Messages in this thread | | | From | Thomas-Mich Richter <> | Subject | Linux 4.15.0-rc3 perf probe/uprobe issue with address randomization | Date | Fri, 15 Dec 2017 15:14:37 +0100 |
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During debugging of perf probe tool I discovered an issue with uprobes and address randomization.
To set a uprobe on a function named inet_pton in libc library, you obtain the address of the symbol inet_pton using command nm and then use the following command to set the uprobe:
# echo "p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x142060" > /sys/kernel/debug/tracing/uprobe_events
0x142060 is the address of inet_pton on my system. This works nicely and the uprobe is usable.
The issue is with the output: # cat /sys/kernel/debug/tracing/uprobe_events p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x000000002d0f8952 #
The displayed address 0x000000002d0f8952 is wrong, probably randomized and post processing of this output with the perf probe tool fails due to this random address:
# linux/tools/perf/perf probe -l Failed to find debug information for address 2d0f8952 probe_libc:inet_pton (on 0x2d0f8952 in /usr/lib64/libc-2.26.so) #
So how to fix this (if at all)? Is replacing %p by %llx in line 612 of file kernel/trace/trace_uprobe.c seq_printf(m, "0x%p", (void *)tu->offset) an option? Or is this broken by design and intention?
Thanks for hints and suggestions. -- Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany -- Vorsitzende des Aufsichtsrats: Martina Koederitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
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