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88ac2921 RM |
1 | /* |
2 | * Tracing hooks | |
3 | * | |
ae6d2ed7 | 4 | * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. |
88ac2921 RM |
5 | * |
6 | * This copyrighted material is made available to anyone wishing to use, | |
7 | * modify, copy, or redistribute it subject to the terms and conditions | |
8 | * of the GNU General Public License v.2. | |
9 | * | |
10 | * This file defines hook entry points called by core code where | |
11 | * user tracing/debugging support might need to do something. These | |
12 | * entry points are called tracehook_*(). Each hook declared below | |
13 | * has a detailed kerneldoc comment giving the context (locking et | |
14 | * al) from which it is called, and the meaning of its return value. | |
15 | * | |
16 | * Each function here typically has only one call site, so it is ok | |
17 | * to have some nontrivial tracehook_*() inlines. In all cases, the | |
18 | * fast path when no tracing is enabled should be very short. | |
19 | * | |
20 | * The purpose of this file and the tracehook_* layer is to consolidate | |
21 | * the interface that the kernel core and arch code uses to enable any | |
22 | * user debugging or tracing facility (such as ptrace). The interfaces | |
23 | * here are carefully documented so that maintainers of core and arch | |
24 | * code do not need to think about the implementation details of the | |
25 | * tracing facilities. Likewise, maintainers of the tracing code do not | |
26 | * need to understand all the calling core or arch code in detail, just | |
27 | * documented circumstances of each call, such as locking conditions. | |
28 | * | |
29 | * If the calling core code changes so that locking is different, then | |
30 | * it is ok to change the interface documented here. The maintainer of | |
31 | * core code changing should notify the maintainers of the tracing code | |
32 | * that they need to work out the change. | |
33 | * | |
34 | * Some tracehook_*() inlines take arguments that the current tracing | |
35 | * implementations might not necessarily use. These function signatures | |
36 | * are chosen to pass in all the information that is on hand in the | |
37 | * caller and might conceivably be relevant to a tracer, so that the | |
38 | * core code won't have to be updated when tracing adds more features. | |
39 | * If a call site changes so that some of those parameters are no longer | |
40 | * already on hand without extra work, then the tracehook_* interface | |
41 | * can change so there is no make-work burden on the core code. The | |
42 | * maintainer of core code changing should notify the maintainers of the | |
43 | * tracing code that they need to work out the change. | |
44 | */ | |
45 | ||
46 | #ifndef _LINUX_TRACEHOOK_H | |
47 | #define _LINUX_TRACEHOOK_H 1 | |
48 | ||
49 | #include <linux/sched.h> | |
50 | #include <linux/ptrace.h> | |
6341c393 | 51 | #include <linux/security.h> |
e73f8959 | 52 | #include <linux/task_work.h> |
b23afb93 | 53 | #include <linux/memcontrol.h> |
d09d8df3 | 54 | #include <linux/blk-cgroup.h> |
6341c393 RM |
55 | struct linux_binprm; |
56 | ||
283d7559 RM |
57 | /* |
58 | * ptrace report for syscall entry and exit looks identical. | |
59 | */ | |
15cab952 | 60 | static inline int ptrace_report_syscall(struct pt_regs *regs) |
283d7559 | 61 | { |
d21142ec | 62 | int ptrace = current->ptrace; |
283d7559 RM |
63 | |
64 | if (!(ptrace & PT_PTRACED)) | |
15cab952 | 65 | return 0; |
283d7559 RM |
66 | |
67 | ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); | |
68 | ||
69 | /* | |
70 | * this isn't the same as continuing with a signal, but it will do | |
71 | * for normal use. strace only continues with a signal if the | |
72 | * stopping signal is not SIGTRAP. -brl | |
73 | */ | |
74 | if (current->exit_code) { | |
75 | send_sig(current->exit_code, current, 1); | |
76 | current->exit_code = 0; | |
77 | } | |
15cab952 ON |
78 | |
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 | * | |
d19f9130 EK |
86 | * This will be called if %TIF_SYSCALL_TRACE or %TIF_SYSCALL_EMU have been set, |
87 | * when the current task has just entered the kernel for a system call. | |
283d7559 RM |
88 | * Full user register state is available here. Changing the values |
89 | * in @regs can affect the system call number and arguments to be tried. | |
90 | * It is safe to block here, preventing the system call from beginning. | |
91 | * | |
92 | * Returns zero normally, or nonzero if the calling arch code should abort | |
93 | * the system call. That must prevent normal entry so no system call is | |
94 | * made. If @task ever returns to user mode after this, its register state | |
95 | * is unspecified, but should be something harmless like an %ENOSYS error | |
828c365c RM |
96 | * return. It should preserve enough information so that syscall_rollback() |
97 | * can work (see asm-generic/syscall.h). | |
283d7559 RM |
98 | * |
99 | * Called without locks, just after entering kernel mode. | |
100 | */ | |
101 | static inline __must_check int tracehook_report_syscall_entry( | |
102 | struct pt_regs *regs) | |
103 | { | |
15cab952 | 104 | return ptrace_report_syscall(regs); |
283d7559 RM |
105 | } |
106 | ||
107 | /** | |
108 | * tracehook_report_syscall_exit - task has just finished a system call | |
109 | * @regs: user register state of current task | |
110 | * @step: nonzero if simulating single-step or block-step | |
111 | * | |
112 | * This will be called if %TIF_SYSCALL_TRACE has been set, when the | |
113 | * current task has just finished an attempted system call. Full | |
114 | * user register state is available here. It is safe to block here, | |
115 | * preventing signals from being processed. | |
116 | * | |
117 | * If @step is nonzero, this report is also in lieu of the normal | |
118 | * trap that would follow the system call instruction because | |
119 | * user_enable_block_step() or user_enable_single_step() was used. | |
120 | * In this case, %TIF_SYSCALL_TRACE might not be set. | |
121 | * | |
122 | * Called without locks, just before checking for pending signals. | |
123 | */ | |
124 | static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) | |
125 | { | |
efc463ad EB |
126 | if (step) |
127 | user_single_step_report(regs); | |
128 | else | |
129 | ptrace_report_syscall(regs); | |
283d7559 RM |
130 | } |
131 | ||
c45aea27 RM |
132 | /** |
133 | * tracehook_signal_handler - signal handler setup is complete | |
c45aea27 RM |
134 | * @stepping: nonzero if debugger single-step or block-step in use |
135 | * | |
136 | * Called by the arch code after a signal handler has been set up. | |
137 | * Register and stack state reflects the user handler about to run. | |
138 | * Signal mask changes have already been made. | |
139 | * | |
140 | * Called without locks, shortly before returning to user mode | |
141 | * (or handling more signals). | |
142 | */ | |
df5601f9 | 143 | static inline void tracehook_signal_handler(int stepping) |
c45aea27 RM |
144 | { |
145 | if (stepping) | |
146 | ptrace_notify(SIGTRAP); | |
147 | } | |
148 | ||
64b1208d RM |
149 | /** |
150 | * set_notify_resume - cause tracehook_notify_resume() to be called | |
151 | * @task: task that will call tracehook_notify_resume() | |
152 | * | |
153 | * Calling this arranges that @task will call tracehook_notify_resume() | |
154 | * before returning to user mode. If it's already running in user mode, | |
155 | * it will enter the kernel and call tracehook_notify_resume() soon. | |
156 | * If it's blocked, it will not be woken. | |
157 | */ | |
158 | static inline void set_notify_resume(struct task_struct *task) | |
159 | { | |
e73f8959 | 160 | #ifdef TIF_NOTIFY_RESUME |
64b1208d RM |
161 | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) |
162 | kick_process(task); | |
e73f8959 | 163 | #endif |
64b1208d RM |
164 | } |
165 | ||
166 | /** | |
167 | * tracehook_notify_resume - report when about to return to user mode | |
168 | * @regs: user-mode registers of @current task | |
169 | * | |
170 | * This is called when %TIF_NOTIFY_RESUME has been set. Now we are | |
171 | * about to return to user mode, and the user state in @regs can be | |
172 | * inspected or adjusted. The caller in arch code has cleared | |
173 | * %TIF_NOTIFY_RESUME before the call. If the flag gets set again | |
174 | * asynchronously, this will be called again before we return to | |
175 | * user mode. | |
176 | * | |
177 | * Called without locks. | |
178 | */ | |
179 | static inline void tracehook_notify_resume(struct pt_regs *regs) | |
180 | { | |
e73f8959 ON |
181 | /* |
182 | * The caller just cleared TIF_NOTIFY_RESUME. This barrier | |
183 | * pairs with task_work_add()->set_notify_resume() after | |
184 | * hlist_add_head(task->task_works); | |
185 | */ | |
4e857c58 | 186 | smp_mb__after_atomic(); |
158e1645 | 187 | if (unlikely(current->task_works)) |
e73f8959 | 188 | task_work_run(); |
b23afb93 TH |
189 | |
190 | mem_cgroup_handle_over_high(); | |
d09d8df3 | 191 | blkcg_maybe_throttle_current(); |
64b1208d | 192 | } |
64b1208d | 193 | |
88ac2921 | 194 | #endif /* <linux/tracehook.h> */ |