![Steven Rostedt](/assets/img/avatar_default.png)
This patch replaces the indirect call to the mcount function pointer with a direct call that will be patched by the dynamic ftrace routines. On boot up, the mcount function calls the ftace_stub function. When the dynamic ftrace code is initialized, the ftrace_stub is replaced with a call to the ftrace_record_ip, which records the instruction pointers of the locations that call it. Later, the ftraced daemon will call kstop_machine and patch all the locations to nops. When a ftrace is enabled, the original calls to mcount will now be set top call ftrace_caller, which will do a direct call to the registered ftrace function. This direct call is also patched when the function that should be called is updated. All patching is performed by a kstop_machine routine to prevent any type of race conditions that is associated with modifying code on the fly. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
697 lines
15 KiB
C
697 lines
15 KiB
C
/*
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* Infrastructure for profiling code inserted by 'gcc -pg'.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2004-2008 Ingo Molnar <mingo@redhat.com>
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*
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* Originally ported from the -rt patch by:
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* Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
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*
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* Based on code in the latency_tracer, that is:
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*
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* Copyright (C) 2004-2006 Ingo Molnar
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* Copyright (C) 2004 William Lee Irwin III
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*/
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#include <linux/stop_machine.h>
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#include <linux/clocksource.h>
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#include <linux/kallsyms.h>
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#include <linux/kthread.h>
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#include <linux/hardirq.h>
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#include <linux/ftrace.h>
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#include <linux/module.h>
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#include <linux/sysctl.h>
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#include <linux/hash.h>
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#include <linux/list.h>
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#include "trace.h"
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int ftrace_enabled;
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static int last_ftrace_enabled;
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static DEFINE_SPINLOCK(ftrace_lock);
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static DEFINE_MUTEX(ftrace_sysctl_lock);
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static struct ftrace_ops ftrace_list_end __read_mostly =
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{
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.func = ftrace_stub,
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};
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static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
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ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
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/* mcount is defined per arch in assembly */
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EXPORT_SYMBOL(mcount);
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notrace void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
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{
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struct ftrace_ops *op = ftrace_list;
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/* in case someone actually ports this to alpha! */
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read_barrier_depends();
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while (op != &ftrace_list_end) {
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/* silly alpha */
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read_barrier_depends();
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op->func(ip, parent_ip);
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op = op->next;
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};
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}
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/**
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* clear_ftrace_function - reset the ftrace function
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*
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* This NULLs the ftrace function and in essence stops
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* tracing. There may be lag
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*/
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void clear_ftrace_function(void)
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{
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ftrace_trace_function = ftrace_stub;
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}
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static int notrace __register_ftrace_function(struct ftrace_ops *ops)
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{
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/* Should never be called by interrupts */
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spin_lock(&ftrace_lock);
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ops->next = ftrace_list;
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/*
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* We are entering ops into the ftrace_list but another
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* CPU might be walking that list. We need to make sure
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* the ops->next pointer is valid before another CPU sees
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* the ops pointer included into the ftrace_list.
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*/
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smp_wmb();
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ftrace_list = ops;
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if (ftrace_enabled) {
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/*
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* For one func, simply call it directly.
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* For more than one func, call the chain.
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*/
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if (ops->next == &ftrace_list_end)
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ftrace_trace_function = ops->func;
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else
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ftrace_trace_function = ftrace_list_func;
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}
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spin_unlock(&ftrace_lock);
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return 0;
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}
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static int notrace __unregister_ftrace_function(struct ftrace_ops *ops)
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{
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struct ftrace_ops **p;
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int ret = 0;
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spin_lock(&ftrace_lock);
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/*
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* If we are removing the last function, then simply point
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* to the ftrace_stub.
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*/
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if (ftrace_list == ops && ops->next == &ftrace_list_end) {
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ftrace_trace_function = ftrace_stub;
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ftrace_list = &ftrace_list_end;
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goto out;
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}
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for (p = &ftrace_list; *p != &ftrace_list_end; p = &(*p)->next)
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if (*p == ops)
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break;
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if (*p != ops) {
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ret = -1;
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goto out;
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}
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*p = (*p)->next;
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if (ftrace_enabled) {
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/* If we only have one func left, then call that directly */
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if (ftrace_list == &ftrace_list_end ||
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ftrace_list->next == &ftrace_list_end)
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ftrace_trace_function = ftrace_list->func;
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}
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out:
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spin_unlock(&ftrace_lock);
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return ret;
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}
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#ifdef CONFIG_DYNAMIC_FTRACE
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enum {
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FTRACE_ENABLE_CALLS = (1 << 0),
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FTRACE_DISABLE_CALLS = (1 << 1),
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FTRACE_UPDATE_TRACE_FUNC = (1 << 2),
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FTRACE_ENABLE_MCOUNT = (1 << 3),
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FTRACE_DISABLE_MCOUNT = (1 << 4),
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};
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static struct hlist_head ftrace_hash[FTRACE_HASHSIZE];
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static DEFINE_PER_CPU(int, ftrace_shutdown_disable_cpu);
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static DEFINE_SPINLOCK(ftrace_shutdown_lock);
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static DEFINE_MUTEX(ftraced_lock);
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struct ftrace_page {
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struct ftrace_page *next;
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int index;
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struct dyn_ftrace records[];
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} __attribute__((packed));
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#define ENTRIES_PER_PAGE \
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((PAGE_SIZE - sizeof(struct ftrace_page)) / sizeof(struct dyn_ftrace))
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/* estimate from running different kernels */
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#define NR_TO_INIT 10000
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static struct ftrace_page *ftrace_pages_start;
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static struct ftrace_page *ftrace_pages;
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static int ftraced_trigger;
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static int ftraced_suspend;
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static int ftrace_record_suspend;
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static inline int
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notrace ftrace_ip_in_hash(unsigned long ip, unsigned long key)
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{
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struct dyn_ftrace *p;
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struct hlist_node *t;
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int found = 0;
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hlist_for_each_entry(p, t, &ftrace_hash[key], node) {
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if (p->ip == ip) {
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found = 1;
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break;
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}
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}
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return found;
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}
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static inline void notrace
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ftrace_add_hash(struct dyn_ftrace *node, unsigned long key)
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{
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hlist_add_head(&node->node, &ftrace_hash[key]);
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}
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static notrace struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
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{
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if (ftrace_pages->index == ENTRIES_PER_PAGE) {
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if (!ftrace_pages->next)
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return NULL;
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ftrace_pages = ftrace_pages->next;
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}
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return &ftrace_pages->records[ftrace_pages->index++];
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}
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static void notrace
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ftrace_record_ip(unsigned long ip)
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{
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struct dyn_ftrace *node;
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unsigned long flags;
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unsigned long key;
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int resched;
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int atomic;
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if (!ftrace_enabled)
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return;
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resched = need_resched();
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preempt_disable_notrace();
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/* We simply need to protect against recursion */
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__get_cpu_var(ftrace_shutdown_disable_cpu)++;
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if (__get_cpu_var(ftrace_shutdown_disable_cpu) != 1)
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goto out;
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if (unlikely(ftrace_record_suspend))
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goto out;
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key = hash_long(ip, FTRACE_HASHBITS);
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WARN_ON_ONCE(key >= FTRACE_HASHSIZE);
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if (ftrace_ip_in_hash(ip, key))
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goto out;
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atomic = irqs_disabled();
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spin_lock_irqsave(&ftrace_shutdown_lock, flags);
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/* This ip may have hit the hash before the lock */
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if (ftrace_ip_in_hash(ip, key))
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goto out_unlock;
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/*
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* There's a slight race that the ftraced will update the
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* hash and reset here. If it is already converted, skip it.
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*/
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if (ftrace_ip_converted(ip))
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goto out_unlock;
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node = ftrace_alloc_dyn_node(ip);
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if (!node)
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goto out_unlock;
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node->ip = ip;
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ftrace_add_hash(node, key);
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ftraced_trigger = 1;
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out_unlock:
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spin_unlock_irqrestore(&ftrace_shutdown_lock, flags);
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out:
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__get_cpu_var(ftrace_shutdown_disable_cpu)--;
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/* prevent recursion with scheduler */
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if (resched)
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preempt_enable_no_resched_notrace();
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else
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preempt_enable_notrace();
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}
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#define FTRACE_ADDR ((long)(&ftrace_caller))
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#define MCOUNT_ADDR ((long)(&mcount))
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static void notrace ftrace_replace_code(int saved)
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{
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unsigned char *new = NULL, *old = NULL;
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struct dyn_ftrace *rec;
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struct ftrace_page *pg;
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unsigned long ip;
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int failed;
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int i;
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if (saved)
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old = ftrace_nop_replace();
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else
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new = ftrace_nop_replace();
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for (pg = ftrace_pages_start; pg; pg = pg->next) {
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for (i = 0; i < pg->index; i++) {
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rec = &pg->records[i];
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/* don't modify code that has already faulted */
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if (rec->flags & FTRACE_FL_FAILED)
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continue;
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ip = rec->ip;
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if (saved)
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new = ftrace_call_replace(ip, FTRACE_ADDR);
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else
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old = ftrace_call_replace(ip, FTRACE_ADDR);
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failed = ftrace_modify_code(ip, old, new);
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if (failed)
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rec->flags |= FTRACE_FL_FAILED;
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}
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}
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}
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static notrace void ftrace_shutdown_replenish(void)
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{
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if (ftrace_pages->next)
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return;
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/* allocate another page */
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ftrace_pages->next = (void *)get_zeroed_page(GFP_KERNEL);
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}
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static notrace void
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ftrace_code_disable(struct dyn_ftrace *rec)
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{
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unsigned long ip;
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unsigned char *nop, *call;
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int failed;
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ip = rec->ip;
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nop = ftrace_nop_replace();
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call = ftrace_call_replace(ip, MCOUNT_ADDR);
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failed = ftrace_modify_code(ip, call, nop);
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if (failed)
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rec->flags |= FTRACE_FL_FAILED;
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}
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static int notrace __ftrace_modify_code(void *data)
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{
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unsigned long addr;
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int *command = data;
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if (*command & FTRACE_ENABLE_CALLS)
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ftrace_replace_code(1);
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else if (*command & FTRACE_DISABLE_CALLS)
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ftrace_replace_code(0);
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if (*command & FTRACE_UPDATE_TRACE_FUNC)
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ftrace_update_ftrace_func(ftrace_trace_function);
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if (*command & FTRACE_ENABLE_MCOUNT) {
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addr = (unsigned long)ftrace_record_ip;
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ftrace_mcount_set(&addr);
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} else if (*command & FTRACE_DISABLE_MCOUNT) {
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addr = (unsigned long)ftrace_stub;
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ftrace_mcount_set(&addr);
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}
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return 0;
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}
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static void notrace ftrace_run_update_code(int command)
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{
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stop_machine_run(__ftrace_modify_code, &command, NR_CPUS);
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}
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static ftrace_func_t saved_ftrace_func;
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static void notrace ftrace_startup(void)
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{
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int command = 0;
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mutex_lock(&ftraced_lock);
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ftraced_suspend++;
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if (ftraced_suspend == 1)
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command |= FTRACE_ENABLE_CALLS;
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if (saved_ftrace_func != ftrace_trace_function) {
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saved_ftrace_func = ftrace_trace_function;
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command |= FTRACE_UPDATE_TRACE_FUNC;
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}
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if (!command || !ftrace_enabled)
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goto out;
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ftrace_run_update_code(command);
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out:
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mutex_unlock(&ftraced_lock);
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}
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static void notrace ftrace_shutdown(void)
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{
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int command = 0;
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mutex_lock(&ftraced_lock);
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ftraced_suspend--;
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if (!ftraced_suspend)
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command |= FTRACE_DISABLE_CALLS;
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if (saved_ftrace_func != ftrace_trace_function) {
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saved_ftrace_func = ftrace_trace_function;
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command |= FTRACE_UPDATE_TRACE_FUNC;
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}
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if (!command || !ftrace_enabled)
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goto out;
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ftrace_run_update_code(command);
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out:
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mutex_unlock(&ftraced_lock);
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}
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static void notrace ftrace_startup_sysctl(void)
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{
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int command = FTRACE_ENABLE_MCOUNT;
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mutex_lock(&ftraced_lock);
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/* Force update next time */
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saved_ftrace_func = NULL;
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/* ftraced_suspend is true if we want ftrace running */
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if (ftraced_suspend)
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command |= FTRACE_ENABLE_CALLS;
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ftrace_run_update_code(command);
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mutex_unlock(&ftraced_lock);
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}
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static void notrace ftrace_shutdown_sysctl(void)
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{
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int command = FTRACE_DISABLE_MCOUNT;
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mutex_lock(&ftraced_lock);
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/* ftraced_suspend is true if ftrace is running */
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if (ftraced_suspend)
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command |= FTRACE_DISABLE_CALLS;
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ftrace_run_update_code(command);
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mutex_unlock(&ftraced_lock);
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}
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static cycle_t ftrace_update_time;
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static unsigned long ftrace_update_cnt;
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unsigned long ftrace_update_tot_cnt;
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static int notrace __ftrace_update_code(void *ignore)
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{
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struct dyn_ftrace *p;
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struct hlist_head head;
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struct hlist_node *t;
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int save_ftrace_enabled;
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cycle_t start, stop;
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int i;
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/* Don't be recording funcs now */
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save_ftrace_enabled = ftrace_enabled;
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ftrace_enabled = 0;
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start = now(raw_smp_processor_id());
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ftrace_update_cnt = 0;
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/* No locks needed, the machine is stopped! */
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for (i = 0; i < FTRACE_HASHSIZE; i++) {
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if (hlist_empty(&ftrace_hash[i]))
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continue;
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head = ftrace_hash[i];
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INIT_HLIST_HEAD(&ftrace_hash[i]);
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/* all CPUS are stopped, we are safe to modify code */
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hlist_for_each_entry(p, t, &head, node) {
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ftrace_code_disable(p);
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ftrace_update_cnt++;
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}
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}
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stop = now(raw_smp_processor_id());
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ftrace_update_time = stop - start;
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ftrace_update_tot_cnt += ftrace_update_cnt;
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ftrace_enabled = save_ftrace_enabled;
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return 0;
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}
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static void notrace ftrace_update_code(void)
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{
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stop_machine_run(__ftrace_update_code, NULL, NR_CPUS);
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}
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static int notrace ftraced(void *ignore)
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{
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unsigned long usecs;
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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/* check once a second */
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schedule_timeout(HZ);
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mutex_lock(&ftrace_sysctl_lock);
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mutex_lock(&ftraced_lock);
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if (ftrace_enabled && ftraced_trigger && !ftraced_suspend) {
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ftrace_record_suspend++;
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ftrace_update_code();
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usecs = nsecs_to_usecs(ftrace_update_time);
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if (ftrace_update_tot_cnt > 100000) {
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ftrace_update_tot_cnt = 0;
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pr_info("hm, dftrace overflow: %lu change%s"
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" (%lu total) in %lu usec%s\n",
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ftrace_update_cnt,
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ftrace_update_cnt != 1 ? "s" : "",
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ftrace_update_tot_cnt,
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usecs, usecs != 1 ? "s" : "");
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WARN_ON_ONCE(1);
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}
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ftraced_trigger = 0;
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ftrace_record_suspend--;
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}
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mutex_unlock(&ftraced_lock);
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mutex_unlock(&ftrace_sysctl_lock);
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ftrace_shutdown_replenish();
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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static int __init ftrace_dyn_table_alloc(void)
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{
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struct ftrace_page *pg;
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int cnt;
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int i;
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/* allocate a few pages */
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ftrace_pages_start = (void *)get_zeroed_page(GFP_KERNEL);
|
|
if (!ftrace_pages_start)
|
|
return -1;
|
|
|
|
/*
|
|
* Allocate a few more pages.
|
|
*
|
|
* TODO: have some parser search vmlinux before
|
|
* final linking to find all calls to ftrace.
|
|
* Then we can:
|
|
* a) know how many pages to allocate.
|
|
* and/or
|
|
* b) set up the table then.
|
|
*
|
|
* The dynamic code is still necessary for
|
|
* modules.
|
|
*/
|
|
|
|
pg = ftrace_pages = ftrace_pages_start;
|
|
|
|
cnt = NR_TO_INIT / ENTRIES_PER_PAGE;
|
|
|
|
for (i = 0; i < cnt; i++) {
|
|
pg->next = (void *)get_zeroed_page(GFP_KERNEL);
|
|
|
|
/* If we fail, we'll try later anyway */
|
|
if (!pg->next)
|
|
break;
|
|
|
|
pg = pg->next;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int __init notrace ftrace_dynamic_init(void)
|
|
{
|
|
struct task_struct *p;
|
|
unsigned long addr;
|
|
int ret;
|
|
|
|
addr = (unsigned long)ftrace_record_ip;
|
|
stop_machine_run(ftrace_dyn_arch_init, &addr, NR_CPUS);
|
|
|
|
/* ftrace_dyn_arch_init places the return code in addr */
|
|
if (addr)
|
|
return addr;
|
|
|
|
ret = ftrace_dyn_table_alloc();
|
|
if (ret)
|
|
return ret;
|
|
|
|
p = kthread_run(ftraced, NULL, "ftraced");
|
|
if (IS_ERR(p))
|
|
return -1;
|
|
|
|
last_ftrace_enabled = ftrace_enabled = 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
core_initcall(ftrace_dynamic_init);
|
|
#else
|
|
# define ftrace_startup() do { } while (0)
|
|
# define ftrace_shutdown() do { } while (0)
|
|
# define ftrace_startup_sysctl() do { } while (0)
|
|
# define ftrace_shutdown_sysctl() do { } while (0)
|
|
#endif /* CONFIG_DYNAMIC_FTRACE */
|
|
|
|
/**
|
|
* register_ftrace_function - register a function for profiling
|
|
* @ops - ops structure that holds the function for profiling.
|
|
*
|
|
* Register a function to be called by all functions in the
|
|
* kernel.
|
|
*
|
|
* Note: @ops->func and all the functions it calls must be labeled
|
|
* with "notrace", otherwise it will go into a
|
|
* recursive loop.
|
|
*/
|
|
int register_ftrace_function(struct ftrace_ops *ops)
|
|
{
|
|
int ret;
|
|
|
|
mutex_lock(&ftrace_sysctl_lock);
|
|
ret = __register_ftrace_function(ops);
|
|
ftrace_startup();
|
|
mutex_unlock(&ftrace_sysctl_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* unregister_ftrace_function - unresgister a function for profiling.
|
|
* @ops - ops structure that holds the function to unregister
|
|
*
|
|
* Unregister a function that was added to be called by ftrace profiling.
|
|
*/
|
|
int unregister_ftrace_function(struct ftrace_ops *ops)
|
|
{
|
|
int ret;
|
|
|
|
mutex_lock(&ftrace_sysctl_lock);
|
|
ret = __unregister_ftrace_function(ops);
|
|
ftrace_shutdown();
|
|
mutex_unlock(&ftrace_sysctl_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
notrace int
|
|
ftrace_enable_sysctl(struct ctl_table *table, int write,
|
|
struct file *filp, void __user *buffer, size_t *lenp,
|
|
loff_t *ppos)
|
|
{
|
|
int ret;
|
|
|
|
mutex_lock(&ftrace_sysctl_lock);
|
|
|
|
ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);
|
|
|
|
if (ret || !write || (last_ftrace_enabled == ftrace_enabled))
|
|
goto out;
|
|
|
|
last_ftrace_enabled = ftrace_enabled;
|
|
|
|
if (ftrace_enabled) {
|
|
|
|
ftrace_startup_sysctl();
|
|
|
|
/* we are starting ftrace again */
|
|
if (ftrace_list != &ftrace_list_end) {
|
|
if (ftrace_list->next == &ftrace_list_end)
|
|
ftrace_trace_function = ftrace_list->func;
|
|
else
|
|
ftrace_trace_function = ftrace_list_func;
|
|
}
|
|
|
|
} else {
|
|
/* stopping ftrace calls (just send to ftrace_stub) */
|
|
ftrace_trace_function = ftrace_stub;
|
|
|
|
ftrace_shutdown_sysctl();
|
|
}
|
|
|
|
out:
|
|
mutex_unlock(&ftrace_sysctl_lock);
|
|
return ret;
|
|
}
|