[RFC 1/3] tracing: function tracer registration

From: Jiri Olsa
Date: Fri Apr 29 2011 - 10:43:29 EST

adding ID and default tracer support for function
tracer registration

---
arch/x86/include/asm/ftrace.h | 2 +
arch/x86/kernel/entry_64.S | 6 +-
arch/x86/kernel/ftrace.c | 13 --
include/linux/ftrace.h | 9 +-
kernel/trace/ftrace.c | 290 +++++++++++++++----------------------
kernel/trace/trace_events.c | 1 +
kernel/trace/trace_functions.c | 2 +
kernel/trace/trace_irqsoff.c | 1 +
kernel/trace/trace_sched_wakeup.c | 1 +
kernel/trace/trace_stack.c | 1 +
10 files changed, 136 insertions(+), 190 deletions(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index db24c22..45ae1fa 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -1,6 +1,8 @@
#ifndef _ASM_X86_FTRACE_H
#define _ASM_X86_FTRACE_H

+#define FTRACE_TRACERS_MAX 4
+
#ifdef __ASSEMBLY__

.macro MCOUNT_SAVE_FRAME
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8a445a0..e0ba7d9 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -79,8 +79,10 @@ ENTRY(ftrace_caller)
movq 8(%rbp), %rsi
subq $MCOUNT_INSN_SIZE, %rdi

-GLOBAL(ftrace_call)
- call ftrace_stub
+ /* by default call all registered handlers */
+ movq $-1, %rdx
+
+ call ftrace_call

MCOUNT_RESTORE_FRAME

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 0ba15a6..dc92378 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -321,19 +321,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return ftrace_modify_code(rec->ip, old, new);
}

-int ftrace_update_ftrace_func(ftrace_func_t func)
-{
- unsigned long ip = (unsigned long)(&ftrace_call);
- unsigned char old[MCOUNT_INSN_SIZE], *new;
- int ret;
-
- memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
- new = ftrace_call_replace(ip, (unsigned long)func);
- ret = ftrace_modify_code(ip, old, new);
-
- return ret;
-}
-
int __init ftrace_dyn_arch_init(void *data)
{
/* The return code is retured via data */
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index ca29e03..b7ab09d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -30,8 +30,9 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip);

struct ftrace_ops {
- ftrace_func_t func;
- struct ftrace_ops *next;
+ char *name;
+ int id;
+ ftrace_func_t func;
};

extern int function_trace_stop;
@@ -175,9 +176,9 @@ int unregister_ftrace_command(struct ftrace_func_command *cmd);
/* defined in arch */
extern int ftrace_ip_converted(unsigned long ip);
extern int ftrace_dyn_arch_init(void *data);
-extern int ftrace_update_ftrace_func(ftrace_func_t func);
extern void ftrace_caller(void);
-extern void ftrace_call(void);
+extern void ftrace_call(unsigned long ip, unsigned long parent_ip,
+ unsigned long flags);
extern void mcount_call(void);

#ifndef FTRACE_ADDR
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ee24fa1..f1eedda 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -76,62 +76,12 @@ static int ftrace_disabled __read_mostly;

static DEFINE_MUTEX(ftrace_lock);

-static struct ftrace_ops ftrace_list_end __read_mostly =
-{
- .func = ftrace_stub,
-};
-
-static struct ftrace_ops *ftrace_list __read_mostly = &ftrace_list_end;
-ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
-ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
-ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
-
-/*
- * Traverse the ftrace_list, invoking all entries. The reason that we
- * can use rcu_dereference_raw() is that elements removed from this list
- * are simply leaked, so there is no need to interact with a grace-period
- * mechanism. The rcu_dereference_raw() calls are needed to handle
- * concurrent insertions into the ftrace_list.
- *
- * Silly Alpha and silly pointer-speculation compiler optimizations!
- */
-static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
-{
- struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/
-
- while (op != &ftrace_list_end) {
- op->func(ip, parent_ip);
- op = rcu_dereference_raw(op->next); /*see above*/
- };
-}
-
-static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip)
-{
- if (!test_tsk_trace_trace(current))
- return;
-
- ftrace_pid_function(ip, parent_ip);
-}
+static struct ftrace_ops *ftrace_tracers[FTRACE_TRACERS_MAX];
+static DECLARE_BITMAP(ftrace_tracers_bm, FTRACE_TRACERS_MAX);
+static int ftrace_tracers_cur = -1;

-static void set_ftrace_pid_function(ftrace_func_t func)
-{
- /* do not set ftrace_pid_function to itself! */
- if (func != ftrace_pid_func)
- ftrace_pid_function = func;
-}
-
-/**
- * clear_ftrace_function - reset the ftrace function
- *
- * This NULLs the ftrace function and in essence stops
- * tracing. There may be lag
- */
-void clear_ftrace_function(void)
-{
- ftrace_trace_function = ftrace_stub;
- __ftrace_trace_function = ftrace_stub;
- ftrace_pid_function = ftrace_stub;
-}
+#define for_each_tracer(id, bm) \
+ for_each_set_bit(id, bm, FTRACE_TRACERS_MAX)

#ifndef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
/*
@@ -147,114 +97,82 @@ static void ftrace_test_stop_func(unsigned long ip, unsigned long parent_ip)
}
#endif

-static int __register_ftrace_function(struct ftrace_ops *ops)
-{
- ops->next = ftrace_list;
- /*
- * We are entering ops into the ftrace_list but another
- * CPU might be walking that list. We need to make sure
- * the ops->next pointer is valid before another CPU sees
- * the ops pointer included into the ftrace_list.
- */
- rcu_assign_pointer(ftrace_list, ops);

- if (ftrace_enabled) {
- ftrace_func_t func;
+void ftrace_call(unsigned long ip, unsigned long parent_ip,
+ unsigned long flags)
+{
+ int id;

- if (ops->next == &ftrace_list_end)
- func = ops->func;
- else
- func = ftrace_list_func;
+ if (!list_empty(&ftrace_pids) &&
+ !test_tsk_trace_trace(current))
+ return;

- if (!list_empty(&ftrace_pids)) {
- set_ftrace_pid_function(func);
- func = ftrace_pid_func;
- }
+ rcu_read_lock();
+ for_each_tracer(id, &flags) {
+ struct ftrace_ops *ops = rcu_dereference(ftrace_tracers[id]);
+ if (!ops)
+ continue;

- /*
- * For one func, simply call it directly.
- * For more than one func, call the chain.
- */
-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
- ftrace_trace_function = func;
-#else
- __ftrace_trace_function = func;
- ftrace_trace_function = ftrace_test_stop_func;
-#endif
+ ops->func(ip, parent_ip);
}
-
- return 0;
+ rcu_read_unlock();
}

-static int __unregister_ftrace_function(struct ftrace_ops *ops)
+static int __register_ftrace_function(struct ftrace_ops *ops)
{
- struct ftrace_ops **p;
+ int id;

- /*
- * If we are removing the last function, then simply point
- * to the ftrace_stub.
- */
- if (ftrace_list == ops && ops->next == &ftrace_list_end) {
- ftrace_trace_function = ftrace_stub;
- ftrace_list = &ftrace_list_end;
- return 0;
- }
+ id = find_first_zero_bit(ftrace_tracers_bm, FTRACE_TRACERS_MAX);
+ if (id >= FTRACE_TRACERS_MAX)
+ return -ENOSPC;

- for (p = &ftrace_list; *p != &ftrace_list_end; p = &(*p)->next)
- if (*p == ops)
- break;
+ ops->id = id;
+ set_bit(id, ftrace_tracers_bm);
+ ftrace_tracers_cur = id;
+ rcu_assign_pointer(ftrace_tracers[id], ops);
+ return 0;
+}

- if (*p != ops)
- return -1;
+static int __unregister_ftrace_function(struct ftrace_ops *ops)
+{
+ int id = ops->id;

- *p = (*p)->next;
+ clear_bit(id, ftrace_tracers_bm);
+ BUG_ON(ops != ftrace_tracers[id]);
+ rcu_assign_pointer(ftrace_tracers[id], NULL);

- if (ftrace_enabled) {
- /* If we only have one func left, then call that directly */
- if (ftrace_list->next == &ftrace_list_end) {
- ftrace_func_t func = ftrace_list->func;
+ if (ftrace_tracers_cur != id)
+ return 0;

- if (!list_empty(&ftrace_pids)) {
- set_ftrace_pid_function(func);
- func = ftrace_pid_func;
- }
-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
- ftrace_trace_function = func;
-#else
- __ftrace_trace_function = func;
-#endif
- }
- }
+ /* find another default tracer */
+ ftrace_tracers_cur = find_first_bit(ftrace_tracers_bm,
+ FTRACE_TRACERS_MAX);
+ if (ftrace_tracers_cur >= FTRACE_TRACERS_MAX)
+ ftrace_tracers_cur = -1;

return 0;
}

-static void ftrace_update_pid_func(void)
+static int ftrace_tracer_default(char *name)
{
- ftrace_func_t func;
+ int id, ret = -EINVAL;

- if (ftrace_trace_function == ftrace_stub)
- return;
+ mutex_lock(&ftrace_lock);
+ for_each_tracer(id, ftrace_tracers_bm) {
+ struct ftrace_ops *ops = ftrace_tracers[id];
+ BUG_ON(!ops);

-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
- func = ftrace_trace_function;
-#else
- func = __ftrace_trace_function;
-#endif
+ if (!strcmp(name, ops->name))
+ break;
+ }

- if (!list_empty(&ftrace_pids)) {
- set_ftrace_pid_function(func);
- func = ftrace_pid_func;
- } else {
- if (func == ftrace_pid_func)
- func = ftrace_pid_function;
+ if (id < FTRACE_TRACERS_MAX) {
+ ftrace_tracers_cur = id;
+ ret = 0;
}

-#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
- ftrace_trace_function = func;
-#else
- __ftrace_trace_function = func;
-#endif
+ mutex_unlock(&ftrace_lock);
+ return ret;
}

#ifdef CONFIG_FUNCTION_PROFILER
@@ -717,6 +635,7 @@ static void unregister_ftrace_profiler(void)
#else
static struct ftrace_ops ftrace_profile_ops __read_mostly =
{
+ .name = "trace_profile",
.func = function_profile_call,
};

@@ -1143,9 +1062,6 @@ static int __ftrace_modify_code(void *data)
else if (*command & FTRACE_DISABLE_CALLS)
ftrace_replace_code(0);

- if (*command & FTRACE_UPDATE_TRACE_FUNC)
- ftrace_update_ftrace_func(ftrace_trace_function);
-
if (*command & FTRACE_START_FUNC_RET)
ftrace_enable_ftrace_graph_caller();
else if (*command & FTRACE_STOP_FUNC_RET)
@@ -1174,11 +1090,6 @@ static int ftrace_start_up;

static void ftrace_startup_enable(int command)
{
- if (saved_ftrace_func != ftrace_trace_function) {
- saved_ftrace_func = ftrace_trace_function;
- command |= FTRACE_UPDATE_TRACE_FUNC;
- }
-
if (!command || !ftrace_enabled)
return;

@@ -1212,11 +1123,6 @@ static void ftrace_shutdown(int command)
if (!ftrace_start_up)
command |= FTRACE_DISABLE_CALLS;

- if (saved_ftrace_func != ftrace_trace_function) {
- saved_ftrace_func = ftrace_trace_function;
- command |= FTRACE_UPDATE_TRACE_FUNC;
- }
-
if (!command || !ftrace_enabled)
return;

@@ -1732,6 +1638,53 @@ ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
return ret;
}

+static int ftrace_tracers_show(struct seq_file *seq, void *v)
+{
+ int id;
+
+ mutex_lock(&ftrace_lock);
+ for_each_tracer(id, ftrace_tracers_bm) {
+ struct ftrace_ops *ops = ftrace_tracers[id];
+
+ BUG_ON(!ops);
+ seq_printf(seq, "%s%s\n",
+ ftrace_tracers_cur == id ? "*" : " ",
+ ops->name);
+ }
+
+ mutex_unlock(&ftrace_lock);
+ return 0;
+}
+
+static int
+ftrace_tracers_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ftrace_tracers_show, NULL);
+}
+
+static ssize_t
+ftrace_tracers_write(struct file *filp, const char __user *ubuf, size_t cnt,
+ loff_t *ppos)
+{
+ char buf[64];
+ int i;
+
+ if (cnt >= sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+ for (i = cnt - 1; i > 0 && isspace(buf[i]); i--)
+ buf[i] = 0;
+
+ if (ftrace_tracer_default(buf))
+ return -EINVAL;
+
+ return cnt;
+}
+
static int ftrace_match(char *str, char *regex, int len, int type)
{
int matched = 0;
@@ -1952,6 +1905,7 @@ function_trace_probe_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_probe_ops __read_mostly =
{
+ .name = "trace_probe",
.func = function_trace_probe_call,
};

@@ -2467,6 +2421,14 @@ static const struct file_operations ftrace_notrace_fops = {
.release = ftrace_notrace_release,
};

+static const struct file_operations ftrace_tracers_fops = {
+ .open = ftrace_tracers_open,
+ .read = seq_read,
+ .release = single_release,
+ .llseek = seq_lseek,
+ .write = ftrace_tracers_write,
+};
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static DEFINE_MUTEX(graph_lock);
@@ -2688,6 +2650,9 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
trace_create_file("set_ftrace_notrace", 0644, d_tracer,
NULL, &ftrace_notrace_fops);

+ trace_create_file("function_tracers", 0644, d_tracer,
+ NULL, &ftrace_tracers_fops);
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
trace_create_file("set_graph_function", 0444, d_tracer,
NULL,
@@ -2950,7 +2915,6 @@ static int ftrace_pid_add(int p)

set_ftrace_pid_task(pid);

- ftrace_update_pid_func();
ftrace_startup_enable(0);

mutex_unlock(&ftrace_lock);
@@ -2979,7 +2943,6 @@ static void ftrace_pid_reset(void)
kfree(fpid);
}

- ftrace_update_pid_func();
ftrace_startup_enable(0);

mutex_unlock(&ftrace_lock);
@@ -3127,7 +3090,6 @@ void ftrace_kill(void)
{
ftrace_disabled = 1;
ftrace_enabled = 0;
- clear_ftrace_function();
}

/**
@@ -3194,24 +3156,10 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,

last_ftrace_enabled = !!ftrace_enabled;

- if (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;
-
+ else
ftrace_shutdown_sysctl();
- }

out:
mutex_unlock(&ftrace_lock);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e88f74f..43600a1 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1651,6 +1651,7 @@ function_test_events_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_ops __initdata =
{
+ .name = "trace_event",
.func = function_test_events_call,
};

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 16aee4d..a991743 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -148,11 +148,13 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_ops __read_mostly =
{
+ .name = "trace",
.func = function_trace_call,
};

static struct ftrace_ops trace_stack_ops __read_mostly =
{
+ .name = "trace_stack",
.func = function_stack_trace_call,
};

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index a4969b4..6983594 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -152,6 +152,7 @@ irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_ops __read_mostly =
{
+ .name = "trace_irqs",
.func = irqsoff_tracer_call,
};
#endif /* CONFIG_FUNCTION_TRACER */
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 7319559..f8b4622 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -128,6 +128,7 @@ wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_ops __read_mostly =
{
+ .name = "trace_wakeup",
.func = wakeup_tracer_call,
};
#endif /* CONFIG_FUNCTION_TRACER */
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 4c5dead..31f361e 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -132,6 +132,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip)

static struct ftrace_ops trace_ops __read_mostly =
{
+ .name = "trace_stack",
.func = stack_trace_call,
};

--
1.7.1

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