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1 : : /* SPDX-License-Identifier: GPL-2.0-only */ 2 : : /* 3 : : * Tracing hooks 4 : : * 5 : : * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. 6 : : * 7 : : * This file defines hook entry points called by core code where 8 : : * user tracing/debugging support might need to do something. These 9 : : * entry points are called tracehook_*(). Each hook declared below 10 : : * has a detailed kerneldoc comment giving the context (locking et 11 : : * al) from which it is called, and the meaning of its return value. 12 : : * 13 : : * Each function here typically has only one call site, so it is ok 14 : : * to have some nontrivial tracehook_*() inlines. In all cases, the 15 : : * fast path when no tracing is enabled should be very short. 16 : : * 17 : : * The purpose of this file and the tracehook_* layer is to consolidate 18 : : * the interface that the kernel core and arch code uses to enable any 19 : : * user debugging or tracing facility (such as ptrace). The interfaces 20 : : * here are carefully documented so that maintainers of core and arch 21 : : * code do not need to think about the implementation details of the 22 : : * tracing facilities. Likewise, maintainers of the tracing code do not 23 : : * need to understand all the calling core or arch code in detail, just 24 : : * documented circumstances of each call, such as locking conditions. 25 : : * 26 : : * If the calling core code changes so that locking is different, then 27 : : * it is ok to change the interface documented here. The maintainer of 28 : : * core code changing should notify the maintainers of the tracing code 29 : : * that they need to work out the change. 30 : : * 31 : : * Some tracehook_*() inlines take arguments that the current tracing 32 : : * implementations might not necessarily use. These function signatures 33 : : * are chosen to pass in all the information that is on hand in the 34 : : * caller and might conceivably be relevant to a tracer, so that the 35 : : * core code won't have to be updated when tracing adds more features. 36 : : * If a call site changes so that some of those parameters are no longer 37 : : * already on hand without extra work, then the tracehook_* interface 38 : : * can change so there is no make-work burden on the core code. The 39 : : * maintainer of core code changing should notify the maintainers of the 40 : : * tracing code that they need to work out the change. 41 : : */ 42 : : 43 : : #ifndef _LINUX_TRACEHOOK_H 44 : : #define _LINUX_TRACEHOOK_H 1 45 : : 46 : : #include <linux/sched.h> 47 : : #include <linux/ptrace.h> 48 : : #include <linux/security.h> 49 : : #include <linux/task_work.h> 50 : : #include <linux/memcontrol.h> 51 : : #include <linux/blk-cgroup.h> 52 : : struct linux_binprm; 53 : : 54 : : /* 55 : : * ptrace report for syscall entry and exit looks identical. 56 : : */ 57 : : static inline int ptrace_report_syscall(struct pt_regs *regs, 58 : : unsigned long message) 59 : : { 60 : : int ptrace = current->ptrace; 61 : : 62 : : if (!(ptrace & PT_PTRACED)) 63 : : return 0; 64 : : 65 : : current->ptrace_message = message; 66 : : ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); 67 : : 68 : : /* 69 : : * this isn't the same as continuing with a signal, but it will do 70 : : * for normal use. strace only continues with a signal if the 71 : : * stopping signal is not SIGTRAP. -brl 72 : : */ 73 : : if (current->exit_code) { 74 : : send_sig(current->exit_code, current, 1); 75 : : current->exit_code = 0; 76 : : } 77 : : 78 : : current->ptrace_message = 0; 79 : : return fatal_signal_pending(current); 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 : : * 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. 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 96 : : * return. It should preserve enough information so that syscall_rollback() 97 : : * can work (see asm-generic/syscall.h). 98 : : * 99 : : * Called without locks, just after entering kernel mode. 100 : : */ 101 : 0 : static inline __must_check int tracehook_report_syscall_entry( 102 : : struct pt_regs *regs) 103 : : { 104 : 0 : return ptrace_report_syscall(regs, PTRACE_EVENTMSG_SYSCALL_ENTRY); 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 : 0 : static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) 125 : : { 126 [ # # ]: 0 : if (step) 127 : 0 : user_single_step_report(regs); 128 : : else 129 : 0 : ptrace_report_syscall(regs, PTRACE_EVENTMSG_SYSCALL_EXIT); 130 : : } 131 : : 132 : : /** 133 : : * tracehook_signal_handler - signal handler setup is complete 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 : : */ 143 : 144 : static inline void tracehook_signal_handler(int stepping) 144 : : { 145 [ - + ]: 144 : if (stepping) 146 : 0 : ptrace_notify(SIGTRAP); 147 : : } 148 : : 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 : 138347 : static inline void set_notify_resume(struct task_struct *task) 159 : : { 160 : : #ifdef TIF_NOTIFY_RESUME 161 [ + + ]: 138347 : if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) 162 : 119237 : kick_process(task); 163 : : #endif 164 : 138347 : } 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 : 186527 : static inline void tracehook_notify_resume(struct pt_regs *regs) 180 : : { 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 : : */ 186 : 186527 : smp_mb__after_atomic(); 187 [ + - ]: 186527 : if (unlikely(current->task_works)) 188 : 186527 : task_work_run(); 189 : : 190 : : #ifdef CONFIG_KEYS_REQUEST_CACHE 191 : : if (unlikely(current->cached_requested_key)) { 192 : : key_put(current->cached_requested_key); 193 : : current->cached_requested_key = NULL; 194 : : } 195 : : #endif 196 : : 197 [ - + ]: 186527 : mem_cgroup_handle_over_high(); 198 [ - + ]: 186527 : blkcg_maybe_throttle_current(); 199 : : } 200 : : 201 : : #endif /* <linux/tracehook.h> */