2018-12-05 08:50 UTC-0800 ~ Alexei Starovoitov
<alexei.starovoi...@gmail.com>
On Wed, Dec 05, 2018 at 10:28:24AM +0000, Quentin Monnet wrote:
BPF programs can use the bpf_trace_printk() helper to print debug
information into the trace pipe. Add a subcommand
"bpftool prog tracelog" to simply dump this pipe to the console.
This is for a good part copied from iproute2, where the feature is
available with "tc exec bpf dbg". Changes include dumping pipe content
to stdout instead of stderr and adding JSON support (content is dumped
as an array of strings, one per line read from the pipe). This version
is dual-licensed, with Daniel's permission.
Cc: Daniel Borkmann <dan...@iogearbox.net>
Suggested-by: Daniel Borkmann <dan...@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.mon...@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
+static bool find_tracefs_pipe(char *mnt)
+{
+ static const char * const known_mnts[] = {
+ "/sys/kernel/debug/tracing",
+ "/sys/kernel/tracing",
+ "/tracing",
+ "/trace",
I wonder where this list came from?
I only knew of 1st one.
I only met the first form too. I took the list from iproute2. I can
change it in the future if we find out trying all these paths is not
relevant.
+ };
+ const char *pipe_name = "/trace_pipe";
+ const char *fstype = "tracefs";
+ char type[100], format[32];
+ const char * const *ptr;
+ bool found = false;
+ FILE *fp;
+
+ for (ptr = known_mnts; ptr < known_mnts + ARRAY_SIZE(known_mnts); ptr++)
+ if (find_tracefs_mnt_single(TRACEFS_MAGIC, mnt, *ptr))
+ goto exit_found;
+
+ fp = fopen("/proc/mounts", "r");
+ if (!fp)
+ return false;
+
+ /* Allow room for NULL terminating byte and pipe file name */
+ snprintf(format, sizeof(format), "%%*s %%%zds %%99s %%*s %%*d %%*d\\n",
+ PATH_MAX - strlen(pipe_name) - 1);
before scanning trace_pipe could you add a check that trace_options are
compatible?
Otherwise there will be a lot of garbage printed.
afaik default is rarely changed, so the patch is ok as-is.
The followup some time in the future would be perfect.
Sure. What do you mean exactly by compatible options? I can check that
"trace_printk" is set, is there any other option that would be relevant?
Thanks,
Quentin
