LCOV - code coverage report
Current view: top level - kernel/events - callchain.c (source / functions) Hit Total Coverage
Test: landlock.info Lines: 0 121 0.0 %
Date: 2021-04-22 12:43:58 Functions: 0 11 0.0 %

          Line data    Source code
       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * Performance events callchain code, extracted from core.c:
       4             :  *
       5             :  *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
       6             :  *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
       7             :  *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
       8             :  *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
       9             :  */
      10             : 
      11             : #include <linux/perf_event.h>
      12             : #include <linux/slab.h>
      13             : #include <linux/sched/task_stack.h>
      14             : 
      15             : #include "internal.h"
      16             : 
      17             : struct callchain_cpus_entries {
      18             :         struct rcu_head                 rcu_head;
      19             :         struct perf_callchain_entry     *cpu_entries[];
      20             : };
      21             : 
      22             : int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
      23             : int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
      24             : 
      25           0 : static inline size_t perf_callchain_entry__sizeof(void)
      26             : {
      27           0 :         return (sizeof(struct perf_callchain_entry) +
      28           0 :                 sizeof(__u64) * (sysctl_perf_event_max_stack +
      29             :                                  sysctl_perf_event_max_contexts_per_stack));
      30             : }
      31             : 
      32             : static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
      33             : static atomic_t nr_callchain_events;
      34             : static DEFINE_MUTEX(callchain_mutex);
      35             : static struct callchain_cpus_entries *callchain_cpus_entries;
      36             : 
      37             : 
      38           0 : __weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
      39             :                                   struct pt_regs *regs)
      40             : {
      41           0 : }
      42             : 
      43           0 : __weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
      44             :                                 struct pt_regs *regs)
      45             : {
      46           0 : }
      47             : 
      48           0 : static void release_callchain_buffers_rcu(struct rcu_head *head)
      49             : {
      50           0 :         struct callchain_cpus_entries *entries;
      51           0 :         int cpu;
      52             : 
      53           0 :         entries = container_of(head, struct callchain_cpus_entries, rcu_head);
      54             : 
      55           0 :         for_each_possible_cpu(cpu)
      56           0 :                 kfree(entries->cpu_entries[cpu]);
      57             : 
      58           0 :         kfree(entries);
      59           0 : }
      60             : 
      61           0 : static void release_callchain_buffers(void)
      62             : {
      63           0 :         struct callchain_cpus_entries *entries;
      64             : 
      65           0 :         entries = callchain_cpus_entries;
      66           0 :         RCU_INIT_POINTER(callchain_cpus_entries, NULL);
      67           0 :         call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
      68           0 : }
      69             : 
      70           0 : static int alloc_callchain_buffers(void)
      71             : {
      72           0 :         int cpu;
      73           0 :         int size;
      74           0 :         struct callchain_cpus_entries *entries;
      75             : 
      76             :         /*
      77             :          * We can't use the percpu allocation API for data that can be
      78             :          * accessed from NMI. Use a temporary manual per cpu allocation
      79             :          * until that gets sorted out.
      80             :          */
      81           0 :         size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
      82             : 
      83           0 :         entries = kzalloc(size, GFP_KERNEL);
      84           0 :         if (!entries)
      85             :                 return -ENOMEM;
      86             : 
      87           0 :         size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS;
      88             : 
      89           0 :         for_each_possible_cpu(cpu) {
      90           0 :                 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
      91             :                                                          cpu_to_node(cpu));
      92           0 :                 if (!entries->cpu_entries[cpu])
      93           0 :                         goto fail;
      94             :         }
      95             : 
      96           0 :         rcu_assign_pointer(callchain_cpus_entries, entries);
      97             : 
      98           0 :         return 0;
      99             : 
     100           0 : fail:
     101           0 :         for_each_possible_cpu(cpu)
     102           0 :                 kfree(entries->cpu_entries[cpu]);
     103           0 :         kfree(entries);
     104             : 
     105           0 :         return -ENOMEM;
     106             : }
     107             : 
     108           0 : int get_callchain_buffers(int event_max_stack)
     109             : {
     110           0 :         int err = 0;
     111           0 :         int count;
     112             : 
     113           0 :         mutex_lock(&callchain_mutex);
     114             : 
     115           0 :         count = atomic_inc_return(&nr_callchain_events);
     116           0 :         if (WARN_ON_ONCE(count < 1)) {
     117           0 :                 err = -EINVAL;
     118           0 :                 goto exit;
     119             :         }
     120             : 
     121             :         /*
     122             :          * If requesting per event more than the global cap,
     123             :          * return a different error to help userspace figure
     124             :          * this out.
     125             :          *
     126             :          * And also do it here so that we have &callchain_mutex held.
     127             :          */
     128           0 :         if (event_max_stack > sysctl_perf_event_max_stack) {
     129           0 :                 err = -EOVERFLOW;
     130           0 :                 goto exit;
     131             :         }
     132             : 
     133           0 :         if (count == 1)
     134           0 :                 err = alloc_callchain_buffers();
     135           0 : exit:
     136           0 :         if (err)
     137           0 :                 atomic_dec(&nr_callchain_events);
     138             : 
     139           0 :         mutex_unlock(&callchain_mutex);
     140             : 
     141           0 :         return err;
     142             : }
     143             : 
     144           0 : void put_callchain_buffers(void)
     145             : {
     146           0 :         if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
     147           0 :                 release_callchain_buffers();
     148           0 :                 mutex_unlock(&callchain_mutex);
     149             :         }
     150           0 : }
     151             : 
     152           0 : struct perf_callchain_entry *get_callchain_entry(int *rctx)
     153             : {
     154           0 :         int cpu;
     155           0 :         struct callchain_cpus_entries *entries;
     156             : 
     157           0 :         *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion));
     158           0 :         if (*rctx == -1)
     159             :                 return NULL;
     160             : 
     161           0 :         entries = rcu_dereference(callchain_cpus_entries);
     162           0 :         if (!entries) {
     163           0 :                 put_recursion_context(this_cpu_ptr(callchain_recursion), *rctx);
     164           0 :                 return NULL;
     165             :         }
     166             : 
     167           0 :         cpu = smp_processor_id();
     168             : 
     169           0 :         return (((void *)entries->cpu_entries[cpu]) +
     170           0 :                 (*rctx * perf_callchain_entry__sizeof()));
     171             : }
     172             : 
     173             : void
     174           0 : put_callchain_entry(int rctx)
     175             : {
     176           0 :         put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
     177           0 : }
     178             : 
     179             : struct perf_callchain_entry *
     180           0 : get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
     181             :                    u32 max_stack, bool crosstask, bool add_mark)
     182             : {
     183           0 :         struct perf_callchain_entry *entry;
     184           0 :         struct perf_callchain_entry_ctx ctx;
     185           0 :         int rctx;
     186             : 
     187           0 :         entry = get_callchain_entry(&rctx);
     188           0 :         if (!entry)
     189             :                 return NULL;
     190             : 
     191           0 :         ctx.entry     = entry;
     192           0 :         ctx.max_stack = max_stack;
     193           0 :         ctx.nr        = entry->nr = init_nr;
     194           0 :         ctx.contexts       = 0;
     195           0 :         ctx.contexts_maxed = false;
     196             : 
     197           0 :         if (kernel && !user_mode(regs)) {
     198           0 :                 if (add_mark)
     199           0 :                         perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
     200           0 :                 perf_callchain_kernel(&ctx, regs);
     201             :         }
     202             : 
     203           0 :         if (user) {
     204           0 :                 if (!user_mode(regs)) {
     205           0 :                         if  (current->mm)
     206           0 :                                 regs = task_pt_regs(current);
     207             :                         else
     208             :                                 regs = NULL;
     209             :                 }
     210             : 
     211           0 :                 if (regs) {
     212           0 :                         mm_segment_t fs;
     213             : 
     214           0 :                         if (crosstask)
     215           0 :                                 goto exit_put;
     216             : 
     217           0 :                         if (add_mark)
     218           0 :                                 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
     219             : 
     220           0 :                         fs = force_uaccess_begin();
     221           0 :                         perf_callchain_user(&ctx, regs);
     222           0 :                         force_uaccess_end(fs);
     223             :                 }
     224             :         }
     225             : 
     226           0 : exit_put:
     227           0 :         put_callchain_entry(rctx);
     228             : 
     229           0 :         return entry;
     230             : }
     231             : 
     232             : /*
     233             :  * Used for sysctl_perf_event_max_stack and
     234             :  * sysctl_perf_event_max_contexts_per_stack.
     235             :  */
     236           0 : int perf_event_max_stack_handler(struct ctl_table *table, int write,
     237             :                                  void *buffer, size_t *lenp, loff_t *ppos)
     238             : {
     239           0 :         int *value = table->data;
     240           0 :         int new_value = *value, ret;
     241           0 :         struct ctl_table new_table = *table;
     242             : 
     243           0 :         new_table.data = &new_value;
     244           0 :         ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos);
     245           0 :         if (ret || !write)
     246             :                 return ret;
     247             : 
     248           0 :         mutex_lock(&callchain_mutex);
     249           0 :         if (atomic_read(&nr_callchain_events))
     250             :                 ret = -EBUSY;
     251             :         else
     252           0 :                 *value = new_value;
     253             : 
     254           0 :         mutex_unlock(&callchain_mutex);
     255             : 
     256           0 :         return ret;
     257             : }

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