linux-kernel - Re: [PATCH] x86/vdso: Conditionally export __vdso_sgx_enter

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Message-ID: <Y5M8SZEN1N5Dt15X@dev-arch.thelio-3990X>
Date:   Fri, 9 Dec 2022 06:46:49 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev
Subject: Re: [PATCH] x86/vdso: Conditionally export __vdso_sgx_enter_enclave

Ping? The default switch was remerged a couple of days ago so builds
with tip of tree LLVM are going to be broken again:

https://github.com/llvm/llvm-project/commit/241dbd310599e3c1a0f1b0c9ced14c8b8760539e

Cheers,
Nathan

On Tue, Nov 08, 2022 at 05:03:07PM -0700, Nathan Chancellor wrote:
> Recently, ld.lld moved from '--undefined-version' to
> '--no-undefined-version' as the default, which breaks building the vDSO
> when CONFIG_X86_SGX is not set:
> 
>   ld.lld: error: version script assignment of 'LINUX_2.6' to symbol '__vdso_sgx_enter_enclave' failed: symbol not defined
> 
> __vdso_sgx_enter_enclave is only included in the vDSO when
> CONFIG_X86_SGX is set. Only export it if it will be present in the final
> object, which clears up the error.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1756
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> 
> It would be nice if this could be picked up for an -rc release but I
> won't argue otherwise.
> 
> Alternatively, we could add '--undefined-version' to the vDSO ldflags
> but this does not seem unreasonable to me.
> 
>  arch/x86/entry/vdso/vdso.lds.S | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/entry/vdso/vdso.lds.S b/arch/x86/entry/vdso/vdso.lds.S
> index 4bf48462fca7..e8c60ae7a7c8 100644
> --- a/arch/x86/entry/vdso/vdso.lds.S
> +++ b/arch/x86/entry/vdso/vdso.lds.S
> @@ -27,7 +27,9 @@ VERSION {
>  		__vdso_time;
>  		clock_getres;
>  		__vdso_clock_getres;
> +#ifdef CONFIG_X86_SGX
>  		__vdso_sgx_enter_enclave;
> +#endif
>  	local: *;
>  	};
>  }
> 
> base-commit: f0c4d9fc9cc9462659728d168387191387e903cc
> -- 
> 2.38.1
> 
>