On 06/11/20 14:52, Ard Biesheuvel wrote: > 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 > > Changes since v1: > - Drop change to linker script, and instead, use the existing FV parsing code > (which is already incorporated into PrePi to load other modules), to find > the start address of the image before relocation. This way, we can support > TE images as well as PE32 images naturally, and not rely on GCC/binutils > specific artifacts that make porting to a native PE/COFF toolchain more > difficult > - Switch to TE format in the SELF_RELOC FDF rule - this is not terribly > likely to matter in practice, but since PrePi is the only module that > is incorporated in uncompressed form, and given that we used TE format > before these changes, it is a more appropriate default.
Right, I noticed that when I compared the new rule in v1 against the pre-existent SEC rule. I'm happy to see my feedback tags carried forward. Thanks Laszlo > - Add acks from Jiewen, Laszlo and Sami. Note that I have dropped the > Tested-bys - apologies for wasting anyone's time, but they could not > be carried over due to the changes. > > Cc: Laszlo Ersek <ler...@redhat.com> > Cc: Leif Lindholm <l...@nuviainc.com> > Cc: Ilias Apalodimas <ilias.apalodi...@linaro.org> > Cc: Julien Grall <jul...@xen.org> > Cc: Jiewen Yao <jiewen....@intel.com> > Cc: Sami Mujawar <sami.muja...@arm.com> > > Ard Biesheuvel (3): > ArmVirtPkg: add FDF rule for self-relocating PrePi > 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 | 35 ++++++++++++++ > ArmVirtPkg/ArmVirtRules.fdf.inc | 5 ++ > ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S | 49 +++++--------------- > ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S | 47 +++++-------------- > ArmVirtPkg/PrePi/Scripts/PrePi-PIE.lds | 41 ---------------- > 11 files changed, 75 insertions(+), 152 deletions(-) > delete mode 100644 ArmVirtPkg/Include/Platform/Hidden.h > delete mode 100644 ArmVirtPkg/PrePi/Scripts/PrePi-PIE.lds > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#61166): https://edk2.groups.io/g/devel/message/61166 Mute This Topic: https://groups.io/mt/74817463/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
