Re: [PATCH bpf-next 2/3] bpf: allow %pB in bpf_seq_printf()

On Jun 23, 2020, at 8:29 AM, Daniel Borkmann [off-list ref] wrote:

On 6/23/20 9:08 AM, Song Liu wrote:

quoted

This makes it easy to dump stack trace with bpf_seq_printf().
Signed-off-by: Song Liu <redacted>
---
 kernel/trace/bpf_trace.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 2c13bcb5c2bce..ced3176801ae8 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -636,7 +636,8 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
 		if (fmt[i] == 'p') {
 			if (fmt[i + 1] == 0 ||
 			    fmt[i + 1] == 'K' ||
-			    fmt[i + 1] == 'x') {
+			    fmt[i + 1] == 'x' ||
+			    fmt[i + 1] == 'B') {
 				/* just kernel pointers */
 				params[fmt_cnt] = args[fmt_cnt];
 				fmt_cnt++;

Why only bpf_seq_printf(), what about bpf_trace_printk()?

The use case we are looking at needs bpf_seq_printf(). Let me also add it to
bpf_trace_printk(). 

Thanks,
Song