600 lines
21 KiB
C
600 lines
21 KiB
C
/*
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* Tracing hooks
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*
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* Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU General Public License v.2.
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*
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* This file defines hook entry points called by core code where
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* user tracing/debugging support might need to do something. These
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* entry points are called tracehook_*(). Each hook declared below
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* has a detailed kerneldoc comment giving the context (locking et
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* al) from which it is called, and the meaning of its return value.
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*
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* Each function here typically has only one call site, so it is ok
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* to have some nontrivial tracehook_*() inlines. In all cases, the
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* fast path when no tracing is enabled should be very short.
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*
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* The purpose of this file and the tracehook_* layer is to consolidate
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* the interface that the kernel core and arch code uses to enable any
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* user debugging or tracing facility (such as ptrace). The interfaces
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* here are carefully documented so that maintainers of core and arch
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* code do not need to think about the implementation details of the
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* tracing facilities. Likewise, maintainers of the tracing code do not
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* need to understand all the calling core or arch code in detail, just
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* documented circumstances of each call, such as locking conditions.
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*
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* If the calling core code changes so that locking is different, then
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* it is ok to change the interface documented here. The maintainer of
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* core code changing should notify the maintainers of the tracing code
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* that they need to work out the change.
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*
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* Some tracehook_*() inlines take arguments that the current tracing
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* implementations might not necessarily use. These function signatures
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* are chosen to pass in all the information that is on hand in the
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* caller and might conceivably be relevant to a tracer, so that the
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* core code won't have to be updated when tracing adds more features.
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* If a call site changes so that some of those parameters are no longer
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* already on hand without extra work, then the tracehook_* interface
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* can change so there is no make-work burden on the core code. The
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* maintainer of core code changing should notify the maintainers of the
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* tracing code that they need to work out the change.
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*/
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#ifndef _LINUX_TRACEHOOK_H
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#define _LINUX_TRACEHOOK_H 1
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#include <linux/sched.h>
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#include <linux/ptrace.h>
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#include <linux/security.h>
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struct linux_binprm;
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/**
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* tracehook_expect_breakpoints - guess if task memory might be touched
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* @task: current task, making a new mapping
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*
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* Return nonzero if @task is expected to want breakpoint insertion in
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* its memory at some point. A zero return is no guarantee it won't
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* be done, but this is a hint that it's known to be likely.
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*
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* May be called with @task->mm->mmap_sem held for writing.
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*/
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static inline int tracehook_expect_breakpoints(struct task_struct *task)
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{
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return (task_ptrace(task) & PT_PTRACED) != 0;
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}
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/*
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* ptrace report for syscall entry and exit looks identical.
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*/
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static inline void ptrace_report_syscall(struct pt_regs *regs)
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{
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int ptrace = task_ptrace(current);
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if (!(ptrace & PT_PTRACED))
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return;
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ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
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/*
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* this isn't the same as continuing with a signal, but it will do
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* for normal use. strace only continues with a signal if the
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* stopping signal is not SIGTRAP. -brl
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*/
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if (current->exit_code) {
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send_sig(current->exit_code, current, 1);
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current->exit_code = 0;
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}
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}
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/**
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* tracehook_report_syscall_entry - task is about to attempt a system call
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* @regs: user register state of current task
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*
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* This will be called if %TIF_SYSCALL_TRACE has been set, when the
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* current task has just entered the kernel for a system call.
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* Full user register state is available here. Changing the values
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* in @regs can affect the system call number and arguments to be tried.
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* It is safe to block here, preventing the system call from beginning.
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*
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* Returns zero normally, or nonzero if the calling arch code should abort
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* the system call. That must prevent normal entry so no system call is
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* made. If @task ever returns to user mode after this, its register state
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* is unspecified, but should be something harmless like an %ENOSYS error
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* return. It should preserve enough information so that syscall_rollback()
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* can work (see asm-generic/syscall.h).
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*
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* Called without locks, just after entering kernel mode.
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*/
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static inline __must_check int tracehook_report_syscall_entry(
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struct pt_regs *regs)
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{
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ptrace_report_syscall(regs);
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return 0;
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}
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/**
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* tracehook_report_syscall_exit - task has just finished a system call
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* @regs: user register state of current task
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* @step: nonzero if simulating single-step or block-step
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*
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* This will be called if %TIF_SYSCALL_TRACE has been set, when the
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* current task has just finished an attempted system call. Full
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* user register state is available here. It is safe to block here,
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* preventing signals from being processed.
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*
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* If @step is nonzero, this report is also in lieu of the normal
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* trap that would follow the system call instruction because
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* user_enable_block_step() or user_enable_single_step() was used.
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* In this case, %TIF_SYSCALL_TRACE might not be set.
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*
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* Called without locks, just before checking for pending signals.
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*/
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static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
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{
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if (step) {
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siginfo_t info;
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user_single_step_siginfo(current, regs, &info);
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force_sig_info(SIGTRAP, &info, current);
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return;
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}
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ptrace_report_syscall(regs);
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}
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/**
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* tracehook_unsafe_exec - check for exec declared unsafe due to tracing
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* @task: current task doing exec
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*
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* Return %LSM_UNSAFE_* bits applied to an exec because of tracing.
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*
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* @task->signal->cred_guard_mutex is held by the caller through the do_execve().
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*/
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static inline int tracehook_unsafe_exec(struct task_struct *task)
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{
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int unsafe = 0;
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int ptrace = task_ptrace(task);
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if (ptrace & PT_PTRACED) {
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if (ptrace & PT_PTRACE_CAP)
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unsafe |= LSM_UNSAFE_PTRACE_CAP;
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else
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unsafe |= LSM_UNSAFE_PTRACE;
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}
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return unsafe;
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}
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/**
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* tracehook_tracer_task - return the task that is tracing the given task
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* @tsk: task to consider
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*
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* Returns NULL if noone is tracing @task, or the &struct task_struct
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* pointer to its tracer.
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*
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* Must called under rcu_read_lock(). The pointer returned might be kept
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* live only by RCU. During exec, this may be called with task_lock()
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* held on @task, still held from when tracehook_unsafe_exec() was called.
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*/
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static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk)
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{
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if (task_ptrace(tsk) & PT_PTRACED)
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return rcu_dereference(tsk->parent);
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return NULL;
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}
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/**
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* tracehook_report_exec - a successful exec was completed
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* @fmt: &struct linux_binfmt that performed the exec
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* @bprm: &struct linux_binprm containing exec details
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* @regs: user-mode register state
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*
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* An exec just completed, we are shortly going to return to user mode.
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* The freshly initialized register state can be seen and changed in @regs.
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* The name, file and other pointers in @bprm are still on hand to be
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* inspected, but will be freed as soon as this returns.
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*
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* Called with no locks, but with some kernel resources held live
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* and a reference on @fmt->module.
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*/
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static inline void tracehook_report_exec(struct linux_binfmt *fmt,
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struct linux_binprm *bprm,
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struct pt_regs *regs)
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{
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if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
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unlikely(task_ptrace(current) & PT_PTRACED))
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send_sig(SIGTRAP, current, 0);
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}
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/**
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* tracehook_report_exit - task has begun to exit
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* @exit_code: pointer to value destined for @current->exit_code
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*
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* @exit_code points to the value passed to do_exit(), which tracing
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* might change here. This is almost the first thing in do_exit(),
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* before freeing any resources or setting the %PF_EXITING flag.
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*
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* Called with no locks held.
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*/
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static inline void tracehook_report_exit(long *exit_code)
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{
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ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
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}
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/**
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* tracehook_prepare_clone - prepare for new child to be cloned
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* @clone_flags: %CLONE_* flags from clone/fork/vfork system call
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*
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* This is called before a new user task is to be cloned.
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* Its return value will be passed to tracehook_finish_clone().
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*
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* Called with no locks held.
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*/
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static inline int tracehook_prepare_clone(unsigned clone_flags)
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{
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if (clone_flags & CLONE_UNTRACED)
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return 0;
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if (clone_flags & CLONE_VFORK) {
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if (current->ptrace & PT_TRACE_VFORK)
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return PTRACE_EVENT_VFORK;
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} else if ((clone_flags & CSIGNAL) != SIGCHLD) {
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if (current->ptrace & PT_TRACE_CLONE)
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return PTRACE_EVENT_CLONE;
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} else if (current->ptrace & PT_TRACE_FORK)
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return PTRACE_EVENT_FORK;
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return 0;
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}
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/**
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* tracehook_finish_clone - new child created and being attached
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* @child: new child task
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* @clone_flags: %CLONE_* flags from clone/fork/vfork system call
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* @trace: return value from tracehook_prepare_clone()
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*
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* This is called immediately after adding @child to its parent's children list.
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* The @trace value is that returned by tracehook_prepare_clone().
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*
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* Called with current's siglock and write_lock_irq(&tasklist_lock) held.
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*/
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static inline void tracehook_finish_clone(struct task_struct *child,
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unsigned long clone_flags, int trace)
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{
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ptrace_init_task(child, (clone_flags & CLONE_PTRACE) || trace);
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}
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/**
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* tracehook_report_clone - in parent, new child is about to start running
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* @regs: parent's user register state
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* @clone_flags: flags from parent's system call
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* @pid: new child's PID in the parent's namespace
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* @child: new child task
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*
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* Called after a child is set up, but before it has been started running.
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* This is not a good place to block, because the child has not started
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* yet. Suspend the child here if desired, and then block in
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* tracehook_report_clone_complete(). This must prevent the child from
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* self-reaping if tracehook_report_clone_complete() uses the @child
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* pointer; otherwise it might have died and been released by the time
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* tracehook_report_clone_complete() is called.
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*
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* Called with no locks held, but the child cannot run until this returns.
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*/
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static inline void tracehook_report_clone(struct pt_regs *regs,
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unsigned long clone_flags,
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pid_t pid, struct task_struct *child)
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{
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if (unlikely(task_ptrace(child))) {
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/*
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* It doesn't matter who attached/attaching to this
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* task, the pending SIGSTOP is right in any case.
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*/
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sigaddset(&child->pending.signal, SIGSTOP);
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set_tsk_thread_flag(child, TIF_SIGPENDING);
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}
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}
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/**
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* tracehook_report_clone_complete - new child is running
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* @trace: return value from tracehook_prepare_clone()
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* @regs: parent's user register state
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* @clone_flags: flags from parent's system call
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* @pid: new child's PID in the parent's namespace
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* @child: child task, already running
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*
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* This is called just after the child has started running. This is
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* just before the clone/fork syscall returns, or blocks for vfork
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* child completion if @clone_flags has the %CLONE_VFORK bit set.
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* The @child pointer may be invalid if a self-reaping child died and
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* tracehook_report_clone() took no action to prevent it from self-reaping.
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*
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* Called with no locks held.
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*/
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static inline void tracehook_report_clone_complete(int trace,
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struct pt_regs *regs,
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unsigned long clone_flags,
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pid_t pid,
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struct task_struct *child)
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{
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if (unlikely(trace))
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ptrace_event(0, trace, pid);
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}
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/**
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* tracehook_report_vfork_done - vfork parent's child has exited or exec'd
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* @child: child task, already running
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* @pid: new child's PID in the parent's namespace
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*
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* Called after a %CLONE_VFORK parent has waited for the child to complete.
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* The clone/vfork system call will return immediately after this.
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* The @child pointer may be invalid if a self-reaping child died and
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* tracehook_report_clone() took no action to prevent it from self-reaping.
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*
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* Called with no locks held.
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*/
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static inline void tracehook_report_vfork_done(struct task_struct *child,
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pid_t pid)
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{
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ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid);
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}
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/**
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* tracehook_prepare_release_task - task is being reaped, clean up tracing
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* @task: task in %EXIT_DEAD state
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*
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* This is called in release_task() just before @task gets finally reaped
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* and freed. This would be the ideal place to remove and clean up any
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* tracing-related state for @task.
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*
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* Called with no locks held.
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*/
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static inline void tracehook_prepare_release_task(struct task_struct *task)
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{
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}
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/**
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* tracehook_finish_release_task - final tracing clean-up
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* @task: task in %EXIT_DEAD state
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*
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* This is called in release_task() when @task is being in the middle of
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* being reaped. After this, there must be no tracing entanglements.
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*
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* Called with write_lock_irq(&tasklist_lock) held.
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*/
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static inline void tracehook_finish_release_task(struct task_struct *task)
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{
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ptrace_release_task(task);
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}
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/**
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* tracehook_signal_handler - signal handler setup is complete
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* @sig: number of signal being delivered
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* @info: siginfo_t of signal being delivered
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* @ka: sigaction setting that chose the handler
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* @regs: user register state
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* @stepping: nonzero if debugger single-step or block-step in use
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*
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* Called by the arch code after a signal handler has been set up.
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* Register and stack state reflects the user handler about to run.
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* Signal mask changes have already been made.
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*
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* Called without locks, shortly before returning to user mode
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* (or handling more signals).
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*/
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static inline void tracehook_signal_handler(int sig, siginfo_t *info,
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const struct k_sigaction *ka,
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struct pt_regs *regs, int stepping)
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{
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if (stepping)
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ptrace_notify(SIGTRAP);
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}
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/**
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* tracehook_consider_ignored_signal - suppress short-circuit of ignored signal
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* @task: task receiving the signal
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* @sig: signal number being sent
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*
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* Return zero iff tracing doesn't care to examine this ignored signal,
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* so it can short-circuit normal delivery and never even get queued.
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*
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* Called with @task->sighand->siglock held.
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*/
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static inline int tracehook_consider_ignored_signal(struct task_struct *task,
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int sig)
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{
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return (task_ptrace(task) & PT_PTRACED) != 0;
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}
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/**
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* tracehook_consider_fatal_signal - suppress special handling of fatal signal
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* @task: task receiving the signal
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* @sig: signal number being sent
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*
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* Return nonzero to prevent special handling of this termination signal.
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* Normally handler for signal is %SIG_DFL. It can be %SIG_IGN if @sig is
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* ignored, in which case force_sig() is about to reset it to %SIG_DFL.
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* When this returns zero, this signal might cause a quick termination
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* that does not give the debugger a chance to intercept the signal.
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*
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* Called with or without @task->sighand->siglock held.
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*/
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static inline int tracehook_consider_fatal_signal(struct task_struct *task,
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int sig)
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{
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return (task_ptrace(task) & PT_PTRACED) != 0;
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}
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/**
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* tracehook_force_sigpending - let tracing force signal_pending(current) on
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*
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* Called when recomputing our signal_pending() flag. Return nonzero
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* to force the signal_pending() flag on, so that tracehook_get_signal()
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* will be called before the next return to user mode.
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*
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* Called with @current->sighand->siglock held.
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*/
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static inline int tracehook_force_sigpending(void)
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{
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return 0;
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}
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/**
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* tracehook_get_signal - deliver synthetic signal to traced task
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* @task: @current
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* @regs: task_pt_regs(@current)
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* @info: details of synthetic signal
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* @return_ka: sigaction for synthetic signal
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*
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* Return zero to check for a real pending signal normally.
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* Return -1 after releasing the siglock to repeat the check.
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* Return a signal number to induce an artifical signal delivery,
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* setting *@info and *@return_ka to specify its details and behavior.
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*
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* The @return_ka->sa_handler value controls the disposition of the
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* signal, no matter the signal number. For %SIG_DFL, the return value
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* is a representative signal to indicate the behavior (e.g. %SIGTERM
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* for death, %SIGQUIT for core dump, %SIGSTOP for job control stop,
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* %SIGTSTP for stop unless in an orphaned pgrp), but the signal number
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* reported will be @info->si_signo instead.
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*
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* Called with @task->sighand->siglock held, before dequeuing pending signals.
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*/
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static inline int tracehook_get_signal(struct task_struct *task,
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struct pt_regs *regs,
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siginfo_t *info,
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struct k_sigaction *return_ka)
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{
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return 0;
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}
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/**
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* tracehook_notify_jctl - report about job control stop/continue
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* @notify: zero, %CLD_STOPPED or %CLD_CONTINUED
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* @why: %CLD_STOPPED or %CLD_CONTINUED
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*
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* This is called when we might call do_notify_parent_cldstop().
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*
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* @notify is zero if we would not ordinarily send a %SIGCHLD,
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* or is the %CLD_STOPPED or %CLD_CONTINUED .si_code for %SIGCHLD.
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*
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* @why is %CLD_STOPPED when about to stop for job control;
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* we are already in %TASK_STOPPED state, about to call schedule().
|
|
* It might also be that we have just exited (check %PF_EXITING),
|
|
* but need to report that a group-wide stop is complete.
|
|
*
|
|
* @why is %CLD_CONTINUED when waking up after job control stop and
|
|
* ready to make a delayed @notify report.
|
|
*
|
|
* Return the %CLD_* value for %SIGCHLD, or zero to generate no signal.
|
|
*
|
|
* Called with the siglock held.
|
|
*/
|
|
static inline int tracehook_notify_jctl(int notify, int why)
|
|
{
|
|
return notify ?: (current->ptrace & PT_PTRACED) ? why : 0;
|
|
}
|
|
|
|
/**
|
|
* tracehook_finish_jctl - report about return from job control stop
|
|
*
|
|
* This is called by do_signal_stop() after wakeup.
|
|
*/
|
|
static inline void tracehook_finish_jctl(void)
|
|
{
|
|
}
|
|
|
|
#define DEATH_REAP -1
|
|
#define DEATH_DELAYED_GROUP_LEADER -2
|
|
|
|
/**
|
|
* tracehook_notify_death - task is dead, ready to notify parent
|
|
* @task: @current task now exiting
|
|
* @death_cookie: value to pass to tracehook_report_death()
|
|
* @group_dead: nonzero if this was the last thread in the group to die
|
|
*
|
|
* A return value >= 0 means call do_notify_parent() with that signal
|
|
* number. Negative return value can be %DEATH_REAP to self-reap right
|
|
* now, or %DEATH_DELAYED_GROUP_LEADER to a zombie without notifying our
|
|
* parent. Note that a return value of 0 means a do_notify_parent() call
|
|
* that sends no signal, but still wakes up a parent blocked in wait*().
|
|
*
|
|
* Called with write_lock_irq(&tasklist_lock) held.
|
|
*/
|
|
static inline int tracehook_notify_death(struct task_struct *task,
|
|
void **death_cookie, int group_dead)
|
|
{
|
|
if (task_detached(task))
|
|
return task->ptrace ? SIGCHLD : DEATH_REAP;
|
|
|
|
/*
|
|
* If something other than our normal parent is ptracing us, then
|
|
* send it a SIGCHLD instead of honoring exit_signal. exit_signal
|
|
* only has special meaning to our real parent.
|
|
*/
|
|
if (thread_group_empty(task) && !ptrace_reparented(task))
|
|
return task->exit_signal;
|
|
|
|
return task->ptrace ? SIGCHLD : DEATH_DELAYED_GROUP_LEADER;
|
|
}
|
|
|
|
/**
|
|
* tracehook_report_death - task is dead and ready to be reaped
|
|
* @task: @current task now exiting
|
|
* @signal: return value from tracheook_notify_death()
|
|
* @death_cookie: value passed back from tracehook_notify_death()
|
|
* @group_dead: nonzero if this was the last thread in the group to die
|
|
*
|
|
* Thread has just become a zombie or is about to self-reap. If positive,
|
|
* @signal is the signal number just sent to the parent (usually %SIGCHLD).
|
|
* If @signal is %DEATH_REAP, this thread will self-reap. If @signal is
|
|
* %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie.
|
|
* The @death_cookie was passed back by tracehook_notify_death().
|
|
*
|
|
* If normal reaping is not inhibited, @task->exit_state might be changing
|
|
* in parallel.
|
|
*
|
|
* Called without locks.
|
|
*/
|
|
static inline void tracehook_report_death(struct task_struct *task,
|
|
int signal, void *death_cookie,
|
|
int group_dead)
|
|
{
|
|
}
|
|
|
|
#ifdef TIF_NOTIFY_RESUME
|
|
/**
|
|
* 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)
|
|
{
|
|
if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
|
|
kick_process(task);
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
}
|
|
#endif /* TIF_NOTIFY_RESUME */
|
|
|
|
#endif /* <linux/tracehook.h> */
|