Re: FAILED: patch "[PATCH] ftrace: Fix removing of second function probe" failed to apply to 4.11-stable tree

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 22 May 2017 18:55:33 +0200
<gregkh@linuxfoundation.org> wrote:

> The patch below does not apply to the 4.11-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git
> commit id to <stable@vger.kernel.org>.
> 

Hi Greg,

This fails because it was already applied to 4.11 with a stable tag.
But I had to cherry pick it into my development tree for 4.12 because
new code depended on it as well as code I already pushed to linux-next
and did not want to rebase. See this thread here:

 http://lkml.kernel.org/r/20170414180547.182f859c@gandalf.local.home

Sorry for the confusion, maybe I should have removed the stable tag
from the cherry picked commit.

-- Steve


> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> >From acceb72e90624ec6c3f2fc62e72dab892cd075da Mon Sep 17 00:00:00
> >2001  
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> Date: Fri, 14 Apr 2017 17:45:45 -0400
> Subject: [PATCH] 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@vger.kernel.org
> Fixes: 59df055f1991 ("ftrace: trace different functions with a
> different tracer") Signed-off-by: Steven Rostedt (VMware)
> <rostedt@goodmis.org>
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 34f63e78d661..4b6459a57fbc 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3780,23 +3780,24 @@ 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;
>  }
>  
>  
> @@ -3926,6 +3927,7 @@ 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;
> @@ -3937,6 +3939,7 @@ __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;
> @@ -3955,6 +3958,10 @@ __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 */
> @@ -3992,12 +3999,17 @@ __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);