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Adding the new code for 3.19, I discovered a couple of minor bugs with 

the accounting of the ftrace_ops trampoline logic. One was that the
 old hash was not updated before calling the modify code for an ftrace_ops.
 The second bug was what let the first bug go unnoticed, as the update would
 check the current hash for all ftrace_ops (where it should only check the
 old hash for modified ones). This let things work when only one ftrace_ops
 was registered to a function, but could break if more than one was
 registered depending on the order of the look ups.
 
 The worse thing that can happen if this bug triggers is that the ftrace
 self checks would find an anomaly and shut itself down.
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Merge tag 'trace-fixes-v3.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull ftrace trampoline accounting fixes from Steven Rostedt:
 "Adding the new code for 3.19, I discovered a couple of minor bugs with
  the accounting of the ftrace_ops trampoline logic.

  One was that the old hash was not updated before calling the modify
  code for an ftrace_ops.  The second bug was what let the first bug go
  unnoticed, as the update would check the current hash for all
  ftrace_ops (where it should only check the old hash for modified
  ones).  This let things work when only one ftrace_ops was registered
  to a function, but could break if more than one was registered
  depending on the order of the look ups.

  The worse thing that can happen if this bug triggers is that the
  ftrace self checks would find an anomaly and shut itself down"

* tag 'trace-fixes-v3.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ftrace: Fix checking of trampoline ftrace_ops in finding trampoline
  ftrace: Set ops->old_hash on modifying what an ops hooks to
This commit is contained in:
Linus Torvalds 2014-10-28 13:27:19 -07:00
Родитель 6e2028aaa1 4fc409048d
Коммит 6234056e13
1 изменённых файлов: 38 добавлений и 18 удалений
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56
kernel/trace/ftrace.c
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@ -1925,8 +1925,16 @@ ftrace_find_tramp_ops_curr(struct dyn_ftrace *rec)
* when we are adding another op to the rec or removing the
* current one. Thus, if the op is being added, we can
* ignore it because it hasn't attached itself to the rec
* yet. That means we just need to find the op that has a
* trampoline and is not beeing added.
* yet.
*
* If an ops is being modified (hooking to different functions)
* then we don't care about the new functions that are being
* added, just the old ones (that are probably being removed).
*
* If we are adding an ops to a function that already is using
* a trampoline, it needs to be removed (trampolines are only
* for single ops connected), then an ops that is not being
* modified also needs to be checked.
*/
do_for_each_ftrace_op(op, ftrace_ops_list) {
@ -1940,17 +1948,23 @@ ftrace_find_tramp_ops_curr(struct dyn_ftrace *rec)
if (op->flags & FTRACE_OPS_FL_ADDING)
continue;
/*
* If the ops is not being added and has a trampoline,
* then it must be the one that we want!
*/
if (hash_contains_ip(ip, op->func_hash))
return op;
/* If the ops is being modified, it may be in the old hash. */
/*
* If the ops is being modified and is in the old
* hash, then it is probably being removed from this
* function.
*/
if ((op->flags & FTRACE_OPS_FL_MODIFYING) &&
hash_contains_ip(ip, &op->old_hash))
return op;
/*
* If the ops is not being added or modified, and it's
* in its normal filter hash, then this must be the one
* we want!
*/
if (!(op->flags & FTRACE_OPS_FL_MODIFYING) &&
hash_contains_ip(ip, op->func_hash))
return op;
} while_for_each_ftrace_op(op);
@ -2293,10 +2307,13 @@ static void ftrace_run_update_code(int command)
FTRACE_WARN_ON(ret);
}
static void ftrace_run_modify_code(struct ftrace_ops *ops, int command)
static void ftrace_run_modify_code(struct ftrace_ops *ops, int command,
struct ftrace_hash *old_hash)
{
ops->flags |= FTRACE_OPS_FL_MODIFYING;
ops->old_hash.filter_hash = old_hash;
ftrace_run_update_code(command);
ops->old_hash.filter_hash = NULL;
ops->flags &= ~FTRACE_OPS_FL_MODIFYING;
}
@ -3340,7 +3357,7 @@ static struct ftrace_ops trace_probe_ops __read_mostly =
static int ftrace_probe_registered;
static void __enable_ftrace_function_probe(void)
static void __enable_ftrace_function_probe(struct ftrace_hash *old_hash)
{
int ret;
int i;
@ -3348,7 +3365,8 @@ static void __enable_ftrace_function_probe(void)
if (ftrace_probe_registered) {
/* still need to update the function call sites */
if (ftrace_enabled)
ftrace_run_modify_code(&trace_probe_ops, FTRACE_UPDATE_CALLS);
ftrace_run_modify_code(&trace_probe_ops, FTRACE_UPDATE_CALLS,
old_hash);
return;
}
@ -3477,13 +3495,14 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
} while_for_each_ftrace_rec();
ret = ftrace_hash_move(&trace_probe_ops, 1, orig_hash, hash);
__enable_ftrace_function_probe(old_hash);
if (!ret)
free_ftrace_hash_rcu(old_hash);
else
count = ret;
__enable_ftrace_function_probe();
out_unlock:
mutex_unlock(&ftrace_lock);
out:
@ -3764,10 +3783,11 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
return add_hash_entry(hash, ip);
}
static void ftrace_ops_update_code(struct ftrace_ops *ops)
static void ftrace_ops_update_code(struct ftrace_ops *ops,
struct ftrace_hash *old_hash)
{
if (ops->flags & FTRACE_OPS_FL_ENABLED && ftrace_enabled)
ftrace_run_modify_code(ops, FTRACE_UPDATE_CALLS);
ftrace_run_modify_code(ops, FTRACE_UPDATE_CALLS, old_hash);
}
static int
@ -3813,7 +3833,7 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
old_hash = *orig_hash;
ret = ftrace_hash_move(ops, enable, orig_hash, hash);
if (!ret) {
ftrace_ops_update_code(ops);
ftrace_ops_update_code(ops, old_hash);
free_ftrace_hash_rcu(old_hash);
}
mutex_unlock(&ftrace_lock);
@ -4058,7 +4078,7 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
ret = ftrace_hash_move(iter->ops, filter_hash,
orig_hash, iter->hash);
if (!ret) {
ftrace_ops_update_code(iter->ops);
ftrace_ops_update_code(iter->ops, old_hash);
free_ftrace_hash_rcu(old_hash);
}
mutex_unlock(&ftrace_lock);