Hi Jeremy, I've added it to the agenda for today's leadership meeting. Martin
Sep 5, 2023, 15:30 by jeremy.composte...@intel.com: > 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 > _______________________________________________ coreboot mailing list -- coreboot@coreboot.org To unsubscribe send an email to coreboot-le...@coreboot.org
