tree 02067ac7393ddf3cdba4c8ac6e735c60b7b06bf1
parent 2c2e55128a1ff2cde55c397ac341421d87d74d4c
author Ilya Leoshkevich <iii@linux.ibm.com> 1752240336 +0200
committer Steven Rostedt (Google) <rostedt@goodmis.org> 1756333107 -0400

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>