linux-kernel - Re: [PATCH v4] rust: compiler_builtins: make stubs non-global

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Message-ID: <Y5CJRuwJlneWifEO@liuwe-devbox-debian-v2>
Date:   Wed, 7 Dec 2022 12:38:30 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Gary Guo <gary@...yguo.net>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Wei Liu <wei.liu@...nel.org>
Subject: Re: [PATCH v4] rust: compiler_builtins: make stubs non-global

On Mon, Dec 05, 2022 at 09:50:00PM +0000, Gary Guo wrote:
> Currently we define a number of stubs for compiler-builtin intrinsics
> that compiled libcore generates. The defined stubs are weak so they will
> not conflict with genuine implementation of these intrinsics, but their
> effect is global and will cause non-libcore code that accidently
> generate these intrinsics calls compile and bug on runtime.
> 
> Instead of defining a stub that can affect all code, this patch uses
> objcopy's `--redefine-sym` flag to redirect these calls (from libcore
> only) to a prefixed version (e.g. redirect `__multi3` to `__rust_multi3`),
> so we can define panciking stubs that are only visible to libcore.
> 
> This patch was previously discussed on GitHub [1]. This approach was also
> independently proposed by Nick Desaulniers in [2].
> 
> Link: https://github.com/Rust-for-Linux/linux/pull/779 [1]
> Link: https://lore.kernel.org/lkml/CAKwvOdkc0Qhwu=gfe1+H23TnAa6jnO6A3ZCO687dH6mSrATmDA@mail.gmail.com/
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Gary Guo <gary@...yguo.net>

Reviewed-by: Wei Liu <wei.liu@...nel.org>

It seems that the only difference between v3 and v4 is Nick's ack.

You can put a changelog by adding a `---` section -- it will be stripped
by git-am automatically.

Thanks,
Wei.