On Tue, 31 Jan, at 03:52:29PM, Ard Biesheuvel wrote: > The ARM decompressor is finicky when it comes to uninitialized variables > with local linkage, the reason being that it may relocate .text and .bss > independently when executing from ROM. This is only possible if all > references into .bss from .text are absolute, and this happens to be the > case for references emitted under -fpic to symbols with external linkage, > and so all .bss references must involve symbols with external linkage. > > When building the ARM stub using clang, the initialized local variable > __chunk_size is optimized into a zero-initialized flag that indicates > whether chunking is in effect or not. This flag is therefore emitted into > .bss, which triggers the ARM decompressor's diagnostics, resulting in a > failed build. > > Under UEFI, we never execute the decompressor from ROM, so the diagnostic > makes little sense here. But we can easily work around the issue by making > __chunk_size global instead. > > However, given that the file I/O chunking that is controlled by the > __chunk_size variable is intended to work around known bugs on various > x86 implementations of UEFI, we can simply make the chunking an x86 > specific feature. This is an improvement by itself, and also removes the > need to parse the efi= options in the stub entirely. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > drivers/firmware/efi/libstub/efi-stub-helper.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) Reviewed-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
