Hi, Here is the 2nd version of adding relative stacktrace for tracing. The previous version is here; https://lore.kernel.org/all/173807861687.1525539.15082309716909038251.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ In this version, I changed the idea to only use the first 32bit of the build_id of the modules instead of using live hash/id to identify the module. Also, save the offset from the .text section for each module instead of using the offset from the _stext for the module address. (For the core kernel text address, keep using the offset from _stext.) This brings the following benefits: - Do not need to save the live module allocation information on somewhere in the reserved memory. - Easy to find the module offline. - We can ensure there are only offsets from the base, no KASLR info. Moreover, encode/decode module build_id, we can show the module name with the symbols on stacktrace. Thus, this relative stacktrace is a better option for the persistent ring buffer with security restricted environment (e.g. no kallsyms access from user.) # echo 1 > options/relative-stacktrace # modprobe trace_events_sample # echo stacktrace > events/sample-trace/foo_bar/trigger # cat trace event-sample-1622 [004] ...1. 397.542659: <stack trace> => event_triggers_post_call => trace_event_raw_event_foo_bar [trace_events_sample] => do_simple_thread_func [trace_events_sample] => simple_thread [trace_events_sample] => kthread => ret_from_fork => ret_from_fork_asm Thank you, --- Masami Hiramatsu (Google) (2): modules: Add __module_build_id() to find module by build_id tracing: Add relative-stacktrace option include/linux/module.h | 8 +++++ include/linux/trace.h | 5 +++ kernel/module/Kconfig | 3 ++ kernel/module/kallsyms.c | 4 +-- kernel/module/main.c | 29 ++++++++++++++++++++ kernel/trace/Kconfig | 1 + kernel/trace/trace.c | 50 ++++++++++++++++++++++++++++++---- kernel/trace/trace.h | 3 ++ kernel/trace/trace_entries.h | 18 ++++++++++++ kernel/trace/trace_output.c | 62 ++++++++++++++++++++++++++++++++++++++++++ lib/Kconfig.debug | 1 + 11 files changed, 175 insertions(+), 9 deletions(-) -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
