Re: [edk2-devel] [PATCH 2/4] BaseTools/Scripts/GccBase.lds: export image base symbol

["Bob Feng" <bob.c.feng@intel.com>]

Reviewed-by: Bob Feng<bob.c.feng@intel.com>

-----Original Message-----
From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ard Biesheuvel
Sent: Tuesday, June 9, 2020 1:34 AM
To: devel@edk2.groups.io
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>; Feng, Bob C <bob.c.feng@intel.com>; Gao, Liming <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>; Yao, Jiewen <jiewen.yao@intel.com>
Subject: [edk2-devel] [PATCH 2/4] BaseTools/Scripts/GccBase.lds: export image base symbol

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>
---
 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-- 
2.26.2


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