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ftrace: Fix breakage of set_ftrace_pid
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Commit 4104d32 ("ftrace: Remove global function list and call function
directly") simplified the ftrace code by removing the global_ops list with a
new design. But this cleanup also broke the filtering of PIDs that are added
to the set_ftrace_pid file.

Add back the proper hooks to have pid filtering working once again.

Cc: stable@vger.kernel.org # 3.16+
Reported-by: Matt Fleming <matt@console-pimps.org>
Reported-by: Richard Weinberger <richard.weinberger@gmail.com>
Tested-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Steven Rostedt (Red Hat) committed Jul 24, 2015
1 parent d6726c8 commit e3eea14
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Showing 2 changed files with 37 additions and 18 deletions.
3 changes: 3 additions & 0 deletions include/linux/ftrace.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,7 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
* SAVE_REGS. If another ops with this flag set is already registered
* for any of the functions that this ops will be registered for, then
* this ops will fail to register or set_filter_ip.
* PID - Is affected by set_ftrace_pid (allows filtering on those pids)
*/
enum {
FTRACE_OPS_FL_ENABLED = 1 << 0,
Expand All @@ -132,6 +133,7 @@ enum {
FTRACE_OPS_FL_MODIFYING = 1 << 11,
FTRACE_OPS_FL_ALLOC_TRAMP = 1 << 12,
FTRACE_OPS_FL_IPMODIFY = 1 << 13,
FTRACE_OPS_FL_PID = 1 << 14,
};

#ifdef CONFIG_DYNAMIC_FTRACE
Expand Down Expand Up @@ -159,6 +161,7 @@ struct ftrace_ops {
struct ftrace_ops *next;
unsigned long flags;
void *private;
ftrace_func_t saved_func;
int __percpu *disabled;
#ifdef CONFIG_DYNAMIC_FTRACE
int nr_trampolines;
Expand Down
52 changes: 34 additions & 18 deletions kernel/trace/ftrace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,13 @@ struct ftrace_pid {
struct pid *pid;
};

static bool ftrace_pids_enabled(void)
{
return !list_empty(&ftrace_pids);
}

static void ftrace_update_trampoline(struct ftrace_ops *ops);

/*
* ftrace_disabled is set when an anomaly is discovered.
* ftrace_disabled is much stronger than ftrace_enabled.
Expand All @@ -109,7 +116,6 @@ static DEFINE_MUTEX(ftrace_lock);
static struct ftrace_ops *ftrace_control_list __read_mostly = &ftrace_list_end;
static struct ftrace_ops *ftrace_ops_list __read_mostly = &ftrace_list_end;
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
static struct ftrace_ops global_ops;
static struct ftrace_ops control_ops;

Expand Down Expand Up @@ -183,14 +189,7 @@ 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, op, regs);
}

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;
op->saved_func(ip, parent_ip, op, regs);
}

/**
Expand All @@ -202,7 +201,6 @@ static void set_ftrace_pid_function(ftrace_func_t func)
void clear_ftrace_function(void)
{
ftrace_trace_function = ftrace_stub;
ftrace_pid_function = ftrace_stub;
}

static void control_ops_disable_all(struct ftrace_ops *ops)
Expand Down Expand Up @@ -436,6 +434,12 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
} else
add_ftrace_ops(&ftrace_ops_list, ops);

/* Always save the function, and reset at unregistering */
ops->saved_func = ops->func;

if (ops->flags & FTRACE_OPS_FL_PID && ftrace_pids_enabled())
ops->func = ftrace_pid_func;

ftrace_update_trampoline(ops);

if (ftrace_enabled)
Expand Down Expand Up @@ -463,15 +467,28 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
if (ftrace_enabled)
update_ftrace_function();

ops->func = ops->saved_func;

return 0;
}

static void ftrace_update_pid_func(void)
{
bool enabled = ftrace_pids_enabled();
struct ftrace_ops *op;

/* Only do something if we are tracing something */
if (ftrace_trace_function == ftrace_stub)
return;

do_for_each_ftrace_op(op, ftrace_ops_list) {
if (op->flags & FTRACE_OPS_FL_PID) {
op->func = enabled ? ftrace_pid_func :
op->saved_func;
ftrace_update_trampoline(op);
}
} while_for_each_ftrace_op(op);

update_ftrace_function();
}

Expand Down Expand Up @@ -1133,7 +1150,8 @@ static struct ftrace_ops global_ops = {
.local_hash.filter_hash = EMPTY_HASH,
INIT_OPS_HASH(global_ops)
.flags = FTRACE_OPS_FL_RECURSION_SAFE |
FTRACE_OPS_FL_INITIALIZED,
FTRACE_OPS_FL_INITIALIZED |
FTRACE_OPS_FL_PID,
};

/*
Expand Down Expand Up @@ -5023,7 +5041,9 @@ static void ftrace_update_trampoline(struct ftrace_ops *ops)

static struct ftrace_ops global_ops = {
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_INITIALIZED,
.flags = FTRACE_OPS_FL_RECURSION_SAFE |
FTRACE_OPS_FL_INITIALIZED |
FTRACE_OPS_FL_PID,
};

static int __init ftrace_nodyn_init(void)
Expand Down Expand Up @@ -5080,11 +5100,6 @@ void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func)
if (WARN_ON(tr->ops->func != ftrace_stub))
printk("ftrace ops had %pS for function\n",
tr->ops->func);
/* Only the top level instance does pid tracing */
if (!list_empty(&ftrace_pids)) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
}
}
tr->ops->func = func;
tr->ops->private = tr;
Expand Down Expand Up @@ -5371,7 +5386,7 @@ static void *fpid_start(struct seq_file *m, loff_t *pos)
{
mutex_lock(&ftrace_lock);

if (list_empty(&ftrace_pids) && (!*pos))
if (!ftrace_pids_enabled() && (!*pos))
return (void *) 1;

return seq_list_start(&ftrace_pids, *pos);
Expand Down Expand Up @@ -5610,6 +5625,7 @@ static struct ftrace_ops graph_ops = {
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_RECURSION_SAFE |
FTRACE_OPS_FL_INITIALIZED |
FTRACE_OPS_FL_PID |
FTRACE_OPS_FL_STUB,
#ifdef FTRACE_GRAPH_TRAMP_ADDR
.trampoline = FTRACE_GRAPH_TRAMP_ADDR,
Expand Down

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