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From: "i at maskray dot me" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug dynamic-link/28676] p_align on PT_LOAD segment in DSO isn't
 honored
Date: Tue, 14 Dec 2021 05:31:41 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28676

Fangrui Song <i at maskray dot me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |i at maskray dot me

--- Comment #3 from Fangrui Song <i at maskray dot me> ---
This is not a bug per se. My reasoning is at
https://sourceware.org/pipermail/libc-alpha/2021-December/134121.html=20

`__attribute__((aligned(0x200000))) =3D 1;` does not necessarily mean the l=
arge
alignment needs to be satisfied on a system with a smaller page size.
Now "elf: Properly align PT_LOAD segments [BZ #28676]" overaligns memory
mappings to p_align to make the use case work. It's a new feature, not a
bugfix.

The 2020 kernel commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?=
id=3Dce81bb256a224259ab686742a6284930cbe4f1fa
has no waste, so it is more justifiable.
The emulation in ld.so, however, would incur significant overhead, so it ne=
eds
more thoughts.
At the very least, the max-page-size=3D0x200000 for -z noseparate-code on x=
86-64
may be problematic.
It looks like we need more thoughts how tools like objcopy and ld can make =
the
cost small, or whether such changes are justifiable.

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