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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 RM |
51 | #include <linux/security.h> |
52 | struct linux_binprm; | |
53 | ||
283d7559 RM |
54 | /* |
55 | * ptrace report for syscall entry and exit looks identical. | |
56 | */ | |
57 | static inline void ptrace_report_syscall(struct pt_regs *regs) | |
58 | { | |
d21142ec | 59 | int ptrace = current->ptrace; |
283d7559 RM |
60 | |
61 | if (!(ptrace & PT_PTRACED)) | |
62 | return; | |
63 | ||
64 | ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); | |
65 | ||
66 | /* | |
67 | * this isn't the same as continuing with a signal, but it will do | |
68 | * for normal use. strace only continues with a signal if the | |
69 | * stopping signal is not SIGTRAP. -brl | |
70 | */ | |
71 | if (current->exit_code) { | |
72 | send_sig(current->exit_code, current, 1); | |
73 | current->exit_code = 0; | |
74 | } | |
75 | } | |
76 | ||
77 | /** | |
78 | * tracehook_report_syscall_entry - task is about to attempt a system call | |
79 | * @regs: user register state of current task | |
80 | * | |
81 | * This will be called if %TIF_SYSCALL_TRACE has been set, when the | |
82 | * current task has just entered the kernel for a system call. | |
83 | * Full user register state is available here. Changing the values | |
84 | * in @regs can affect the system call number and arguments to be tried. | |
85 | * It is safe to block here, preventing the system call from beginning. | |
86 | * | |
87 | * Returns zero normally, or nonzero if the calling arch code should abort | |
88 | * the system call. That must prevent normal entry so no system call is | |
89 | * made. If @task ever returns to user mode after this, its register state | |
90 | * is unspecified, but should be something harmless like an %ENOSYS error | |
828c365c RM |
91 | * return. It should preserve enough information so that syscall_rollback() |
92 | * can work (see asm-generic/syscall.h). | |
283d7559 RM |
93 | * |
94 | * Called without locks, just after entering kernel mode. | |
95 | */ | |
96 | static inline __must_check int tracehook_report_syscall_entry( | |
97 | struct pt_regs *regs) | |
98 | { | |
99 | ptrace_report_syscall(regs); | |
100 | return 0; | |
101 | } | |
102 | ||
103 | /** | |
104 | * tracehook_report_syscall_exit - task has just finished a system call | |
105 | * @regs: user register state of current task | |
106 | * @step: nonzero if simulating single-step or block-step | |
107 | * | |
108 | * This will be called if %TIF_SYSCALL_TRACE has been set, when the | |
109 | * current task has just finished an attempted system call. Full | |
110 | * user register state is available here. It is safe to block here, | |
111 | * preventing signals from being processed. | |
112 | * | |
113 | * If @step is nonzero, this report is also in lieu of the normal | |
114 | * trap that would follow the system call instruction because | |
115 | * user_enable_block_step() or user_enable_single_step() was used. | |
116 | * In this case, %TIF_SYSCALL_TRACE might not be set. | |
117 | * | |
118 | * Called without locks, just before checking for pending signals. | |
119 | */ | |
120 | static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) | |
121 | { | |
2f0edac5 ON |
122 | if (step) { |
123 | siginfo_t info; | |
124 | user_single_step_siginfo(current, regs, &info); | |
125 | force_sig_info(SIGTRAP, &info, current); | |
126 | return; | |
127 | } | |
128 | ||
283d7559 RM |
129 | ptrace_report_syscall(regs); |
130 | } | |
131 | ||
c45aea27 RM |
132 | /** |
133 | * tracehook_signal_handler - signal handler setup is complete | |
134 | * @sig: number of signal being delivered | |
135 | * @info: siginfo_t of signal being delivered | |
136 | * @ka: sigaction setting that chose the handler | |
137 | * @regs: user register state | |
138 | * @stepping: nonzero if debugger single-step or block-step in use | |
139 | * | |
140 | * Called by the arch code after a signal handler has been set up. | |
141 | * Register and stack state reflects the user handler about to run. | |
142 | * Signal mask changes have already been made. | |
143 | * | |
144 | * Called without locks, shortly before returning to user mode | |
145 | * (or handling more signals). | |
146 | */ | |
147 | static inline void tracehook_signal_handler(int sig, siginfo_t *info, | |
148 | const struct k_sigaction *ka, | |
149 | struct pt_regs *regs, int stepping) | |
150 | { | |
151 | if (stepping) | |
152 | ptrace_notify(SIGTRAP); | |
153 | } | |
154 | ||
64b1208d RM |
155 | #ifdef TIF_NOTIFY_RESUME |
156 | /** | |
157 | * set_notify_resume - cause tracehook_notify_resume() to be called | |
158 | * @task: task that will call tracehook_notify_resume() | |
159 | * | |
160 | * Calling this arranges that @task will call tracehook_notify_resume() | |
161 | * before returning to user mode. If it's already running in user mode, | |
162 | * it will enter the kernel and call tracehook_notify_resume() soon. | |
163 | * If it's blocked, it will not be woken. | |
164 | */ | |
165 | static inline void set_notify_resume(struct task_struct *task) | |
166 | { | |
167 | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) | |
168 | kick_process(task); | |
169 | } | |
170 | ||
171 | /** | |
172 | * tracehook_notify_resume - report when about to return to user mode | |
173 | * @regs: user-mode registers of @current task | |
174 | * | |
175 | * This is called when %TIF_NOTIFY_RESUME has been set. Now we are | |
176 | * about to return to user mode, and the user state in @regs can be | |
177 | * inspected or adjusted. The caller in arch code has cleared | |
178 | * %TIF_NOTIFY_RESUME before the call. If the flag gets set again | |
179 | * asynchronously, this will be called again before we return to | |
180 | * user mode. | |
181 | * | |
182 | * Called without locks. | |
183 | */ | |
184 | static inline void tracehook_notify_resume(struct pt_regs *regs) | |
185 | { | |
186 | } | |
187 | #endif /* TIF_NOTIFY_RESUME */ | |
188 | ||
88ac2921 | 189 | #endif /* <linux/tracehook.h> */ |