195 lines
7.1 KiB
C
195 lines
7.1 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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#include <linux/task_work.h>
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#include <linux/memcontrol.h>
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#include <linux/blk-cgroup.h>
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struct linux_binprm;
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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 int ptrace_report_syscall(struct pt_regs *regs)
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{
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int ptrace = current->ptrace;
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if (!(ptrace & PT_PTRACED))
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return 0;
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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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return fatal_signal_pending(current);
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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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return ptrace_report_syscall(regs);
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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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user_single_step_report(regs);
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else
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ptrace_report_syscall(regs);
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}
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/**
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* tracehook_signal_handler - signal handler setup is complete
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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 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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* set_notify_resume - cause tracehook_notify_resume() to be called
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* @task: task that will call tracehook_notify_resume()
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*
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* Calling this arranges that @task will call tracehook_notify_resume()
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* before returning to user mode. If it's already running in user mode,
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* it will enter the kernel and call tracehook_notify_resume() soon.
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* If it's blocked, it will not be woken.
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*/
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static inline void set_notify_resume(struct task_struct *task)
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{
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#ifdef TIF_NOTIFY_RESUME
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if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
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kick_process(task);
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#endif
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}
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/**
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* tracehook_notify_resume - report when about to return to user mode
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* @regs: user-mode registers of @current task
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*
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* This is called when %TIF_NOTIFY_RESUME has been set. Now we are
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* about to return to user mode, and the user state in @regs can be
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* inspected or adjusted. The caller in arch code has cleared
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* %TIF_NOTIFY_RESUME before the call. If the flag gets set again
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* asynchronously, this will be called again before we return to
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* user mode.
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*
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* Called without locks.
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*/
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static inline void tracehook_notify_resume(struct pt_regs *regs)
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{
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/*
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* The caller just cleared TIF_NOTIFY_RESUME. This barrier
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* pairs with task_work_add()->set_notify_resume() after
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* hlist_add_head(task->task_works);
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*/
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smp_mb__after_atomic();
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if (unlikely(current->task_works))
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task_work_run();
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mem_cgroup_handle_over_high();
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blkcg_maybe_throttle_current();
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}
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#endif /* <linux/tracehook.h> */
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