Re: [PATCH 0/3] support '%pd' and '%pD' for print file name

[yebin (H)]

On 2024/1/19 22:43, Masami Hiramatsu (Google) wrote:
> On Fri, 19 Jan 2024 09:38:45 +0800
> Ye Bin <yebin10@xxxxxxxxxx> wrote:
>
> > During fault locating, the file name needs to be printed based on the
> > dentry/file address. The offset needs to be calculated each time, which
> > is troublesome. Similar to printk, kprobe supports printing file names
> > for dentry/file addresses.
> Hi Ye,
>
> Thanks for your proposal!
>
> Generically, I think this type of hack is not good for the tracing
> because there are already some ways to do that. e.g.
>   - Use perf probe to specify dentry->name:string or file->name:string
>   - Use BTF to specify in the same way (but only for function entry)
> And those are more obvious what it does.
>
> However, if this is implemented in more generic syntax, it will be
> acceptable.
> For example, type specifying with "arg1:printfmt(%pD)" will be
> more generic because it is apparently one of the printfmt and output
> string. Or, maybe we can just allow to use ":%pD" as a fetch type
> (start with '%' means the printfmt)
>
> Also, could you update readme_msg[] in kernel/trace/trace.c if
> you add a type, and add a testcase of selftests/ftrace, for this
> feature? Documentation should also be updated with more syntax
> information.
>
> Thank you,
Thank you very much for your suggestion.
I will re-implement this function according to your suggestion.
> > Ye Bin (3):
> >    tracing/probes: support '%pd' type for print struct dentry's name
> >    tracing/probes: support '%pD' type for print struct file's name
> >    Documentation: tracing: add new type 'pd' and 'pD' for kprobe
> >
> >   Documentation/trace/kprobetrace.rst |  3 +-
> >   kernel/trace/trace_probe.c          | 50 +++++++++++++++++++++++++++++
> >   2 files changed, 52 insertions(+), 1 deletion(-)
> >
> > --
> > 2.31.1