As suggested by Jiewen in response to Ilias RFC [0], it is better to use the PE/COFF metadata for self-relocating executables than to rely on ELF metadata, given how the latter is only available when using ELF based toolchains. Also, we have had some maintenance issues with this code in the past, as PIE linking of non-position independent objects is not a well tested code path in toolchains in general.
So implement this for the self-relocating PrePi in ArmVirtPkg first. First, we need to ensure that the module in question is emitted with its PE/COFF relocation metadata preserved, by creating a special FDF rule. We also need to provide a way for the code to refer to the start of the image directly, by adding it to the linker script. Then, it is simply a matter of swapping out the two assembly routines, and adding the C code that serves the same purpose but based on PE/COFF base relocations. Note that PE/COFF relocations are considerably more compact than ELF RELA relocations, so this does not impact the memory footprint of the resulting image adversely. [0] https://edk2.groups.io/g/devel/message/60835 Cc: Bob Feng <[email protected]> Cc: Liming Gao <[email protected]> Cc: Laszlo Ersek <[email protected]> Cc: Leif Lindholm <[email protected]> Cc: Ilias Apalodimas <[email protected]> Cc: Julien Grall <[email protected]> Cc: Jiewen Yao <[email protected]> Ard Biesheuvel (4): ArmVirtPkg: add FDF rule for self-relocating PrePi BaseTools/Scripts/GccBase.lds: export image base symbol ArmVirtPkg/PrePi: use standard PeCoff routines for self-relocation ArmVirtPkg: remove unused files ArmVirtPkg/ArmVirtQemuKernel.dsc | 10 ++-- ArmVirtPkg/ArmVirtXen.dsc | 10 ++-- ArmVirtPkg/ArmVirtQemuKernel.fdf | 2 +- ArmVirtPkg/ArmVirtXen.fdf | 2 +- ArmVirtPkg/PrePi/ArmVirtPrePiUniCoreRelocatable.inf | 4 +- ArmVirtPkg/Include/Platform/Hidden.h | 22 --------- ArmVirtPkg/PrePi/PrePi.c | 21 +++++++++ ArmVirtPkg/ArmVirtRules.fdf.inc | 5 ++ ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S | 49 +++++--------------- ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S | 47 +++++-------------- ArmVirtPkg/PrePi/Scripts/PrePi-PIE.lds | 41 ---------------- BaseTools/Scripts/GccBase.lds | 2 + 12 files changed, 63 insertions(+), 152 deletions(-) delete mode 100644 ArmVirtPkg/Include/Platform/Hidden.h delete mode 100644 ArmVirtPkg/PrePi/Scripts/PrePi-PIE.lds -- 2.26.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#60891): https://edk2.groups.io/g/devel/message/60891 Mute This Topic: https://groups.io/mt/74757206/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
