Re: [PING PATCH v7] kallsyms: new /proc/kallmodsyms with builtin modules

From: Daniel Xu
Date: Wed Feb 02 2022 - 13:11:02 EST


Hi Luis, Nick,

On Tue, Feb 01, 2022 at 07:09:23PM -0800, Luis Chamberlain wrote:
[...]
>
> I don't see much traction based on what you have said on dtrace
> on anything other than Oracle Linux stuff, it would be nice if bpftrace
> folks were excited about your changes and we had support for that
> there.

I took a quick look at the v7 cover letter (I'll take a look at
discussion from previous versions later if I get time) and it's not
immediately obvious to me why a stable mapping is beneficial.

Nick, could you elaborate why it's beneficial for dtrace to have a
stable mapping?

For what it's worth, bpftrace uses /proc/kallsyms rather rarely.
bpftrace relies on perf_event_open()'s config1 parameter to resolve
kernel symbol name to address for kprobe attachment. /proc/kallsyms is
mostly used to resolve kaddr() calls in bpftrace scripts.

Kernel symbol size information would be useful, though. bpftrace
currently uses the vmlinux ELF to acquire that information.

[...]

Thanks,
Daniel