diff options
| author | Joe Maples <joe@frap129.org> | 2017-05-01 19:45:34 -0500 |
|---|---|---|
| committer | Moyster <oysterized@gmail.com> | 2017-05-20 19:48:46 +0200 |
| commit | 69de2265845f7c51e7c33d1415897f99f57aa77c (patch) | |
| tree | 40816654ed1545c66a1133bd71ea1bc3149b036a /kernel/trace | |
| parent | 2e3eef83c62657e5b1c32861a774e1a1cc122b14 (diff) | |
UPSTREAM: tracing: Fix trace_printk() to print when not using bprintk()
The trace_printk() code will allocate extra buffers if the compile detects
that a trace_printk() is used. To do this, the format of the trace_printk()
is saved to the __trace_printk_fmt section, and if that section is bigger
than zero, the buffers are allocated (along with a message that this has
happened).
If trace_printk() uses a format that is not a constant, and thus something
not guaranteed to be around when the print happens, the compiler optimizes
the fmt out, as it is not used, and the __trace_printk_fmt section is not
filled. This means the kernel will not allocate the special buffers needed
for the trace_printk() and the trace_printk() will not write anything to the
tracing buffer.
Adding a "__used" to the variable in the __trace_printk_fmt section will
keep it around, even though it is set to NULL. This will keep the string
from being printed in the debugfs/tracing/printk_formats section as it is
not needed.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Fixes: 07d777fe8c398 "tracing: Add percpu buffers for trace_printk()"
Cc: stable@vger.kernel.org # v3.5+
Bug: 34277115
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Change-Id: I10ce56caa41c7644d9d290d9ed272a6d156c938c
Signed-off-by: Joe Maples <joe@frap129.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/trace_printk.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c index 08de52c09..9008103db 100644 --- a/kernel/trace/trace_printk.c +++ b/kernel/trace/trace_printk.c @@ -299,7 +299,7 @@ static int t_show(struct seq_file *m, void *v) if (!*fmt) return 0; - seq_printf(m, "0x%lx : \"", 0L); + seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt); /* * Tabs and new lines need to be converted. |