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225 lines
7.9 KiB
225 lines
7.9 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* |
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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 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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unsigned long message) |
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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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current->ptrace_message = message; |
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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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current->ptrace_message = 0; |
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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 %SYSCALL_WORK_SYSCALL_TRACE or |
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* %SYSCALL_WORK_SYSCALL_EMU have been set, when the current task has just |
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* entered the kernel for a system call. Full user register state is |
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* available here. Changing the values in @regs can affect the system |
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* call number and arguments to be tried. It is safe to block here, |
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* 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, PTRACE_EVENTMSG_SYSCALL_ENTRY); |
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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 %SYSCALL_WORK_SYSCALL_TRACE has been set, when |
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* the 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, %SYSCALL_WORK_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, PTRACE_EVENTMSG_SYSCALL_EXIT); |
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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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clear_thread_flag(TIF_NOTIFY_RESUME); |
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/* |
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* This barrier 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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#ifdef CONFIG_KEYS_REQUEST_CACHE |
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if (unlikely(current->cached_requested_key)) { |
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key_put(current->cached_requested_key); |
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current->cached_requested_key = NULL; |
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} |
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#endif |
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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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/* |
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* called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This |
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* is currently used by TWA_SIGNAL based task_work, which requires breaking |
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* wait loops to ensure that task_work is noticed and run. |
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*/ |
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static inline void tracehook_notify_signal(void) |
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{ |
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clear_thread_flag(TIF_NOTIFY_SIGNAL); |
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smp_mb__after_atomic(); |
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if (current->task_works) |
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task_work_run(); |
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} |
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/* |
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* Called when we have work to process from exit_to_user_mode_loop() |
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*/ |
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static inline void set_notify_signal(struct task_struct *task) |
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{ |
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if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && |
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!wake_up_state(task, TASK_INTERRUPTIBLE)) |
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kick_process(task); |
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} |
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#endif /* <linux/tracehook.h> */
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