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2522fe45 | 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
88ac2921 RM |
2 | /* |
3 | * Tracing hooks | |
4 | * | |
ae6d2ed7 | 5 | * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. |
88ac2921 | 6 | * |
88ac2921 RM |
7 | * This file defines hook entry points called by core code where |
8 | * user tracing/debugging support might need to do something. These | |
9 | * entry points are called tracehook_*(). Each hook declared below | |
10 | * has a detailed kerneldoc comment giving the context (locking et | |
11 | * al) from which it is called, and the meaning of its return value. | |
12 | * | |
13 | * Each function here typically has only one call site, so it is ok | |
14 | * to have some nontrivial tracehook_*() inlines. In all cases, the | |
15 | * fast path when no tracing is enabled should be very short. | |
16 | * | |
17 | * The purpose of this file and the tracehook_* layer is to consolidate | |
18 | * the interface that the kernel core and arch code uses to enable any | |
19 | * user debugging or tracing facility (such as ptrace). The interfaces | |
20 | * here are carefully documented so that maintainers of core and arch | |
21 | * code do not need to think about the implementation details of the | |
22 | * tracing facilities. Likewise, maintainers of the tracing code do not | |
23 | * need to understand all the calling core or arch code in detail, just | |
24 | * documented circumstances of each call, such as locking conditions. | |
25 | * | |
26 | * If the calling core code changes so that locking is different, then | |
27 | * it is ok to change the interface documented here. The maintainer of | |
28 | * core code changing should notify the maintainers of the tracing code | |
29 | * that they need to work out the change. | |
30 | * | |
31 | * Some tracehook_*() inlines take arguments that the current tracing | |
32 | * implementations might not necessarily use. These function signatures | |
33 | * are chosen to pass in all the information that is on hand in the | |
34 | * caller and might conceivably be relevant to a tracer, so that the | |
35 | * core code won't have to be updated when tracing adds more features. | |
36 | * If a call site changes so that some of those parameters are no longer | |
37 | * already on hand without extra work, then the tracehook_* interface | |
38 | * can change so there is no make-work burden on the core code. The | |
39 | * maintainer of core code changing should notify the maintainers of the | |
40 | * tracing code that they need to work out the change. | |
41 | */ | |
42 | ||
43 | #ifndef _LINUX_TRACEHOOK_H | |
44 | #define _LINUX_TRACEHOOK_H 1 | |
45 | ||
46 | #include <linux/sched.h> | |
47 | #include <linux/ptrace.h> | |
6341c393 | 48 | #include <linux/security.h> |
e73f8959 | 49 | #include <linux/task_work.h> |
b23afb93 | 50 | #include <linux/memcontrol.h> |
d09d8df3 | 51 | #include <linux/blk-cgroup.h> |
6341c393 RM |
52 | struct linux_binprm; |
53 | ||
283d7559 RM |
54 | /* |
55 | * ptrace report for syscall entry and exit looks identical. | |
56 | */ | |
201766a2 EK |
57 | static inline int ptrace_report_syscall(struct pt_regs *regs, |
58 | unsigned long message) | |
283d7559 | 59 | { |
d21142ec | 60 | int ptrace = current->ptrace; |
283d7559 RM |
61 | |
62 | if (!(ptrace & PT_PTRACED)) | |
15cab952 | 63 | return 0; |
283d7559 | 64 | |
201766a2 | 65 | current->ptrace_message = message; |
283d7559 RM |
66 | ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); |
67 | ||
68 | /* | |
69 | * this isn't the same as continuing with a signal, but it will do | |
70 | * for normal use. strace only continues with a signal if the | |
71 | * stopping signal is not SIGTRAP. -brl | |
72 | */ | |
73 | if (current->exit_code) { | |
74 | send_sig(current->exit_code, current, 1); | |
75 | current->exit_code = 0; | |
76 | } | |
15cab952 | 77 | |
201766a2 | 78 | current->ptrace_message = 0; |
15cab952 | 79 | return fatal_signal_pending(current); |
283d7559 RM |
80 | } |
81 | ||
82 | /** | |
83 | * tracehook_report_syscall_entry - task is about to attempt a system call | |
84 | * @regs: user register state of current task | |
85 | * | |
64c19ba2 | 86 | * This will be called if %SYSCALL_WORK_SYSCALL_TRACE or |
64eb35f7 | 87 | * %SYSCALL_WORK_SYSCALL_EMU have been set, when the current task has just |
64c19ba2 GKB |
88 | * entered the kernel for a system call. Full user register state is |
89 | * available here. Changing the values in @regs can affect the system | |
90 | * call number and arguments to be tried. It is safe to block here, | |
91 | * preventing the system call from beginning. | |
283d7559 RM |
92 | * |
93 | * Returns zero normally, or nonzero if the calling arch code should abort | |
94 | * the system call. That must prevent normal entry so no system call is | |
95 | * made. If @task ever returns to user mode after this, its register state | |
96 | * is unspecified, but should be something harmless like an %ENOSYS error | |
828c365c RM |
97 | * return. It should preserve enough information so that syscall_rollback() |
98 | * can work (see asm-generic/syscall.h). | |
283d7559 RM |
99 | * |
100 | * Called without locks, just after entering kernel mode. | |
101 | */ | |
102 | static inline __must_check int tracehook_report_syscall_entry( | |
103 | struct pt_regs *regs) | |
104 | { | |
201766a2 | 105 | return ptrace_report_syscall(regs, PTRACE_EVENTMSG_SYSCALL_ENTRY); |
283d7559 RM |
106 | } |
107 | ||
108 | /** | |
109 | * tracehook_report_syscall_exit - task has just finished a system call | |
110 | * @regs: user register state of current task | |
111 | * @step: nonzero if simulating single-step or block-step | |
112 | * | |
64c19ba2 GKB |
113 | * This will be called if %SYSCALL_WORK_SYSCALL_TRACE has been set, when |
114 | * the current task has just finished an attempted system call. Full | |
283d7559 RM |
115 | * user register state is available here. It is safe to block here, |
116 | * preventing signals from being processed. | |
117 | * | |
118 | * If @step is nonzero, this report is also in lieu of the normal | |
119 | * trap that would follow the system call instruction because | |
120 | * user_enable_block_step() or user_enable_single_step() was used. | |
64c19ba2 | 121 | * In this case, %SYSCALL_WORK_SYSCALL_TRACE might not be set. |
283d7559 RM |
122 | * |
123 | * Called without locks, just before checking for pending signals. | |
124 | */ | |
125 | static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) | |
126 | { | |
efc463ad EB |
127 | if (step) |
128 | user_single_step_report(regs); | |
129 | else | |
201766a2 | 130 | ptrace_report_syscall(regs, PTRACE_EVENTMSG_SYSCALL_EXIT); |
283d7559 RM |
131 | } |
132 | ||
c45aea27 RM |
133 | /** |
134 | * tracehook_signal_handler - signal handler setup is complete | |
c45aea27 RM |
135 | * @stepping: nonzero if debugger single-step or block-step in use |
136 | * | |
137 | * Called by the arch code after a signal handler has been set up. | |
138 | * Register and stack state reflects the user handler about to run. | |
139 | * Signal mask changes have already been made. | |
140 | * | |
141 | * Called without locks, shortly before returning to user mode | |
142 | * (or handling more signals). | |
143 | */ | |
df5601f9 | 144 | static inline void tracehook_signal_handler(int stepping) |
c45aea27 RM |
145 | { |
146 | if (stepping) | |
147 | ptrace_notify(SIGTRAP); | |
148 | } | |
149 | ||
64b1208d RM |
150 | /** |
151 | * set_notify_resume - cause tracehook_notify_resume() to be called | |
152 | * @task: task that will call tracehook_notify_resume() | |
153 | * | |
154 | * Calling this arranges that @task will call tracehook_notify_resume() | |
155 | * before returning to user mode. If it's already running in user mode, | |
156 | * it will enter the kernel and call tracehook_notify_resume() soon. | |
157 | * If it's blocked, it will not be woken. | |
158 | */ | |
159 | static inline void set_notify_resume(struct task_struct *task) | |
160 | { | |
e73f8959 | 161 | #ifdef TIF_NOTIFY_RESUME |
64b1208d RM |
162 | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) |
163 | kick_process(task); | |
e73f8959 | 164 | #endif |
64b1208d RM |
165 | } |
166 | ||
167 | /** | |
168 | * tracehook_notify_resume - report when about to return to user mode | |
169 | * @regs: user-mode registers of @current task | |
170 | * | |
171 | * This is called when %TIF_NOTIFY_RESUME has been set. Now we are | |
172 | * about to return to user mode, and the user state in @regs can be | |
173 | * inspected or adjusted. The caller in arch code has cleared | |
174 | * %TIF_NOTIFY_RESUME before the call. If the flag gets set again | |
175 | * asynchronously, this will be called again before we return to | |
176 | * user mode. | |
177 | * | |
178 | * Called without locks. | |
179 | */ | |
180 | static inline void tracehook_notify_resume(struct pt_regs *regs) | |
181 | { | |
3c532798 | 182 | clear_thread_flag(TIF_NOTIFY_RESUME); |
e73f8959 | 183 | /* |
3c532798 | 184 | * This barrier pairs with task_work_add()->set_notify_resume() after |
e73f8959 ON |
185 | * hlist_add_head(task->task_works); |
186 | */ | |
4e857c58 | 187 | smp_mb__after_atomic(); |
158e1645 | 188 | if (unlikely(current->task_works)) |
e73f8959 | 189 | task_work_run(); |
b23afb93 | 190 | |
7743c48e DH |
191 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
192 | if (unlikely(current->cached_requested_key)) { | |
193 | key_put(current->cached_requested_key); | |
194 | current->cached_requested_key = NULL; | |
195 | } | |
196 | #endif | |
197 | ||
b23afb93 | 198 | mem_cgroup_handle_over_high(); |
d09d8df3 | 199 | blkcg_maybe_throttle_current(); |
64b1208d | 200 | } |
64b1208d | 201 | |
12db8b69 JA |
202 | /* |
203 | * called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This | |
204 | * is currently used by TWA_SIGNAL based task_work, which requires breaking | |
205 | * wait loops to ensure that task_work is noticed and run. | |
206 | */ | |
207 | static inline void tracehook_notify_signal(void) | |
208 | { | |
12db8b69 JA |
209 | clear_thread_flag(TIF_NOTIFY_SIGNAL); |
210 | smp_mb__after_atomic(); | |
211 | if (current->task_works) | |
212 | task_work_run(); | |
12db8b69 JA |
213 | } |
214 | ||
215 | /* | |
216 | * Called when we have work to process from exit_to_user_mode_loop() | |
217 | */ | |
218 | static inline void set_notify_signal(struct task_struct *task) | |
219 | { | |
12db8b69 JA |
220 | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && |
221 | !wake_up_state(task, TASK_INTERRUPTIBLE)) | |
222 | kick_process(task); | |
12db8b69 JA |
223 | } |
224 | ||
88ac2921 | 225 | #endif /* <linux/tracehook.h> */ |