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1 : : /*
2 : : * Tracing hooks
3 : : *
4 : : * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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>
51 : : #include <linux/security.h>
52 : : #include <linux/task_work.h>
53 : : struct linux_binprm;
54 : :
55 : : /*
56 : : * ptrace report for syscall entry and exit looks identical.
57 : : */
58 : : static inline int ptrace_report_syscall(struct pt_regs *regs)
59 : : {
60 : : int ptrace = current->ptrace;
61 : :
62 : : if (!(ptrace & PT_PTRACED))
63 : : return 0;
64 : :
65 : : ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
66 : :
67 : : /*
68 : : * this isn't the same as continuing with a signal, but it will do
69 : : * for normal use. strace only continues with a signal if the
70 : : * stopping signal is not SIGTRAP. -brl
71 : : */
72 : : if (current->exit_code) {
73 : : send_sig(current->exit_code, current, 1);
74 : : current->exit_code = 0;
75 : : }
76 : :
77 : : return fatal_signal_pending(current);
78 : : }
79 : :
80 : : /**
81 : : * tracehook_report_syscall_entry - task is about to attempt a system call
82 : : * @regs: user register state of current task
83 : : *
84 : : * This will be called if %TIF_SYSCALL_TRACE has been set, when the
85 : : * current task has just entered the kernel for a system call.
86 : : * Full user register state is available here. Changing the values
87 : : * in @regs can affect the system call number and arguments to be tried.
88 : : * It is safe to block here, preventing the system call from beginning.
89 : : *
90 : : * Returns zero normally, or nonzero if the calling arch code should abort
91 : : * the system call. That must prevent normal entry so no system call is
92 : : * made. If @task ever returns to user mode after this, its register state
93 : : * is unspecified, but should be something harmless like an %ENOSYS error
94 : : * return. It should preserve enough information so that syscall_rollback()
95 : : * can work (see asm-generic/syscall.h).
96 : : *
97 : : * Called without locks, just after entering kernel mode.
98 : : */
99 : : static inline __must_check int tracehook_report_syscall_entry(
100 : : struct pt_regs *regs)
101 : : {
102 : : return ptrace_report_syscall(regs);
103 : : }
104 : :
105 : : /**
106 : : * tracehook_report_syscall_exit - task has just finished a system call
107 : : * @regs: user register state of current task
108 : : * @step: nonzero if simulating single-step or block-step
109 : : *
110 : : * This will be called if %TIF_SYSCALL_TRACE has been set, when the
111 : : * current task has just finished an attempted system call. Full
112 : : * user register state is available here. It is safe to block here,
113 : : * preventing signals from being processed.
114 : : *
115 : : * If @step is nonzero, this report is also in lieu of the normal
116 : : * trap that would follow the system call instruction because
117 : : * user_enable_block_step() or user_enable_single_step() was used.
118 : : * In this case, %TIF_SYSCALL_TRACE might not be set.
119 : : *
120 : : * Called without locks, just before checking for pending signals.
121 : : */
122 : : static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
123 : : {
124 : : if (step) {
125 : : siginfo_t info;
126 : : user_single_step_siginfo(current, regs, &info);
127 : : force_sig_info(SIGTRAP, &info, current);
128 : : return;
129 : : }
130 : :
131 : : ptrace_report_syscall(regs);
132 : : }
133 : :
134 : : /**
135 : : * tracehook_signal_handler - signal handler setup is complete
136 : : * @sig: number of signal being delivered
137 : : * @info: siginfo_t of signal being delivered
138 : : * @ka: sigaction setting that chose the handler
139 : : * @regs: user register state
140 : : * @stepping: nonzero if debugger single-step or block-step in use
141 : : *
142 : : * Called by the arch code after a signal handler has been set up.
143 : : * Register and stack state reflects the user handler about to run.
144 : : * Signal mask changes have already been made.
145 : : *
146 : : * Called without locks, shortly before returning to user mode
147 : : * (or handling more signals).
148 : : */
149 : : static inline void tracehook_signal_handler(int sig, siginfo_t *info,
150 : : const struct k_sigaction *ka,
151 : : struct pt_regs *regs, int stepping)
152 : : {
153 [ - + ]: 1323454 : if (stepping)
154 : 0 : ptrace_notify(SIGTRAP);
155 : : }
156 : :
157 : : /**
158 : : * set_notify_resume - cause tracehook_notify_resume() to be called
159 : : * @task: task that will call tracehook_notify_resume()
160 : : *
161 : : * Calling this arranges that @task will call tracehook_notify_resume()
162 : : * before returning to user mode. If it's already running in user mode,
163 : : * it will enter the kernel and call tracehook_notify_resume() soon.
164 : : * If it's blocked, it will not be woken.
165 : : */
166 : : static inline void set_notify_resume(struct task_struct *task)
167 : : {
168 : : #ifdef TIF_NOTIFY_RESUME
169 [ + + ]: 4985467 : if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
170 : 3316052 : kick_process(task);
171 : : #endif
172 : : }
173 : :
174 : : /**
175 : : * tracehook_notify_resume - report when about to return to user mode
176 : : * @regs: user-mode registers of @current task
177 : : *
178 : : * This is called when %TIF_NOTIFY_RESUME has been set. Now we are
179 : : * about to return to user mode, and the user state in @regs can be
180 : : * inspected or adjusted. The caller in arch code has cleared
181 : : * %TIF_NOTIFY_RESUME before the call. If the flag gets set again
182 : : * asynchronously, this will be called again before we return to
183 : : * user mode.
184 : : *
185 : : * Called without locks.
186 : : */
187 : : static inline void tracehook_notify_resume(struct pt_regs *regs)
188 : : {
189 : : /*
190 : : * The caller just cleared TIF_NOTIFY_RESUME. This barrier
191 : : * pairs with task_work_add()->set_notify_resume() after
192 : : * hlist_add_head(task->task_works);
193 : : */
194 : : smp_mb__after_clear_bit();
195 : : if (unlikely(current->task_works))
196 : : task_work_run();
197 : : }
198 : :
199 : : #endif /* <linux/tracehook.h> */
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