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![Peter Zijlstra](/assets/img/avatar_default.png)
While auditing all module notifiers I noticed a whole bunch of fail wrt the return value. Notifiers have a 'special' return semantics. As is; NOTIFY_DONE vs NOTIFY_OK is a bit vague; but notifier_from_errno(0) results in NOTIFY_OK and NOTIFY_DONE has a comment that says "Don't care". From this I've used NOTIFY_DONE when the function completely ignores the callback and notifier_to_error() isn't used. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Reviewed-by: Robert Richter <rric@kernel.org> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20200818135804.385360407@infradead.org
591 lines
13 KiB
C
591 lines
13 KiB
C
/**
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* @file buffer_sync.c
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*
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* @remark Copyright 2002-2009 OProfile authors
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* @remark Read the file COPYING
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*
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* @author John Levon <levon@movementarian.org>
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* @author Barry Kasindorf
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* @author Robert Richter <robert.richter@amd.com>
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*
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* This is the core of the buffer management. Each
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* CPU buffer is processed and entered into the
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* global event buffer. Such processing is necessary
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* in several circumstances, mentioned below.
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*
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* The processing does the job of converting the
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* transitory EIP value into a persistent dentry/offset
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* value that the profiler can record at its leisure.
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*
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* See fs/dcookies.c for a description of the dentry/offset
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* objects.
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*/
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/workqueue.h>
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#include <linux/notifier.h>
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#include <linux/dcookies.h>
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#include <linux/profile.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/oprofile.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/task.h>
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#include <linux/gfp.h>
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#include "oprofile_stats.h"
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#include "event_buffer.h"
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#include "cpu_buffer.h"
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#include "buffer_sync.h"
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static LIST_HEAD(dying_tasks);
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static LIST_HEAD(dead_tasks);
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static cpumask_var_t marked_cpus;
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static DEFINE_SPINLOCK(task_mortuary);
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static void process_task_mortuary(void);
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/* Take ownership of the task struct and place it on the
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* list for processing. Only after two full buffer syncs
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* does the task eventually get freed, because by then
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* we are sure we will not reference it again.
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* Can be invoked from softirq via RCU callback due to
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* call_rcu() of the task struct, hence the _irqsave.
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*/
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static int
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task_free_notify(struct notifier_block *self, unsigned long val, void *data)
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{
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unsigned long flags;
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struct task_struct *task = data;
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spin_lock_irqsave(&task_mortuary, flags);
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list_add(&task->tasks, &dying_tasks);
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spin_unlock_irqrestore(&task_mortuary, flags);
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return NOTIFY_OK;
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}
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/* The task is on its way out. A sync of the buffer means we can catch
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* any remaining samples for this task.
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*/
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static int
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task_exit_notify(struct notifier_block *self, unsigned long val, void *data)
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{
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/* To avoid latency problems, we only process the current CPU,
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* hoping that most samples for the task are on this CPU
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*/
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sync_buffer(raw_smp_processor_id());
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return 0;
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}
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/* The task is about to try a do_munmap(). We peek at what it's going to
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* do, and if it's an executable region, process the samples first, so
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* we don't lose any. This does not have to be exact, it's a QoI issue
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* only.
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*/
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static int
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munmap_notify(struct notifier_block *self, unsigned long val, void *data)
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{
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unsigned long addr = (unsigned long)data;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *mpnt;
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mmap_read_lock(mm);
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mpnt = find_vma(mm, addr);
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if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
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mmap_read_unlock(mm);
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/* To avoid latency problems, we only process the current CPU,
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* hoping that most samples for the task are on this CPU
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*/
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sync_buffer(raw_smp_processor_id());
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return 0;
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}
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mmap_read_unlock(mm);
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return 0;
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}
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/* We need to be told about new modules so we don't attribute to a previously
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* loaded module, or drop the samples on the floor.
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*/
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static int
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module_load_notify(struct notifier_block *self, unsigned long val, void *data)
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{
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#ifdef CONFIG_MODULES
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if (val != MODULE_STATE_COMING)
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return NOTIFY_DONE;
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/* FIXME: should we process all CPU buffers ? */
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mutex_lock(&buffer_mutex);
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add_event_entry(ESCAPE_CODE);
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add_event_entry(MODULE_LOADED_CODE);
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mutex_unlock(&buffer_mutex);
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#endif
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return NOTIFY_OK;
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}
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static struct notifier_block task_free_nb = {
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.notifier_call = task_free_notify,
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};
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static struct notifier_block task_exit_nb = {
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.notifier_call = task_exit_notify,
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};
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static struct notifier_block munmap_nb = {
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.notifier_call = munmap_notify,
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};
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static struct notifier_block module_load_nb = {
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.notifier_call = module_load_notify,
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};
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static void free_all_tasks(void)
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{
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/* make sure we don't leak task structs */
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process_task_mortuary();
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process_task_mortuary();
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}
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int sync_start(void)
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{
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int err;
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if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL))
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return -ENOMEM;
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err = task_handoff_register(&task_free_nb);
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if (err)
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goto out1;
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err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
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if (err)
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goto out2;
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err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
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if (err)
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goto out3;
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err = register_module_notifier(&module_load_nb);
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if (err)
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goto out4;
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start_cpu_work();
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out:
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return err;
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out4:
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profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
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out3:
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profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
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out2:
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task_handoff_unregister(&task_free_nb);
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free_all_tasks();
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out1:
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free_cpumask_var(marked_cpus);
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goto out;
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}
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void sync_stop(void)
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{
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end_cpu_work();
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unregister_module_notifier(&module_load_nb);
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profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
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profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
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task_handoff_unregister(&task_free_nb);
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barrier(); /* do all of the above first */
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flush_cpu_work();
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free_all_tasks();
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free_cpumask_var(marked_cpus);
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}
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/* Optimisation. We can manage without taking the dcookie sem
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* because we cannot reach this code without at least one
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* dcookie user still being registered (namely, the reader
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* of the event buffer). */
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static inline unsigned long fast_get_dcookie(const struct path *path)
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{
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unsigned long cookie;
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if (path->dentry->d_flags & DCACHE_COOKIE)
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return (unsigned long)path->dentry;
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get_dcookie(path, &cookie);
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return cookie;
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}
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/* Look up the dcookie for the task's mm->exe_file,
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* which corresponds loosely to "application name". This is
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* not strictly necessary but allows oprofile to associate
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* shared-library samples with particular applications
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*/
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static unsigned long get_exec_dcookie(struct mm_struct *mm)
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{
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unsigned long cookie = NO_COOKIE;
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struct file *exe_file;
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if (!mm)
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goto done;
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exe_file = get_mm_exe_file(mm);
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if (!exe_file)
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goto done;
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cookie = fast_get_dcookie(&exe_file->f_path);
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fput(exe_file);
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done:
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return cookie;
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}
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/* Convert the EIP value of a sample into a persistent dentry/offset
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* pair that can then be added to the global event buffer. We make
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* sure to do this lookup before a mm->mmap modification happens so
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* we don't lose track.
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*
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* The caller must ensure the mm is not nil (ie: not a kernel thread).
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*/
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static unsigned long
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lookup_dcookie(struct mm_struct *mm, unsigned long addr, off_t *offset)
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{
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unsigned long cookie = NO_COOKIE;
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struct vm_area_struct *vma;
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mmap_read_lock(mm);
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for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
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if (addr < vma->vm_start || addr >= vma->vm_end)
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continue;
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if (vma->vm_file) {
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cookie = fast_get_dcookie(&vma->vm_file->f_path);
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*offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
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vma->vm_start;
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} else {
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/* must be an anonymous map */
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*offset = addr;
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}
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break;
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}
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if (!vma)
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cookie = INVALID_COOKIE;
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mmap_read_unlock(mm);
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return cookie;
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}
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static unsigned long last_cookie = INVALID_COOKIE;
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static void add_cpu_switch(int i)
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{
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add_event_entry(ESCAPE_CODE);
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add_event_entry(CPU_SWITCH_CODE);
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add_event_entry(i);
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last_cookie = INVALID_COOKIE;
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}
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static void add_kernel_ctx_switch(unsigned int in_kernel)
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{
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add_event_entry(ESCAPE_CODE);
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if (in_kernel)
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add_event_entry(KERNEL_ENTER_SWITCH_CODE);
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else
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add_event_entry(KERNEL_EXIT_SWITCH_CODE);
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}
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static void
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add_user_ctx_switch(struct task_struct const *task, unsigned long cookie)
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{
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add_event_entry(ESCAPE_CODE);
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add_event_entry(CTX_SWITCH_CODE);
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add_event_entry(task->pid);
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add_event_entry(cookie);
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/* Another code for daemon back-compat */
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add_event_entry(ESCAPE_CODE);
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add_event_entry(CTX_TGID_CODE);
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add_event_entry(task->tgid);
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}
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static void add_cookie_switch(unsigned long cookie)
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{
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add_event_entry(ESCAPE_CODE);
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add_event_entry(COOKIE_SWITCH_CODE);
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add_event_entry(cookie);
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}
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static void add_trace_begin(void)
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{
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add_event_entry(ESCAPE_CODE);
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add_event_entry(TRACE_BEGIN_CODE);
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}
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static void add_data(struct op_entry *entry, struct mm_struct *mm)
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{
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unsigned long code, pc, val;
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unsigned long cookie;
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off_t offset;
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if (!op_cpu_buffer_get_data(entry, &code))
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return;
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if (!op_cpu_buffer_get_data(entry, &pc))
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return;
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if (!op_cpu_buffer_get_size(entry))
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return;
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if (mm) {
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cookie = lookup_dcookie(mm, pc, &offset);
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if (cookie == NO_COOKIE)
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offset = pc;
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if (cookie == INVALID_COOKIE) {
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atomic_inc(&oprofile_stats.sample_lost_no_mapping);
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offset = pc;
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}
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if (cookie != last_cookie) {
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add_cookie_switch(cookie);
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last_cookie = cookie;
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}
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} else
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offset = pc;
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add_event_entry(ESCAPE_CODE);
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add_event_entry(code);
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add_event_entry(offset); /* Offset from Dcookie */
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while (op_cpu_buffer_get_data(entry, &val))
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add_event_entry(val);
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}
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static inline void add_sample_entry(unsigned long offset, unsigned long event)
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{
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add_event_entry(offset);
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add_event_entry(event);
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}
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/*
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* Add a sample to the global event buffer. If possible the
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* sample is converted into a persistent dentry/offset pair
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* for later lookup from userspace. Return 0 on failure.
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*/
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static int
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add_sample(struct mm_struct *mm, struct op_sample *s, int in_kernel)
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{
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unsigned long cookie;
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off_t offset;
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if (in_kernel) {
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add_sample_entry(s->eip, s->event);
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return 1;
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}
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/* add userspace sample */
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if (!mm) {
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atomic_inc(&oprofile_stats.sample_lost_no_mm);
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return 0;
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}
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cookie = lookup_dcookie(mm, s->eip, &offset);
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if (cookie == INVALID_COOKIE) {
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atomic_inc(&oprofile_stats.sample_lost_no_mapping);
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return 0;
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}
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if (cookie != last_cookie) {
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add_cookie_switch(cookie);
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last_cookie = cookie;
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}
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add_sample_entry(offset, s->event);
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return 1;
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}
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static void release_mm(struct mm_struct *mm)
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{
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if (!mm)
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return;
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mmput(mm);
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}
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static inline int is_code(unsigned long val)
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{
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return val == ESCAPE_CODE;
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}
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/* Move tasks along towards death. Any tasks on dead_tasks
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* will definitely have no remaining references in any
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* CPU buffers at this point, because we use two lists,
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* and to have reached the list, it must have gone through
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* one full sync already.
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*/
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static void process_task_mortuary(void)
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{
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unsigned long flags;
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LIST_HEAD(local_dead_tasks);
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struct task_struct *task;
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struct task_struct *ttask;
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spin_lock_irqsave(&task_mortuary, flags);
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list_splice_init(&dead_tasks, &local_dead_tasks);
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list_splice_init(&dying_tasks, &dead_tasks);
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spin_unlock_irqrestore(&task_mortuary, flags);
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list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
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list_del(&task->tasks);
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free_task(task);
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}
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}
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static void mark_done(int cpu)
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{
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int i;
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cpumask_set_cpu(cpu, marked_cpus);
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for_each_online_cpu(i) {
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if (!cpumask_test_cpu(i, marked_cpus))
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return;
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}
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/* All CPUs have been processed at least once,
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* we can process the mortuary once
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*/
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process_task_mortuary();
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cpumask_clear(marked_cpus);
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}
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/* FIXME: this is not sufficient if we implement syscall barrier backtrace
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* traversal, the code switch to sb_sample_start at first kernel enter/exit
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* switch so we need a fifth state and some special handling in sync_buffer()
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*/
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typedef enum {
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sb_bt_ignore = -2,
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sb_buffer_start,
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sb_bt_start,
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sb_sample_start,
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} sync_buffer_state;
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/* Sync one of the CPU's buffers into the global event buffer.
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* Here we need to go through each batch of samples punctuated
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* by context switch notes, taking the task's mmap_lock and doing
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* lookup in task->mm->mmap to convert EIP into dcookie/offset
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* value.
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*/
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void sync_buffer(int cpu)
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{
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struct mm_struct *mm = NULL;
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struct mm_struct *oldmm;
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unsigned long val;
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struct task_struct *new;
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unsigned long cookie = 0;
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int in_kernel = 1;
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sync_buffer_state state = sb_buffer_start;
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unsigned int i;
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unsigned long available;
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unsigned long flags;
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struct op_entry entry;
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struct op_sample *sample;
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mutex_lock(&buffer_mutex);
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add_cpu_switch(cpu);
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op_cpu_buffer_reset(cpu);
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available = op_cpu_buffer_entries(cpu);
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for (i = 0; i < available; ++i) {
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sample = op_cpu_buffer_read_entry(&entry, cpu);
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if (!sample)
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break;
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if (is_code(sample->eip)) {
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flags = sample->event;
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if (flags & TRACE_BEGIN) {
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state = sb_bt_start;
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add_trace_begin();
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}
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if (flags & KERNEL_CTX_SWITCH) {
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/* kernel/userspace switch */
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in_kernel = flags & IS_KERNEL;
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if (state == sb_buffer_start)
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state = sb_sample_start;
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add_kernel_ctx_switch(flags & IS_KERNEL);
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}
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if (flags & USER_CTX_SWITCH
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&& op_cpu_buffer_get_data(&entry, &val)) {
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/* userspace context switch */
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new = (struct task_struct *)val;
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oldmm = mm;
|
|
release_mm(oldmm);
|
|
mm = get_task_mm(new);
|
|
if (mm != oldmm)
|
|
cookie = get_exec_dcookie(mm);
|
|
add_user_ctx_switch(new, cookie);
|
|
}
|
|
if (op_cpu_buffer_get_size(&entry))
|
|
add_data(&entry, mm);
|
|
continue;
|
|
}
|
|
|
|
if (state < sb_bt_start)
|
|
/* ignore sample */
|
|
continue;
|
|
|
|
if (add_sample(mm, sample, in_kernel))
|
|
continue;
|
|
|
|
/* ignore backtraces if failed to add a sample */
|
|
if (state == sb_bt_start) {
|
|
state = sb_bt_ignore;
|
|
atomic_inc(&oprofile_stats.bt_lost_no_mapping);
|
|
}
|
|
}
|
|
release_mm(mm);
|
|
|
|
mark_done(cpu);
|
|
|
|
mutex_unlock(&buffer_mutex);
|
|
}
|
|
|
|
/* The function can be used to add a buffer worth of data directly to
|
|
* the kernel buffer. The buffer is assumed to be a circular buffer.
|
|
* Take the entries from index start and end at index end, wrapping
|
|
* at max_entries.
|
|
*/
|
|
void oprofile_put_buff(unsigned long *buf, unsigned int start,
|
|
unsigned int stop, unsigned int max)
|
|
{
|
|
int i;
|
|
|
|
i = start;
|
|
|
|
mutex_lock(&buffer_mutex);
|
|
while (i != stop) {
|
|
add_event_entry(buf[i++]);
|
|
|
|
if (i >= max)
|
|
i = 0;
|
|
}
|
|
|
|
mutex_unlock(&buffer_mutex);
|
|
}
|
|
|