[for-linus][PATCH 1/5] ftrace: Fix char print issue in print_ip_ins()

Steven Rostedt
2022-10-12T22:03:57Z

From: Zheng Yejian <zhengyejian1@huawei.com>

When ftrace bug happened, following log shows every hex data in
problematic ip address:
actual: ffffffe8:6b:ffffffd9:01:21

But so many 'f's seem a little confusing, and that is because format
'%x' being used to print signed chars in array 'ins'. As suggested
by Joe, change to use format "%*phC" to print array 'ins'.

After this patch, the log is like:
actual: e8:6b:d9:01:21

Link: https://lkml.kernel.org/r/20221011120352.1878494-1-zhengyejian1@huawei.com

Fixes: 6c14133d2d3f ("ftrace: Do not blindly read the ip address in ftrace_bug()")
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 83362a155791..75c16215d065 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2028,7 +2028,6 @@ static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
static void print_ip_ins(const char *fmt, const unsigned char *p)
{
char ins[MCOUNT_INSN_SIZE];
- int i;

if (copy_from_kernel_nofault(ins, p, MCOUNT_INSN_SIZE)) {
printk(KERN_CONT "%s[FAULT] %px\n", fmt, p);
@@ -2036,9 +2035,7 @@ static void print_ip_ins(const char *fmt, const unsigned char *p)
}

printk(KERN_CONT "%s", fmt);
-
- for (i = 0; i < MCOUNT_INSN_SIZE; i++)
- printk(KERN_CONT "%s%02x", i ? ":" : "", ins[i]);
+ pr_cont("%*phC", MCOUNT_INSN_SIZE, ins);
}

enum ftrace_bug_type ftrace_bug_type;
--
2.35.1