[Bug dynamic-link/31076] Extra struct vm_area_struct with ---p created when PAGE_SIZE < max-page-size

["corsix at corsix dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31076

Peter Cawley <corsix at corsix dot org> changed:

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                 CC|                            |corsix at corsix dot org

--- Comment #22 from Peter Cawley <corsix at corsix dot org> ---
(In reply to Adhemerval Zanella from comment #11)
> It does indeed, which makes me realize that _dl_find_object does not work correctly if the loader is built with -Wl,-z,max-page-size= different than the system one.

FWIW, I've just hit this issue in practice on off-the-shelf Debian on aarch64:
/lib/ld-linux-aarch64.so.1 specifies 64K alignment for its segments, but the
system page size is 4K, so the kernel leaves gaps when mapping it in. Other
shared objects can then get loaded into those gaps (if they are small and
specify only 4K alignment for their segments), and then _dl_find_object against
those shared objects will return /lib/ld-linux-aarch64.so.1 rather than
returning the correct shared object. In turn, this causes _Unwind_Backtrace et.
al. to fail to unwind through these shared objects, as _Unwind_Backtrace relies
on _dl_find_object to find the unwind data.

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