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Subject: Re: [PATCH 2/4] BaseTools/Scripts/GccBase.lds: export image base symbol
To: devel@edk2.groups.io
Cc: Bob Feng <bob.c.feng@intel.com>, Liming Gao <liming.gao@intel.com>,
 Laszlo Ersek <lersek@redhat.com>, Leif Lindholm <leif@nuviainc.com>,
 Ilias Apalodimas <ilias.apalodimas@linaro.org>, Julien Grall
 <julien@xen.org>, Jiewen Yao <jiewen.yao@intel.com>
References: <20200608173413.1100679-1-ard.biesheuvel@arm.com>
 <20200608173413.1100679-3-ard.biesheuvel@arm.com>
From: "Ard Biesheuvel" <ard.biesheuvel@arm.com>
Message-ID: <8f5cd985-c47e-b500-fca9-4ab449515a64@arm.com>
Date: Wed, 10 Jun 2020 23:48:10 +0200
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On 6/8/20 7:34 PM, Ard Biesheuvel wrote:
> To help converted ELF images perform self-relocation, export a symbol
> 'ElfImageBase' that can be used in the code to discover the start of
> the image in memory.
> 
> Note the use of PROVIDE() - this ensures that the symbol is only emitted
> if a reference to it exists in the code being linked, but no definition.
> This means the symbol is never emitted in a way that can conflict with
> existing code.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

Bob, Liming, any objections?

> ---
>   BaseTools/Scripts/GccBase.lds | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
> index a9dd2138d4b5..e73c1206a2e2 100644
> --- a/BaseTools/Scripts/GccBase.lds
> +++ b/BaseTools/Scripts/GccBase.lds
> @@ -12,6 +12,8 @@
>   
>   SECTIONS {
>   
> +  PROVIDE(ElfImageBase = .);
> +
>     /*
>      * The PE/COFF binary consists of DOS and PE/COFF headers, and a sequence of
>      * section headers adding up to PECOFF_HEADER_SIZE bytes (which differs
>