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, 170 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/thermal.rst b/Documentation/gpu/amdgpu/thermal.rst
new file mode 100644
index 000000000..1768a106a
--- /dev/null
+++ b/Documentation/gpu/amdgpu/thermal.rst
@@ -0,0 +1,170 @@
+===========================================
+ GPU Power/Thermal Controls and Monitoring
+===========================================
+
+HWMON Interfaces
+================
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: hwmon
+
+GPU sysfs Power State Interfaces
+================================
+
+GPU power controls are exposed via sysfs files.
+
+power_dpm_state
+---------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: power_dpm_state
+
+power_dpm_force_performance_level
+---------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: power_dpm_force_performance_level
+
+pp_table
+--------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pp_table
+
+pp_od_clk_voltage
+-----------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pp_od_clk_voltage
+
+pp_dpm_*
+--------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pp_dpm_sclk pp_dpm_mclk pp_dpm_socclk pp_dpm_fclk pp_dpm_dcefclk pp_dpm_pcie
+
+pp_power_profile_mode
+---------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pp_power_profile_mode
+
+pm_policy
+---------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: pm_policy
+
+\*_busy_percent
+---------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: gpu_busy_percent
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: mem_busy_percent
+
+gpu_metrics
+-----------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: gpu_metrics
+
+fan_curve
+---------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: fan_curve
+
+acoustic_limit_rpm_threshold
+----------------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: acoustic_limit_rpm_threshold
+
+acoustic_target_rpm_threshold
+-----------------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: acoustic_target_rpm_threshold
+
+fan_target_temperature
+----------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: fan_target_temperature
+
+fan_minimum_pwm
+---------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: fan_minimum_pwm
+
+fan_zero_rpm_enable
+----------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: fan_zero_rpm_enable
+
+fan_zero_rpm_stop_temperature
+-----------------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
+   :doc: fan_zero_rpm_stop_temperature
+
+GFXOFF
+======
+
+GFXOFF is a feature found in most recent GPUs that saves power at runtime. The
+card's RLC (RunList Controller) firmware powers off the gfx engine
+dynamically when there is no workload on gfx or compute pipes. GFXOFF is on by
+default on supported GPUs.
+
+Userspace can interact with GFXOFF through a debugfs interface (all values in
+`uint32_t`, unless otherwise noted):
+
+``amdgpu_gfxoff``
+-----------------
+
+Use it to enable/disable GFXOFF, and to check if it's current enabled/disabled::
+
+  $ xxd -l1 -p /sys/kernel/debug/dri/0/amdgpu_gfxoff
+  01
+
+- Write 0 to disable it, and 1 to enable it.
+- Read 0 means it's disabled, 1 it's enabled.
+
+If it's enabled, that means that the GPU is free to enter into GFXOFF mode as
+needed. Disabled means that it will never enter GFXOFF mode.
+
+``amdgpu_gfxoff_status``
+------------------------
+
+Read it to check current GFXOFF's status of a GPU::
+
+  $ xxd -l1 -p /sys/kernel/debug/dri/0/amdgpu_gfxoff_status
+  02
+
+- 0: GPU is in GFXOFF state, the gfx engine is powered down.
+- 1: Transition out of GFXOFF state
+- 2: Not in GFXOFF state
+- 3: Transition into GFXOFF state
+
+If GFXOFF is enabled, the value will be transitioning around [0, 3], always
+getting into 0 when possible. When it's disabled, it's always at 2. Returns
+``-EINVAL`` if it's not supported.
+
+``amdgpu_gfxoff_count``
+-----------------------
+
+Read it to get the total GFXOFF entry count at the time of query since system
+power-up. The value is an `uint64_t` type, however, due to firmware limitations,
+it can currently overflow as an `uint32_t`. *Only supported in vangogh*
+
+``amdgpu_gfxoff_residency``
+---------------------------
+
+Write 1 to amdgpu_gfxoff_residency to start logging, and 0 to stop. Read it to
+get average GFXOFF residency % multiplied by 100 during the last logging
+interval. E.g. a value of 7854 means 78.54% of the time in the last logging
+interval the GPU was in GFXOFF mode. *Only supported in vangogh*