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> 52struct linux_binprm; 53 54/* 55 * ptrace report for syscall entry and exit looks identical. 56 */ 57static inline int ptrace_report_syscall(struct pt_regs *regs) 58{ 59 int ptrace = current->ptrace; 60 61 if (!(ptrace & PT_PTRACED)) 62 return 0; 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 return fatal_signal_pending(current); 77} 78 79/** 80 * tracehook_report_syscall_entry - task is about to attempt a system call 81 * @regs: user register state of current task 82 * 83 * This will be called if %TIF_SYSCALL_TRACE has been set, when the 84 * current task has just entered the kernel for a system call. 85 * Full user register state is available here. Changing the values 86 * in @regs can affect the system call number and arguments to be tried. 87 * It is safe to block here, preventing the system call from beginning. 88 * 89 * Returns zero normally, or nonzero if the calling arch code should abort 90 * the system call. That must prevent normal entry so no system call is 91 * made. If @task ever returns to user mode after this, its register state 92 * is unspecified, but should be something harmless like an %ENOSYS error 93 * return. It should preserve enough information so that syscall_rollback() 94 * can work (see asm-generic/syscall.h). 95 * 96 * Called without locks, just after entering kernel mode. 97 */ 98static inline __must_check int tracehook_report_syscall_entry( 99 struct pt_regs *regs) 100{ 101 return ptrace_report_syscall(regs); 102} 103 104/** 105 * tracehook_report_syscall_exit - task has just finished a system call 106 * @regs: user register state of current task 107 * @step: nonzero if simulating single-step or block-step 108 * 109 * This will be called if %TIF_SYSCALL_TRACE has been set, when the 110 * current task has just finished an attempted system call. Full 111 * user register state is available here. It is safe to block here, 112 * preventing signals from being processed. 113 * 114 * If @step is nonzero, this report is also in lieu of the normal 115 * trap that would follow the system call instruction because 116 * user_enable_block_step() or user_enable_single_step() was used. 117 * In this case, %TIF_SYSCALL_TRACE might not be set. 118 * 119 * Called without locks, just before checking for pending signals. 120 */ 121static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) 122{ 123 if (step) { 124 siginfo_t info; 125 user_single_step_siginfo(current, regs, &info); 126 force_sig_info(SIGTRAP, &info, current); 127 return; 128 } 129 130 ptrace_report_syscall(regs); 131} 132 133/** 134 * tracehook_signal_handler - signal handler setup is complete 135 * @sig: number of signal being delivered 136 * @info: siginfo_t of signal being delivered 137 * @ka: sigaction setting that chose the handler 138 * @regs: user register state 139 * @stepping: nonzero if debugger single-step or block-step in use 140 * 141 * Called by the arch code after a signal handler has been set up. 142 * Register and stack state reflects the user handler about to run. 143 * Signal mask changes have already been made. 144 * 145 * Called without locks, shortly before returning to user mode 146 * (or handling more signals). 147 */ 148static inline void tracehook_signal_handler(int sig, siginfo_t *info, 149 const struct k_sigaction *ka, 150 struct pt_regs *regs, int stepping) 151{ 152 if (stepping) 153 ptrace_notify(SIGTRAP); 154} 155 156#ifdef TIF_NOTIFY_RESUME 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 */ 166static inline void set_notify_resume(struct task_struct *task) 167{ 168 if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) 169 kick_process(task); 170} 171 172/** 173 * tracehook_notify_resume - report when about to return to user mode 174 * @regs: user-mode registers of @current task 175 * 176 * This is called when %TIF_NOTIFY_RESUME has been set. Now we are 177 * about to return to user mode, and the user state in @regs can be 178 * inspected or adjusted. The caller in arch code has cleared 179 * %TIF_NOTIFY_RESUME before the call. If the flag gets set again 180 * asynchronously, this will be called again before we return to 181 * user mode. 182 * 183 * Called without locks. 184 */ 185static inline void tracehook_notify_resume(struct pt_regs *regs) 186{ 187} 188#endif /* TIF_NOTIFY_RESUME */ 189 190#endif /* <linux/tracehook.h> */ 191