From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- include/drm/drm_debugfs.h | 197 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 197 insertions(+) create mode 100644 include/drm/drm_debugfs.h (limited to 'include/drm/drm_debugfs.h') diff --git a/include/drm/drm_debugfs.h b/include/drm/drm_debugfs.h new file mode 100644 index 000000000..eb93512b0 --- /dev/null +++ b/include/drm/drm_debugfs.h @@ -0,0 +1,197 @@ +/* + * Internal Header for the Direct Rendering Manager + * + * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. + * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. + * Copyright (c) 2009-2010, Code Aurora Forum. + * All rights reserved. + * + * Author: Rickard E. (Rik) Faith + * Author: Gareth Hughes + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR + * OTHER DEALINGS IN THE SOFTWARE. + */ + +#ifndef _DRM_DEBUGFS_H_ +#define _DRM_DEBUGFS_H_ + +#include +#include + +#include + +/** + * DRM_DEBUGFS_GPUVA_INFO - &drm_info_list entry to dump a GPU VA space + * @show: the &drm_info_list's show callback + * @data: driver private data + * + * Drivers should use this macro to define a &drm_info_list entry to provide a + * debugfs file for dumping the GPU VA space regions and mappings. + * + * For each DRM GPU VA space drivers should call drm_debugfs_gpuva_info() from + * their @show callback. + */ +#define DRM_DEBUGFS_GPUVA_INFO(show, data) {"gpuvas", show, 0, data} + +/** + * struct drm_info_list - debugfs info list entry + * + * This structure represents a debugfs file to be created by the drm + * core. + */ +struct drm_info_list { + /** @name: file name */ + const char *name; + /** + * @show: + * + * Show callback. &seq_file->private will be set to the &struct + * drm_info_node corresponding to the instance of this info on a given + * &struct drm_minor. + */ + int (*show)(struct seq_file*, void*); + /** @driver_features: Required driver features for this entry */ + u32 driver_features; + /** @data: Driver-private data, should not be device-specific. */ + void *data; +}; + +/** + * struct drm_info_node - Per-minor debugfs node structure + * + * This structure represents a debugfs file, as an instantiation of a &struct + * drm_info_list on a &struct drm_minor. + * + * FIXME: + * + * No it doesn't make a hole lot of sense that we duplicate debugfs entries for + * both the render and the primary nodes, but that's how this has organically + * grown. It should probably be fixed, with a compatibility link, if needed. + */ +struct drm_info_node { + /** @minor: &struct drm_minor for this node. */ + struct drm_minor *minor; + /** @info_ent: template for this node. */ + const struct drm_info_list *info_ent; + /* private: */ + struct list_head list; + struct dentry *dent; +}; + +/** + * struct drm_debugfs_info - debugfs info list entry + * + * This structure represents a debugfs file to be created by the drm + * core. + */ +struct drm_debugfs_info { + /** @name: File name */ + const char *name; + + /** + * @show: + * + * Show callback. &seq_file->private will be set to the &struct + * drm_debugfs_entry corresponding to the instance of this info + * on a given &struct drm_device. + */ + int (*show)(struct seq_file*, void*); + + /** @driver_features: Required driver features for this entry. */ + u32 driver_features; + + /** @data: Driver-private data, should not be device-specific. */ + void *data; +}; + +/** + * struct drm_debugfs_entry - Per-device debugfs node structure + * + * This structure represents a debugfs file, as an instantiation of a &struct + * drm_debugfs_info on a &struct drm_device. + */ +struct drm_debugfs_entry { + /** @dev: &struct drm_device for this node. */ + struct drm_device *dev; + + /** @file: Template for this node. */ + struct drm_debugfs_info file; + + /** @list: Linked list of all device nodes. */ + struct list_head list; +}; + +#if defined(CONFIG_DEBUG_FS) +void drm_debugfs_create_files(const struct drm_info_list *files, + int count, struct dentry *root, + struct drm_minor *minor); +int drm_debugfs_remove_files(const struct drm_info_list *files, int count, + struct dentry *root, struct drm_minor *minor); + +void drm_debugfs_add_file(struct drm_device *dev, const char *name, + int (*show)(struct seq_file*, void*), void *data); + +void drm_debugfs_add_files(struct drm_device *dev, + const struct drm_debugfs_info *files, int count); + +int drm_debugfs_gpuva_info(struct seq_file *m, + struct drm_gpuvm *gpuvm); + +void drm_debugfs_clients_add(struct drm_file *file); +void drm_debugfs_clients_remove(struct drm_file *file); +#else +static inline void drm_debugfs_create_files(const struct drm_info_list *files, + int count, struct dentry *root, + struct drm_minor *minor) +{} + +static inline int drm_debugfs_remove_files(const struct drm_info_list *files, + int count, struct dentry *root, + struct drm_minor *minor) +{ + return 0; +} + +static inline void drm_debugfs_add_file(struct drm_device *dev, const char *name, + int (*show)(struct seq_file*, void*), + void *data) +{} + +static inline void drm_debugfs_add_files(struct drm_device *dev, + const struct drm_debugfs_info *files, + int count) +{} + +static inline int drm_debugfs_gpuva_info(struct seq_file *m, + struct drm_gpuvm *gpuvm) +{ + return 0; +} + +static inline void drm_debugfs_clients_add(struct drm_file *file) +{ +} + +static inline void drm_debugfs_clients_remove(struct drm_file *file) +{ +} +#endif + +#endif /* _DRM_DEBUGFS_H_ */ -- cgit v1.3.1