libtracecmd: Support changing /proc/kallsyms
Running BPF selftests under trace-cmd intermittently fails with:
error in size of file '/proc/kallsyms'
This is because these selftests load and unload BPF programs.
bpf_prog_put() uses workqueues and RCU, so these programs disappear
from /proc/kallsyms after a delay.
trace-cmd reads /proc/kallsyms twice: the first time to compute its
size, and the second time to copy it into the trace file. If the
resulting sizes don't match, which is what happens in this case,
recording fails.
Fix by updating the size. This will work even for sending trace data
over the network thanks to trace_msg_cache.
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Link: https://lore.kernel.org/20250711132802.1781-3-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
1 file changed
