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, 111 insertions, 0 deletions

diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
new file mode 100644
index 000000000..f4058e8e9
--- /dev/null
+++ b/Documentation/trace/index.rst
@@ -0,0 +1,111 @@
+================================
+Linux Tracing Technologies Guide
+================================
+
+Tracing in the Linux kernel is a powerful mechanism that allows
+developers and system administrators to analyze and debug system
+behavior. This guide provides documentation on various tracing
+frameworks and tools available in the Linux kernel.
+
+Introduction to Tracing
+-----------------------
+
+This section provides an overview of Linux tracing mechanisms
+and debugging approaches.
+
+.. toctree::
+   :maxdepth: 1
+
+   debugging
+   tracepoints
+   tracepoint-analysis
+   ring-buffer-map
+
+Core Tracing Frameworks
+-----------------------
+
+The following are the primary tracing frameworks integrated into
+the Linux kernel.
+
+.. toctree::
+   :maxdepth: 1
+
+   ftrace
+   ftrace-design
+   ftrace-uses
+   kprobes
+   kprobetrace
+   fprobetrace
+   eprobetrace
+   fprobe
+   ring-buffer-design
+
+Event Tracing and Analysis
+--------------------------
+
+A detailed explanation of event tracing mechanisms and their
+applications.
+
+.. toctree::
+   :maxdepth: 1
+
+   events
+   events-kmem
+   events-power
+   events-nmi
+   events-msr
+   events-landlock
+   events-pci
+   events-pci-controller
+   boottime-trace
+   histogram
+   histogram-design
+
+Hardware and Performance Tracing
+--------------------------------
+
+This section covers tracing features that monitor hardware
+interactions and system performance.
+
+.. toctree::
+   :maxdepth: 1
+
+   intel_th
+   stm
+   sys-t
+   coresight/index
+   rv/index
+   hisi-ptt
+   mmiotrace
+   hwlat_detector
+   osnoise-tracer
+   timerlat-tracer
+
+User-Space Tracing
+------------------
+
+These tools allow tracing user-space applications and
+interactions.
+
+.. toctree::
+   :maxdepth: 1
+
+   user_events
+   uprobetracer
+
+Remote Tracing
+--------------
+
+This section covers the framework to read compatible ring-buffers, written by
+entities outside of the kernel (most likely firmware or hypervisor)
+
+.. toctree::
+   :maxdepth: 1
+
+   remotes
+
+Additional Resources
+--------------------
+
+For more details, refer to the respective documentation of each
+tracing tool and framework.