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Subject[RFC PATCH] Kernel Tracepoints
** note : this patch is submitted for early review. It applies after my
current unreleased 2.6.26-rc8 LTTng patchset. Comments are welcome.

Implementation of kernel tracepoints. Inspired from the Linux Kernel Markers.

Allows complete typing verification. No format string required.

TODO : Documentation/tracepoint.txt

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: 'Peter Zijlstra' <peterz@infradead.org>
CC: "Frank Ch. Eigler" <fche@redhat.com>
CC: 'Ingo Molnar' <mingo@elte.hu>
CC: 'Hideo AOKI' <haoki@redhat.com>
CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com>
CC: 'Steven Rostedt' <rostedt@goodmis.org>
---
include/asm-generic/vmlinux.lds.h | 4
include/linux/module.h | 17 +
include/linux/tracepoint.h | 154 +++++++++++
init/Kconfig | 7
kernel/Makefile | 1
kernel/module.c | 71 +++++
kernel/tracepoint.c | 495 ++++++++++++++++++++++++++++++++++++++
7 files changed, 748 insertions(+), 1 deletion(-)

Index: linux-2.6.26-rc7-lttng/init/Kconfig
===================================================================
--- linux-2.6.26-rc7-lttng.orig/init/Kconfig 2008-06-25 18:11:05.000000000 -0400
+++ linux-2.6.26-rc7-lttng/init/Kconfig 2008-06-25 19:01:50.000000000 -0400
@@ -782,6 +782,13 @@
Say Y here to enable the extended profiling support mechanisms used
by profilers such as OProfile.

+config TRACEPOINTS
+ bool "Activate tracepoints"
+ default y
+ help
+ Place an empty function call at each tracepoint site. Can be
+ dynamically changed for a probe function.
+
config MARKERS
bool "Activate markers"
help
Index: linux-2.6.26-rc7-lttng/kernel/Makefile
===================================================================
--- linux-2.6.26-rc7-lttng.orig/kernel/Makefile 2008-06-25 18:11:04.000000000 -0400
+++ linux-2.6.26-rc7-lttng/kernel/Makefile 2008-06-25 19:01:50.000000000 -0400
@@ -69,6 +69,7 @@
obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
obj-$(USE_IMMEDIATE) += immediate.o
obj-$(CONFIG_MARKERS) += marker.o
+obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
obj-$(CONFIG_LATENCYTOP) += latencytop.o

ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
Index: linux-2.6.26-rc7-lttng/include/linux/tracepoint.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.26-rc7-lttng/include/linux/tracepoint.h 2008-06-25 19:04:17.000000000 -0400
@@ -0,0 +1,154 @@
+#ifndef _LINUX_TRACEPOINT_H
+#define _LINUX_TRACEPOINT_H
+
+/*
+ * Kernel Tracepoint API.
+ *
+ * See Documentation/tracepoint.txt.
+ *
+ * (C) Copyright 2008 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * Heavily inspired from the Linux Kernel Markers.
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/immediate.h>
+#include <linux/types.h>
+
+struct module;
+struct tracepoint;
+
+struct tracepoint_probe_closure {
+ void *func; /* Callback */
+ void *probe_private; /* Private probe data */
+};
+
+struct tracepoint {
+ const char *name; /* Tracepoint name */
+ DEFINE_IMV(char, state); /* Immediate value state. */
+ struct tracepoint_probe_closure *multi; /* Closures */
+} __attribute__((aligned(8)));
+
+
+#define TPPROTO(args...) args
+#define TPARGS(args...) args
+
+#ifdef CONFIG_TRACEPOINTS
+
+/*
+ * Note : the empty asm volatile with read constraint is used here instead of a
+ * "used" attribute to fix a gcc 4.1.x bug.
+ * Make sure the alignment of the structure in the __markers section will
+ * not add unwanted padding between the beginning of the section and the
+ * structure. Force alignment to the same alignment as the section start.
+ *
+ * The "generic" argument controls which marker enabling mechanism must be used.
+ * If generic is true, a variable read is used.
+ * If generic is false, immediate values are used.
+ */
+#define DEFINE_TRACE(name, proto, args) \
+ static inline void _do_trace_##name(struct tracepoint *tp, proto) \
+ { \
+ int i; \
+ struct tracepoint_probe_closure *multi; \
+ preempt_disable(); \
+ multi = tp->multi; \
+ smp_read_barrier_depends(); \
+ if (multi) { \
+ for (i = 0; multi[i].func; i++) { \
+ ((void(*)(void *private_data, proto)) \
+ (multi[i].func))(multi[i].probe_private, args);\
+ } \
+ } \
+ preempt_enable(); \
+ } \
+ static inline void __trace_##name(int generic, proto) \
+ { \
+ static const char __tpstrtab_##name[] \
+ __attribute__((section("__tracepoints_strings"))) \
+ = #name; \
+ static struct tracepoint __tracepoint_##name \
+ __attribute__((section("__tracepoints"), aligned(8))) = \
+ { __tpstrtab_##name, 0, NULL }; \
+ if (!generic) { \
+ if (unlikely(imv_cond(__tracepoint_##name.state))) { \
+ imv_cond_end(); \
+ _do_trace_##name(&__tracepoint_##name, args); \
+ } else \
+ imv_cond_end(); \
+ } else { \
+ if (unlikely(_imv_read(__tracepoint_##name.state))) \
+ _do_trace_##name(&__tracepoint_##name, args); \
+ } \
+ } \
+ static inline void trace_##name(proto) \
+ { \
+ __trace_##name(0, args); \
+ } \
+ static inline void _trace_##name(proto) \
+ { \
+ __trace_##name(1, args); \
+ } \
+ static inline int register_trace_##name( \
+ void (*probe)(void *private_data, proto), \
+ void *private_data) \
+ { \
+ return tracepoint_probe_register(#name, (void *)probe, \
+ private_data); \
+ } \
+ static inline void unregister_trace_##name( \
+ void (*probe)(void *private_data, proto), \
+ void *private_data) \
+ { \
+ tracepoint_probe_unregister(#name, (void *)probe, \
+ private_data); \
+ }
+
+extern void tracepoint_update_probe_range(struct tracepoint *begin,
+ struct tracepoint *end);
+
+#else /* !CONFIG_TRACEPOINTS */
+#define DEFINE_TRACE(name, proto, args) \
+ static inline void _do_trace_##name(struct tracepoint *tp, proto) \
+ { } \
+ static inline void __trace_##name(int generic, proto) \
+ { } \
+ static inline void trace_##name(proto) \
+ { } \
+ static inline void _trace_##name(proto) \
+ { }
+
+static inline void tracepoint_update_probe_range(struct tracepoint *begin,
+ struct tracepoint *end)
+{ }
+#endif /* CONFIG_TRACEPOINTS */
+
+/*
+ * Connect a probe to a tracepoint.
+ * Internal API, should not be used directly.
+ */
+extern int tracepoint_probe_register(const char *name,
+ void *probe, void *probe_private);
+
+/*
+ * Disconnect a probe from a tracepoint.
+ * Internal API, should not be used directly.
+ */
+extern int tracepoint_probe_unregister(const char *name,
+ void *probe, void *probe_private);
+
+struct tracepoint_iter {
+ struct module *module;
+ struct tracepoint *tracepoint;
+};
+
+extern void tracepoint_iter_start(struct tracepoint_iter *iter);
+extern void tracepoint_iter_next(struct tracepoint_iter *iter);
+extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
+extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
+extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
+ struct tracepoint *begin, struct tracepoint *end);
+
+#endif
Index: linux-2.6.26-rc7-lttng/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.26-rc7-lttng.orig/include/asm-generic/vmlinux.lds.h 2008-06-25 18:11:04.000000000 -0400
+++ linux-2.6.26-rc7-lttng/include/asm-generic/vmlinux.lds.h 2008-06-25 18:11:05.000000000 -0400
@@ -53,6 +53,9 @@
VMLINUX_SYMBOL(__start___markers) = .; \
*(__markers) \
VMLINUX_SYMBOL(__stop___markers) = .; \
+ VMLINUX_SYMBOL(__start___tracepoints) = .; \
+ *(__tracepoints) \
+ VMLINUX_SYMBOL(__stop___tracepoints) = .; \
VMLINUX_SYMBOL(__start___imv) = .; \
*(__imv) /* Immediate values: pointers */ \
VMLINUX_SYMBOL(__stop___imv) = .;
@@ -68,6 +71,7 @@
*(__imv_cond_end) /* Immediate condition end pointers */\
VMLINUX_SYMBOL(__stop___imv_cond_end) = .; \
*(__markers_strings) /* Markers: strings */ \
+ *(__tracepoints_strings)/* Tracepoints: strings */ \
} \
\
.rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \
Index: linux-2.6.26-rc7-lttng/kernel/tracepoint.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.26-rc7-lttng/kernel/tracepoint.c 2008-06-25 18:11:05.000000000 -0400
@@ -0,0 +1,495 @@
+/*
+ * Copyright (C) 2007 Mathieu Desnoyers
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/jhash.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/tracepoint.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/immediate.h>
+
+extern struct tracepoint __start___tracepoints[];
+extern struct tracepoint __stop___tracepoints[];
+
+/* Set to 1 to enable tracepoint debug output */
+static const int tracepoint_debug;
+
+/*
+ * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
+ * builtin and module tracepoints and the hash table.
+ */
+static DEFINE_MUTEX(tracepoints_mutex);
+
+/*
+ * Tracepoint hash table, containing the active tracepoints.
+ * Protected by tracepoints_mutex.
+ */
+#define TRACEPOINT_HASH_BITS 6
+#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
+
+/*
+ * Note about RCU :
+ * It is used to make sure every handler has finished using its private data
+ * between two consecutive operation (add or remove) on a given tracepoint. It
+ * is also used to delay the free of multiple probes array until a quiescent
+ * state is reached.
+ * tracepoint entries modifications are protected by the tracepoints_mutex.
+ */
+struct tracepoint_entry {
+ struct hlist_node hlist;
+ struct tracepoint_probe_closure *multi;
+ int refcount; /* Number of times armed. 0 if disarmed. */
+ struct rcu_head rcu;
+ void *oldptr;
+ unsigned char rcu_pending:1;
+ char name[0];
+};
+
+static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+
+static void free_old_closure(struct rcu_head *head)
+{
+ struct tracepoint_entry *entry = container_of(head,
+ struct tracepoint_entry, rcu);
+ kfree(entry->oldptr);
+ /* Make sure we free the data before setting the pending flag to 0 */
+ smp_wmb();
+ entry->rcu_pending = 0;
+}
+
+static void debug_print_probes(struct tracepoint_entry *entry)
+{
+ int i;
+
+ if (!tracepoint_debug)
+ return;
+
+ for (i = 0; entry->multi[i].func; i++)
+ printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
+ entry->multi[i].func,
+ entry->multi[i].probe_private);
+}
+
+static struct tracepoint_probe_closure *
+tracepoint_entry_add_probe(struct tracepoint_entry *entry,
+ void *probe, void *probe_private)
+{
+ int nr_probes = 0;
+ struct tracepoint_probe_closure *old, *new;
+
+ WARN_ON(!probe);
+
+ debug_print_probes(entry);
+ old = entry->multi;
+ if (old) {
+ /* (N -> N+1), (N != 0, 1) probes */
+ for (nr_probes = 0; old[nr_probes].func; nr_probes++)
+ if (old[nr_probes].func == probe
+ && old[nr_probes].probe_private
+ == probe_private)
+ return ERR_PTR(-EBUSY);
+ }
+ /* + 2 : one for new probe, one for NULL func */
+ new = kzalloc((nr_probes + 2) * sizeof(struct tracepoint_probe_closure),
+ GFP_KERNEL);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ if (old)
+ memcpy(new, old,
+ nr_probes * sizeof(struct tracepoint_probe_closure));
+ new[nr_probes].func = probe;
+ new[nr_probes].probe_private = probe_private;
+ entry->refcount = nr_probes + 1;
+ entry->multi = new;
+ debug_print_probes(entry);
+ return old;
+}
+
+static struct tracepoint_probe_closure *
+tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
+ void *probe, void *probe_private)
+{
+ int nr_probes = 0, nr_del = 0, i;
+ struct tracepoint_probe_closure *old, *new;
+
+ old = entry->multi;
+
+ debug_print_probes(entry);
+ /* (N -> M), (N > 1, M >= 0) probes */
+ for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+ if ((!probe || old[nr_probes].func == probe)
+ && old[nr_probes].probe_private
+ == probe_private)
+ nr_del++;
+ }
+
+ if (nr_probes - nr_del == 0) {
+ /* N -> 0, (N > 1) */
+ entry->multi = NULL;
+ entry->refcount = 0;
+ debug_print_probes(entry);
+ return old;
+ } else {
+ int j = 0;
+ /* N -> M, (N > 1, M > 0) */
+ /* + 1 for NULL */
+ new = kzalloc((nr_probes - nr_del + 1)
+ * sizeof(struct tracepoint_probe_closure), GFP_KERNEL);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ for (i = 0; old[i].func; i++)
+ if ((probe && old[i].func != probe) ||
+ old[i].probe_private != probe_private)
+ new[j++] = old[i];
+ entry->refcount = nr_probes - nr_del;
+ entry->multi = new;
+ }
+ debug_print_probes(entry);
+ return old;
+}
+
+/*
+ * Get tracepoint if the tracepoint is present in the tracepoint hash table.
+ * Must be called with tracepoints_mutex held.
+ * Returns NULL if not present.
+ */
+static struct tracepoint_entry *get_tracepoint(const char *name)
+{
+ struct hlist_head *head;
+ struct hlist_node *node;
+ struct tracepoint_entry *e;
+ u32 hash = jhash(name, strlen(name), 0);
+
+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
+ hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name))
+ return e;
+ }
+ return NULL;
+}
+
+/*
+ * Add the tracepoint to the tracepoint hash table. Must be called with
+ * tracepoints_mutex held.
+ */
+static struct tracepoint_entry *add_tracepoint(const char *name)
+{
+ struct hlist_head *head;
+ struct hlist_node *node;
+ struct tracepoint_entry *e;
+ size_t name_len = strlen(name) + 1;
+ u32 hash = jhash(name, name_len-1, 0);
+
+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
+ hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name)) {
+ printk(KERN_NOTICE
+ "tracepoint %s busy\n", name);
+ return ERR_PTR(-EBUSY); /* Already there */
+ }
+ }
+ /*
+ * Using kmalloc here to allocate a variable length element. Could
+ * cause some memory fragmentation if overused.
+ */
+ e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
+ if (!e)
+ return ERR_PTR(-ENOMEM);
+ memcpy(&e->name[0], name, name_len);
+ e->multi = NULL;
+ e->refcount = 0;
+ e->rcu_pending = 0;
+ hlist_add_head(&e->hlist, head);
+ return e;
+}
+
+/*
+ * Remove the tracepoint from the tracepoint hash table. Must be called with
+ * mutex_lock held.
+ */
+static int remove_tracepoint(const char *name)
+{
+ struct hlist_head *head;
+ struct hlist_node *node;
+ struct tracepoint_entry *e;
+ int found = 0;
+ size_t len = strlen(name) + 1;
+ u32 hash = jhash(name, len-1, 0);
+
+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
+ hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name)) {
+ found = 1;
+ break;
+ }
+ }
+ if (!found)
+ return -ENOENT;
+ hlist_del(&e->hlist);
+ /* Make sure the call_rcu has been executed */
+ if (e->rcu_pending)
+ rcu_barrier();
+ kfree(e);
+ return 0;
+}
+
+/*
+ * Sets the probe callback corresponding to one tracepoint.
+ */
+static void set_tracepoint(struct tracepoint_entry **entry,
+ struct tracepoint *elem, int active)
+{
+ WARN_ON(strcmp((*entry)->name, elem->name) != 0);
+
+ smp_wmb();
+ /*
+ * We also make sure that the new probe callbacks array is consistent
+ * before setting a pointer to it.
+ */
+ rcu_assign_pointer(elem->multi, (*entry)->multi);
+ elem->state__imv = active;
+}
+
+/*
+ * Disable a tracepoint and its probe callback.
+ * Note: only waiting an RCU period after setting elem->call to the empty
+ * function insures that the original callback is not used anymore. This insured
+ * by preempt_disable around the call site.
+ */
+static void disable_tracepoint(struct tracepoint *elem)
+{
+ elem->state__imv = 0;
+}
+
+/**
+ * tracepoint_update_probe_range - Update a probe range
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Updates the probe callback corresponding to a range of tracepoints.
+ */
+void tracepoint_update_probe_range(struct tracepoint *begin,
+ struct tracepoint *end)
+{
+ struct tracepoint *iter;
+ struct tracepoint_entry *mark_entry;
+
+ mutex_lock(&tracepoints_mutex);
+ for (iter = begin; iter < end; iter++) {
+ mark_entry = get_tracepoint(iter->name);
+ if (mark_entry) {
+ set_tracepoint(&mark_entry, iter,
+ !!mark_entry->refcount);
+ } else {
+ disable_tracepoint(iter);
+ }
+ }
+ mutex_unlock(&tracepoints_mutex);
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ */
+static void tracepoint_update_probes(void)
+{
+ /* Core kernel tracepoints */
+ tracepoint_update_probe_range(__start___tracepoints,
+ __stop___tracepoints);
+ /* tracepoints in modules. */
+ module_update_tracepoints();
+ /* Update immediate values */
+ core_imv_update();
+ module_imv_update();
+}
+
+/**
+ * tracepoint_probe_register - Connect a probe to a tracepoint
+ * @name: tracepoint name
+ * @probe: probe handler
+ * @probe_private: probe private data
+ *
+ * private data must be a valid allocated memory address, or NULL.
+ * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
+ */
+int tracepoint_probe_register(const char *name,
+ void *probe, void *probe_private)
+{
+ struct tracepoint_entry *entry;
+ int ret = 0;
+ struct tracepoint_probe_closure *old;
+
+ mutex_lock(&tracepoints_mutex);
+ entry = get_tracepoint(name);
+ if (!entry) {
+ entry = add_tracepoint(name);
+ if (IS_ERR(entry)) {
+ ret = PTR_ERR(entry);
+ goto end;
+ }
+ }
+ /*
+ * If we detect that a call_rcu is pending for this tracepoint,
+ * make sure it's executed now.
+ */
+ if (entry->rcu_pending)
+ rcu_barrier();
+ old = tracepoint_entry_add_probe(entry, probe, probe_private);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+ mutex_unlock(&tracepoints_mutex);
+ tracepoint_update_probes(); /* may update entry */
+ mutex_lock(&tracepoints_mutex);
+ entry = get_tracepoint(name);
+ WARN_ON(!entry);
+ entry->oldptr = old;
+ entry->rcu_pending = 1;
+ /* write rcu_pending before calling the RCU callback */
+ smp_wmb();
+#ifdef CONFIG_PREEMPT_RCU
+ synchronize_sched(); /* Until we have the call_rcu_sched() */
+#endif
+ call_rcu(&entry->rcu, free_old_closure);
+end:
+ mutex_unlock(&tracepoints_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_register);
+
+/**
+ * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
+ * @name: tracepoint name
+ * @probe: probe function pointer
+ * @probe_private: probe private data
+ *
+ * Returns the private data given to tracepoint_probe_register, or an ERR_PTR().
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
+ */
+int tracepoint_probe_unregister(const char *name,
+ void *probe, void *probe_private)
+{
+ struct tracepoint_entry *entry;
+ struct tracepoint_probe_closure *old;
+ int ret = -ENOENT;
+
+ mutex_lock(&tracepoints_mutex);
+ entry = get_tracepoint(name);
+ if (!entry)
+ goto end;
+ if (entry->rcu_pending)
+ rcu_barrier();
+ old = tracepoint_entry_remove_probe(entry, probe, probe_private);
+ mutex_unlock(&tracepoints_mutex);
+ tracepoint_update_probes(); /* may update entry */
+ mutex_lock(&tracepoints_mutex);
+ entry = get_tracepoint(name);
+ if (!entry)
+ goto end;
+ entry->oldptr = old;
+ entry->rcu_pending = 1;
+ /* write rcu_pending before calling the RCU callback */
+ smp_wmb();
+#ifdef CONFIG_PREEMPT_RCU
+ synchronize_sched(); /* Until we have the call_rcu_sched() */
+#endif
+ call_rcu(&entry->rcu, free_old_closure);
+ remove_tracepoint(name); /* Ignore busy error message */
+ ret = 0;
+end:
+ mutex_unlock(&tracepoints_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
+
+/**
+ * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
+ * @tracepoint: current tracepoints (in), next tracepoint (out)
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Returns whether a next tracepoint has been found (1) or not (0).
+ * Will return the first tracepoint in the range if the input tracepoint is NULL.
+ */
+int tracepoint_get_iter_range(struct tracepoint **tracepoint,
+ struct tracepoint *begin, struct tracepoint *end)
+{
+ if (!*tracepoint && begin != end) {
+ *tracepoint = begin;
+ return 1;
+ }
+ if (*tracepoint >= begin && *tracepoint < end)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
+
+static void tracepoint_get_iter(struct tracepoint_iter *iter)
+{
+ int found = 0;
+
+ /* Core kernel tracepoints */
+ if (!iter->module) {
+ found = tracepoint_get_iter_range(&iter->tracepoint,
+ __start___tracepoints, __stop___tracepoints);
+ if (found)
+ goto end;
+ }
+ /* tracepoints in modules. */
+ found = module_get_iter_tracepoints(iter);
+end:
+ if (!found)
+ tracepoint_iter_reset(iter);
+}
+
+void tracepoint_iter_start(struct tracepoint_iter *iter)
+{
+ tracepoint_get_iter(iter);
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_start);
+
+void tracepoint_iter_next(struct tracepoint_iter *iter)
+{
+ iter->tracepoint++;
+ /*
+ * iter->tracepoint may be invalid because we blindly incremented it.
+ * Make sure it is valid by marshalling on the tracepoints, getting the
+ * tracepoints from following modules if necessary.
+ */
+ tracepoint_get_iter(iter);
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_next);
+
+void tracepoint_iter_stop(struct tracepoint_iter *iter)
+{
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
+
+void tracepoint_iter_reset(struct tracepoint_iter *iter)
+{
+ iter->module = NULL;
+ iter->tracepoint = NULL;
+}
+EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
Index: linux-2.6.26-rc7-lttng/kernel/module.c
===================================================================
--- linux-2.6.26-rc7-lttng.orig/kernel/module.c 2008-06-25 18:11:05.000000000 -0400
+++ linux-2.6.26-rc7-lttng/kernel/module.c 2008-06-25 18:11:05.000000000 -0400
@@ -48,6 +48,7 @@
#include <linux/license.h>
#include <asm/sections.h>
#include <linux/marker.h>
+#include <linux/tracepoint.h>

#if 0
#define DEBUGP printk
@@ -1791,6 +1792,8 @@
unsigned int immediatecondendindex;
unsigned int markersindex;
unsigned int markersstringsindex;
+ unsigned int tracepointsindex;
+ unsigned int tracepointsstringsindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -2083,6 +2086,9 @@
markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
markersstringsindex = find_sec(hdr, sechdrs, secstrings,
"__markers_strings");
+ tracepointsindex = find_sec(hdr, sechdrs, secstrings, "__tracepoints");
+ tracepointsstringsindex = find_sec(hdr, sechdrs, secstrings,
+ "__tracepoints_strings");

/* Now do relocations. */
for (i = 1; i < hdr->e_shnum; i++) {
@@ -2110,6 +2116,12 @@
mod->num_markers =
sechdrs[markersindex].sh_size / sizeof(*mod->markers);
#endif
+#ifdef CONFIG_TRACEPOINTS
+ mod->tracepoints = (void *)sechdrs[tracepointsindex].sh_addr;
+ mod->num_tracepoints =
+ sechdrs[tracepointsindex].sh_size / sizeof(*mod->tracepoints);
+#endif
+

/* Find duplicate symbols */
err = verify_export_symbols(mod);
@@ -2133,8 +2145,16 @@
marker_update_probe_range(mod->markers,
mod->markers + mod->num_markers);
#endif
+#ifdef CONFIG_TRACEPOINTS
+ tracepoint_update_probe_range(mod->tracepoints,
+ mod->tracepoints + mod->num_tracepoints);
+#endif
+
#ifdef USE_IMMEDIATE
- /* Immediate values must be updated after markers */
+ /*
+ * Immediate values must be updated after markers and
+ * tracepoints.
+ */
imv_update_range(mod->immediate,
mod->immediate + mod->num_immediate);
#endif
@@ -2746,6 +2766,55 @@
}
#endif

+#ifdef CONFIG_TRACEPOINTS
+void module_update_tracepoints(void)
+{
+ struct module *mod;
+
+ mutex_lock(&module_mutex);
+ list_for_each_entry(mod, &modules, list)
+ if (!mod->taints)
+ tracepoint_update_probe_range(mod->tracepoints,
+ mod->tracepoints + mod->num_tracepoints);
+ mutex_unlock(&module_mutex);
+}
+
+/*
+ * Returns 0 if current not found.
+ * Returns 1 if current found.
+ */
+int module_get_iter_tracepoints(struct tracepoint_iter *iter)
+{
+ struct module *iter_mod;
+ int found = 0;
+
+ mutex_lock(&module_mutex);
+ list_for_each_entry(iter_mod, &modules, list) {
+ if (!iter_mod->taints) {
+ /*
+ * Sorted module list
+ */
+ if (iter_mod < iter->module)
+ continue;
+ else if (iter_mod > iter->module)
+ iter->tracepoint = NULL;
+ found = tracepoint_get_iter_range(&iter->tracepoint,
+ iter_mod->tracepoints,
+ iter_mod->tracepoints
+ + iter_mod->num_tracepoints);
+ if (found) {
+ iter->module = iter_mod;
+ break;
+ }
+ }
+ }
+ mutex_unlock(&module_mutex);
+ return found;
+}
+#endif
+
+
+
#ifdef USE_IMMEDIATE
/**
* _module_imv_update - update all immediate values in the kernel
Index: linux-2.6.26-rc7-lttng/include/linux/module.h
===================================================================
--- linux-2.6.26-rc7-lttng.orig/include/linux/module.h 2008-06-25 18:11:05.000000000 -0400
+++ linux-2.6.26-rc7-lttng/include/linux/module.h 2008-06-25 18:11:05.000000000 -0400
@@ -17,6 +17,7 @@
#include <linux/moduleparam.h>
#include <linux/immediate.h>
#include <linux/marker.h>
+#include <linux/tracepoint.h>
#include <asm/local.h>

#include <asm/module.h>
@@ -349,6 +350,10 @@
struct marker *markers;
unsigned int num_markers;
#endif
+#ifdef CONFIG_TRACEPOINTS
+ struct tracepoint *tracepoints;
+ unsigned int num_tracepoints;
+#endif
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
@@ -459,6 +464,9 @@
extern void module_update_markers(void);
extern int module_get_iter_markers(struct marker_iter *iter);

+extern void module_update_tracepoints(void);
+extern int module_get_iter_tracepoints(struct tracepoint_iter *iter);
+
#else /* !CONFIG_MODULES... */
#define EXPORT_SYMBOL(sym)
#define EXPORT_SYMBOL_GPL(sym)
@@ -568,6 +576,15 @@
return 0;
}

+static inline void module_update_tracepoints(void)
+{
+}
+
+static inline int module_get_iter_tracepoints(struct tracepoint_iter *iter)
+{
+ return 0;
+}
+
#endif /* CONFIG_MODULES */

#if defined(CONFIG_MODULES) && defined(USE_IMMEDIATE)
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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