linux-kernel - Re: [PATCH 13/15] modpost: Add support for hashing long symbol names

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Message-ID: <20240618200745.GB1611012@google.com>
Date: Tue, 18 Jun 2024 13:07:45 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Matthew Maurer <mmaurer@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Gary Guo <gary@...yguo.net>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 13/15] modpost: Add support for hashing long symbol names

On Wed, Jun 19, 2024 at 01:47:13AM +0900, Masahiro Yamada wrote:
> On Tue, Jun 18, 2024 at 2:58 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
> >
> > +#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
> 
> 
> 
> 
> I know this is a copy-paste of the kernel space code,
> but is barrier_data() also necessary for host programs?

I tested this with Clang and it worked fine without the barrier, but
with gcc, the code no longer produces correct values. Presumably this is
a load bearing data barrier.

Sami