
+              * Component 0: R(10)
+              * Component 1: G(10)
+              * Component 2: B(10)
+              * Component 3: A(2)
+
+   * - DRM_FORMAT_ABGR8888
+     - 8-bit per component RGB, with 8-bit alpha
+     - Plane 0: 4 components
+              * Component 0: R(8)
+              * Component 1: G(8)
+              * Component 2: B(8)
+              * Component 3: A(8)
+
+   * - DRM_FORMAT_BGR888
+     - 8-bit per component RGB
+     - Plane 0: 3 components
+              * Component 0: R(8)
+              * Component 1: G(8)
+              * Component 2: B(8)
+
+   * - DRM_FORMAT_BGR565
+     - 5/6-bit per component RGB
+     - Plane 0: 3 components
+              * Component 0: R(5)
+              * Component 1: G(6)
+              * Component 2: B(5)
+
+   * - DRM_FORMAT_ABGR1555
+     - 5-bit per component RGB, with 1-bit alpha
+     - Plane 0: 4 components
+              * Component 0: R(5)
+              * Component 1: G(5)
+              * Component 2: B(5)
+              * Component 3: A(1)
+
+   * - DRM_FORMAT_VUY888
+     - 8-bit per component YCbCr 444, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(8)
+              * Component 1: Cb(8)
+              * Component 2: Cr(8)
+
+   * - DRM_FORMAT_VUY101010
+     - 10-bit per component YCbCr 444, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(10)
+              * Component 1: Cb(10)
+              * Component 2: Cr(10)
+
+   * - DRM_FORMAT_YUYV
+     - 8-bit per component YCbCr 422, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(8)
+              * Component 1: Cb(8, 2x1 subsampled)
+              * Component 2: Cr(8, 2x1 subsampled)
+
+   * - DRM_FORMAT_NV16
+     - 8-bit per component YCbCr 422, two plane
+     - Plane 0: 1 component
+              * Component 0: Y(8)
+       Plane 1: 2 components
+              * Component 0: Cb(8, 2x1 subsampled)
+              * Component 1: Cr(8, 2x1 subsampled)
+
+   * - DRM_FORMAT_Y210
+     - 10-bit per component YCbCr 422, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(10)
+              * Component 1: Cb(10, 2x1 subsampled)
+              * Component 2: Cr(10, 2x1 subsampled)
+
+   * - DRM_FORMAT_P210
+     - 10-bit per component YCbCr 422, two plane
+     - Plane 0: 1 component
+              * Component 0: Y(10)
+       Plane 1: 2 components
+              * Component 0: Cb(10, 2x1 subsampled)
+              * Component 1: Cr(10, 2x1 subsampled)
+
+   * - DRM_FORMAT_YUV420_8BIT
+     - 8-bit per component YCbCr 420, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(8)
+              * Component 1: Cb(8, 2x2 subsampled)
+              * Component 2: Cr(8, 2x2 subsampled)
+
+   * - DRM_FORMAT_YUV420_10BIT
+     - 10-bit per component YCbCr 420, single plane
+     - Plane 0: 3 components
+              * Component 0: Y(10)
+              * Component 1: Cb(10, 2x2 subsampled)
+              * Component 2: Cr(10, 2x2 subsampled)
+
+   * - DRM_FORMAT_NV12
+     - 8-bit per component YCbCr 420, two plane
+     - Plane 0: 1 component
+              * Component 0: Y(8)
+       Plane 1: 2 components
+              * Component 0: Cb(8, 2x2 subsampled)
+              * Component 1: Cr(8, 2x2 subsampled)
+
+   * - DRM_FORMAT_P010
+     - 10-bit per component YCbCr 420, two plane
+     - Plane 0: 1 component
+              * Component 0: Y(10)
+       Plane 1: 2 components
+              * Component 0: Cb(10, 2x2 subsampled)
+              * Component 1: Cr(10, 2x2 subsampled)