Hi, Any feedback on this topic ?
I made some significant changes and made sure to cover all the cases we identified including non-XIP stages. Cf. <https://review.coreboot.org/q/topic:x86-pre-ram-data-section> Thanks, Jeremy "Compostella, Jeremy" <jeremy.composte...@intel.com> writes: > Dear coreboot community, > > I am looking for feedback on the following topic. > > x86 Pre-memory stages do not support the `.data' section and as a result > developers are required to include runtime initialization code instead > of relying on C global variable definition. > > To illustrate the impact of this lack of .data section support, here > are two limitations I personally ran into: > 1. The inclusion of libgfxinit in romstage last year has required some > changes in libgfxinit to ensure data is initialized at runtime. In > addition, we had to manually map some .data symbols in the _bss > region. > 2. CBFS cache is currently not supported in pre-memory stages and > enabling it would require to add an initialization function and > find a generic spot to call it. > > Instead of going though these workarounds and as it was suggested on > [[RFC] VGA Text mode in romstage] last year, I believe we could add > support for a `.data' section. I have been working on a solution for > eXecute-In-Place (XIP) pre-memory stages (`bootblock', `verstage' and > `romstage') which deliver good results > (cf. <https://review.coreboot.org/c/coreboot/+/77289>). > > In short this patch: > 1. creates a new ELF segment to hold the `.data' section > 2. creates a `.data' section with its Virtual Memory Address (VMA) > within Cache-as-RAM (CAR) boundaries and its Load Memory Address > (LMA) following the .text section (at `_etext'). > > cbfstools is also updated: > - To process this new segment and `.data' section > - To place the .data section content right after the > code (cf. `parse_elf_to_xip_stage' function) > > At the moment, this patch makes cbfstool detects the presence of the > segment automatically and assume this is a "data" segment. But we > could add a new parameter to make this new behavior less automatic if > you think this would be better. > > This patch also adds a piece of assembly code (or C-code for > bootblock) to copy the `.data' section content to Cache-As-RAM at > runtime. > > Regards, _______________________________________________ coreboot mailing list -- coreboot@coreboot.org To unsubscribe send an email to coreboot-le...@coreboot.org
