From 8252ecf346474cfe46315bd0a7ca655c293c34a9 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 24 Oct 2014 14:56:01 -0400 Subject: [PATCH 1/2] ftrace: Set ops->old_hash on modifying what an ops hooks to The code that checks for trampolines when modifying function hooks tests against a modified ops "old_hash". But the ops old_hash pointer is not being updated before the changes are made, making it possible to not find the right hash to the callback and possibly causing ftrace to break in accounting and disable itself. Have the ops set its old_hash before the modifying takes place. Signed-off-by: Steven Rostedt --- kernel/trace/ftrace.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index fb186b9ddf51..483b8c1b1de0 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2293,10 +2293,13 @@ 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 +3343,7 @@ 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 +3351,8 @@ 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 +3481,14 @@ 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 +3769,11 @@ 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 +3819,7 @@ 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 +4064,7 @@ 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); From 4fc409048d5afb1ad853f294b4262ecf2c980a49 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 24 Oct 2014 14:48:35 -0400 Subject: [PATCH 2/2] ftrace: Fix checking of trampoline ftrace_ops in finding trampoline When modifying code, ftrace has several checks to make sure things are being done correctly. One of them is to make sure any code it modifies is exactly what it expects it to be before it modifies it. In order to do so with the new trampoline logic, it must be able to find out what trampoline a function is hooked to in order to see if the code that hooks to it is what's expected. The logic to find the trampoline from a record (accounting descriptor for a function that is hooked) needs to only look at the "old_hash" of an ops that is being modified. The old_hash is the list of function an ops is hooked to before its update. Since a record would only be pointing to an ops that is being modified if it was already hooked before. Currently, it can pick a modified ops based on its new functions it will be hooked to, and this picks the wrong trampoline and causes the check to fail, disabling ftrace. Signed-off-by: Steven Rostedt ftrace: squash into ordering of ops for modification --- kernel/trace/ftrace.c | 32 +++++++++++++++++++++++--------- 1 file changed, 23 insertions(+), 9 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 483b8c1b1de0..31c90fec4158 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -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);