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Message-ID: <20170415171135.4b85d5c2@gandalf.local.home>
Date: Sat, 15 Apr 2017 17:11:35 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] ftrace: Fix removing of second function probe
Linus,
While rewriting the function probe code, I stumbled over a long standing
bug. This bug has been there since function tracing was added way back
when. But my new development depends on this bug being fixed, and it
should be fixed regardless as it causes ftrace to disable itself when
triggered, and a reboot is required to enable it again.
The bug is that the function probe does not disable itself properly
if there's another probe of its type still enabled. For example:
# cd /sys/kernel/debug/tracing
# echo schedule:traceoff > set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
# echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
The above registers two traceoff probes (one for schedule and one for
do_IRQ, and then removes do_IRQ. But since there still exists one for
schedule, it is not done properly. When adding do_IRQ back, the breakage
in the accounting is noticed by the ftrace self tests, and it causes
a warning and disables ftrace.
Please pull the latest trace-v4.11-rc5-2 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-v4.11-rc5-2
Tag SHA1: fe8a1251ab0940f3807c2cc1228906681b3880da
Head SHA1: 82cc4fc2e70ec5baeff8f776f2773abc8b2cc0ae
Steven Rostedt (VMware) (1):
ftrace: Fix removing of second function probe
----
kernel/trace/ftrace.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
---------------------------
commit 82cc4fc2e70ec5baeff8f776f2773abc8b2cc0ae
Author: Steven Rostedt (VMware) <rostedt@...dmis.org>
Date: Fri Apr 14 17:45:45 2017 -0400
ftrace: Fix removing of second function probe
When two function probes are added to set_ftrace_filter, and then one of
them is removed, the update to the function locations is not performed, and
the record keeping of the function states are corrupted, and causes an
ftrace_bug() to occur.
This is easily reproducable by adding two probes, removing one, and then
adding it back again.
# cd /sys/kernel/debug/tracing
# echo schedule:traceoff > set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
# echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
Causes:
------------[ cut here ]------------
WARNING: CPU: 2 PID: 1098 at kernel/trace/ftrace.c:2369 ftrace_get_addr_curr+0x143/0x220
Modules linked in: [...]
CPU: 2 PID: 1098 Comm: bash Not tainted 4.10.0-test+ #405
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
Call Trace:
dump_stack+0x68/0x9f
__warn+0x111/0x130
? trace_irq_work_interrupt+0xa0/0xa0
warn_slowpath_null+0x1d/0x20
ftrace_get_addr_curr+0x143/0x220
? __fentry__+0x10/0x10
ftrace_replace_code+0xe3/0x4f0
? ftrace_int3_handler+0x90/0x90
? printk+0x99/0xb5
? 0xffffffff81000000
ftrace_modify_all_code+0x97/0x110
arch_ftrace_update_code+0x10/0x20
ftrace_run_update_code+0x1c/0x60
ftrace_run_modify_code.isra.48.constprop.62+0x8e/0xd0
register_ftrace_function_probe+0x4b6/0x590
? ftrace_startup+0x310/0x310
? debug_lockdep_rcu_enabled.part.4+0x1a/0x30
? update_stack_state+0x88/0x110
? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
? preempt_count_sub+0x18/0xd0
? mutex_lock_nested+0x104/0x800
? ftrace_regex_write.isra.43.part.44+0x1d3/0x320
? __unwind_start+0x1c0/0x1c0
? _mutex_lock_nest_lock+0x800/0x800
ftrace_trace_probe_callback.isra.3+0xc0/0x130
? func_set_flag+0xe0/0xe0
? __lock_acquire+0x642/0x1790
? __might_fault+0x1e/0x20
? trace_get_user+0x398/0x470
? strcmp+0x35/0x60
ftrace_trace_onoff_callback+0x48/0x70
ftrace_regex_write.isra.43.part.44+0x251/0x320
? match_records+0x420/0x420
ftrace_filter_write+0x2b/0x30
__vfs_write+0xd7/0x330
? do_loop_readv_writev+0x120/0x120
? locks_remove_posix+0x90/0x2f0
? do_lock_file_wait+0x160/0x160
? __lock_is_held+0x93/0x100
? rcu_read_lock_sched_held+0x5c/0xb0
? preempt_count_sub+0x18/0xd0
? __sb_start_write+0x10a/0x230
? vfs_write+0x222/0x240
vfs_write+0xef/0x240
SyS_write+0xab/0x130
? SyS_read+0x130/0x130
? trace_hardirqs_on_caller+0x182/0x280
? trace_hardirqs_on_thunk+0x1a/0x1c
entry_SYSCALL_64_fastpath+0x18/0xad
RIP: 0033:0x7fe61c157c30
RSP: 002b:00007ffe87890258 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: ffffffff8114a410 RCX: 00007fe61c157c30
RDX: 0000000000000010 RSI: 000055814798f5e0 RDI: 0000000000000001
RBP: ffff8800c9027f98 R08: 00007fe61c422740 R09: 00007fe61ca53700
R10: 0000000000000073 R11: 0000000000000246 R12: 0000558147a36400
R13: 00007ffe8788f160 R14: 0000000000000024 R15: 00007ffe8788f15c
? trace_hardirqs_off_caller+0xc0/0x110
---[ end trace 99fa09b3d9869c2c ]---
Bad trampoline accounting at: ffffffff81cc3b00 (do_IRQ+0x0/0x150)
Cc: stable@...r.kernel.org
Fixes: 59df055f1991 ("ftrace: trace different functions with a different tracer")
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b9691ee8f6c1..27bb2e61276e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3755,23 +3755,24 @@ static void __enable_ftrace_function_probe(struct ftrace_ops_hash *old_hash)
ftrace_probe_registered = 1;
}
-static void __disable_ftrace_function_probe(void)
+static bool __disable_ftrace_function_probe(void)
{
int i;
if (!ftrace_probe_registered)
- return;
+ return false;
for (i = 0; i < FTRACE_FUNC_HASHSIZE; i++) {
struct hlist_head *hhd = &ftrace_func_hash[i];
if (hhd->first)
- return;
+ return false;
}
/* no more funcs left */
ftrace_shutdown(&trace_probe_ops, 0);
ftrace_probe_registered = 0;
+ return true;
}
@@ -3901,6 +3902,7 @@ static void
__unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
void *data, int flags)
{
+ struct ftrace_ops_hash old_hash_ops;
struct ftrace_func_entry *rec_entry;
struct ftrace_func_probe *entry;
struct ftrace_func_probe *p;
@@ -3912,6 +3914,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
struct hlist_node *tmp;
char str[KSYM_SYMBOL_LEN];
int i, ret;
+ bool disabled;
if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
func_g.search = NULL;
@@ -3930,6 +3933,10 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
mutex_lock(&trace_probe_ops.func_hash->regex_lock);
+ old_hash_ops.filter_hash = old_hash;
+ /* Probes only have filters */
+ old_hash_ops.notrace_hash = NULL;
+
hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
if (!hash)
/* Hmm, should report this somehow */
@@ -3967,12 +3974,17 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
}
}
mutex_lock(&ftrace_lock);
- __disable_ftrace_function_probe();
+ disabled = __disable_ftrace_function_probe();
/*
* Remove after the disable is called. Otherwise, if the last
* probe is removed, a null hash means *all enabled*.
*/
ret = ftrace_hash_move(&trace_probe_ops, 1, orig_hash, hash);
+
+ /* still need to update the function call sites */
+ if (ftrace_enabled && !disabled)
+ ftrace_run_modify_code(&trace_probe_ops, FTRACE_UPDATE_CALLS,
+ &old_hash_ops);
synchronize_sched();
if (!ret)
free_ftrace_hash_rcu(old_hash);
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