Re: [PATCH 0/2] trace-cmd record: Handle persistent ring buffers

On Tue,  3 Feb 2026 20:18:04 -0500
Steven Rostedt <[email protected]> wrote:

> From: "Steven Rostedt (Google)" <[email protected]>
> 
> Now that a ring buffer instance can be from a previous boot, allow trace-cmd
> to be able to read its content and still get the function names from the
> addresses.
> 
> If a persistent ring buffer is from a previous boot, it will have a
> "last_boot_info" file. This contains the address of the _text section of the
> core kernel as well as where all the modules were loaded. This can be used
> to calculate the addresses in the previous boot ring buffer to the addresses
> in the current kallsyms to find out the name of the function an address
> belongs to.
> 
> Also if the last_boot_info file exists, the /proc/modules file is read. This
> is because functions in modules needs to have its address calculated from
> where its module was loaded in the previous boot to where it is loaded in
> the current boot. The last_boot_info contains the addresses of the modules
> of the previous boot, and /proc/modules contains the addresses of the
> modules from the current boot. With both the addresses of functions in
> modules can be converted to the corresponding address in kallsyms.
> 

Both looks good to me. BTW, both only records the information, and
resolving symbol will be the next series?

Reviewed-by: Masami Hiramatsu (Google) <[email protected]>

for the series.

Thank you,

> Steven Rostedt (Google) (2):
>   trace-cmd record: Handle last_boot_info file
>   trace-cmd record: Add section for /proc/modules
> 
>  .../trace-cmd/trace-cmd.dat.v7.5.txt          | 31 +++++++++--
>  .../include/private/trace-cmd-private.h       |  3 ++
>  lib/trace-cmd/trace-ftrace.c                  |  4 +-
>  lib/trace-cmd/trace-input.c                   | 31 +++++++++++
>  lib/trace-cmd/trace-output.c                  | 32 ++++++++++++
>  tracecmd/include/trace-local.h                |  2 +
>  tracecmd/trace-dump.c                         | 32 ++++++++++++
>  tracecmd/trace-record.c                       | 52 +++++++++++++++++++
>  8 files changed, 180 insertions(+), 7 deletions(-)
> 
> -- 
> 2.51.0
> 


-- 
Masami Hiramatsu (Google) <[email protected]>