Hello all,
This is an RFC series to elicit discussion regarding the use of linker script,
and the fact that we use the somewhat obscure 'large' C model for building
EDK2 for AArch64.
Some observations that brought about this series:
- the -Ttext=0x0 LD command line option appears to have no beneficial effect
- the builtin LD script that we have been using so far prevents .text and .data
from sharing any 64 KB page frames; this is intentional since .text and .data
are typically mapped with different permissions when executing under an OS,
and the maximum page size on AArch64 is 64 KB;
- we have been using the 'large' C model, which may be suboptimal
- the Property Table support in UEFI 2.5 requires the use of an explicit linker
script so that sections are 4 KB aligned, and .text and .data are guaranteed
not to share a 4 KB page frame, again for allowing them to be mapped with
different permissions. This maps poorly onto AArch64, again due to its maximum
page size of 64 KB.
These patches propose a linker script to be used with AArch64 that preserves the
layout between ELF and PE/COFF, i.e., the placement of .text and .data is the
same for both binaries. It also places .text such that ADRP based PC relative
symbol references can be supported, provided that the PE/COFF binaries are
always loaded at a 4 KB aligned offset.
As said, this is meant to elicit discussion, so fire away ...
Ard Biesheuvel (4):
BaseTools: AArch64: conditionally allow page-based PC relative
relocations
BaseTools: AArch64: use an explicit linker script
BaseTools: move ARCHCC_ and PLATFORM_FLAGS to end of GCC command line
ArmVirtPkg: ArmVirtQemu: use GCC 'small' C model on AArch64
ArmVirtPkg/ArmVirtQemu.dsc | 2 +-
ArmVirtPkg/ArmVirtQemu.fdf | 24 +++++++++++++++++++++---
BaseTools/Conf/tools_def.template | 25 ++++++++++++++-----------
BaseTools/Scripts/gcc-aarch64-ld-script | 33 +++++++++++++++++++++++++++++++++
BaseTools/Source/C/GenFw/Elf64Convert.c | 51
+++++++++++++++++++++++++++++++++++++++++----------
5 files changed, 110 insertions(+), 25 deletions(-)
create mode 100644 BaseTools/Scripts/gcc-aarch64-ld-script
--
1.9.1
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