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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2014-07-24 09:56:27 -0400
committerSteven Rostedt <rostedt@goodmis.org>2014-07-24 10:06:41 -0400
commit2a0343baa4cc0d4e618898f8bdae8136bbb6e1b2 (patch)
treec85d25e03eb287bc9261ae7f49709aaa3c07dc0b /kernel
parent10e83fd01ccbb7122ad2c9dce68fb01bebb3fc46 (diff)
ftrace: Fix trampoline hash update check on rec->flags
In the loop of ftrace_save_ops_tramp_hash(), it adds all the recs to the ops hash if the rec has only one callback attached and the ops is connected to the rec. It gives a nasty warning and shuts down ftrace if the rec doesn't have a trampoline set for it. But this can happen with the following scenario: # cd /sys/kernel/debug/tracing # echo schedule do_IRQ > set_ftrace_filter # mkdir instances/foo # echo schedule > instances/foo/set_ftrace_filter # echo function_graph > current_function # echo function > instances/foo/current_function # echo nop > instances/foo/current_function The above would then trigger the following warning and disable ftrace: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 3145 at kernel/trace/ftrace.c:2212 ftrace_run_update_code+0xe4/0x15b() Modules linked in: ipt_MASQUERADE sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ip [...] CPU: 1 PID: 3145 Comm: bash Not tainted 3.16.0-rc3-test+ #136 Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007 0000000000000000 ffffffff81808a88 ffffffff81502130 0000000000000000 ffffffff81040ca1 ffff880077c08000 ffffffff810bd286 0000000000000001 ffffffff81a56830 ffff88007a041be0 ffff88007a872d60 00000000000001be Call Trace: [<ffffffff81502130>] ? dump_stack+0x4a/0x75 [<ffffffff81040ca1>] ? warn_slowpath_common+0x7e/0x97 [<ffffffff810bd286>] ? ftrace_run_update_code+0xe4/0x15b [<ffffffff810bd286>] ? ftrace_run_update_code+0xe4/0x15b [<ffffffff810bda1a>] ? ftrace_shutdown+0x11c/0x16b [<ffffffff810bda87>] ? unregister_ftrace_function+0x1e/0x38 [<ffffffff810cc7e1>] ? function_trace_reset+0x1a/0x28 [<ffffffff810c924f>] ? tracing_set_tracer+0xc1/0x276 [<ffffffff810c9477>] ? tracing_set_trace_write+0x73/0x91 [<ffffffff81132383>] ? __sb_start_write+0x9a/0xcc [<ffffffff8120478f>] ? security_file_permission+0x1b/0x31 [<ffffffff81130e49>] ? vfs_write+0xac/0x11c [<ffffffff8113115d>] ? SyS_write+0x60/0x8e [<ffffffff81508112>] ? system_call_fastpath+0x16/0x1b ---[ end trace 938c4415cbc7dc96 ]--- ------------[ cut here ]------------ Link: http://lkml.kernel.org/r/20140723120805.GB21376@redhat.com Reported-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ftrace.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eda69c9f78d0..6ef1989c2b2e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2208,6 +2208,14 @@ static int ftrace_save_ops_tramp_hash(struct ftrace_ops *ops)
if (ftrace_rec_count(rec) == 1 &&
ftrace_ops_test(ops, rec->ip, rec)) {
+ /*
+ * If another ops adds to a rec, the rec will
+ * lose its trampoline and never get it back
+ * until all ops are off of it.
+ */
+ if (!(rec->flags & FTRACE_FL_TRAMP))
+ continue;
+
/* This record had better have a trampoline */
if (FTRACE_WARN_ON(!(rec->flags & FTRACE_FL_TRAMP_EN)))
return -1;