Extend -Y option to decode PIDs in arguments and return values

This change extends -Y/--decode-pids=comm option.  In addition to the
information printed before this change, command names would be printed
also for PIDs appeared in syscall arguments and return values.

For example:

  getppid()                  = 3781395<strace>
  getpid()                   = 3781398<a.out>
  pidfd_open(1<systemd>, 0)  = 3<pid:1<systemd>>

NOTE: The code printing the pid in printclockname() is not changed in
this commit.  CLOCKID_TO_FD macro used in printclockname() was removed
from the kernel, so printclockname() may change drastically in the
near future.

* src/defs.h (maybe_printpid_comm): New function declaration.
* src/strace.c (maybe_printpid_comm): New function printing
command name for the given PID.
* src/pidns.c (printpid_translation): Call `maybe_printpid_comm'.
* tests/strace--decode-pids-comm.c (do_default_action): Update expected
output.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Co-authored-by: Dmitry V. Levin <ldv@strace.io>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/strace.c b/src/strace.c
index 950644040..38165a1a3 100644
--- a/src/strace.c
+++ b/src/strace.c
@@ -948,6 +948,19 @@ load_pid_comm(int pid, char *buf, size_t buf_size)
 }
 
 void
+maybe_printpid_comm(int pid)
+{
+	if (!(pid_decoding & PID_DECODING_COMM))
+		return;
+
+	char buf[PROC_COMM_LEN];
+	load_pid_comm(pid, buf, sizeof(buf));
+	tprints("<");
+	tprints(buf);
+	tprints(">");
+}
+
+void
 maybe_load_task_comm(struct tcb *tcp)
 {
 	if (!(pid_decoding & PID_DECODING_COMM))