4 * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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.
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.
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.
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.
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.
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.
46 #ifndef _LINUX_TRACEHOOK_H
47 #define _LINUX_TRACEHOOK_H 1
49 #include <linux/sched.h>
50 #include <linux/ptrace.h>
51 #include <linux/security.h>
52 #include <linux/task_work.h>
56 * ptrace report for syscall entry and exit looks identical.
58 static inline int ptrace_report_syscall(struct pt_regs
*regs
)
60 int ptrace
= current
->ptrace
;
62 if (!(ptrace
& PT_PTRACED
))
65 ptrace_notify(SIGTRAP
| ((ptrace
& PT_TRACESYSGOOD
) ? 0x80 : 0));
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
72 if (current
->exit_code
) {
73 send_sig(current
->exit_code
, current
, 1);
74 current
->exit_code
= 0;
77 return fatal_signal_pending(current
);
81 * tracehook_report_syscall_entry - task is about to attempt a system call
82 * @regs: user register state of current task
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.
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).
97 * Called without locks, just after entering kernel mode.
99 static inline __must_check
int tracehook_report_syscall_entry(
100 struct pt_regs
*regs
)
102 return ptrace_report_syscall(regs
);
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
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.
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.
120 * Called without locks, just before checking for pending signals.
122 static inline void tracehook_report_syscall_exit(struct pt_regs
*regs
, int step
)
126 user_single_step_siginfo(current
, regs
, &info
);
127 force_sig_info(SIGTRAP
, &info
, current
);
131 ptrace_report_syscall(regs
);
135 * tracehook_signal_handler - signal handler setup is complete
136 * @stepping: nonzero if debugger single-step or block-step in use
138 * Called by the arch code after a signal handler has been set up.
139 * Register and stack state reflects the user handler about to run.
140 * Signal mask changes have already been made.
142 * Called without locks, shortly before returning to user mode
143 * (or handling more signals).
145 static inline void tracehook_signal_handler(int stepping
)
148 ptrace_notify(SIGTRAP
);
152 * set_notify_resume - cause tracehook_notify_resume() to be called
153 * @task: task that will call tracehook_notify_resume()
155 * Calling this arranges that @task will call tracehook_notify_resume()
156 * before returning to user mode. If it's already running in user mode,
157 * it will enter the kernel and call tracehook_notify_resume() soon.
158 * If it's blocked, it will not be woken.
160 static inline void set_notify_resume(struct task_struct
*task
)
162 #ifdef TIF_NOTIFY_RESUME
163 if (!test_and_set_tsk_thread_flag(task
, TIF_NOTIFY_RESUME
))
169 * tracehook_notify_resume - report when about to return to user mode
170 * @regs: user-mode registers of @current task
172 * This is called when %TIF_NOTIFY_RESUME has been set. Now we are
173 * about to return to user mode, and the user state in @regs can be
174 * inspected or adjusted. The caller in arch code has cleared
175 * %TIF_NOTIFY_RESUME before the call. If the flag gets set again
176 * asynchronously, this will be called again before we return to
179 * Called without locks.
181 static inline void tracehook_notify_resume(struct pt_regs
*regs
)
184 * The caller just cleared TIF_NOTIFY_RESUME. This barrier
185 * pairs with task_work_add()->set_notify_resume() after
186 * hlist_add_head(task->task_works);
188 smp_mb__after_atomic();
189 if (unlikely(current
->task_works
))
193 #endif /* <linux/tracehook.h> */
This page took 0.03382 seconds and 5 git commands to generate.