[PATCH] elf: Add la_objsearch2 with lmid parameter for rtld-audit [BZ #34093]

[DJ Delorie]

On Wed, Sep 23, 2026 at 3:55 PM Adhemerval Zanella Netto
<adhemerval.zanella@linaro.org> wrote:
> Right, but then you move the version check from glibc to the audit
> module itself.  I am not sure if this is a better semantic.

I think there's a couple of scenarios to consider:

1. Existing auditors will request the old LAV_CURRENT (say, 2).  New
   glibc will need to support that version.  sysdeps/generic has the
   right logic, but aarch64 and loongarch will need a range check
   (currently they use ==) since the previous version is incompatible.

2. A new auditor that allows but does not require the new function can
   return the OLD version (LAV_CURRENT-1) and dynamically adapt to
   whatever callbacks happen.

3. An auditor requires the new callback, is built with the new
   headers, and will fail to load on old glibc's.

4. A new auditor wants the old callback, but builds with the new
   LAV_CURRENT.

I think bumping LAV_CURRENT will work in all cases.  Not bumping it
works for 1 and 2 but not 3.

Case 4 requires glibc internals to detect which is requested, which
Fred's patch does.

Case 2 is more flexible for auditor deployers but is trickier to code,
especially as the LAV_CURRENT values are inconsistent across targets.

The only time we MUST bump LAV_CURRENT is when an existing callback
changes in a way that breaks existing auditors.