From: Minchan Kim minchan@kernel.org

With 5.9 kernel on ARM64, I found ftrace_dump output was broken but it had no problem with normal output "cat /sys/kernel/debug/tracing/trace".

With investigation, it seems coping the data into temporal buffer seems to break the align binary printf expects if the static buffer is not aligned with 4-byte. IIUC, get_arg in bstr_printf expects that args has already right align to be decoded and seq_buf_bprintf says ``the arguments are saved in a 32bit word array that is defined by the format string constraints``. So if we don't keep the align under copy to temporal buffer, the output will be broken by shifting some bytes.

This patch fixes it.

Link: https://lkml.kernel.org/r/20201125225654.1618966-1-minchan@kernel.org

Cc: stable@vger.kernel.org Fixes: 8e99cf91b99bb ("tracing: Do not allocate buffer in trace_find_next_entry() in atomic") Signed-off-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Minchan Kim minchan@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- kernel/trace/trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 410cfeb16db5..7d53c5bdea3e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3534,7 +3534,7 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu, }

#define STATIC_TEMP_BUF_SIZE 128 -static char static_temp_buf[STATIC_TEMP_BUF_SIZE]; +static char static_temp_buf[STATIC_TEMP_BUF_SIZE] __aligned(4);

/* Find the next real entry, without updating the iterator itself */ struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,