Re: [PATCH dwarves] pahole: Avoid generating artificial inlined functions for BTF

[Jakub Sitnicki <jakub@cloudflare.com>]

On Fri, Oct 03, 2025 at 10:36 AM -07, Yonghong Song wrote:
> But actually, one of function 'foo' is marked as DW_INL_inlined which means
> we should not treat it as an elf funciton. The patch fixed this issue
> by filtering subprograms if the corresponding function__inlined() is true.

I have a semi-related question: are there any plans for BTF to indicate
when a function has been inlined? Not necessarily where it has been
inlined, just that it has, somewhere, at least once.

When tracing with bpftrace or perf without a vmlinux available, it's
easy to assume you're tracing all calls to a function, when in fact some
calls may be inlined within the same compilation unit.

A good example is tracing the rtnl_lock - there are multiple inlined
copies, but neither bpftrace nor perf can warn you about it when debug
info is absent.

$ sudo perf probe -a rtnl_lock
Added new event:
  probe:rtnl_lock      (on rtnl_lock)
 
You can now use it in all perf tools, such as:
 
        perf record -e probe:rtnl_lock -aR sleep 1
 
$ sudo apt install linux-image-`uname -r`-dbg
Installing:
  linux-image-6.12.53-cloudflare-2025.10.4-dbg
[…]
$ sudo perf probe -d rtnl_lock
Removed event: probe:rtnl_lock
$ sudo perf probe -a rtnl_lock
Added new events:
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
  probe:rtnl_lock      (on rtnl_lock)
 
You can now use it in all perf tools, such as:
 
        perf record -e probe:rtnl_lock -aR sleep 1
 
$

Thanks,
-jkbs