linux-kernel - Re: [PATCH] tools/nolibc: completely remove optional environ support

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Message-ID: <804671ba-3884-4700-b367-2f84dace89f4@t-8ch.de>
Date:   Mon, 10 Jul 2023 19:51:53 +0200
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Willy Tarreau <w@....eu>
Cc:     linux-kernel@...r.kernel.org, Zhangjin Wu <falcon@...ylab.org>
Subject: Re: [PATCH] tools/nolibc: completely remove optional environ support

On 2023-07-10 19:43:27+0200, Willy Tarreau wrote:
> Hi Thomas,
> 
> On Mon, Jul 10, 2023 at 07:22:53PM +0200, Thomas Weißschuh wrote:
> > In commit 52e423f5b93e ("tools/nolibc: export environ as a weak symbol on i386")
> > and friends the asm startup logic was extended to directly populate the
> > "environ" array.
> > 
> > This makes it impossible for "environ" to be dropped by the linker.
> > Therefore also drop the other logic to handle non-present "environ".
> 
> Hmmm OK but at least I'd like that we continue to reference it from
> nolibc-test to make sure it's still visible. Maybe we could just check
> that it's always equal to envp ? If we drop its reference from there,
> sooner or later someone will find it interesting to rename it and some
> programs referencing it will break.

Easy enough to test for. I'll send a v2.

> > Note:
> > 
> > Given that nowadays both _auxv and environ are mandatory symbols imposed
> > by nolibc of pointer size does it make sense to keep the code to make
> > int-sized errno optional?
> 
> While it indeed used to be related to having a data segment or not
> initially, it still has an impact on our ability to completely drop
> the errno setting code from all syscalls. Given the SET_ERRNO() macro
> now I guess it's very cheap to keep it, don't you think ?

SET_ERRNO irks me a tiny bit :-)

But it's easy enough to keep, let's do so.
Just wanted to have brought it up.

Thomas