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Diffstat (limited to 'kernel/include/linux/tracehook.h')
| -rw-r--r-- | kernel/include/linux/tracehook.h | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/kernel/include/linux/tracehook.h b/kernel/include/linux/tracehook.h new file mode 100644 index 000000000..84d497297 --- /dev/null +++ b/kernel/include/linux/tracehook.h @@ -0,0 +1,193 @@ +/* + * Tracing hooks + * + * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. + * + * This copyrighted material is made available to anyone wishing to use, + * modify, copy, or redistribute it subject to the terms and conditions + * of the GNU General Public License v.2. + * + * This file defines hook entry points called by core code where + * user tracing/debugging support might need to do something. These + * entry points are called tracehook_*(). Each hook declared below + * has a detailed kerneldoc comment giving the context (locking et + * al) from which it is called, and the meaning of its return value. + * + * Each function here typically has only one call site, so it is ok + * to have some nontrivial tracehook_*() inlines. In all cases, the + * fast path when no tracing is enabled should be very short. + * + * The purpose of this file and the tracehook_* layer is to consolidate + * the interface that the kernel core and arch code uses to enable any + * user debugging or tracing facility (such as ptrace). The interfaces + * here are carefully documented so that maintainers of core and arch + * code do not need to think about the implementation details of the + * tracing facilities. Likewise, maintainers of the tracing code do not + * need to understand all the calling core or arch code in detail, just + * documented circumstances of each call, such as locking conditions. + * + * If the calling core code changes so that locking is different, then + * it is ok to change the interface documented here. The maintainer of + * core code changing should notify the maintainers of the tracing code + * that they need to work out the change. + * + * Some tracehook_*() inlines take arguments that the current tracing + * implementations might not necessarily use. These function signatures + * are chosen to pass in all the information that is on hand in the + * caller and might conceivably be relevant to a tracer, so that the + * core code won't have to be updated when tracing adds more features. + * If a call site changes so that some of those parameters are no longer + * already on hand without extra work, then the tracehook_* interface + * can change so there is no make-work burden on the core code. The + * maintainer of core code changing should notify the maintainers of the + * tracing code that they need to work out the change. + */ + +#ifndef _LINUX_TRACEHOOK_H +#define _LINUX_TRACEHOOK_H 1 + +#include <linux/sched.h> +#include <linux/ptrace.h> +#include <linux/security.h> +#include <linux/task_work.h> +struct linux_binprm; + +/* + * ptrace report for syscall entry and exit looks identical. + */ +static inline int ptrace_report_syscall(struct pt_regs *regs) +{ + int ptrace = current->ptrace; + + if (!(ptrace & PT_PTRACED)) + return 0; + + ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0)); + + /* + * this isn't the same as continuing with a signal, but it will do + * for normal use. strace only continues with a signal if the + * stopping signal is not SIGTRAP. -brl + */ + if (current->exit_code) { + send_sig(current->exit_code, current, 1); + current->exit_code = 0; + } + + return fatal_signal_pending(current); +} + +/** + * tracehook_report_syscall_entry - task is about to attempt a system call + * @regs: user register state of current task + * + * This will be called if %TIF_SYSCALL_TRACE has been set, when the + * current task has just entered the kernel for a system call. + * Full user register state is available here. Changing the values + * in @regs can affect the system call number and arguments to be tried. + * It is safe to block here, preventing the system call from beginning. + * + * Returns zero normally, or nonzero if the calling arch code should abort + * the system call. That must prevent normal entry so no system call is + * made. If @task ever returns to user mode after this, its register state + * is unspecified, but should be something harmless like an %ENOSYS error + * return. It should preserve enough information so that syscall_rollback() + * can work (see asm-generic/syscall.h). + * + * Called without locks, just after entering kernel mode. + */ +static inline __must_check int tracehook_report_syscall_entry( + struct pt_regs *regs) +{ + return ptrace_report_syscall(regs); +} + +/** + * tracehook_report_syscall_exit - task has just finished a system call + * @regs: user register state of current task + * @step: nonzero if simulating single-step or block-step + * + * This will be called if %TIF_SYSCALL_TRACE has been set, when the + * current task has just finished an attempted system call. Full + * user register state is available here. It is safe to block here, + * preventing signals from being processed. + * + * If @step is nonzero, this report is also in lieu of the normal + * trap that would follow the system call instruction because + * user_enable_block_step() or user_enable_single_step() was used. + * In this case, %TIF_SYSCALL_TRACE might not be set. + * + * Called without locks, just before checking for pending signals. + */ +static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) +{ + if (step) { + siginfo_t info; + user_single_step_siginfo(current, regs, &info); + force_sig_info(SIGTRAP, &info, current); + return; + } + + ptrace_report_syscall(regs); +} + +/** + * tracehook_signal_handler - signal handler setup is complete + * @stepping: nonzero if debugger single-step or block-step in use + * + * Called by the arch code after a signal handler has been set up. + * Register and stack state reflects the user handler about to run. + * Signal mask changes have already been made. + * + * Called without locks, shortly before returning to user mode + * (or handling more signals). + */ +static inline void tracehook_signal_handler(int stepping) +{ + if (stepping) + ptrace_notify(SIGTRAP); +} + +/** + * set_notify_resume - cause tracehook_notify_resume() to be called + * @task: task that will call tracehook_notify_resume() + * + * Calling this arranges that @task will call tracehook_notify_resume() + * before returning to user mode. If it's already running in user mode, + * it will enter the kernel and call tracehook_notify_resume() soon. + * If it's blocked, it will not be woken. + */ +static inline void set_notify_resume(struct task_struct *task) +{ +#ifdef TIF_NOTIFY_RESUME + if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) + kick_process(task); +#endif +} + +/** + * tracehook_notify_resume - report when about to return to user mode + * @regs: user-mode registers of @current task + * + * This is called when %TIF_NOTIFY_RESUME has been set. Now we are + * about to return to user mode, and the user state in @regs can be + * inspected or adjusted. The caller in arch code has cleared + * %TIF_NOTIFY_RESUME before the call. If the flag gets set again + * asynchronously, this will be called again before we return to + * user mode. + * + * Called without locks. + */ +static inline void tracehook_notify_resume(struct pt_regs *regs) +{ + /* + * The caller just cleared TIF_NOTIFY_RESUME. This barrier + * pairs with task_work_add()->set_notify_resume() after + * hlist_add_head(task->task_works); + */ + smp_mb__after_atomic(); + if (unlikely(current->task_works)) + task_work_run(); +} + +#endif /* <linux/tracehook.h> */ |